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

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.

MethodsSubjects

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

MethodsInstrumentation

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)

Methods

Ankle Joint Stiffness =

0.00

0.50

1.00

1.50

2.00

2.50

3.00

-5 0 5 10 15 20

An

kle

Join

tM

om

en

t(N

m/k

g)

Ankle Joint Angular Displacement (deg)

Peak Joint Moment

Peak Joint Angular Displacement

MethodsMuscle-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.

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)

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.

ResultsPRE 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

ResultsPRE 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

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

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)

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

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)

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.

ReferencesFarup, 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.

Questions?