Motor Unit Conduction Velocity During Sustained Contraction Of The Vastus Med...Nosrat hedayatpour
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.
The Epidemic of ACL Injuries in Female Youth Athletesthegraymatters
Orthopedic Grand Rounds at Univ. of Missouri by Aaron Gray, MD, Sports Medicine Specialist. Discusses Epidemiology, risk factors, and focuses on prevention of ACL injuries in female youth athletes.
Motor Unit Conduction Velocity During Sustained Contraction Of The Vastus Med...Nosrat hedayatpour
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.
The Epidemic of ACL Injuries in Female Youth Athletesthegraymatters
Orthopedic Grand Rounds at Univ. of Missouri by Aaron Gray, MD, Sports Medicine Specialist. Discusses Epidemiology, risk factors, and focuses on prevention of ACL injuries in female youth athletes.
Bryan Heiderscheit
Professor, Department of Orthopedics and Rehabilitation, Department of Biomedical Engineering, Director, UW Runners' Clinic, Director, Badger Athletic Performance Research, Co-director, UW Neuromuscular Biomechanics Lab, University of Wisconsin-Madison, Madison, WI, USA.
-
Hamstrings are most susceptible to injury during the early stance phase of sprinting
(13th October, Barcelona)
6th MuscleTech Network Workshop
To examine the acute effects of generic (Running Drills, RD) and specific (Small-
Sided Games, SSG) Long Sprint Ability (LSA) drills on internal and external load of male
soccer-players. Methods: Fourteen academy-level soccer-players (mean±SD; age 17.6±0.61
years, height 1.81±0.63 m, body-mass 69.53±4.65 kg) performed four 30s LSA bouts for
maintenance (work:rest, 1:2) and production (1:5) with RD and SSG drills. Players’ external-
load was tracked with GPS technology (20Hz) and heart-rate (HR), blood-lactate
concentrations (BLc) and rate of perceived exertion (RPE) were used to characterize players’
internal-load. Individual peak BLc was assessed with a 30s all-out test on a non-motorized
treadmill (NMT). Results: Compared to SSGs the RDs had a greater effect on external-load
and BLc (large and small, respectively). During SSGs players covered more distance with
high-intensity decelerations (moderate-to-small). Muscular-RPE was higher (small-to-large)
in RD than in SSG. The production mode exerted a moderate effect on BLc while the
maintenance condition elicited higher cardiovascular effects (small-to-large). Conclusion:
The results of this study showed the superiority of generic over specific drills in inducing
LSA related physiological responses. In this regard production RD showed the higher post-
exercise BLc. Interestingly, individual peak blood-lactate responses were found after the
NMT 30s all-out test, suggesting this drill as a valid option to RD bouts. The practical
physiological diversity among the generic and specific LSA drills here considered, enable
fitness trainers to modulate prescription of RD and SSG drills for LSA according to training
schedule.
The effect of instability training on knee joint proprioception and core stre...Fernando Farias
A general 10-week IT program utilizing Swiss balls and body mass as a resistance proved effective for improving knee proprioception as well as trunk flexion and extension strength in previously inactive individuals. The present study demonstrates that the use of body weight as a resis- tance under unstable conditions can provide significant improvements in knee proprioception (for as long as 9 months after training) and trunk strength for the untrained population that should contribute to general health and functionality.
Bilateral and unilateral vertical ground reaction forcesFernando Farias
The purposes of this study were to assess unilateral and bilateral vertical jump performance
characteristics, and to compare the vertical ground reaction force characteristics of the impulse and landing
phase of a vertical jump between the dominant and non-dominant leg in soccer players.
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.
Anthony Shield - is nmi a risk factor for hamstring strain injury MuscleTech Network
Anthony Shield
Senior lecturer, School of Exercise and Nutrition Science Institute of Health and Biomedical Innovation Queensland University of Technology, Brisbane, Australia.
-
Is neuromuscular inhibition a risk factor for hamstring strain?
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.
