This study investigated the effect of knee joint angle on plantar flexor performance in resistance-trained and untrained men. Seventeen participants performed plantar flexion contractions at 90 degrees of knee flexion and 10 degrees of extension while torque was measured. There were no significant differences found in torque or rate of torque development between the knee positions or between the trained and untrained groups. The calibration process of the new dynamometer was found to be reliable.

1. 1
THE EFFECT OF KNEE JOINT ANGLE ON PLANTAR FLEXOR PERFORMANCE
IN RESISTANCE TRAINED AND UNTRAINED MEN.
By
Joel Huskisson
A Major Project submitted to the School of Sport and Exercise Sciences, Liverpool John
Moores University, in partial fulfilment of the degree of B.Sc. (Hons) Sports and Exercise
Science April (2016).
Acknowledgements:
Thanks to Dr Thomas O’Brien for the supervision of this study. Also a special thank you to
fellow undergraduates Carl Chatfield and Keith Mitchell for their help with organising and
running of data collecting sessions. Lastly thank you to Liverpool John Moores University for
providing the dynamometer for this major project.
Abstract:
Background: Triceps surae consists of soleus and gastrocnemius muscles. Due the
differences in anatomy, various knee angles can affect the plantar flexion performance of the
triceps surae. Limited research has investigated the effect of resistance training on the knee
angle-torque relationship. The aim is to investigate the training effect on the change of moment
production and RTD. Another aim was to investigate the calibration process of the new ankle
dynamometer.
Methods: A custom-ankle dynamometer was used to measure the torque of resistance-
trained (n=10) and untrained (n=7) participants at knee flexed (90°) and extended position
(10°) whilst performing fast maximal voluntary contractions.
Results: There was no significant difference in moment and RTD between the knee flexed
and knee extended position. There was also no significant difference between the percentage
change in moment and RTD as knee angle two groups. There was a significant correlation
(R2
=1, P<0.001) between the moment and voltage values during calibration.
Conclusions The null hypothesis was accepted due to insignificant differences in percentage
change in moment and RTD as a result of knee angle change between the resistance-trained
and untrained groups. Calibration process is reliable and reproducible.

2. 2
Introduction
The triceps surae is a muscle group consisting of the gastrocnemius and the soleus
muscles. The triceps surae is the main synergists for plantar flexion (Kawakami et al,
1998) of the foot which is required in many sporting movements such as the
propulsion phase during walking and running (Mero, A. & Komi, P., 1987) and during
the push-off phase in countermovement jumps (Bobbert et al, 1986). Whilst
performing these movements, there are various knee joint angles during particular
stages of these movements and according to previous studies (Landin et al, 2015),
various knee joint angles can influence the performance of plantar flexors. The
soleus force production is considered to be unaffected when the knee is flexed
because the muscle crosses the ankle joint only (Kawakami et al, 1998) where the
insertion of the soleus is at the calcaneus and origin is at the fibula (Thompson &
Floyd, 1994). However, the gastrocnemius is largely affected (Landin et al, 2015),
due to the muscle being bi-articulate crossing both the knee (origin at the femur) and
the ankle joints (insertion at the calcaneus) (Thompson & Floyd, 1994).
The changes in torque and rate of torque development (RTD) is predominantly
because of the different physiological characteristics of the gastrocnemius and the
soleus. The gastrocnemius which mainly consists of fast twitch muscle fibres (Burke
et al, 1973), producing powerful and strong contractions. As the gastrocnemius is bi-
articulate, the decrease in knee joint angle will consequentially reduce muscle
tension (Signorile et al, 2002) and the muscle fibre lengths (Avancini et al, 2015) of
the gastrocnemius muscle. Based on the fibre length/sarcomere force relationship
(Maganaris, 2001), reducing fibre length will reduce sarcomeric force production
therefore as knee joint angle decreases, the gastrocnemius muscle strength and
power is reduced. However, the soleus is unaffected when knee joint angle
decreases and according to Miaki et al (1999), the optimal force production of the
soleus when there are 60 degrees of knee flexion. As the soleus consists of mainly
type I fibre types (Kawakami et al, 1998), the soleus will produce slow contractions
as a result of the slow twitch type I fibres (Gilliver et al, 2009) when the knee is
flexed. Therefore, my hypothesis is that when knee joint angle decreases, there
should be a significant reduction in strength and rate of torque development during
plantar flexion.

