Effects of Training on Muscle and Tendon in Knee Extensors and Plantar Flexors in Vivo

Abstract

The purpose of this study was to compare the effects of resistance training on muscle and tendon properties between knee extensors and plantar flexors in vivo. Twenty healthy young men voluntarily participated in this study. The subjects were randomly divided into two training groups: knee extension group (n= 10) and plantar flexion group (n= 10). They performed five sets of exercises with a 1-min rest between sets, which consisted of unilateral knee extension for the knee extension group and plantar flexion for the plantar flexion group at 80% of 1 repetition maximum with 10 repetitions per set (4 days/wk, 12 wk). Before and after training, muscle strength, neural activation level (by interpolated twitch), muscle volume (by magnetic resonance imaging), and tendon stiffness (by ultrasonography) were measured. There were no differences in the training-induced increases in muscle strength, activation level, muscle volume, and tendon stiffness between knee extensors and plantar flexors. These results suggested that if the used protocol of training (i.e., intensity, repetition, etc.) were the same, there were no differences in the training-induced changes in muscle and tendon properties between knee extensors and plantar flexors.

Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing

“…The corresponding increase in muscle size was 6–8% in quadriceps femoris muscle volume during a 9‐week, 3 days/week strength training program . Similar gains in knee extensor strength (32–34%), muscle volume (6–8%), and 30–58% increase in vastus lateralis musculotendon stiffness were found in young males after a 12‐week knee extensor strength training program . It is also possible to achieve a 34% gain in musculotendon stiffness in 4 weeks by increasing muscle activation, rather than muscle strength .…”

“…Knee extensor strength training in humans will produce an increase in type II muscle fiber cross‐sectional area within the vastus lateralis as well as an increase in quadriceps rectus femoris volume . The associated increase in vastus lateralis musculotendon stiffness, ranging from 16% to 58% after 12 weeks of training, was more strongly associated with gains in strength than in muscle activation . While previous studies have shown that a large quadriceps force can increase the risk of ACL injury, a knowledge gap exists regarding whether achievable training‐related increases in quadriceps tensile stiffness in females via prevention programs could reduce peak ACL strain during a given pivot landing .…”

Measurement of ageing effects on muscle tone and mechanical properties of rectus femoris and biceps brachii in healthy males and females using a novel hand-held myometric device

“…Stiffness is also reported to increase with hypertrophy due to strength training (Kubo et al 2010) and with increasing muscle activation (Blanpied & Smidt 1993). Gender differences in muscle stiffness measured using different laboratory based technologies are conflicting in the literature.…”

Method and strain rate dependence of Achilles tendon stiffness

“…Hansen et al, 2006, for example, measured the mechanical properties of the patellar tendon under loading conditions, but used a slow ramped force rise ($10 s), which resulted in a relatively low strain rate. Kubo et al (2010) and Maganaris and Paul (1999) used shorter durations of force rise ($5 s and $1 s, respectively). In light of our findings, the velocity-dependence of stiffness needs to be taken into consideration when comparing stiffness values reported in these studies.…”

“…Within this context, tendon stiffness has been widely studied in athletic McNair and Stanley, 1996) and clinical populations (Vaz et al, 2006;Tardieu et al, 1982). The findings of such studies have led to an enhanced understanding of how tendon stiffness influences force production (Reeves, 2006) as well as how tendon stiffness adapts to changes in loading (Kubo et al, 2010;Seynnes et al, 2009). Tendon stiffness is calculated by dividing the estimated tendon force by the tendon's elongation (Kubo et al, 2002;Maganaris and Paul, 1999).…”