in the current study, we analyzed the
Effect of eccentric exercise on the conduction velocity of
individual motor units at two locations of the vastus
medialis muscle during sustained contractions.
This study investigated changes in sensory and electromyography (EMG) measurements over different regions of the quadriceps muscle before and after eccentric exercise intended to induce delayed-onset muscle soreness (DOMS). Surface EMG signals and pressure pain thresholds were measured at 15 locations on the quadriceps during sustained isometric contractions and at rest. After eccentric exercise, time to failure during contractions, EMG amplitude, and pain thresholds all decreased significantly and were lowest in the distal region of the quadriceps. This suggests DOMS manifestations vary by muscle region, likely due to differences in fiber morphology and architecture. The distal quadriceps may be more susceptible to further injury after eccentric exercise.
Motor unit conduction velocity during sustained contraction of the vastus med...Nosrat hedayatpour
The aim of the study was to analyze motor unit conduction
velocity at varying force in the distal part of the
vastus medialis muscle during sustained contraction.
A tipologia da fibra muscular influencia substancialmente o tempo de recupera...FranciscoJulio12
1) The study investigated the effects of muscle fiber typology on fatigue and recovery following high-intensity exercise.
2) Thirty-two male athletes underwent proton magnetic resonance spectroscopy to estimate their muscle fiber typology as predominantly slow (ST) or fast (FT) based on calf muscle carnosine levels.
3) The ST and FT groups then performed repeated Wingate tests to induce fatigue. The FT group experienced greater power drop during exercise and had not fully recovered torque levels 5 hours later, while the ST group recovered within 20 minutes, indicating muscle fiber typology influences exercise-induced fatigue and recovery time.
This document describes a study that investigated the reliability of different electromyography (EMG) normalization methods for cycling analyses. The study tested 25 male cyclists and examined four lower leg muscles. Participants performed isometric maximum voluntary contractions (IMVC) on a dynamometer and submaximal and maximum cycling trials. The study found that different normalization methods produced significantly different EMG amplitude reference values and that the peak dynamic amplitude (PDA) method demonstrated the highest reliability for all muscles. Therefore, the study supports the use of the PDA method for EMG normalization in cycling analyses.
ISMST 2015 Abstract 2 - The influence of medical shockwaves on muscle activat...Kenneth Craig
This study investigated the effects of medical shockwave therapy on muscle activation patterns and performance in healthy athletes. Golfers and weightlifters underwent shockwave therapy targeting specific muscles. Post-treatment, golfers showed increased swing speed, ball distance, and faster muscle activation. Weightlifters showed faster muscle activation but lower energy output during squats, though they were able to lift more weight. The study suggests shockwave therapy may induce favorable biological responses in healthy muscles, reducing fatigue and potential for overuse injuries over time. Further research is warranted.
This study aimed to determine which exercises best activate the gluteus medius and superior portion of the gluteus maximus muscles while minimizing activation of the tensor fascia lata muscle. Researchers used fine-wire electromyography to measure muscle activity in the gluteus medius, gluteus maximus, and tensor fascia lata muscles during 11 different exercises in 20 healthy subjects. They found that the clam exercise, sidestepping, unilateral bridging, and quadruped hip extension activated the gluteal muscles significantly more than the tensor fascia lata muscle.
This study aimed to detect the electromechanical delay (EMD) and its components during voluntary isometric contractions of the quadriceps femoris muscle. The researchers measured time delays between the onsets of EMG-MMG, EMG-US, MMG-FORCE, US-FORCE, and EMG-FORCE signals. They found ultrasonography (US) provided more reliable detection of muscle fiber motion onset compared to mechanomyography (MMG). The study concluded synchronization of US with EMG and force sensors can reveal reliable results about EMD and its components during voluntary muscle contractions by detecting fiber motion onset from a certain muscle depth.
1) The study examined electromyographic (EMG) activity in the anterior, middle, and posterior subdivisions of gluteus medius (GM) muscle during three weight-bearing exercises: wall squat, pelvic drop, and wall press.
2) The results showed significant differences in activation levels between the three GM subdivisions and between the three exercises.
3) The wall press produced the highest activation overall and was most effective at activating the posterior GM subdivision, which typically displays higher activation than the other two subdivisions.
This study investigated changes in sensory and electromyography (EMG) measurements over different regions of the quadriceps muscle before and after eccentric exercise intended to induce delayed-onset muscle soreness (DOMS). Surface EMG signals and pressure pain thresholds were measured at 15 locations on the quadriceps during sustained isometric contractions and at rest. After eccentric exercise, time to failure during contractions, EMG amplitude, and pain thresholds all decreased significantly and were lowest in the distal region of the quadriceps. This suggests DOMS manifestations vary by muscle region, likely due to differences in fiber morphology and architecture. The distal quadriceps may be more susceptible to further injury after eccentric exercise.
Motor unit conduction velocity during sustained contraction of the vastus med...Nosrat hedayatpour
The aim of the study was to analyze motor unit conduction
velocity at varying force in the distal part of the
vastus medialis muscle during sustained contraction.
A tipologia da fibra muscular influencia substancialmente o tempo de recupera...FranciscoJulio12
1) The study investigated the effects of muscle fiber typology on fatigue and recovery following high-intensity exercise.
2) Thirty-two male athletes underwent proton magnetic resonance spectroscopy to estimate their muscle fiber typology as predominantly slow (ST) or fast (FT) based on calf muscle carnosine levels.
3) The ST and FT groups then performed repeated Wingate tests to induce fatigue. The FT group experienced greater power drop during exercise and had not fully recovered torque levels 5 hours later, while the ST group recovered within 20 minutes, indicating muscle fiber typology influences exercise-induced fatigue and recovery time.
This document describes a study that investigated the reliability of different electromyography (EMG) normalization methods for cycling analyses. The study tested 25 male cyclists and examined four lower leg muscles. Participants performed isometric maximum voluntary contractions (IMVC) on a dynamometer and submaximal and maximum cycling trials. The study found that different normalization methods produced significantly different EMG amplitude reference values and that the peak dynamic amplitude (PDA) method demonstrated the highest reliability for all muscles. Therefore, the study supports the use of the PDA method for EMG normalization in cycling analyses.
ISMST 2015 Abstract 2 - The influence of medical shockwaves on muscle activat...Kenneth Craig
This study investigated the effects of medical shockwave therapy on muscle activation patterns and performance in healthy athletes. Golfers and weightlifters underwent shockwave therapy targeting specific muscles. Post-treatment, golfers showed increased swing speed, ball distance, and faster muscle activation. Weightlifters showed faster muscle activation but lower energy output during squats, though they were able to lift more weight. The study suggests shockwave therapy may induce favorable biological responses in healthy muscles, reducing fatigue and potential for overuse injuries over time. Further research is warranted.
This study aimed to determine which exercises best activate the gluteus medius and superior portion of the gluteus maximus muscles while minimizing activation of the tensor fascia lata muscle. Researchers used fine-wire electromyography to measure muscle activity in the gluteus medius, gluteus maximus, and tensor fascia lata muscles during 11 different exercises in 20 healthy subjects. They found that the clam exercise, sidestepping, unilateral bridging, and quadruped hip extension activated the gluteal muscles significantly more than the tensor fascia lata muscle.
This study aimed to detect the electromechanical delay (EMD) and its components during voluntary isometric contractions of the quadriceps femoris muscle. The researchers measured time delays between the onsets of EMG-MMG, EMG-US, MMG-FORCE, US-FORCE, and EMG-FORCE signals. They found ultrasonography (US) provided more reliable detection of muscle fiber motion onset compared to mechanomyography (MMG). The study concluded synchronization of US with EMG and force sensors can reveal reliable results about EMD and its components during voluntary muscle contractions by detecting fiber motion onset from a certain muscle depth.
1) The study examined electromyographic (EMG) activity in the anterior, middle, and posterior subdivisions of gluteus medius (GM) muscle during three weight-bearing exercises: wall squat, pelvic drop, and wall press.
2) The results showed significant differences in activation levels between the three GM subdivisions and between the three exercises.
3) The wall press produced the highest activation overall and was most effective at activating the posterior GM subdivision, which typically displays higher activation than the other two subdivisions.
Delayed-Onset Muscle Soreness Alters the Response to Postural PerturbationsNosrat hedayatpour
The purpose of this study was to assess the EMG activity
of knee muscles during destabilizing perturbations performed
before, immediately after, and 24 and 48 h after eccentric
exercise.