Bryan Heiderscheit
Professor, Department of Orthopedics and Rehabilitation, Department of Biomedical Engineering, Director, UW Runners' Clinic, Director, Badger Athletic Performance Research, Co-director, UW Neuromuscular Biomechanics Lab, University of Wisconsin-Madison, Madison, WI, USA.
-
Hamstrings are most susceptible to injury during the early stance phase of sprinting
(13th October, Barcelona)
6th MuscleTech Network Workshop
To examine the acute effects of generic (Running Drills, RD) and specific (Small-
Sided Games, SSG) Long Sprint Ability (LSA) drills on internal and external load of male
soccer-players. Methods: Fourteen academy-level soccer-players (mean±SD; age 17.6±0.61
years, height 1.81±0.63 m, body-mass 69.53±4.65 kg) performed four 30s LSA bouts for
maintenance (work:rest, 1:2) and production (1:5) with RD and SSG drills. Players’ external-
load was tracked with GPS technology (20Hz) and heart-rate (HR), blood-lactate
concentrations (BLc) and rate of perceived exertion (RPE) were used to characterize players’
internal-load. Individual peak BLc was assessed with a 30s all-out test on a non-motorized
treadmill (NMT). Results: Compared to SSGs the RDs had a greater effect on external-load
and BLc (large and small, respectively). During SSGs players covered more distance with
high-intensity decelerations (moderate-to-small). Muscular-RPE was higher (small-to-large)
in RD than in SSG. The production mode exerted a moderate effect on BLc while the
maintenance condition elicited higher cardiovascular effects (small-to-large). Conclusion:
The results of this study showed the superiority of generic over specific drills in inducing
LSA related physiological responses. In this regard production RD showed the higher post-
exercise BLc. Interestingly, individual peak blood-lactate responses were found after the
NMT 30s all-out test, suggesting this drill as a valid option to RD bouts. The practical
physiological diversity among the generic and specific LSA drills here considered, enable
fitness trainers to modulate prescription of RD and SSG drills for LSA according to training
schedule.
The effect of instability training on knee joint proprioception and core stre...Fernando Farias
A general 10-week IT program utilizing Swiss balls and body mass as a resistance proved effective for improving knee proprioception as well as trunk flexion and extension strength in previously inactive individuals. The present study demonstrates that the use of body weight as a resis- tance under unstable conditions can provide significant improvements in knee proprioception (for as long as 9 months after training) and trunk strength for the untrained population that should contribute to general health and functionality.
Bilateral and unilateral vertical ground reaction forcesFernando Farias
The purposes of this study were to assess unilateral and bilateral vertical jump performance
characteristics, and to compare the vertical ground reaction force characteristics of the impulse and landing
phase of a vertical jump between the dominant and non-dominant leg in soccer players.
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.
Anthony Shield - is nmi a risk factor for hamstring strain injury MuscleTech Network
Anthony Shield
Senior lecturer, School of Exercise and Nutrition Science Institute of Health and Biomedical Innovation Queensland University of Technology, Brisbane, Australia.
-
Is neuromuscular inhibition a risk factor for hamstring strain?
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.
1. INTRODUCTION In recent years, energy harvesting fro.docxambersalomon88660
1. INTRODUCTION
In recent years, energy harvesting from ambient vibration [I and human motion [2] has received both considerable industrial and academic interest due to advances in micro-electronic technology leading to an increased computation efficiency and reduced power consumption of wireless sensors and portable electronic devices. In addition to environmental benefits associated with limiting the disposal of traditional batteries, energy harvesting technologies [3] provide a great promising of autonomous and self-powered electronic devices for safety monitoring, structure-embedded diagnosis and medical implants. The narrowband issues of linear resonant piezoelectric energy harvesters have motivated several research groups to develop the nonlinear monostable [4], bistable [5] and tristable [6] approaches to enhance frequency bandwidth and output power. The theoretical analysis and experimental verification of those nonlinear energy harvesters have been extensively investigated under harmonic and stochastic excitations [7-9]. For the realistic excitation, Green [2] numerically analyzed the efficiency of nonlinear energy harvesting from human motion and Cao [10] applied the time-varying potential bistable energy harvester to human motion to demonstrate its better performance than the linear one. However, tristable energy harvesting performance has not yet been evaluated under realistic excitations induced by human motions. Therefore, the paper employs tristable magnetic coupled piezoelectric cantilever to harvest energy from human walking and running. Based on the characteristics of human motion, theoretical model of nonlinear tristable energy harvester with time-varying potential energy function is established. And experiment results show that the tristable energy harvester exhibits better performance than the linear one when applied to harvesting energy from human walking and running.