3. 3
Previous studies have investigated whether knee joint angle can affect plantar
flexion performance in various groups. Hérbert-Losier and Holmberg (2014)
investigated whether gender is particularly affected. They discovered that knee
flexion had a greater impact on the plantar flexor performance in males compared to
females. Also, Dalton et al (2014) looked at the effect of knee angle on
gastrocnemius power in young and old individuals. They found that the percentage
difference in gastrocnemius power from the knee extended to the knee flexed
position was 22% for young and 12% for old. Based on these two studies, there is
evidence to support that knee joint angle can have a different impact on plantar
flexion performance on various groups. There are a limited number of studies that
have investigated whether training status can affect the reduction in plantar flexion
performance at the knee flexed position. Therefore, this study aims to focus on
resistance training and to observe the effect of training on the impact of plantar flexor
performance as a result of changes in knee angle.
Also, knee angle affects the collagenous tissue in the muscle (aponeurosis) and the
tendon mechanics of the Achilles. The primary function of the tendon is to transfer
the contractile force of the muscle to the bone (Duclay et al, 2009). The Achilles
tendon is the strongest tendon in the human body (Komi et al,1992) and decreases
in knee angle has caused a reduction in Achilles tendon tension (Orishimo et al,
2008). However in the knee extended position, there's a greater tension in the
Achilles tendon due to the stretching of the Achilles tendon as muscle-tendon unit
length increases (Visser et al, 1990). This increases the elastic energy stored in the
muscle-tendon unit (Biewener & Roberts, 2000) enabling a better force production.
Therefore as a result of the decrease in muscle and tendon tension in the knee
flexed compared to the knee extended, there should be a reduction in plantar flexor
performance supporting the previous hypothesis.
After weeks of either isometric (Kubo et al, 2006), plyometric (Burgess et al, 2007),
eccentric (Morrissey et al, 2011) and concentric resistance training, there has been
an increase in tendon stiffness. As tendon stiffness is a key contributor to muscle
performance during isometric contractions (Bojsen-Møller et al, 2005) and in addition
variations in Achilles tendon tension when knee angle decreases, there should be a
greater variation in moment production at various knee angles for the resistance
trained groups compared to untrained groups. Therefore, my hypothesis is that knee

4. 4
angle will effect plantar flexor moment and RTD more for the resistance trained
group compared to the untrained group. This research can provide insight on the
roles of knee position on training methods to improve the performance of triceps
surae.
Lastly, this study is using a portable custom-ankle dynamometer which has been
constructed by the university. This could provide many benefits by being able to use
the dynamometer outside of the university. This study aims to investigate the
repeatability of the calibration process and see whether the production of moment
values are consistent.
Methods
Participants: Seventeen participants took part in this study (age, 20.88 ±1.08 years,
height 1.78 ± 0.05 m, weight 77.44 ± 9.17 kg, and BMI 24.45 ± 1.97). Participants
had given written consent and completed a Physical Activity Readiness
Questionnaire (PAR-Q) to make sure that they were ready to take part in this study.
They also completed a ‘resistance training’ questionnaire to assist the allocation of
participants into training groups. The participants that have been training for more
than 6 weeks were placed in the resistance-trained group, and less than 6 weeks of
training were placed in the untrained group. Participants also filled in an international
physical activity questionnaire (IPAQ) to see if any differences in this study were due
to levels of physical activity. The participants were separated into 2 groups,
resistance trained (n=10) and untrained group (n=7), where the training
characteristics are on table 1.
Table 1. Mean ± S.D of the training levels of the resistant trained group and the untrained group.
Also the levels of vigorous physical activity (VPA) and moderate physical activity (MPA).
Resistant Trained Untrained
Height (m) 1.78 ± 0.04 1.78 ± 0.05
Weight (kg) 77.7 ± 7.35 77.07 ± 10.22
BMI 24.62 ± 1.68 24.21 ± 2.05
Training Period (Weeks) 107.5 ± 86.74 0.57 ± 1.399
Number of sessions per week 4 ± 0.77 0.57 ± 1.399
Minutes per session 81± 19.2 8.57 ± 21
Number of sessions training legs 1.5 ± 1.2 0.29 ± 0.7
Minutes per session 99 ± 70.09 4.29 ± 10.5
Vigorous Physical Activity (min) 346.5 ± 101.83 77.14 ± 59.69

5. 5
All experimental procedures were approved by the Liverpool John Moores University
ethics committee. Unfortunately, two of the participant's data was not used as a
result of an error caused by the dynamometer during testing.
Design: Participants performed a total of 6 maximal fast and explosive isometric
contractions on the dynamometer. Knee positions used was the knee extended (10°
flexed) and flexed position (90°) and the foot position was 90° to the shank. All
participants performed maximal contractions in the knee flexed position first and
finished at the knee extended position. Prior testing, participants was allowed to
familiarise themselves with the equipment by performing fast and explosive maximal
voluntary contractions before collecting data. During the actual contractions, the
participants held their contractions for 3 seconds and were given 1-minute rest in
between each contraction.
Experimental Protocol: Participant's height and weight were measured before
testing. Then they performed a warm-up on a cycle ergometer for 5 minutes at an
intensity of 25W and maintaining a speed of 70 rpm. They were placed at the knee
flexed position (90°) where the foot was 90° to the shank. The angles of the knee
and ankle were measured using a goniometer and an adjustable chair was used to
adjust knee angle. The ankle malleoli had to be at the same level with the hinge of
A
B
C
90°
90°
E
d
D
Weight
Woodblock
Figure 1. A) & B) displays the dynamometer being set at the knee extended position where the
knee angle is at 10°. C) The dynamometer set at the knee flexed position where the knee is set at
90°. D) is the calibration process where the weight (20kg) and the woodblock (0.756kg) was
placed directly on top of the sensor. E) Displays how the moment arm (d) was derived (20cm).

