This study examined changes in medial gastrocnemius (MG) muscle-tendon interaction following 8 weeks of resistance training in 11 trained males. Following training, MG muscle elongation increased more than MG tendon elongation at hopping frequencies of 2.5 Hz and 3.0 Hz. While ankle joint strength increased, ankle joint stiffness decreased at these hopping frequencies. The results suggest that short-term resistance training disproportionately increases muscle strength relative to tendon stiffness, leading to greater reliance on the tendon during fast stretch-shortening cycle tasks.

1. CHANGES IN MEDIAL GASTROCNEMIUS
MUSCLE-TENDON INTERACTION
FOLLOWING 8 WEEKS OF RESISTANCE
TRAINING
John McMahon, CSCS, ASCC
Stephen Pearson, PhD
Paul Comfort, CSCS*D, ASCC
NSCA National Conference
Thursday 11th July 2013

2. Introduction
It is well documented that muscle and tendon adapts
to resistance training by ↑ strength, size and stiffness
(Kubo et al., 2001; Pearson et al., 2007; Vissing et al., 2008; Farup et al., 2012).
The effect of such adaptations on subsequent muscle-
tendon interaction (as measured during functional
performance), however, has not yet been examined.
Purpose
To determine the effects of loading on medial
gastrocnemius (MG) muscle-tendon interaction in
order to inform resistance training practice.

3. Methods
Subjects
11 resistance trained males gave informed consent
(27.0 ± 8.4 years, 180.8 ± 5.8 cm, 86.3 ± 10.2 kg)
Procedures
3 single-leg (SL) hopping trials
(performed at 2.0, 2.5 & 3.0 Hz)
One repetition maximum (1-RM) SL calf raise
(performed ≥48hrs after the hopping conditions)
8 weeks of resistance training
(4 x 12 reps with 67% of 1-RM) 2 days/week

4. Methods
Instrumentation
Inclined Sledge Apparatus
10 Qualisys Pro-Reflex Cameras (200 Hz)
Kistler Force Platform (1200 Hz)
Echoblaster Ultrasound System (50 Hz)
Smith Machine
Software
QTrack (Qualisys AB, Partille, Sweden)
Visual3D (C-Motion, Inc., Rockville, USA)
Image J (Wayne Rasband NIH, Bethesda, USA)
Quintic Biomechanics (Quintic Consultancy Ltd, Coventry, UK)
MATLAB (MathWorks, Inc., Natick, USA)

5. Methods
Ankle Joint Stiffness =
0.00
0.50
1.00
1.50
2.00
2.50
3.00
-5 0 5 10 15 20
AnkleJointMoment(Nm/kg)
Ankle Joint Angular Displacement (deg)
Peak Joint Moment
Peak Joint Angular Displacement

6. Methods
Muscle-Tendon Unit (MTU)
MG MTU length was determined as a function of shank
segment length and joint angle data (Hawkins and Hull, 1990).
MG muscle length was calculated as MG fascicle length
multiplied by the cosine of the pennation angle.
MG tendon length was determined by subtracting MG
muscle length from MG MTU length (Fukunaga et al., 2001).
The elongation and shortening phase for each component
of the MTU was determined based on the peak MTU
elongation during the ground contact phase of each hop.

7. Methods
Lf = fascicle length
α = pennation angle
Lpt = proximal tendon length
Ldt = distal tendon length
Lmtu = MTU length
Tendon length (Lpt + Lpt)
= Lmtu – (Lf x cosα)
(Fukunaga et al., 2001)

8. Methods
Statistical Analysis
Dependent t-tests were used to compare mean differences
between variables measured both pre- and post-training.
The alpha level was set at p=0.05.
Data represents the mean ± SD of three trials performed
at each hopping frequency.

9. Results
PRE POST
2.5 Hz -0.6 ± 0.2 mm -1.4 ± 0.2 mm
3.0 Hz -1.3 ± 0.4 mm -2.4 ± 0.6 mm
MG Muscle Elongation
* = p<0.05

10. Results
PRE POST
2.5 Hz 15.1 ± 1.7 mm 18.2 ± 3.9 mm
3.0 Hz 11.0 ± 1.9 mm 13.7 ± 3.0 mm
MG Tendon Elongation
* = p<0.05

11. Results
* = p<0.05
PRE POST
2.5 Hz 14.6 ± 2.0 mm 16.9 ± 4.1 mm
3.0 Hz -9.8 ± 2.1 mm 11.4 ± 3.1 mm
MG MTU Elongation

12. Results
1-RM Calf Raise:
PRE POST
82.0 ± 16.4 kg 93.5 ± 23.0 kg (p<0.05)
Ankle Joint Stiffness:
PRE POST
2.0 Hz 0.12 ± 0.03 Nm/kg/deg 0.12 ± 0.03 Nm/kg/deg NS
2.5 Hz 0.29 ± 0.05 Nm/kg/deg 0.25 ± 0.04 Nm/kg/deg (p<0.01)
3.0 Hz 0.40 ± 0.07 Nm/kg/deg 0.36 ± 0.08 Nm/kg/deg (p<0.05)

13. Conclusion
Despite a post-training ↑ in muscle strength:
Ankle joint stiffness ↓
(when hopping at 2.5 & 3.0 Hz)
Mostly due to:
An ↑ in MG tendon elongation

14. Practical Applications
Short-term resistance training leads to:
A disproportionate ↑ in muscle strength
(in comparison to tendon stiffness)
Which in turn leads to:
↑ reliance on the series-elastic component
(during fast stretch-shortening cycle tasks)

15. Acknowledgements
I would like to thank the NSCA Foundation
for funding this PhD project.
I would also like to thank the lab technicians
at the University of Salford.

16. References
Farup, J., Kjolhede, T., Sorensen, H., Dalgas, U., Moller, A.B., Vestergaard, P.F., Ringga
ard, S., Bojsen-Moller, J. and Vissing, K. (2012). Muscle Morphological and Strength
Adaptations to Endurance Vs. Resistance Training. The Journal of Strength and
Conditioning Research, 26(2), 398-407.
Fukunaga, T., Kubo, K., Kawakami, Y., Fukashiro, S., Kanehisa, H. and Maganaris, C.N.
(2001). In Vivo Behaviour of Human Muscle Tendon During Walking. Proceedings of the
Royal Society of London, 268(1464), 229-233.
Hawkins, D. and Hull, M.L. (1990). A Method for Determining Lower Extremity Muscle-
Tendon Lengths During Flexion/Extension Movements. Journal of
Biomechanics, 23(5), 487-94.
Kubo, K., Kanehisa, H., Kawakami, Y. and Fukunaga, T. (2001). Influences of Repetitive
Muscle Contractions with Different Modes on Tendon Elasticity in Vivo. Journal of
Applied Physiology, 91(1), 277-282.
Pearson, S.J., Burgess, K. and Onambele, G.N. (2007). Creep and the in Vivo
Assessment of Human Patellar Tendon Mechanical Properties. Clinical
Biomechanics, 22(6), 712-7.
Vissing, K., Brink, M., Lønbro, S., Sørensen, H., Overgaard, K., Danborg, K., Mortensen
, J., Elstrøm, O., Rosenhøj, N., Ringgaard, S., Andersen, J.L. and Aagaard, P. (2008).
Muscle Adaptations to Plyometric Vs. Resistance Training in Untrained Young Men. The
Journal of Strength and Conditioning Research, 22(6), 1799-1810.

17. Questions?