Effect of Endurance on Gastrocnemius Muscle with Exercise by Employing EMG Am...ijtsrd
Muscle fatigue is a common experience in daily life. Many authors have defined it as the incapacity to maintain the required or expected force, and therefore, force, power and torque recordings have been used as direct measurements of muscle fatigue. In addition, the measurement of these variables combined with the measurement of surface electromyography sEMG recordings which can be measured during all types of movements during exercise may be useful to assess and understand muscle fatigue. EMG signal can be easily analyzed in time domain, frequency domain and time frequency domain. The time domain features are the most popular in EMG pattern recognition because they are easy and quick to calculate and they do not require a transformation. The purpose of this study was to analyze the fatigue and to study the endurance occurrence in the Gastrocnemius muscle with a pre defined exercise protocol for the targeted muscle. For this purpose, sEMG Amplitude parameters were characterized. Relation between EMG features like mean, force, standard deviation, etc. is verified for fatigue detection as well as to identify the Endurance developed in the Gastrocnemius muscle. Gaurav Patti | Poonam Kumari "Effect of Endurance on Gastrocnemius Muscle with Exercise by Employing EMG Amplitude Parameters" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-5 , August 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33222.pdf Paper Url :https://www.ijtsrd.com/engineering/other/33222/effect-of-endurance-on-gastrocnemius-muscle-with-exercise-by-employing-emg-amplitude-parameters/gaurav-patti
Acute effect of different combined stretching methodsFernando Farias
The purpose of this study was to investigate the acute effect of different stretching methods, during a warm-up,
on the acceleration and speed of soccer players. The acceleration performance of 20 collegiate soccer players (body height:
177.25 ± 5.31 cm; body mass: 65.10 ± 5.62 kg; age: 16.85 ± 0.87 years; BMI: 20.70 ± 5.54; experience: 8.46 ± 1.49
years) was evaluated after different warm-up procedures, using 10 and 20 m tests. Subjects performed five types of a
warm-up: static, dynamic, combined static + dynamic, combined dynamic + static, and no-stretching. Subjects were
divided into five groups. Each group performed five different warm-up protocols in five non-consecutive days. The
warm-up protocol used for each group was randomly assigned. The protocols consisted of 4 min jogging, a 1 min
stretching program (except for the no-stretching protocol), and 2 min rest periods, followed by the 10 and 20 m sprint
test, on the same day. The current findings showed significant differences in the 10 and 20 m tests after dynamic
stretching compared with static, combined, and no-stretching protocols. There were also significant differences between
the combined stretching compared with static and no-stretching protocols. We concluded that soccer players performed
better with respect to acceleration and speed, after dynamic and combined stretching, as they were able to produce more
force for a faster execution.
The effects of self-myofascial release using a foam roll or roller massager on joint range of motion, muscle recovery, and performance: a systematic review
Non-uniform electromyographic activity during fatigue and recovery of the vas...Nosrat hedayatpour
The aim of the study was to investigate EMG signal features
during fatigue and recovery at three locations of the vastus
medialis and lateralis muscles.
Sprint running acceleration is a key feature of physical performance in team sports, and recent
literature shows that the ability to generate large magnitudes of horizontal ground reaction force
and mechanical effectiveness of force application are paramount. We tested the hypothesis that
very-heavy loaded sled sprint training would induce an improvement in horizontal force
production, via an increased effectiveness of application. Training-induced changes in sprint
performance and mechanical outputs were computed using a field method based on velocity-
time data, before and after an 8-week protocol (16 sessions of 10x20-m sprints). 16 male
amateur soccer players were assigned to either a very-heavy sled (80% body-mass sled load)
or a control group (unresisted sprints). The main outcome of this pilot study is that very-heavy
sled resisted sprint training, using much greater loads than traditionally recommended, clearly
increased maximal horizontal force production compared to standard unloaded sprint training
(effect size of 0.80 vs 0.20 for controls, unclear between-group difference) and mechanical
effectiveness (i.e. more horizontally applied force; effect size of 0.95 vs -0.11, moderate
between-group difference)
Melhorar ou até mesmo manter o desempenho atlético em jogadores de esportes de equipe competitivos durante o longo período da temporada é um dos maiores desafios para qualquer treinador comprometido. Tempo muito limitado está disponível entre as partidas semanais para introduzir sessões intensivas de treinamento de força e poder, com uma freqüência normal de 1-2 unidades por semana. Este fato estimula a busca de métodos de treinamento mais eficientes capazes de melhorar uma ampla variedade de habilidades funcionais, evitando ao mesmo tempo os efeitos de fadiga.
This study aimed to investigate the neuromotor effects of transverse friction massage (TFM) on the quadriceps femoris tendon using surface electromyography, force sensors, and ultrafast ultrasound. Fourteen healthy males received TFM on their quadriceps tendon while fifteen controls rested. Signals were recorded before and after TFM/resting to analyze time delays related to excitation-contraction coupling, force transmission, and electromechanical delay during voluntary contractions. Results showed TFM increased the time of excitation-contraction coupling and electromechanical delay, while decreasing time of force transmission, suggesting TFM influences neuro-motor mechanisms and changes muscle and tendon stiffness. The study provides insight into how TFM applied
Brodersen_Kinesio Tape_Finalized_Jan 2017 (54 inch version) (1)Josh Brodersen
1) Researchers applied EMG electrodes to paraspinal muscles and quadriceps of 32 participants to measure muscle activation during back squats.
2) Participants performed squats with and without Kinesio tape applied to paraspinal muscles.
3) Analysis found no statistically significant changes in muscle activation of the paraspinals, quadriceps, or hamstrings with the application of Kinesio tape.
Eccentric training can improve muscle strength, power, and stretch-shortening cycle function to a greater extent than concentric or traditional resistance training. While both eccentric and concentric training increase muscle strength, the increases tend to be mode-specific. Eccentric training with loads greater than concentric strength limits elicits greater overall strength gains. Faster contraction velocities during eccentric training may further enhance strength and power adaptations. Eccentric training appears especially effective for improving performance requiring stretch-shortening cycle function.
EMG of the Transverse Abdominus and Multifidus During Pilates ExercisesGrandFinalTechnologies
This study evaluated the intensity of muscle activation in the transverse abdominis and multifidus muscles during four Pilates exercises using electromyography. Eight healthy women performed exercises including shoulder bridges, leg circles, and scissors. The results found that shoulder bridges and variations extending the right or left leg produced greater co-activation of the transverse abdominis and multifidus muscles compared to other exercises. Therefore, these exercises are most effective for rehabilitating lumbar spine stability through activation of the core muscles.
Hamstring strain prevention in elite soccer playersFernando Farias
Hamstring strains are among the most
common injury in sport and are most
often observed in sports that involve
sprinting, turning, and jumping
(8,38,63). The prevalence of hamstring
strains has been measured between 11
and 16% in studies of soccer, Australian
rules football, and cricket (92). This can
result in an average of 6 players per squad
suffering a hamstring injury (defined as
“preventing player participation in
a match”) each season in professional
soccer and Australian rules football
Cold water immersion alters muscle recruitment and balanceFernando Farias
The purpose of this study was to evaluate the effects of cold-water immersion on the electromyographic (EMG) response of
the lower limb and balance during unipodal jump landing. The evaluation comprised 40 individuals (20 basketball players
and 20 non-athletes). The EMG response in the lateral gastrocnemius, tibialis anterior, fibular longus, rectus femoris,
hamstring and gluteus medius; amplitude and mean speed of the centre of pressure, flight time and ground reaction force
(GRF) were analysed. All volunteers remained for 20 min with their ankle immersed in cold-water, and were re-evaluated
immediately post and after 10, 20 and 30 min of reheating
This study examined the metabolic activity patterns of hamstring muscles in football players with and without a history of hamstring injuries using MRI. It found that the semitendinosus muscle had significantly higher metabolic activity than the biceps femoris and semimembranosus muscles in both groups. In players with previous injuries, metabolic activity was more symmetric across hamstring muscles compared to controls, with lower semitendinosus and higher biceps femoris activity. This suggests biceps femoris compensates for weaker semitendinosus after injury, leading to less efficient movement and increased risk of reinjury. The study concludes rehabilitation should focus on strengthening the semitendinosus muscle.
Short inter-set rest blunts resistance exercise-inducedFernando Farias
Manipulating the rest-recovery interval between sets of resistance exercise may influence
training-induced muscle remodelling. The aim of this study was to determine the acute muscle
anabolic response to resistance exercise performed with short or long inter-set rest intervals.
In a study with a parallel-group design, 16 males completed four sets of bilateral leg-press and
knee-extension exercise at 75% of one-repetition maximum to momentary muscular failure,
followed by ingestion of 25 g of whey protein. Resistance exercise sets were interspersed by
1 min (n = 8) or 5 min of passive rest (n = 8). Muscle biopsies were obtained at rest, 0, 4, 24
and 28 h postexercise during a primed continuous infusion of l-[ring-13C6]phenylalanine to
determine myofibrillar protein synthesis and intracellular signalling.
Impact of the Nordic hamstring and hip extension exercises on hamstring archi...Fernando Farias
The architectural and morphological adaptations of the hamstrings in response to training
33 with different exercises have not been explored. PURPOSE: To evaluate changes in biceps
34 femoris long head (BFLH) fascicle length and hamstring muscle size following 10-weeks of
35 Nordic hamstring exercise (NHE) or hip extension (HE) training. METHODS: Thirty
36 recreationally active male athletes (age, 22.0 ± 3.6 years, height, 180.4 ± 7 cm, weight, 80.8 ±
37 11.1 kg) were allocated to one of three groups: 1) HE training (n=10), NHE training (n=10),
38 or no training (CON) (n=10). BFLH fascicle length was assessed before, during (Week 5) and
39 after the intervention with 2D-ultrasound. Hamstring muscle size was determined before and
40 after training via magnetic resonance imaging.