6. 6
the dynamometer, therefore, wooden blocks were used to adjust malleoli vertical
position. The foot was translated forwards or backwards to align the malleoli's
horizontal position. Straps were positioned over the quadriceps to prevent variation
in knee angle. Participants performed 3 isometric contractions with 1-minute rest
between each contraction. Then they were placed in the knee extended position
(10°) using foot straps to prevent heel lift and a strap was held by a participant to
reduce movement of the dynamometer. The back was flexed at 60°. Wooden blocks
were used to align the malleoli which were placed under the heel of the foot, and a
cushion was placed under the knee to prevent hyperextension of the knee. Then
they performed 3 maximal isometric contractions with 1-minute rests between each
contraction. Visual feedback was provided via a computer screen and motivation
was provided by the same researcher.
Dynamometer: A custom-ankle dynamometer (built by the university) was used to
measure torque data at the two knee positions. Calibration was performed before
testing for each participant, however calibration was only possible when the
dynamometer was set at the knee flexed position (see fig 1D). Calibration was done
by placing a known weight (20kg) onto a woodblock (0.756 kg) which was directly
above the sensor. The screw was part of the force transducer, therefore, tightness of
the screw was critical for the detection of torque. The screw was tightened by the
same researcher to make sure that the tightness of the screw was consistent to
ensure reproducible results. Torque produced by the weights during calibration was
calculated by:
𝑴 = 𝒎 × 𝒈 × 𝒅
Adjustable straps were positioned over the distal end of the femur and parallel to the
shank to prevent heel lift and changes in knee angle. Pads were used to increase
comfortability. An adjustable chair was used to adjust knee angle to 90° and
translated the chair forwards or backwards to align the foot to the rotational axis of
the dynamometer.
Statistical Analysis: Plantar flexor torque data was collected using AcqKnowledge
4.0 software via the Biopac MP100 system (BN-RX, BIOPAC Systems, Inc., Goleta,
California) and was sampled at a frequency of 200 Hz. The maximal moment was
M= moment m=mass g= 9.81 m.s-2
d= moment arm (see fig. 1E)

7. 7
considered to be the greatest moment produced out of the contractions performed.
Calculations were made to calculate resultant moment:
𝑲𝒏𝒆𝒆 𝑭𝒍𝒆𝒙𝒆𝒅 ∶ 𝑴 𝒓 = 𝑴 𝒑𝒇 − 𝑾 𝒑 − 𝑾 𝒇
𝑲𝒏𝒆𝒆 𝑬𝒙𝒕𝒆𝒏𝒅𝒆𝒅: 𝑴 𝒓 = 𝑴 𝒑𝒇 − 𝑾 𝒑
The rate torque development was calculated by (∆moment/∆time) (Aagaard et al,
2002) during the first 0.1 seconds of contraction. Previous literature (Thompson et al,
2012) used the manual contraction onset detection methodology (Tillin et al, 2010)
and found that it produced less reliable measurements compared to an automated
contraction detection method (Tillin et al, 2013). Therefore, the identification of the
contraction onset was achieved by using a Butterworth low-pass filter to smooth the
data and onset were classed as the first indication of a change in moment. Cut-off
frequency for the Butterworth low-pass filter was derived by using residual analysis
(Yu et al, 1999), and the maximum frequency to calculate residuals was at 50 Hz.
Maximal plantar flexor torque and RTD of the two groups was calculated (mean and
SD) on excel. A two-way mixed design factorial analysis of variance (ANOVA) was
used to analyse the differences in the means of maximal torque and RTD between
the resistance-trained and untrained groups. An independent t-test was used to
analyse the differences in percentage change between the two groups. Lastly, a
simple regression analysis was performed to evaluate the calibration process by
looking at the relationship of the actual moment being produced compared to voltage
and to look at the repeatability of the calibration process. Calibration was performed
for 3 consecutive days collecting the voltage data based on the 4 known weights
used (No weight, 0.756kg, 20.756kg and 40.756 kg). Statistical tests was generated
on SPSS version 23.
Results
Maximal Moment Production: There was not a significant main effect for training
status (F1,13=1.411, P=0.256) on moment production (Figure 2A). However, the
resistance trained group did produce the greatest moment in both the knee flexed
and the knee extended position by a difference of 5.9 N.m and 24.65 N.m
Mr = Resultant Moment Mpf = Moment produced by the resting foot and plate of dynamometer
Wp = Moment produced by the plate of dynamometer Wf = Moment produced by the resting foot.