2. ELEC TROMECHANICAL MODEL
The magnetic coupled piezoelectric energy harvester with external magnets is illustrated in Fig.1 (a). The configuration consists of a stainless steel substrate, two symmetric PZT-51 piezoelectric layers at the root, tip magnet attachments and two external magnets.
Tristable energy harvester can be obtained by adjusting the parameters h, d and a.When harvester is applied to harvesting energy from human motion , the lower limb swing motion will drive the cantilever to swing a certain angle (shown in Fig.1 (b) which results in a time-varying potential energy function due of the beam. On these conditions, the electromechanical model of the nonlinear piezoelectric energy harvesters with time-varying potential energy function can be given by the following equation:
Where m is the equivalent mass and c is the equivalent damping. 0 is the equivalent electromechanical coupling coefficient, Cp is the equivalent capacitance of the piezoelectric materials, R is the load resistance, v(t) is the voltage across the electrical load, x.
Rowing ergometers as an aide to on-water training pros and consrowperfect
Ivan Hooper from Australian Institute of Sport gave this presentation about the advantages and disadvantages of training on ergos. They don't replicate the water well, sliders and variable K drag factors and ratings don't match water boat rates.
Discus throwing performances and medical classification of wheelchair athlete...Ciro Winckler
CHOW, J. W.; MINDOCK, L. A. Discus throwing performances and medical classification of wheelchair athletes. Medicine and Science in Sports and Exercise, v. 31, n. 9, p. 1272-1279, 1999.
Training the vertical jump to head the ball in soccer Fernando Farias
IN MODERN SOCCER, HEADING
THE BALL IS BOTH AN OFFENSIVE
TOOL USED TO SCORE GOALS
AND A DEFENSIVE MEASURE
AGAINST OPPOSING TEAMS. PRO-
FICIENCY IN HEADING THE BALL
REQUIRES PROPER TECHNIQUE IN
CONJUNCTION WITH AN EFFEC-
TIVE VERTICAL JUMP. THE AIM OF
THIS ARTICLE IS TO ADDRESS THE
FACTORS INVOLVED IN VERTICAL
JUMP PERFORMANCE AND HOW
THEY RELATE SPECIFICALLY TO
HEADING THE BALL
1. Differences between sagittal plane static start and mid-cycle stroke biomechanics
during skating for the sport of sledge hockey: Task naïve population
A.M. Gal, A.D.C. Chan, and D.C. Hay
Knowledge to improve repetitive cyclical weight-bearing locomotion can be provided by
identifying differences between movement production from 1) rest, and 2) continuous
motion, if they exist [1]. Skating in sledge hockey is the foundational skillset and only
mechanical method for motion production. Biomechanically, skating is the product of
muscular force produced from the torso and each arm, which is transmitted along the
respective stick to the pick-surface interface, where muscular energy is transferred into
forward propulsion as a result of the picks digging into the ice surface. Typically, a task
naïve population displays greater observable differences in areas of difficulty than elite
populations [2]. Bilateral forward skating in elite sledge hockey is typically produced with a
flexed torso creating the possibility for a more horizontal pick plant, mechanically
producing greater forward force transfer [3], [4]. The ability to flex the torso during skating
is predicted to be proportional to skill level, which implies that optimal pick plant is more
likely to be achieved in elite players. The objective of this study was to identify sagittal
plane biomechanical difference(s) between a 1) start cycle (SC), and 2) mid-cycle (MC)
stroke at peak impact and push-off during skating off-ice, if they exist.