DETRAINING IN RELATION TO SKELETAL MUSCLE Dzevad Saric
Detraining occurs when there is a reduction or cessation of training, leading to partial or complete loss of physiological and performance adaptations. Periods of detraining are common for athletes during injuries or holidays. Muscle atrophy is characterized by a decrease in muscle mass and occurs due to inhibition of protein synthesis during inactivity. The degree of atrophy depends on the length of inactivity. While short detraining periods under 2 weeks may not affect muscle fibers, longer periods can decrease fiber size, especially in fast-twitch fibers. Maintaining some exercise during injury can help limit muscle atrophy.
Foam Rolling for Delayed-Onset Muscle Soreness and Recovery of Dynamic Perfor...Fernando Farias
Foam rolling may help reduce delayed-onset muscle soreness (DOMS) and enhance recovery of athletic performance after intense exercise. The study examined the effects of foam rolling on pressure-pain threshold, sprint speed, power, change-of-direction speed, and strength-endurance in 8 men after a back squat protocol designed to induce DOMS. Participants either did not foam roll or foam rolled major muscle groups immediately and 24 and 48 hours post-exercise. Foam rolling substantially reduced quadriceps muscle tenderness and largely improved sprint speed, power, and strength-endurance in the days following exercise compared to not foam rolling.
Does static stretching reduce maximal muscle performance?Fernando Farias
Kay and Blazevich systemati-
cally examined research that showed
the effects of static stretching on mus-
cle strength and other performance
measures by separating the studies into
total stretch durations of ,30 seconds,
30 to 45 seconds, 1 to 2 minutes, or
.2 minutes. Some practical and tech-
nical considerations may be helpful in
considering their conclusion that static
stretching only impairs muscle function
with longer stretches.
Effect of delayed-onset muscle soreness on muscle recovery after a fatiguing ...Nosrat hedayatpour
the aim of the study was to assess EMG MPF during
recovery following a fatiguing contraction at multiple
locations of the quadriceps femoris muscle injured
by eccentric exercise.
Three applications of mechanical vibration to the quadriceps muscle for 10 minutes each over three consecutive days improved body balance in subjects who underwent ACL reconstruction, as shown by decreased length of trace, mean speed of shifts, and ellipse area when standing on the operated leg up to 90 days later. While leg force did not differ between treated and untreated groups, treated subjects showed greater confidence standing on the operated leg, suggesting vibration facilitated proprioceptive learning. The long-lasting effects may be due to conditioning of the neural network controlling the muscle and joint from association of voluntary contraction during vibration.
Delayed-Onset Muscle Soreness Alters the Response to Postural PerturbationsNosrat hedayatpour
The purpose of this study was to assess the EMG activity
of knee muscles during destabilizing perturbations performed
before, immediately after, and 24 and 48 h after eccentric
exercise.
Effect of Endurance on Gastrocnemius Muscle with Exercise by Employing EMG Am...ijtsrd
Muscle fatigue is a common experience in daily life. Many authors have defined it as the incapacity to maintain the required or expected force, and therefore, force, power and torque recordings have been used as direct measurements of muscle fatigue. In addition, the measurement of these variables combined with the measurement of surface electromyography sEMG recordings which can be measured during all types of movements during exercise may be useful to assess and understand muscle fatigue. EMG signal can be easily analyzed in time domain, frequency domain and time frequency domain. The time domain features are the most popular in EMG pattern recognition because they are easy and quick to calculate and they do not require a transformation. The purpose of this study was to analyze the fatigue and to study the endurance occurrence in the Gastrocnemius muscle with a pre defined exercise protocol for the targeted muscle. For this purpose, sEMG Amplitude parameters were characterized. Relation between EMG features like mean, force, standard deviation, etc. is verified for fatigue detection as well as to identify the Endurance developed in the Gastrocnemius muscle. Gaurav Patti | Poonam Kumari "Effect of Endurance on Gastrocnemius Muscle with Exercise by Employing EMG Amplitude Parameters" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-5 , August 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33222.pdf Paper Url :https://www.ijtsrd.com/engineering/other/33222/effect-of-endurance-on-gastrocnemius-muscle-with-exercise-by-employing-emg-amplitude-parameters/gaurav-patti
Acute effect of different combined stretching methodsFernando Farias
The purpose of this study was to investigate the acute effect of different stretching methods, during a warm-up,
on the acceleration and speed of soccer players. The acceleration performance of 20 collegiate soccer players (body height:
177.25 ± 5.31 cm; body mass: 65.10 ± 5.62 kg; age: 16.85 ± 0.87 years; BMI: 20.70 ± 5.54; experience: 8.46 ± 1.49
years) was evaluated after different warm-up procedures, using 10 and 20 m tests. Subjects performed five types of a
warm-up: static, dynamic, combined static + dynamic, combined dynamic + static, and no-stretching. Subjects were
divided into five groups. Each group performed five different warm-up protocols in five non-consecutive days. The
warm-up protocol used for each group was randomly assigned. The protocols consisted of 4 min jogging, a 1 min
stretching program (except for the no-stretching protocol), and 2 min rest periods, followed by the 10 and 20 m sprint
test, on the same day. The current findings showed significant differences in the 10 and 20 m tests after dynamic
stretching compared with static, combined, and no-stretching protocols. There were also significant differences between
the combined stretching compared with static and no-stretching protocols. We concluded that soccer players performed
better with respect to acceleration and speed, after dynamic and combined stretching, as they were able to produce more
force for a faster execution.
The effects of self-myofascial release using a foam roll or roller massager on joint range of motion, muscle recovery, and performance: a systematic review
Non-uniform electromyographic activity during fatigue and recovery of the vas...Nosrat hedayatpour
The aim of the study was to investigate EMG signal features
during fatigue and recovery at three locations of the vastus
medialis and lateralis muscles.
Sprint running acceleration is a key feature of physical performance in team sports, and recent
literature shows that the ability to generate large magnitudes of horizontal ground reaction force
and mechanical effectiveness of force application are paramount. We tested the hypothesis that
very-heavy loaded sled sprint training would induce an improvement in horizontal force
production, via an increased effectiveness of application. Training-induced changes in sprint
performance and mechanical outputs were computed using a field method based on velocity-
time data, before and after an 8-week protocol (16 sessions of 10x20-m sprints). 16 male
amateur soccer players were assigned to either a very-heavy sled (80% body-mass sled load)
or a control group (unresisted sprints). The main outcome of this pilot study is that very-heavy
sled resisted sprint training, using much greater loads than traditionally recommended, clearly
increased maximal horizontal force production compared to standard unloaded sprint training
(effect size of 0.80 vs 0.20 for controls, unclear between-group difference) and mechanical
effectiveness (i.e. more horizontally applied force; effect size of 0.95 vs -0.11, moderate
between-group difference)
Melhorar ou até mesmo manter o desempenho atlético em jogadores de esportes de equipe competitivos durante o longo período da temporada é um dos maiores desafios para qualquer treinador comprometido. Tempo muito limitado está disponível entre as partidas semanais para introduzir sessões intensivas de treinamento de força e poder, com uma freqüência normal de 1-2 unidades por semana. Este fato estimula a busca de métodos de treinamento mais eficientes capazes de melhorar uma ampla variedade de habilidades funcionais, evitando ao mesmo tempo os efeitos de fadiga.
This study aimed to investigate the neuromotor effects of transverse friction massage (TFM) on the quadriceps femoris tendon using surface electromyography, force sensors, and ultrafast ultrasound. Fourteen healthy males received TFM on their quadriceps tendon while fifteen controls rested. Signals were recorded before and after TFM/resting to analyze time delays related to excitation-contraction coupling, force transmission, and electromechanical delay during voluntary contractions. Results showed TFM increased the time of excitation-contraction coupling and electromechanical delay, while decreasing time of force transmission, suggesting TFM influences neuro-motor mechanisms and changes muscle and tendon stiffness. The study provides insight into how TFM applied
Brodersen_Kinesio Tape_Finalized_Jan 2017 (54 inch version) (1)Josh Brodersen
1) Researchers applied EMG electrodes to paraspinal muscles and quadriceps of 32 participants to measure muscle activation during back squats.
2) Participants performed squats with and without Kinesio tape applied to paraspinal muscles.
3) Analysis found no statistically significant changes in muscle activation of the paraspinals, quadriceps, or hamstrings with the application of Kinesio tape.
Eccentric training can improve muscle strength, power, and stretch-shortening cycle function to a greater extent than concentric or traditional resistance training. While both eccentric and concentric training increase muscle strength, the increases tend to be mode-specific. Eccentric training with loads greater than concentric strength limits elicits greater overall strength gains. Faster contraction velocities during eccentric training may further enhance strength and power adaptations. Eccentric training appears especially effective for improving performance requiring stretch-shortening cycle function.
EMG of the Transverse Abdominus and Multifidus During Pilates ExercisesGrandFinalTechnologies
This study evaluated the intensity of muscle activation in the transverse abdominis and multifidus muscles during four Pilates exercises using electromyography. Eight healthy women performed exercises including shoulder bridges, leg circles, and scissors. The results found that shoulder bridges and variations extending the right or left leg produced greater co-activation of the transverse abdominis and multifidus muscles compared to other exercises. Therefore, these exercises are most effective for rehabilitating lumbar spine stability through activation of the core muscles.