8. 8
respectively. There was not a significant main effect of knee position (F1,13=0.372,
P=0.552) on maximal torque production. However, the resistance trained group
found a greater torque production in the knee extended position (103.5±35.36 N.m)
compared to knee flexed (87.8 ± 31.87 N.m) by a difference of 15.7 N.m. The
untrained group had a slight decrease in torque production from the knee flexed
position (81.92 ± 31.87 N.m) to the knee extended position (78.85 N.m) by a small
difference of 3.07 N.m. Lastly, there was not a significant interaction between
training group and knee position (F1,13=0.821, P=0.381) however resistance group
had increases in torque from the knee flexed position to extended however the
untrained group had a small decrease in torque production.
RTD: There was not a significant main effect for training status (F1,13=1.319,
P=0.272) on the RTD (Figure 2B). The resistance trained group had a greater RTD
in both the knee flexed and extended position by a difference of 174.06 N.m.s-1 and
19.4 N.m.s-1 respectively. There was not a significant main effect of knee position
(F1,13=0.153, P=0.702) on RTD, however for the resistance trained group there was
a decrease in RTD from the knee flexed (467.14 ± 200.69 N.m.s-1) to the knee
extended (374.9 ± 109.71 N.m.s-1) positon by a difference of 92.1 N.m.s-1. Whereas
the untrained group had an increase in RTD from the knee flexed (293.07 ± 207.69
N.m.s-1) to the knee extended (355.51 ± 151.93 N.m.s-1) position by a difference of
62.44 N.m.s-1. Lastly, there was not a significant interaction (F1,13=4.118, P=0.063)
between knee position and training status on RTD during fast maximal contraction.
Change in maximal moment production and RTD (%) from the knee flexed to knee
extended position: There was not a significant difference (t13=1.019, P=0.327) in the
percentage change of moment production (Table 2) between the resistance trained
group and the untrained group. However, the resistance trained group had a greater
reduction in maximal moment production by 33.55±70.55%, whereas untrained
subjects only decreased moment production by 4.46±28.11%.
There was not a significant difference (t13=-1.669, P=0.119) between the resistance
trained and untrained group on the percentage change in RTD from the knee flexed
to knee extended position. However, the resistance trained group had a decrease in
rate of force development by 9.94 ± 38.13%, whereas the untrained group had
increases in rate of force development by 104 ± 189.9%

9. 9
The analysis in the reproducibility and reliability of calibration process: Multiple
regression analysis (Table 3) has found a significant relationship between the
moment produced and the amount of voltage produced by the dynamometer. There
is also a very strong correlation between the moment and the voltage produced by
having an R value of 1 (P<0.05). Therefore, the test supports the reliability of the
calibration by having an R2=1 showing that 100% of the variance in voltage is due to
moment production. There is also little difference in the y-intercepts and gradients
(Table 3) of on the regression line of best fit between days 1 (c=-0.0032, x=
0.00159), 2 (c=-0.0328, x=0.00159) and 3 (c=-0.034, x=0.0158).
Table 2- Mean ± S.D. Percentage changes in moment production and rate of force development
from the knee flexed position to the knee extended position in the resistance trained and untrained
participants.
Resistance trained Untrained
Moment 33.55 ± 70.55% 4.46 ± 26.03%
Rate of Force Development -9.94 ± 38.13% 104.08 ± 175%
Figure 2. A) The moment (N.m) production about the ankle between the resistance trained (black)
and untrained (grey) participants at various knee angles. There was no significant main effect of
training status and knee angle on maximal torque. Also no significant interaction was observed
between knee position and training on moment production during maximal contractions. B) The
rate of force development (N.m.s-1) during fast contractions for both resistance trained (black) and
untrained (grey) groups at the knee flexed and knee extended position. There was also no
significant main effect of both training status on rate of force development. Lastly there was no
significant interaction between training status and knee position.
60
70
80
90
100
110
120
130
140
Knee Flexed Knee Extended
Moment(N.m)
Knee Position
Resistance trained
Untrained
200
250
300
350
400
450
500
550
600
650
700
Knee Flexed Knee Extended
RateofForceDevelopmnt
(N.m.s-1)
Knee Position
Resistance trained
UntrainedA B

10. 10
Discussion
This present study is the first study to look at the effect of resistance training on the
change in moment production and RTD from the knee flexed to the knee extended
position. This study aims to observe whether training does affect the overall
percentage change in torque production and RTD. Based on findings, there was not
a significant difference in percentage change of moment and RTD (Table 2) between
the two groups. However for moment production (Figure 2A) there was a greater
percentage increase from the knee flexed to the knee extended position for the
resistance trained group however for the untrained group there was overall a slight
decrease in moment production. There was also a decrease in RTD (Figure 2B) for
Table 3. The statistical regression analysis between the actual moment and the voltages produced
during calibration for 3 consecutive days.
Y intercept
(c)
Gradient
(x)
95% CI for
coefficients
R value R2 value
Day 1 -0.0332 0.0159 0.016 to 0.016 0.9997 0.9996
Day 2 -0.0328 0.0159 0.016 to 0.016 0.9998 0.9997
Day 3 -0.034 0.0158 0.016 to 0.016 0.9998 0.9997
Day 1: y = 0.0159x - 0.0332
R² = 0.9996
Day 2: y = 0.0159x - 0.0328
R² = 0.9997
Day 3: y = 0.0158x - 0.034
R² = 0.9997
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 10 20 30 40 50 60 70 80 90
Voltage(V)
Moment (N.m)
Day 1
Day 2
Day 3
Figure 3. The regression lines for the voltages produced at various moments in for the 3
consecutive days. The trend line equation and R2 values are also displayed for the 3 consecutive
days.