Five adult male able-bodied athletes propelled themselves in a study-specific indoor, off-ice
sledge (two wheels per youth sized chassis replaced the blades, and a front wheel) through
a Vicon motion capture system equipped with five bilateral upper torso/limb BTS-wireless
surface electromyography (sEMG) electrodes [5], [6]; sEMG were not analyzed for this
study. Participants were sledge hockey and poling sport naïve; asymmetrical bilateral
skating was predicted. Left, right, and sledge-body ground reaction forces were acquired in
a study-specific 4-force plate design [7], [8]. Three useable trials (good force plate contact)
were collected per i) submaximal, and ii) maximal effort test for both the 1) SC, and 2) MC.
Two participants performed an additional MC maximal effort test adding variation to the
protocol. Data were processed offline using MATLAB [10]. A low pass zero-lag 2nd order
Butterworth filter (12 Hz) was applied to motion capture raw signals.
SC torso (𝑇𝑆𝐶 )flexion (parallel to ground upwards) was 85° ± 4° with left (𝐿 𝑆𝐶) and right
(𝑅 𝑆𝐶) pick plants equalling 83° ± 3° and 84° ± 3, respectively. The difference between
MC and SC angles at pick plant were 𝑇 𝑀𝐶−𝑆𝐶 = 1° ± 3°, 𝐿 𝑀𝐶−𝑆𝐶 = 2° ± 1° and 𝑅 𝑀𝐶−𝑆𝐶 =
−1° ± 0°. MC torso flexion was 67° ± 9° with push-off pick angles equalling 𝐿 𝑀𝐶 = 80° ±
10°and 𝑅 𝑀𝐶 = 83° ± 4°. The difference between MC and SC angles at push-off were
𝑇 𝑀𝐶−𝑆𝐶 = 18° ± 5°, 𝐿 𝑀𝐶−𝑆𝐶 = 1° ± 3°, and 𝑅 𝑀𝐶−𝑆𝐶 = 3° ± 2°.
From these results, increased stability within skating was predicted to exist at pick off,
especially during MC. Increasing on and off-ice practice improving stability in the sledge is
recommended, with heightened focus creating torso flexion during arm extension. By
improving the SC, skating as a whole may improve in turn creating a more valuable player.
Increased momentum was suggested to be a product of improved MC skating. Further
biomechanical investigations are currently being implemented concerning skating as a
whole for sledge hockey.
2. References:
[1] A. Tözeren, Human body dynamics: classical mechanics and human movement. New
York: Springer, 2000.
[2] Chris Kirtley, Clinical gait analysis theory and practice. Edinburgh: Churchill
Livingstone, 2006.
[3] A. M. Gal, D. C. Hay, and A. D. C. Chan, “2 and 3-dimensional biomechanical analysis of
the linear stroking cycle in the sport of sledge hockey (Glenohumeral joint kinematic,
kinetic and surface EMG muscle modeling on and off ice),” in 13th International
Symposium on 3D Analysis of Human Movement, 2014, pp. 108–111.
[4] Hockey Canada, “Sledge hockey coaching resource.” 2009.
[5] Vicon Motion Systems Ltd., Nexus. U.K.: Vicon Motion Systems Ltd.
[6] BTS Bioengineering, “BTS Wireless sEMG,” BTS Bioengineering, 2016. [Online].
Available: http://www.btsbioengineering.com/.
[7] Bertec Corp., “Bertec Force Plate,” Bertec, 2016. [Online]. Available:
http://bertec.com/products/force-plates/.
[8] Kistler Instrument Corp., “Kistler Force Plate,” Kistler: measure. analyze. innovate., 2016.
[Online]. Available: https://www.kistler.com/ca/en/.
[9] J. R. Potvin and S. H. . Brown, “Less is more: high pass filtering, to remove up to 99% of
the surface EMG signal power, improves EMG-based biceps brachii muscle force
estimates,” J. Electromyogr. Kinesiol., vol. 14, no. 3, pp. 389–399, Jun. 2004.
[10] MathWorks, MATLAB. The Mathworks Inc., 1994.