Hamstring strain prevention in elite soccer playersFernando Farias
Hamstring strains are among the most
common injury in sport and are most
often observed in sports that involve
sprinting, turning, and jumping
(8,38,63). The prevalence of hamstring
strains has been measured between 11
and 16% in studies of soccer, Australian
rules football, and cricket (92). This can
result in an average of 6 players per squad
suffering a hamstring injury (defined as
“preventing player participation in
a match”) each season in professional
soccer and Australian rules football
Cold water immersion alters muscle recruitment and balanceFernando Farias
The purpose of this study was to evaluate the effects of cold-water immersion on the electromyographic (EMG) response of
the lower limb and balance during unipodal jump landing. The evaluation comprised 40 individuals (20 basketball players
and 20 non-athletes). The EMG response in the lateral gastrocnemius, tibialis anterior, fibular longus, rectus femoris,
hamstring and gluteus medius; amplitude and mean speed of the centre of pressure, flight time and ground reaction force
(GRF) were analysed. All volunteers remained for 20 min with their ankle immersed in cold-water, and were re-evaluated
immediately post and after 10, 20 and 30 min of reheating
This study examined the metabolic activity patterns of hamstring muscles in football players with and without a history of hamstring injuries using MRI. It found that the semitendinosus muscle had significantly higher metabolic activity than the biceps femoris and semimembranosus muscles in both groups. In players with previous injuries, metabolic activity was more symmetric across hamstring muscles compared to controls, with lower semitendinosus and higher biceps femoris activity. This suggests biceps femoris compensates for weaker semitendinosus after injury, leading to less efficient movement and increased risk of reinjury. The study concludes rehabilitation should focus on strengthening the semitendinosus muscle.
Short inter-set rest blunts resistance exercise-inducedFernando Farias
Manipulating the rest-recovery interval between sets of resistance exercise may influence
training-induced muscle remodelling. The aim of this study was to determine the acute muscle
anabolic response to resistance exercise performed with short or long inter-set rest intervals.
In a study with a parallel-group design, 16 males completed four sets of bilateral leg-press and
knee-extension exercise at 75% of one-repetition maximum to momentary muscular failure,
followed by ingestion of 25 g of whey protein. Resistance exercise sets were interspersed by
1 min (n = 8) or 5 min of passive rest (n = 8). Muscle biopsies were obtained at rest, 0, 4, 24
and 28 h postexercise during a primed continuous infusion of l-[ring-13C6]phenylalanine to
determine myofibrillar protein synthesis and intracellular signalling.
Impact of the Nordic hamstring and hip extension exercises on hamstring archi...Fernando Farias
The architectural and morphological adaptations of the hamstrings in response to training
33 with different exercises have not been explored. PURPOSE: To evaluate changes in biceps
34 femoris long head (BFLH) fascicle length and hamstring muscle size following 10-weeks of
35 Nordic hamstring exercise (NHE) or hip extension (HE) training. METHODS: Thirty
36 recreationally active male athletes (age, 22.0 ± 3.6 years, height, 180.4 ± 7 cm, weight, 80.8 ±
37 11.1 kg) were allocated to one of three groups: 1) HE training (n=10), NHE training (n=10),
38 or no training (CON) (n=10). BFLH fascicle length was assessed before, during (Week 5) and
39 after the intervention with 2D-ultrasound. Hamstring muscle size was determined before and
40 after training via magnetic resonance imaging.
DETRAINING IN RELATION TO SKELETAL MUSCLE Dzevad Saric
Detraining occurs when there is a reduction or cessation of training, leading to partial or complete loss of physiological and performance adaptations. Periods of detraining are common for athletes during injuries or holidays. Muscle atrophy is characterized by a decrease in muscle mass and occurs due to inhibition of protein synthesis during inactivity. The degree of atrophy depends on the length of inactivity. While short detraining periods under 2 weeks may not affect muscle fibers, longer periods can decrease fiber size, especially in fast-twitch fibers. Maintaining some exercise during injury can help limit muscle atrophy.
Foam Rolling for Delayed-Onset Muscle Soreness and Recovery of Dynamic Perfor...Fernando Farias
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Does static stretching reduce maximal muscle performance?Fernando Farias
Kay and Blazevich systemati-
cally examined research that showed
the effects of static stretching on mus-
cle strength and other performance
measures by separating the studies into
total stretch durations of ,30 seconds,
30 to 45 seconds, 1 to 2 minutes, or
.2 minutes. Some practical and tech-
nical considerations may be helpful in
considering their conclusion that static
stretching only impairs muscle function
with longer stretches.
Effect of delayed-onset muscle soreness on muscle recovery after a fatiguing ...Nosrat hedayatpour
the aim of the study was to assess EMG MPF during
recovery following a fatiguing contraction at multiple
locations of the quadriceps femoris muscle injured
by eccentric exercise.
Three applications of mechanical vibration to the quadriceps muscle for 10 minutes each over three consecutive days improved body balance in subjects who underwent ACL reconstruction, as shown by decreased length of trace, mean speed of shifts, and ellipse area when standing on the operated leg up to 90 days later. While leg force did not differ between treated and untreated groups, treated subjects showed greater confidence standing on the operated leg, suggesting vibration facilitated proprioceptive learning. The long-lasting effects may be due to conditioning of the neural network controlling the muscle and joint from association of voluntary contraction during vibration.
The document summarizes a study that investigated the effects of applying vibratory stimulation to the quadriceps muscle of subjects who underwent anterior cruciate ligament (ACL) reconstruction surgery. The study found that applying short periods of vibration for a few consecutive days led to improved balance and equilibrium over longer periods of time, as measured by various parameters, compared to a control group. While leg force was not significantly different between groups, the treated subjects showed a preference for standing on the operated leg, indicating the vibration helped them regain confidence in using that leg for balance. The long-lasting positive effects are believed to be due to improvements in proprioceptive control and learning in the central nervous system.
Mechanics of the human hamstring muscles during sprintingFernando Farias
As peak musculotendon
force and strain for BF
LH
, ST, and SM occurred around the same time during terminal swing, it is suggested that this period in the
stride cycle may be when the biarticular hamstrings are at greatest injury risk. On this basis, hamstring injury prevention or rehabilitation
programs should preferentially target strengthening exercises that involve eccentric contractions performed with high loads at longer
musculotendon lengths.
Delayed onset of vastii muscle activity in response to rapid postural perturb...Nosrat hedayatpour
In the current study, we analysed the relative timing of activation of the VMO and VL muscles during unexpected knee
perturbations performed before and after eccentric
exercise. The type of perturbation used resembles
perturbations that might commonly be encountered
during sport activities
This document discusses muscle plasticity, which refers to the ability of skeletal muscle to adapt structurally and functionally in response to environmental changes such as increased or decreased activity levels. It provides definitions and history of the concept. It describes the effects of chronic low frequency electrical stimulation on muscles, including fiber type transformations, increased mitochondria and vascularization, and changes to contractile properties. Over time periods of hours to weeks, stimulated muscles demonstrate metabolic and structural adaptations that increase their fatigue resistance and transform them from fast-twitch to slow-twitch phenotypes. Several studies are summarized that investigate muscle adaptations to long-term stimulation in animals and humans.
1. The Biomechanics and Medical Application Laboratory conducts research on stroke neuro-rehabilitation, integrated smart living technology, and developing light weight vehicles for the elderly.
2. The lab has 10 graduate students, 10 undergraduate students, and 1 part-time assistant. It collaborates with hospitals and other universities.
3. Current research topics include using vibratory input for stroke hand rehabilitation, the effects of floor material changes on gait stability, and developing assistive vehicles for the elderly.
Statistical analysis of range of motion and surface electromyography data for...IJECEIAES
This work introduces a statistical analysis of knee range of motion (ROM) and surface electromyography (EMG) data gathered from a knee extension rehabilitation device. Real-time ROM and EMG signals of rehabilitation users are measured using a single angle sensor and a two-channel EMG device (for the vastus lateralis and vastus medialis muscles). These signals are collected by the NI-myRIO embedded device in accordance with the designed rehabilitation program. The main contribution and novelty of this study is that real-time signals are automatically processed and transformed into statistical data for use by users and medical experts. A solution for extracting raw signals is proposed, in which several statistical functions such as range, mean, standard deviation, skewness, percentiles, interquartile range, and total knee holding times above the threshold level, are implemented and applied. The proposed solution is tested using data acquired from healthy people, which includes gender, age, body size, knee side, exercise behavior, and surgical experience. Results indicated that real- time signals and related statistical data on the knee’s performance can be efficiently monitored. With this solution, rehabilitation users can practice and learn about their knee performance, while medical experts can evaluate the data and design the best rehabilitation program for users.
This study investigated how localized muscle fatigue of the ankle plantarflexors affects spatial electromyography (EMG) patterns in the medial gastrocnemius muscle during walking and running. The researchers recorded high-density EMG from the medial gastrocnemius before and after subjects performed a calf raise task to induce fatigue. They found that after fatigue, peak EMG activity decreased but mean power frequency increased during locomotion. Additionally, the location of peak EMG shifted proximally compared to the pre-fatigue location, suggesting altered motor unit recruitment to distribute muscle loads. Despite these EMG changes, lower limb biomechanics were similar before and after fatigue.
This study examined the relationship between cycling economy, measured as oxygen consumption (VO2), and simultaneous measurements of 3D kinematics and electromyography in trained cyclists. A multiple regression analysis showed that peak knee extension velocity and mean activity of the rectus femoris muscle were significant predictors of VO2 during steady state cycling. This was the first study to relate cycling economy to 3D kinematic and electromyography measurements, providing insight into optimizing biomechanical parameters to improve cycling performance.