11. 11
the resistance trained group from the knee flexed to knee extended position however
the untrained group had an overall increase in RTD by 104%.
Based on these findings, the results was consistent with previous research (Landin
et al, 2015) by finding a greater moment in the knee extended position compared to
the knee flexed position for resistance trained group. However in this study, the
torque values were much lower compared to ours by a difference of 60 N.m. This is
probably due to using isokinetic contractions which can effect toque output (Knapik &
Ramos, 1980). Dalton et al (2014) also found a similar relationship using isometric
contractions, however found different results by having greater moment values of
more than 120 N.m compared to this study's moment mean values of ≤103 N.m. This
is probably due to the muscle contractions being electrically evoked improving motor
unit recruitment therefore, greater activation of muscle fibres. This is proven by
Landin et al (2015) which found a greater moment produced in the electrically
stimulated muscle compared to the moment produced by the muscle tissue. Even
though different methods were used, both studies found the same relationship by
finding a greater power and moment production in the knee extended position
compared to knee flexed position. However, the untrained group had a lower
moment production in the knee extended position compared to knee flexed position.
This might be due to a number of errors in methodology and a smaller sample size
(n=7). A decrease in moment production may be due to fatigue (Rafolt et al, 1999)
caused by insufficient rest period. The gastrocnemius has a greater fatigue index
compared to soleus (Enoka, 2008), therefore may have underperformed on the knee
extended position compared to knee flexed.
Furthermore, the results of the RTD are questionable as there was a reduction in
RTD for the resistance trained group (Figure 2B). Dalton et al (2014) found that there
was a greater rate of force development in the knee extended position compared to
knee flexed position by a difference of 112 N.m.s-1. Compared to our results, the
resistance trained group had a decrease in RTD when changing knee angle from the
flexed position to the knee extended position by 92.1 N.m.s-1 which was opposite to
the relationship found in Dalton et al (2014) study. Whereas the untrained group
produce a greater RTD in the knee extended position by a difference of 62.44.
However, our values were again much smaller compared to Dalton et al (2014)
study.

12. 12
Effect of knee angle on torque and rate of torque development: Changes in moment
production for the resistance trained group whilst changing knee angle is proven by
finding a lower static EMG activity of the gastrocnemius medialis and lateralis in the
knee flexed (Herbert-Losier & Holmberg, 2013) compared to extended position. Also
in the knee flexed position, there is a greater dependence on the moment production
of the soleus due to this reduction in gastrocnemius performance (Herbert-Losier et
al, 2012). The soleus has predominantly a type I fibre composition (80% (Enoka et
al, 2008)) which produces less force compared to type II fibres (Gilliver et al, 2009).
Soleus also has a greater pennation angle (20°) compared to gastrocnemius (16°)
(Wickiewicz et al, 1983). Greater pennation angle has been found to reduce the
muscle fibres ability to transfer muscle force to the aponeurosis and the tendon
(Blazavich et al, 2006). Therefore as a consequence of the properties in pennation
angle, fibre length and fibre type composition, soleus has been shown to produce
less forceful contractions compared to the gastrocnemius. This demonstrates that in
knee flexed position, less forceful and powerful contractions were observed
(Cresswell et al, 1995)
The reduction in gastrocnemius force production capacity in the knee flexed position
is because of the little elongation of the muscle tendon unit, therefore limiting the
shortening range of the fascicles (Arampatzis et al, 2006). In the knee extended
position, a greater force production was observed for resistance trained group. One
of the mechanisms is the increase in fascicle length of the gastrocnemius.
Gastrocnemius fascicle length is greatest when the knee is extended at 160° and
when the ankle is dorsi-flexed (Arampatzis et al, 2006). Based on the force-length
theory (Magnaris, 2001), greater fibre length increases the force-generating capacity
of the muscle fibres until optimum point as a result of greater number of cross
bridges formed between actin and myosin. This was observed by Maganaris (2003)
by finding a proportional relationship between the gastrocnemius fascicle length and
fascicle force. Increases in fibre length of the gastrocnemius as a result of knee
extension also produced greater motor unit activation (Cresswell et al, 1995) which
facilitates the torque production. The second reason is the effect of pennation angle.
There is a smaller pennation angle in the knee extended position compared to flexed
(Arampatzis et al, 2006). Blazavich (2006) described that increasing pennation angle
caused the decrease in tendon force and Arampatzis et al (2006) had found a

13. 13
significant increase in pennation angle from the knee extended compared to flexed,
therefore this proves that knee extended position facilitates transfer of
gastrocnemius muscle force to the aponeurosis and Achilles tendon. As the
gastrocnemius predominantly consists of fast-twitch fibres (Burke et al, 1973) and
the greater activation of gastrconemius at the knee extended position (Herbert-Losier
& Holmberg, 2013), a greater force production was observed for the resistance
trained group.
Effect of Resistance training on moment production at various knee angles: For the
resistance trained group there was a greater decrease in moment production
compared to untrained group as knee angle decreases. During resistance training,
the key architectural and physiological changes of the muscles are the enhanced
motor unit recruitment and activation capacity (Reeves et al, 2004), fibre
hypertrophy, muscle PCSA and increases in pennation angle (Aagaard et al, 2001).
These changes contribute to the greater increase in strength and power production
of the triceps surae muscle due to a greater number of fascicles in parallel and the
greater ability to activate the contraction of muscle fibres (Folland & Williams, 2007).
Also there is a significantly greater pennation angle in the resistance-trained
compared to untrained (Aagaard et al, 2001) however this is to facilitate increases in
PCSA therefore pennation angle differences between the groups should not
differentiate moment production (Folland & Williams, 2007). There are also changes
in tendon properties, in particular there were increases in Achilles tendon stiffness
following 8 weeks of resistance training (Kubo et al, 2002). Based on research, the
reduction in tendon stiffness increases elongation therefore greater shortening of the
muscle tendon unit during isometric contractions and affecting fibre force-length
properties (Sanderson & Amoroso, 2009). Furthermore in the knee extended, there
was a greater muscle-tendon tension and activation of the gastrocnemius for the
resistance trained compared to untrained (Signorile et al, 2002) as knee angle
decreases. This was supported by Ferri et al (2003) as this study found that at the
greatest muscle-tendon length (knee extended), resistance-trained participants had
greatest torque production compared to untrained subjects. However at the lowest
muscle-tendon length (knee flexed) there was no significant difference in torque
between trained and untrained. Therefore overall there is a greater reduction in
moment production for the resistance trained group.

14. 14
For RTD, the relationships basically switched between the two groups which should
not have been observed. One of the main problems with the custom-ankle
dynamometer is that straps were not used to prevent the flexion of the back whilst
performing contraction. Flexion of the back provided momentum in the direction of
contraction causing a greater RTD. However for the knee extended, flexion of the
back will be unlikely to enhance RTD. This might explain the observed decrease in
rate of force development for the resistance trained group however, unsure whether
this is the case. RTD is determined by the level of neural activation, muscle size and
fibre type composition (Aagaard, 2002). However according to Weiss et al (1988),
there was not a significant change in the triceps surae muscle size and Kubo et al
(2010) found small increases (5%) in ability for neural activation after more than 8
weeks of resistance training. Based on research, this implicates that the RTD may
be unaffected by changes in knee positions and differences between the two groups
however there are contradictions by finding greater rate of force development in the
knee extended position (Aagaard et al, 2002).
Calibration review: Based on the regression statistical tests, there was little variation
in voltage outcomes between consecutive days by finding an R2 value of 1 for all
consecutive days. During the calibration process there was little variation in voltage
values as the size of moment increases therefore the magnitude of the weight used
should not affect the predicted voltage outcomes. During the contraction data
collection on the custom ankle dynamometer, the tightness of the screw has to be
consistent throughout testing procedures to ensure reproducibility of results however
contractions may have affected the tightness of the screw which may affect validity
of results.
Limitations & Implications: As mentioned before fatigue might have caused the
reduction of force and rate of force development for the resistance trained and
untrained respectively as testing was performed in the knee flexed first for each
participant before the knee extended position. Also for the resistance trained group,
even though they have been training for 107.5 ± 86.74 weeks (Table 1), the mean
number of sessions per week was 1.5 ±1.2 therefore there may be a lack of training
stimulus to cause triceps muscle adaptation. Also for the untrained group, even
though there was little activity in resistance training, untrained subjects did perform
77.14 ± 59.69 minutes of vigorous physical activity therefore can affect the strength

15. 15
(Moliner-Urdiales et al, 2010) and muscle size (Morishita et al, 2014) of the untrained
group. Also during resistance training, mainly dynamic contractions are performed
rather than isometric contractions. Therefore there will be variations in optimum knee
angles for isometric contractions for the resistance trained which can affect the
actual force-generating capacity of the muscle. There was only a small number of
subjects in the study, therefore a small representation of the overall population.
Lastly there was small translation of the heel in the knee extended position during
contraction as a result of the movement of the woodblocks supporting the heel which
may affect torque output.
Future Research: Future research should focus on the effect of resistance training
at various knee positions on the performance of the triceps surae by implementing a
resistance training programme for participants to ensure maximal architectural and
physiological adaptations of the triceps surae and that all participants are at the
similar level of adaptations. Also further investigate the effect of the combination of
the knee angle and ankle angle on the performance of triceps surae. Also,
investigate the triceps surae but also on other muscle groups such as the hamstrings
and the quadriceps to look at the effect of resistance training on the variation of
muscle function as knee angle changes. In addition further use of ultrasound to look
at the muscle architectural and tendon behaviour during isometric contractions to
provide further insight into the topic.
Conclusions: The hypotheses stated was 1) Knee joint angle decrease would result
in a significant reduction in strength and rate of torque development during plantar
flexion. 2) Knee angle will effect plantar flexor moment and RTD more for the
resistance trained group compared to the untrained group. Based on the research
findings there were no significant changes in moment and RTD as a result of the
change in knee angle knee flexed position compared to knee extended. Also, there
were no significant differences between the percentage change in moment and RTD
from knee extended to the knee flexed position between the resistance-trained and
untrained groups. Therefore, this study accepts the null hypotheses. However, there
were differences found by the resistance trained having a greater decrease in
moment production as knee angle decreases compared to untrained. Therefore
further research should take place to be made certain. Calibration process suggests