Tunnel Enlargement in Single Bundle ACL Reconstruction Using Bio-Interference...TheRightDoctors
Tunnel Enlargement in Single Bundle ACL Reconstruction Using Bio-Interference Screw, Transfix and Tight Rope RT: A Comparitive Study Using Computed Tomography-Dr. Ankit Goyal
IRJET- A Review on Biomechanics of Knee JointIRJET Journal
This document reviews the biomechanics of the knee joint. It discusses the role of the knee joint in allowing locomotion with minimal energy and stability over different terrains. The document outlines the movements of the knee including flexion, extension, and rotation. It describes the forces acting on the knee joint, which can be 2-3 times body weight during walking. The document provides an example calculation of the net joint forces and moments at the knee using inverse dynamics. It determines the horizontal and vertical reaction forces at the knee and calculates the net joint moment to be 592.3 Nm, indicating knee extension.
This document summarizes a seminar presentation on biomechanics of the human hip joint. It discusses two methods for determining contact stress in the hip joint: 1) In vivo measurements using an instrumented hip prosthesis with pressure transducers, which found very high local pressures up to 18 MPa during activities like rising from a chair. 2) A mathematical model using x-ray images as input to model hip forces and stress distribution. The conclusions indicate that understanding hip biomechanics can help optimize treatment for diseased hips and the rehabilitation process.
Crimson Publishers- The Effect of Medial Hamstring Weakness on Soft Tissue Lo...CrimsonPublishers-SBB
Anterior cruciate ligament (ACL) reconstructions are frequently performed in the United States of America. The medial hamstrings graft has been shown to produce lower rates of osteoarthritis (OA) than the patellar tendon graft. The goal of this study was to determine how altering medial hamstring strength during surgery affects soft tissue loading, and hence the joint’s proclivity towards OA. Muscle-actuated forward dynamic simulations of running were performed for normal muscle strength and decreased medial hamstring strength. The results show weakening the medial hamstrings caused an overall decrease in total hamstrings force by 7%, in total quadriceps force by 35%, and in cartilage contact force by 6%. This decreased force may be protective against long-term OA.
This study used multichannel electromyography to measure muscle activity in the hamstring muscles of 29 male basketball players during high-speed treadmill running. It found heterogeneous activity within each hamstring muscle across different phases of the running stride cycle. In late swing phase, the semimembranosus muscle showed significantly higher activity and relative contribution compared to the semitendinosus. Peak muscle activity within each hamstring muscle and location occurred at similar hip and knee joint angles. The study provides new insights into load sharing and activation patterns within and between hamstring muscles during high-speed running.
Knee strenght after total knee arthroplastyFUAD HAZIME
1) Knee strength was measured in 52 healthy control knees and 32 knees more than 2 years after total knee arthroplasty (TKA).
2) On average, isometric extension peak torque values in TKA patients were reduced by up to 30.7% compared to controls. Isometric flexion peak torque values in TKA patients were on average 32.2% lower than controls.
3) Relatively greater quadriceps strength in TKA patients was associated with better Knee Society Functional Scores, while a higher hamstring to quadriceps ratio was associated with worse scores. Older and more overweight TKA patients also had lower strength.
A STUDY ON THE MOTION CHANGE UNDER LOADED CONDITION INDUCED BY VIBRATION STIM...csandit
To assist not only motor function but also perception ability of elderly and/or handicapped
persons, the power-assist robots which have perception-assist function have been developed.
These robots can automatically modify the user’s motion when the robot detects inappropriate
user’s motion or a possibility of accident such as collision between the user and obstacles. For
this motion modification in perception-assist, some actuators of power-assist robot are used. On
the other hand, since some elderly persons, handicapped persons or some workers need not use
power-assist function but perception-assist function only, another new concept perception-assist
method was investigated in our previous study. In this perception-assist method, only vibrators
are used for generating motion change with kinesthetic illusion to assist perception-ability only.
In this study, since the perception-assist is often used during tasks under a loaded condition, the
features of motion change under the loaded condition are investigated.
EFFECT OF SPECIFIC CORE AND STATIC STRETCHING TRAINING PROGRAMME ON MUSKULOSK...IAEME Publication
To determine the effectiveness of 12 weeks specific core and static stretching training programme on musculoskeletal flexibility and balance among selected Tripura cricketers. Pre test – post test randomized group design were undertaken for the present study which consist of an experimental group and control group. Equal number of subjects (n= 30) were assigned randomly to both the groups. The experimental group was exposed to 12 weeks specific core and static stretching training programme whereas, no treatment was given to control group. For the purpose of the present
research work a total of 60 Cricketers were randomly selected for the present research work
1) The study investigated the role of sensory feedback from working muscles on central motor drive and the development of peripheral muscle fatigue during high-intensity cycling.
2) Eight competitive cyclists performed three 5 km cycling time trials under different conditions: control, placebo injection, and intrathecal fentanyl injection to impair sensory feedback.
3) Impairing sensory feedback with fentanyl increased central motor drive and power output early in exercise but led to greater peripheral muscle fatigue and poorer performance later in exercise, emphasizing the role of sensory feedback in regulating central motor drive and limiting fatigue development.
Similar to Motor Unit Conduction Velocity During Sustained Contraction Of The Vastus Medialis Muscle Injured By Eccentric Exercise (20)
Match By Match Detailed Schedule Of The ICC Men's T20 World Cup 2024.pdfmouthhunt5
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The ICC Men's T20 World Cup 2024 is set to be an exciting event, co-hosted by the West Indies and the USA from June 1 to June 29, 2024. This edition of the tournament will feature a record 20 teams divided into four groups, competing across 55 matches for the prestigious title.
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Understanding Golf Simulator Equipment A Beginner's Guide.pdfMy Garage Golf
Dive into golf simulation with our beginner's guide, perfect for anyone new to the concept. Understand the critical components like sturdy frames, high-quality impact screens, and side netting that ensure your safety and enrich your practice sessions. Learn the benefits of proper projector mounts and compatibility with your existing setup. This guide helps you make informed choices, transforming your home into a realistic and effective golfing practice environment.
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Belgium coach Domenico Tedesco will wait for several key players to recover from injury. Even if it means they miss the opening Euro Cup Germany stages of the European Championship in Germany this month. Veteran defender Jan Vertonghen, midfielder Youri Tielemans and defender Arthur. Theate are being given time to play in the tournament because they are considered vital to Belgium’s cause, Tedesco said on Tuesday.
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"Of course, you prefer to take players who are fully fit, but that's okay. We want to wait and be patient for some players even if they cannot play in those first matches," he told a press conference. The 37-year-old Vertonghen, Belgium’s Euro Cup 2024 most-capped international with 154 appearances, is struggling to shake off a groin injury.
"He will be there normally. This also applies to Youri Tielemans and Arthur Theate. The latter's position is very sensitive. We don't have many choices at left back. "It will only change if it turns out that they will only be available when, say, the final of the Euro 2024 Championship comes around. That's too long to wait. "However, I am confident that the injured boys are on track for the Euros.
Belgium vs Romania: Radu Dragusin Prepares for Crucial Role in Euro Cup Germany
Some of them have taken not one but two steps forward in their rehabilitation," he said. None of the injured players will feature in this week’s warm-up friendlies against Montenegro and Luxembourg. Romania centre-back Radu Dragusin found chances limited at Tottenham Hotspur in the second half of the 2023-24 season.
But is crucial to his country's cause at UEFA Euro 2024 where his aerial ability, physicality and hard graft make him a standout player. The 22-year-old moved to North London from Italian side Genoa in January but was kept on the sidelines by the form of another new arrival for the season, Mickey van de Ven, something Romania coach Edward Iordanescu admitted was a concern.
It will mean limited game-time going into the finals, but Dragusin, who cites Netherlands defender Virgil van Dijk as a role model, started every Euro Cup Germany qualifier as Romania went through the campaign unbeaten in their 10 games. He will be among their most important players in their first game in Germany against Ukraine in Munich on June 17, taking the right centre-back role in what is likely to be a back four.
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Psaroudakis: Family and Football – The Psaroudakis Success StoryPsaroudakis
Psaroudakis, a name that resonates with football fans around the globe, is a testament to the powerful synergy between familial support and individual passion. Born on March 10, 1992, in the historic city of Heraklion, Crete, Psaroudakis’ journey to international football stardom is a compelling narrative of dedication, perseverance, and unwavering family support. His story not only highlights his athletic prowess but also underscores the crucial role his family played in shaping his career and character.
Psaroudakis’ early life in Heraklion was deeply influenced by a supportive and nurturing family environment. His father, a former semi-professional footballer, recognized Psaroudakis’ potential from an early age. Acting as his first coach, his father’s guidance was instrumental in igniting Psaroudakis’ passion for football. This paternal influence instilled in him a strong work ethic and fundamental skills that would become the foundation of his future success. His mother, a dedicated homemaker, provided a stable and nurturing environment, ensuring that Psaroudakis could pursue his dreams without any hindrances.