16. 16
that the moment values are reliable and reproducible however investigation into the
validity of the dynamometer during contractions should be performed in near future.
References
1. Aagaard, P., Andersen, J.L., Dyhre‐Poulsen, P., Leffers, A.M., Wagner, A.,
Magnusson, S.P., Halkjær‐Kristensen, J. and Simonsen, E.B., 2001. A
mechanism for increased contractile strength of human pennate muscle in
response to strength training: changes in muscle architecture. The journal of
physiology, 534(2), pp.613-623.
2. Aagaard, P., Simonsen, E.B., Andersen, J.L., Magnusson, P. and Dyhre-
Poulsen, P., 2002. Increased rate of force development and neural drive of
human skeletal muscle following resistance training. Journal of applied
physiology, 93(4), pp.1318-1326.
3. Arampatzis, A., Karamanidis, K., Stafilidis, S., Morey-Klapsing, G., DeMonte,
G. and Brüggemann, G.P., 2006. Effect of different ankle-and knee-joint
positions on gastrocnemius medialis fascicle length and EMG activity during
isometric plantar flexion. Journal of biomechanics, 39(10), pp.1891-1902.
4. Avancini, C., de Oliveira, L.F., Menegaldo, L.L. and Vieira, T.M., 2015.
Variations in the Spatial Distribution of the Amplitude of Surface
Electromyograms Are Unlikely Explained by Changes in the Length of Medial
Gastrocnemius Fibres with Knee Joint Angle. PloS one, 10(5), p.e0126888.
5. Biewener, A.A. and Roberts, T.J., 2000. Muscle and tendon contributions to
force, work, and elastic energy savings: a comparative perspective. Exercise
and sport sciences reviews, 28(3), pp.99-107.
6. Blazevich, A.J., 2006. Effects of physical training and detraining,
immobilisation, growth and aging on human fascicle geometry. Sports
Medicine, 36(12), pp.1003-1017.
7. Bojsen-Møller, J., Magnusson, S.P., Rasmussen, L.R., Kjaer, M. and
Aagaard, P., 2005. Muscle performance during maximal isometric and
dynamic contractions is influenced by the stiffness of the tendinous structures.
Journal of Applied Physiology, 99(3), pp.986-994.
8. Burgess, K.E., Connick, M.J., Graham-Smith, P. and Pearson, S.J., 2007.
Plyometric vs. isometric training influences on tendon properties and muscle
output. The Journal of Strength & Conditioning Research, 21(3), pp.986-989.

17. 17
9. Burke, R.E., Levine, D.N., Tsairis, P. and Zajac III, F.E., 1973. Physiological
types and histochemical profiles in motor units of the cat gastrocnemius. The
Journal of physiology, 234(3), p.723.
10.Cresswell, A.G., Löscher, W.N. and Thorstensson, A., 1995. Influence of
gastrocnemius muscle length on triceps surae torque development and
electromyographic activity in man. Experimental brain research, 105(2),
pp.283-290.
11.Dalton, B.H., Allen, M.D., Power, G.A., Vandervoort, A.A. and Rice, C.L.,
2014. The effect of knee joint angle on plantar flexor power in young and old
men. Experimental gerontology, 52, pp.70-76.Landin, D., Thompson, M. and
Reid, M., 2015. Knee and Ankle Joint Angles Influence the Plantarflexion
Torque of the Gastrocnemius. Journal of clinical medicine research, 7(8),
p.602.
12.Dalton, B.H., Allen, M.D., Power, G.A., Vandervoort, A.A. and Rice, C.L.,
2014. The effect of knee joint angle on plantar flexor power in young and old
men. Experimental gerontology, 52, pp.70-76.
13.Duclay, J., Martin, A., Duclay, A., Cometti, G. and Pousson, M., 2009.
Behavior of fascicles and the myotendinous junction of human medial
gastrocnemius following eccentric strength training. Muscle & nerve, 39(6),
pp.819-827.
14.Enoka, R.M. (2008). Neuromechanics of Human Movement. Champaign:
Human Kinetics.
15.Ferri, A., Scaglioni, G., Pousson, M., Capodaglio, P., Van Hoecke, J. and
Narici, M., 2003. Strength and power changes of the human plantar flexors
and knee extensors in response to resistance training in old age. Acta
Physiologica Scandinavica, 177(1), pp.69-78.
16.Folland, J.P. and Williams, A.G., 2007. Morphological and neurological
contributions to increased strength. Sports medicine, 37(2), pp.145-168.
17.Gilliver, S.F., Degens, H., Rittweger, J., Sargeant, A.J. and Jones, D.A., 2009.
Variation in the determinants of power of chemically skinned human muscle
fibres. Experimental physiology, 94(10), pp.1070-1078.
18.Hébert-Losier, K. and Holmberg, H.C., 2014. Dynamometric indicators of
fatigue from repeated maximal concentric isokinetic plantar flexion
contractions are independent of knee flexion angles and age but differ for