From a young age, Psaroudakis showed an innate talent for football. Growing up in Heraklion, he spent countless hours playing football in local parks and streets with friends and family. His natural ability was evident even in these informal settings, and his enthusiasm for the game was infectious. By the age of five, Psaroudakis had joined a local youth football club, where his skills began to flourish. His father’s role as his first coach during these formative years was crucial, as he emphasized not only technical skills but also the importance of discipline and teamwork.
The transition from playing in local parks to joining a structured football environment marked a significant step in Psaroudakis’ journey. At the age of ten, he joined the youth academy of OFI Crete, one of Greece’s most esteemed football clubs. This move marked the beginning of a more rigorous and professional approach to his training. The academy environment was demanding, focusing on honing technical abilities and instilling values of sportsmanship and dedication. Psaroudakis’ dedication to his craft was evident as he quickly rose through the ranks, becoming a standout player in the youth teams.
The support of Psaroudakis’ family was unwavering during this critical period. His father continued to be a source of guidance and mentorship, while his mother ensured that he had everything he needed to succeed. Their collective efforts created a balanced environment where Psaroudakis could focus entirely on his development as a footballer. This familial support was not just about providing the basics; it was about creating an environment where Psaroudakis felt encouraged and motivated to pursue his dreams relentlessly.
As Psaroudakis transitioned from the youth academy to professional football, the challenges became more significant.
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Boletin de la I Copa Panamericana de Voleibol Femenino U17 Guatemala 2024Judith Chuquipul
holaesungusto.- Boletín final de la I Copa Panamericana de Voleibol Femenino U17 - Ciudad de Guatemala 2024 que se realizó del 27 de mayo al 01 de julio, en el Domo Polideportivo Zona 13.
Fuente: norceca.net
2. Copyright @ 2009 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Motor Unit Conduction Velocity during
Sustained Contraction after
Eccentric Exercise
NOSRATOLLAHAQ1 HEDAYATPOUR, DEBORAH FALLA, LARS ARENDT-NIELSEN, CAROLINA VILA-CHA˜ ,
and DARIO FARINA
Centre for Sensory–Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, DENMARK
ABSTRACT
HEDAYATPOUR, N., D. FALLA, L. ARENDT-NIELSEN, C. VILA-CHA˜ , and D. FARINA. Motor Unit Conduction Velocity during
Sustained Contraction after Eccentric Exercise. Med. Sci. Sports Exerc., Vol. 41, No. 10, pp. 00–00, 2009. Background: Eccentric
contractions induce muscle fiber damage that is associated with a decreased capacity to generate voluntary force and increased fiber
membrane permeability. Changes in fiber membrane permeability cause cell depolarization that is expected to have an effect on the
action potential propagation velocity of the muscle fibers. Purpose: The aim of the study was to investigate the action potential
propagation velocity in individual motor units before and 24 and 48 h after eccentric exercise. Methods: Multichannel surface and fine-
wire intramuscular EMG signals were concurrently recorded from two locations of the right vastus medialis muscle of 10 healthy men
during 60-s isometric contractions at 10% and 30% of the maximal force. Results: The maximal force decreased by 26.1 T 16.1%
(P G 0.0001) at 24 h and remained reduced by 23.6 T 14.5% (P G 0.0001) 48 h after exercise with respect to baseline. With respect
to baseline, motor unit conduction velocity decreased (P G 0.05) by (average over 24 and 48 h after exercise) 7.7 T 2.7% (10% maximal
voluntary contraction (MVC), proximal), 7.2 T 2.8% (10% MVC, distal), 8.6 T 3.8% (30% MVC, proximal), and 6.2 T 1.5% (30%
MVC, distal). Moreover, motor unit conduction velocity decreased over time during the sustained contractions at faster rates when
assessed 24 and 48 h after exercise with respect to baseline for both contraction forces and locations (P G 0.05). Conclusions: These
results indicate that the electrophysiological membrane properties of muscle fibers are altered by exercise-induced muscle fiber damage.
Key Words: DOMS, MUSCLE DAMAGE, MUSCLE FIBER, INTRAMUSCULAR EMG
E
ccentric contractions induce muscle fiber injury that
is associated with a decreased ability of the muscle
to generate force (29). Damage to sarcomeres (27)
and failure of excitation–contraction (E–C) coupling are
two prominent signs of damage in skeletal muscles after
eccentric exercise (31,39). Thus, the cause of a force deficit
after an eccentric task has been commonly attributed to a
disturbance in the mechanisms involved in generating force
within the skeletal muscle (1) and action potential conduc-
tion in the E–C coupling pathways (39). Decreased neural
drive to the muscle after eccentric exercise has also been
demonstrated by an increase in force production with
stimulation to the motor cortex or motor nerve with respect
to the force obtained during a maximal voluntary contrac-
tion (MVC) (31).
The sarcolemma, which conducts the action potential, is
subjected to substantial tears during eccentric contractions
(26). Increased sarcolemmal membrane permeability has
been indicated as one of the features of the damaged muscle
fiber, as assessed by loss of soluble intracellular proteins
(e.g., creatine kinase, myoglobin) and uptake of membrane-
impermeant dyes by damaged cells (26). An abnormal
sarcolemmal membrane permeability would also depolarize
the fiber membrane because of increased intracellular
sodium [Na+
] and calcium [Ca2+
] and extracellular potas-
sium [K+
] (23,24).
Changes in membrane depolarization are expected to have
an effect on the action potential propagation velocity of the
muscle fibers. A recent animal study has shown that eccentric
contractions did not affect muscle fiber conduction velocity
measured during evoked twitch contractions via electrical
stimulation (34). However, there are no human studies that
have investigated action potential conduction velocity at the
level of the single motor unit during sustained voluntary
contraction of a muscle injured by eccentric exercise. The
extent of damage to the muscle fiber depends on the mor-
phological and architectural characteristics of the muscle
fibers within the skeletal muscle (3,37). The vastus medialis
muscle is characterized by varying fiber-type composition
with a greater proportion of IIb fibers and lower proportion
of Type I fibers in distal region compared with proximal
Address for correspondence: Dario Farina, Ph.D., Center for Sensory–
Motor Interaction (SMI), Department of Health Science and Technology,
Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark;
E-mail: df@hst.aau.dk.
Submitted for publication November 2008.
Accepted for publication February 2009.
0195-9131/09/4110-0000/0
MEDICINE & SCIENCE IN SPORTS & EXERCISEÒ
Copyright Ó 2009 by the American College of Sports Medicine
DOI: 10.1249/MSS.0b013e3181a3a505
1
Copyeditor: Jamaica Polintan
3. Copyright @ 2009 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
regions (35). In addition, the fascicle angle is significantly
greater in more distal than proximal regions of the vastus
medialis muscle (2), which may contribute to nonuniform
changes in muscle fiber membrane properties after eccentric
exercise. Therefore, in the current study, we analyzed the
effect of eccentric exercise on the conduction velocity of
individual motor units at two locations of the vastus
medialis muscle during sustained contractions.
METHODS
Subjects. Ten healthy men (age (mean T SD) 25 T 4.4 yr,
body mass 72.4 T 7.6 kg, height 1.80 T 0.06 m) participated
in the study. All subjects were right leg-dominant and
were not involved in regular exercise of their knee extensor
muscles for at least 1 yr before the experiment. The study
was conducted in accordance with the Declaration of
Helsinki and was approved by the local ethics committee
(N-20070019). Subjects provided informed written consent
before participating in the study.
Procedures. Torque produced during MVC, subjective
pain ratings, and intramuscular and surface EMG signals
were recorded before and 24 and 48 h after an eccentric
exercise protocol. A KinCom Isokinetic Dynamometer
(Chattanooga Corp., Chattanooga, TN) was used to measure
knee extension torque. The subject was seated comfortably
on the adjustable chair of the KinCom with the hip in 90-
flexion. The chair position was modified until the knee axis
of rotation (tibiofemoral joint) was aligned with the axis of
rotation of the dynamometer’s attachment arm. The subject
was fixed with straps secured across the chest and hips. The
right leg was secured to the attachment arm in 90- knee
flexion with a Velcro strap. Visual feedback of torque was
provided on a screen positioned in front of the subject. The
subject was asked to perform three maximal isometric knee
extensions of 3 to 5 s in duration in 90- knee flexion, with
2-min rest intervals between contractions. The subject was
encouraged verbally during each trial to exceed the pre-
viously obtained torque level. The highest MVC value was
used as a reference for the definition of the submaximal
torque level for the subsequent sustained contractions. The
submaximal torque was relative to the MVC measured on
the same day of the test. Subjects were asked to maintain a
constant torque at 10% and 30% MVC for 60 s with 30 min
of rest between the two contractions. Visual feedback of the
torque produced was provided to the subject. The torque
signal was sampled at 2048 Hz concurrently with the
surface and intramuscular EMG signals.
Eccentric exercise. The eccentric exercise was per-
formed with a KinCom Isokinetic Dynamometer (Chatta-
nooga Corp.). Subjects resisted against the dynamometer’s
attachment arm from È170- of knee extension to 90- knee
flexion. Angular velocity was set at 60-Isj1
, and the load
was set to twice the value of the maximal voluntary iso-
metric torque produced during the eccentric exercise phase.
The exercise consisted of a series of four sets of 25 repeti-
tions with 3-min rest between each set. During the exercise,
the subject was provided with visual feedback of torque and
was encouraged to maintain maximal torque.