18. 18
males and females. The Journal of Strength & Conditioning Research, 28(3),
pp.843-855.
19.Kawakami, Y., Ichinose, Y. and Fukunaga, T., 1998. Architectural and
functional features of human triceps surae muscles during contraction.
Journal of Applied Physiology, 85(2), pp.398-404.
20.Komi, P.V., Fukashiro, S. and Järvinen, M., 1992. Biomechanical loading of
Achilles tendon during normal locomotion. Clinics in sports medicine, 11(3),
pp.521-531.
21.Kubo, K., Ikebukuro, T., Yata, H., Tsunoda, N. and Kanehisa, H., 2010. Time
course of changes in muscle and tendon properties during strength training
and detraining. The Journal of Strength & Conditioning Research, 24(2),
pp.322-331.
22.Kubo, K., Kanehisa, H. and Fukunaga, T., 2002. Effects of resistance and
stretching training programmes on the viscoelastic properties of human
tendon structures in vivo. The journal of physiology, 538(1), pp.219-226.
23.Kubo, K., Yata, H., Kanehisa, H. and Fukunaga, T., 2006. Effects of isometric
squat training on the tendon stiffness and jump performance. European
journal of applied physiology, 96(3), pp.305-314.
24.Maganaris, C.N., 2001. Force–length characteristics of in vivo human skeletal
muscle. Acta Physiologica Scandinavica, 172(4), pp.279-285.
25.Mero, A.N.T.T.I. and Komi, P.V., 1987. Electromyographic activity in sprinting
at speeds ranging from sub-maximal to supra-maximal. Medicine and science
in sports and exercise, 19(3), pp.266-274.
26.Miaki, H., Someya, F. and Tachino, K., 1999. A comparison of electrical
activity in the triceps surae at maximum isometric contraction with the knee
and ankle at various angles. European journal of applied physiology and
occupational physiology, 80(3), pp.185-191.
27.Moliner-Urdiales, D., Ortega, F.B., Vicente-Rodriguez, G., Rey-Lopez, J.P.,
Gracia-Marco, L., Widhalm, K., Sjöström, M., Moreno, L.A., Castillo, M.J. and
Ruiz, J.R., 2010. Association of physical activity with muscular strength and
fat-free mass in adolescents: the HELENA study. European journal of applied
physiology, 109(6), pp.1119-1127.
28.Morishita Y, Kubo K, Miki A, Ishibashi K, Kusano E, Nagata D. Positive
association of vigorous and moderate physical activity volumes with skeletal

19. 19
muscle mass but not bone density or metabolism markers in hemodialysis
patients. International urology and nephrology. 2014 Mar 1;46(3):633-9.
29.Morrissey, D., Roskilly, A., Twycross-Lewis, R., Isinkaye, T., Screen, H.,
Woledge, R. and Bader, D., 2011. The effect of eccentric and concentric calf
muscle training on Achilles tendon stiffness. Clinical rehabilitation, 25(3),
pp.238-247.
30.Orishimo, K.F., Burstein, G., Mullaney, M.J., Kremenic, I.J., Nesse, M.,
McHugh, M.P. and Lee, S.J., 2008. Effect of knee flexion angle on Achilles
tendon force and ankle joint plantarflexion moment during passive
dorsiflexion. The Journal of Foot and Ankle Surgery, 47(1), pp.34-39.
31.Rafolt, D., Gallasch, E., Mayr, W. and Lanmüller, H., 1999. Dynamic force
responses in electrically stimulated triceps surae muscles: effects of fatigue
and temperature. Artificial organs, 23(5), pp.436-439.
32.Reeves, N.D., Narici, M.V. and Maganaris, C.N., 2004. In vivo human muscle
structure and function: adaptations to resistance training in old age.
Experimental physiology, 89(6), pp.675-689.
33.Signorile, I.E., Applegate, B., Duque, M., Cole, N. and Zink, A., 2002.
Selective recruitment of the triceps surae muscles with changes in knee
angle. The Journal of Strength & Conditioning Research, 16(3), pp.433-439.
34.Thompson, B.J., Ryan, E.D., Herda, T.J., Costa, P.B., Walter, A.A.,
Sobolewski, E.J. and Cramer, J.T., 2012. Consistency of rapid muscle force
characteristics: influence of muscle contraction onset detection methodology.
Journal of Electromyography and Kinesiology, 22(6), pp.893-900.
35.Tillin, N.A., Jimenez-Reyes, P., Pain, M.T. and Folland, J.P., 2010.
Neuromuscular performance of explosive power athletes versus untrained
individuals.
36.Tillin, N.A., Pain, M.T. and Folland, J.P., 2013. Identification of contraction
onset during explosive contractions. Response to Thompson et
al.“Consistency of rapid muscle force characteristics: influence of muscle
contraction onset detection methodology”[J Electromyogr Kinesiol 2012; 22
(6): 893–900]. Journal of Electromyography and Kinesiology, 23(4), pp.991-
994.
37.Visser, J.J., Hoogkamer, J.E., Bobbert, M.F. and Huijing, P.A., 1990. Length
and moment arm of human leg muscles as a function of knee and hip-joint

20. 20
angles. European journal of applied physiology and occupational physiology,
61(5-6), pp.453-460.
38.Weiss, L.W., Clark, F.C. and Howard, D.G., 1988. Effects of heavy-resistance
triceps surae muscle training on strength and muscularity of men and women.
Physical therapy, 68(2), pp.208-213.
39.Wickiewicz, T.L., Roy, R.R., Powell, P.L. and Edgerton, V.R., 1983. Muscle
architecture of the human lower limb. Clinical orthopaedics and related
research, 179, pp.275-283.
40.Yu, B., Gabriel, D., Noble, L. and An, K.N., 1999. Estimate of the optimum
cutoff frequency for the Butterworth low-pass digital filter. Journal of Applied
Biomechanics, 15, pp.318-329.