Sensory assessment of muscle pain. The subjects
were asked to rate the average pain intensity of their quad-
riceps during regular activities of daily living (e.g., climbing
stairs) since their last visit to the laboratory (during the past
24 h). Pain was rated on a continuous 10-cm visual analog
scale, where ‘‘0’’ represented ‘‘no pain’’ and 10 represented
the ‘‘worst pain imaginable.’’
EMG recordings. Surface and intramuscular EMG
signals were recorded from two locations of the right vastus
medialis muscle. Intramuscular signals allowed the identi-
fication of single motor unit action potentials, which were
used as triggers for averaging the multichannel surface EMG
signals (9). The length from the anterior superior iliac
spine to the medial border of the patella was measured as
an anatomical reference for positioning the electrodes (40).
Two adhesive arrays of eight equispaced electrodes
(ELSCH008; SPES Medica, Salerno, Italy; interelectrode
distance 5 mm, electrodes 5 mm  1 mm) were placed at
a distance from the patella of 10% and 30% (distal and
proximal site) of the measured anatomical length, distant
from innervation zones. The muscle innervation zones
were identified during test contractions with a dry array
of 16 electrodes (silver bars, 5 mm long, 1 mm diameter,
5 mm interelectrode distance). Before placing the adhesive
electrode arrays, the skin was shaved, lightly abraded, and
cleansed with water. The positions of the electrodes were
marked on the skin during the first session (day 1),
enabling to replace the electrodes in a similar location at
24 and 48 h after exercise. The surface EMG signals were
amplified (EMG16; LISiN – Ottino Bioelettronica, Torino,
Italy; bandwidth 10–500 Hz), sampled at 2048 Hz, and
stored after 12-bit A/D conversion.
Pairs of wire electrodes made of Teflon-coated stainless
steel (A-M Systems, Carlsborg, WA) were used to record
intramuscular EMG signals at each location. The wires were
cut to expose only the cross-section and were inserted with
25-gauge needles, 10–20 mm proximal to each array of
surface electrodes. The depth of insertion of the needles was
a few millimeters below the muscle fascia. The needles
were removed with the wire electrodes left inside the
muscle. Intramuscular EMG signals were amplified (Coun-
terpoint EMG; DANTEC Medical, Skovlunde, Denmark),
band-pass–filtered (500 Hz to 4 kHz), sampled at 10,240 Hz,
and stored after 12-bit A/D conversion.
Data analysis. The intramuscular EMG signals were
decomposed with an algorithm that has been previously
validated (25). For each contraction, only motor units active
for the entire duration of the contraction were analyzed. The
discharge times of the motor unit action potentials were
used as a trigger for averaging the multichannel surface
EMG signals (20 triggers in each case AQ2; F1Fig. 1). Conduction
velocity of single motor units was estimated from each
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4. Copyright @ 2009 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
averaged surface potential by a multichannel technique
previously described (9). The channels of the surface array
selected for conduction of velocity estimation were the
same for all motor units recorded from the same subject.
The percent change in muscle fiber conduction velocity
over time was calculated by subtracting the final value from
the initial value of conduction velocity and dividing by the
initial value. Variability was calculated as the coefficient of
variation (SD/mean) for both discharge rate and force over
the sustained contractions.
Statistical analysis. Three-way ANOVA was applied
to assess changes in the initial values of motor unit conduction
velocity, discharge rate, and coefficient of variation of dis-
charge rate. The factors were time (before and 24 and 48 h
after exercise), torque level (10%, 30% MVC), and electrode
location (distal, proximal). A three-way ANOVA was also
applied to the percent change in conduction velocity and with
factors time, torque level, and electrode location. For the
sustained contraction, a two-way repeated-measures ANOVA
was used to analyze the coefficient of variation of force with
time (before and 24 and 48 h after exercise) and torque level
(10%, 30% MVC) as factors. A one-way ANOVA with factor
time (before and 24 and 48 h after exercise) was applied to the
MVC torque and pain intensity scores.
Pairwise comparisons were performed with the Student–
Newman–Keuls post hoc test when ANOVA was signi-
ficant. The significance level was set to P G 0.05. Results
are reported as mean and SD in the text and SE in the
figures.
RESULTS
Force production and sensory assessment. The
eccentric exercise protocol reduced the maximal voluntary
isometric torque produced by the knee extensors (F = 19.2,
P G 0.0001) and induced delayed-onset muscle soreness
(DOMS). The MVC decreased from 541.7 T 41.7 NIm at
baseline to 400.8 T 48.9 NIm at 24 h after exercise (26.1 T
16.1%, P G 0.0001) and 413.3 T 41.1 NIm at 48 h after
exercise (23.6 T 14.5%, P G 0.0001). The soreness level
during activities of daily living (e.g., climbing stairs) was
graded 3.8 T 1.4 and 3.6 T 1.3 at 24 and 48 h after eccentric
exercise, respectively.
Motor unit discharge rate. The total number of
analyzed motor units in the distal location was 111 (10%
MVC = 42, 30% MVC = 69) before exercise, 116 (10%
MVC = 45, 30% MVC = 71) 24 h after exercise, and 149
(10% MVC = 51, 30% MVC = 98) 48 h after exercise.
For the proximal location, 113 (10% MVC = 44, 30%
MVC = 69) motor units were analyzed before exercise, 119
(10% MVC = 46, 30% MVC = 73) 24 h after exercise, and
139 (10% MVC = 51, 30% MVC = 88) 48 h after exercise.
The range of analyzed motor units per subject was 3–6 (10%
MVC; distal location), 3–8 (10% MVC, proximal location),
5–10 (30% MVC, distal location), and 4–9 (30% MVC,
FIGURE 1—Example of
AQ3
intramuscular and surface EMG signals
concurrently detected at the beginning (left) and the end (right) of
sustained contractions from the distal portion of the right vastus
medialis muscle of one subject during 30% MVC isometric contraction
before the eccentric phase (A) and 24 (B) and 48 h after the eccentric
phase (C).
TABLE 1. Mean discharge rate (mean T SD, pps AQ4, n = 10 subjects) of vastus medialis
motor units detected at two locations (distal: 10% distant from patella; proximal: 30%
distant from patella) at the beginning of 10% and 30% MVC sustained contractions
performed before and 24 and 48 h after exercise.
Location
Before
Eccentric Exercise
(pps)
24 h after
Eccentric Exercise
(pps)
48 h after
Eccentric Exercise
(pps)
Distal (10% MVC) 9.3 T 1.6 9.1 T 1.3 8.9 T 1.5
Proximal (10% MVC) 9.1 T 1.4 8.7 T 1.2 8.8 T 1. 3
Distal (30% MVC) 11.1 T 1.2 10.7 T 1.6 10.8 T 1.4
Proximal (30% MVC) 10.9 T 1.5 10.6 T 1.8 10.5 T 1.7
* P G 0.05. AQ5
TABLE 2. Mean coefficient of variation of interspike interval (mean T SD, mIsj1
, n = 10
subjects) of vastus medialis motor units detected at two locations over the vastus
medialis muscle (distal: 10% distant from patella; proximal: 30% distant from patella)
during 10% and 30% MVC sustained contractions performed before and 24 and 48 h
after exercise.
Location
Before
Eccentric Exercise
(%)
24 h after
Eccentric Exercise
(%)
48 h after
Eccentric Exercise
(%)
Distal (10% MVC) 11.9 T 3.4 12.1 T 3.4 11.8 T 3.2
Proximal (10% MVC) 11.8 T 2.5 12.2 T 2.8 12.1 T 3.1
Distal (30% MVC) 12.8 T 2.8 13.1 T 4.1 12.9 T 3.8
Proximal (30% MVC) 12.7 T 3.6 13.1 T 3.5 12.8 T 3.4
* P G 0.05. AQ6
MOTOR UNIT CONDUCTION VELOCITY AND DOMS Medicine & Science in Sports & Exercised 3
5. Copyright @ 2009 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
proximal location). Motor unit discharge rate at the begin-
ning of the sustained contraction depended on the level of
torque (F = 30.3, P G 0.0001). Discharge rate increased by
16.5 T 4.2% (P G 0.0001) from 10% to 30% MVC in the
proximal location and by 16.2 T 5.2% (P G 0.0001) in the
distal location (T1 Table 1). Motor unit discharge rate at the
beginning of the posteccentric contractions was not signif-
icantly different from that at the beginning of preeccentric
contractions (Table 1).
In all conditions (before eccentric exercise and 24 and 48 h
after eccentric exercise), motor unit discharge rate at the end
of the sustained contraction was not significantly different
from that at the beginning of the sustained contraction. The
coefficient of variation for both interspike interval and force
was not significantly different between the two contraction
levels and across the three testing days (T2 Tables 2 andT3 3).
Motor unit conduction velocity. Motor unit conduc-
tion velocity at the beginning of the sustained contraction de-
pended on torque (F = 44.3, P G 0.0001) and time (F = 9.1,
P G 0.001). Initial values of conduction velocity increased
(P G 0.05) by 15.3 T 1.5% from 10% MVC to 30% MVC in
the proximal location and by 11.4 T 1.1% in the distal
location. The initial value of conduction velocity at 10%
MVC decreased at 24 and 48 h with respect to baseline by
5.7 T 1.9% and 9.7 T 3.5% (proximal location) and by 6.6 T
2.1% and 7.8 T 3.4% (distal location), respectively (P G
0.05). Similarly, at 30% MVC, conduction velocity was
reduced 24 and 48 h after exercise with respect to baseline
by 7.1 T 3.6% and 10.1 T 4.1% (proximal location) and
by 6.1 T 1.1% and 6.3 T 1.8% (distal location), respectively
(P G 0.05; F2Fig. 2).
Conduction velocity decreased during the sustained con-
tractions. The percent decrease depended on the level of
torque (F = 4.9, P G 0.05) and was higher at 30% MVC
(j7.1 T 4.5%) than at 10% MVC (j4.8 T 4.1%). The per-
cent decrease also depended on time (F = 2.7, P G 0.05) with
a greater reduction in conduction velocity observed in both
posteccentric conditions with respect to baseline. In addition,
the percent decrease in conduction velocity depended on the
interaction among time, electrode location, and torque level
(F = 2.4, P G 0.05; F3Fig. 3). At 24 and 48 h after exercise, a
greater reduction in conduction velocity was observed at the
distal location during the contraction at 30% MVC compared
with that at the proximal location (P G 0.05).
DISCUSSION
The study demonstrates lower values of motor unit con-
duction velocity and greater conduction velocity rate of
change over sustained contractions of the vastus medialis
muscle at 24 and 48 h after eccentric exercise as compared
with the preexercise condition.
TABLE 3. Coefficient of variation of knee extension force (mean T SD, n = 10 subjects)
during sustained isometric contractions at 10% and 30% MVC analyzed before and 24
and 48 h after exercise.
Force Level
Before
Eccentric Exercise
(%)
24 h after
Eccentric Exercise
(%)
48 h after
Eccentric Exercise
(%)
10% MVC 1.7 T 0.5 1.8 T 0.3 2.1 T 0.6
30% MVC 2.2 T 0.8 2.4 T 0.9 2.3 T 0.7
* P G 0.05.AQ7
FIGURE 2—Initial values of motor unit conduction velocity (MUCV;
mean T SE, mIsj1
, n = 10 subjects) for the vastus medialis muscle at
two locations (distal: 10% distant from patella; proximal: 30% distant
from patella) recorded before the eccentric exercise (baseline) and 24
and 48 h after the eccentric exercise. Contraction levels: 10% MVC
(dashed line) and 30% MVC (solid line). *P G 0.05.
FIGURE 3—Percent decrease in motor unit conduction velocity
(MUCV; mean T SE, %, n = 10 subjects) for the vastus medialis
muscle at two locations (distal: 10% distant from patella; proximal:
30% distant from patella) during sustained contractions performed at
10% MVC (dashed line) and 30% MVC (solid line) recorded before the
eccentric exercise (baseline) and 24 and 48 h after the eccentric
exercise. *P G 0.05.
http://www.acsm-msse.org4 Official Journal of the American College of Sports Medicine
6. Copyright @ 2009 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Muscle performance. A significant reduction in MVC
of the knee extensors was observed 24 h after eccentric ex-
ercise and persisted 48 h after exercise, in agreement with
pervious studies (10,14,15). The observation of reduced iso-
metric strength after eccentric exercise indirectly suggests
that the muscle was damaged by the exercise, most likely
because of the mechanical disruption of sarcomeres and/or
the sarcolemma membrane (10,19). Reduced neural drive to
the muscle may also partly explain the decrease in maximal
force generation capacity. However, the relative role of
peripheral and central factors in the reduction in MVC
cannot be estimated from the present results because
measures of central drive, such as twitch interpolation, were
not performed. Subjects also reported soreness in the
quadriceps muscle 24 and 48 h after exercise, which may
be related to damage of the contractile elements and
connective tissue (30).
Motor unit discharge rate. As in previous studies,
the mean motor unit discharge rate increased with the
increasing force level of the sustained contractions, whereas
the coefficient of variation of the interspike interval and of
force did not change between the two force levels (12,17).
There were no significant changes in either discharge rate
or variability of discharge at the end of the sustained con-
tractions with respect to the beginning of the contractions.
These results are in agreement with previous findings on
motor unit behavior over sustained fatiguing contractions at
the same or at different force levels (20–22). The motor unit
discharge rate, the coefficient of variation in interspike
interval, and the coefficient of variation in force were not
different across the testing days. Accordingly, Dartnall et al.
(5) reported no significant changes in the coefficient of
variation of the interspike interval and force 24 h after
eccentric exercise of the biceps brachii muscle.
Motor unit conduction velocity. After eccentric
exercise, the conduction velocity of single motor units
decreased with respect to baseline in both the distal and the
proximal locations of the vastus medialis muscle. In add-
ition, conduction velocity decreased at a faster rate during
the sustained contractions after eccentric exercise with
respect to the preexercise condition. A recent animal study
showed that eccentric contractions changed the integrated
EMG and action potential waveforms but did not affect
muscle fiber conduction velocity measured during evoked
twitch contractions via electrical stimulation (34). However,
the current study is the first human study in which
conduction velocity is measured in vivo in single motor
units during sustained voluntary contractions after eccentric
exercise. The observed change in motor unit conduction
velocity after eccentric exercise may indicate membrane
depolarization most likely because of alteration in the
resting membrane permeability of the injured fibers (24).
Ruff et al. (32) proposed that muscle fiber depolarization is
associated with impairment of propagation velocity because
of slow inactivation of a proportion of the voltage-gated
Na+
channels. In the damaged muscle fibers, an increase in
the leak conductance to K+
would further contribute to the
slow inactivation process of the voltage-gated Na+
channels
(38) and consequently lead to a further reduction of action
potential propagation velocity over a sustained contraction.
In addition, the elevated K+
in the interfiber space as result
of membrane damage may expose further muscle fibers to a
reduced membrane excitability and conduction velocity
during a sustained task (11).
The reduction in motor unit conduction velocity may also be
due to an insufficient activity of the Na+
–K+
pump and/or
decreased muscle fiber volume. It is apparent from the
increase in extracellular potassium ([K+
]o) and intracellular
sodium ([Na+
]i) that the pump capacity is not sufficient to
fully compensate for the ionic fluxes during sustained
fatiguing contractions (18). In the injured muscle fiber, an
increase in fiber ionic membrane permeability would further
decrease the capacity of the Na+
–K+
pump to maintain the
normal concentration gradients for Na+
and K+
during
sustained fatiguing contractions (4) and thus lead to a further
reduction in propagation velocity over time. In addition, an
insufficient activity of the Na+
–K+
pump to recover the
normal ionic gradient across the cell membrane within 24 to
48 h after exercise (8) would cause cell shrinkage because of
the net loss of cellular cations and anions (mostly K+
and
Clj
) and an osmotic equivalent of water (6). This process
would also decrease muscle fiber diameter and the absolute
initial value of conduction velocity (6). The increased [Na+
]i
as result of impairment in Na+
–K+
pump activity has been
suggested to increase the degree of phosphorylation of the
Na+
–K+
pump on the fiber membrane after exercise (4,36).
Taken together, the results of this study indicate that the
adaptation of the muscle fiber to eccentric exercise is asso-
ciated with membrane dysfunction within the first 24 to 48 h
after exercise. The prolonged cell depolarization after eccen-
tric exercise may provide a safety mechanism to protect the
cell against Ca2+
accumulation and thus further protein
degradation (7). This observation may partly explain why
performance can remain depressed for days after eccentric
exercise, although all the known fatigue agents (e.g., lactic
acid, inorganic phosphate, creatinine) have long since
recovered (13).
The distal location of vastus medialis muscle showed a
greater decrease in motor unit conduction velocity over the
sustained contraction. This may be related to more ex-
tensive damage of this area (14,15) because of differences
in fiber-type composition (35) and/or high force production
in this area to stabilize the patella during eccentric exercise
(33). This finding may explain preferential muscle soreness
and hypertrophy of the distal region of the quadriceps after
exercise training (14,15,28).
Limitations. In addition to muscle fiber membrane dys-
function, a reduction in the initial value of motor unit con-
duction velocity could be partly explained by the reduction in
MVC or by a predominant damage of fast twitch motor units.
However, at the contraction forces analyzed, all motor units
recruited were probably of the same type (slow twitch) (34).
MOTOR UNIT CONDUCTION VELOCITY AND DOMS Medicine & Science in Sports & Exercised 5
7. Copyright @ 2009 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
The effects of other factors on conduction velocity, such
as muscle fiber swelling, change in fiber pennation angle,
and changes in muscle temperature after eccentric exercise
and across the experimental days, cannot be excluded from
the present results and may have accounted for some of the
changes observed.
Conclusions. Heavy knee extensor exercise results in a
reduction of vastus medialis single motor unit conduction
velocity in low submaximal isometric contractions, proba-
bly due to alterations in muscle cell membrane dynamics
and inhomogeneous damage of muscle fibers.
This study was supported by the Ministry of Science, Research
and Technology of Iran (N.H.) and the Danish Technical Research
Council (project: Centre for Neuroengineering (CEN), contract no.
26-04-0100) (D.F.).
The authors state that the results of the present study do not
constitute endorsement by ACSM.
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MOTOR UNIT CONDUCTION VELOCITY AND DOMS Medicine & Science in Sports & Exercised 7
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