Effect of strength training on musculotendinous stiffness in elderly individuals

Abstract

The present study deals with the question whether 24-week strength training alters neuromechanical properties of plantar flexors in elderly people (73-83 years). The first purpose of the present study was to evaluate the effect of strength training on musculotendinous (MT) stiffness of the triceps surae (TS). The training was performed twice per week and mainly consisted of three series of ten repetitions of calf-rise and leg-press exercises at 75% of the three-repetition maximum. Using quick-release movements at different levels of submaximal torques performed measurements of MT stiffness. Surface electromyograms (EMG) of each part of the TS and the tibialis anterior were also recorded. A stiffness index (SI), defined as the slope of the angular stiffness-torque relationship (SI(MT-Torque)), was used to quantify changes in MT stiffness. Results showed a significant decrease in SI(MT-Torque) by 25.2% following training (P < 0.05). The second purpose of the study was to evaluate whether neural mechanism has influences on this decrease. Therefore, an activation SI, defined as the slope of the angular stiffness-EMG relationship (SI(MT-EMG)) was used to overcome the influence of changes in agonist activity, and thus to quantify changes in MT intrinsic elastic properties. SI(MT-EMG) only decreased by 11.2% following training (P < 0.05). The present results underlined that MT stiffness decreases following training in elderly individuals, counterbalancing the effect of ageing. These changes seem not only to be due to peripheral but also to neural adaptations.

Peak triceps surae muscle activity is not specific to knee flexion angles during MVIC

“…Furthermore, using two KF positions is common practice in everyday assessment, rehabilitation, conditioning, and strengthening of the distinct TS muscles (del Porto et al, 2010;Magnussen et al, 2009). Despite this underlying knowledge and widespread clinical use, many studies still employ only one KF position for the simultaneous acquisition of EMG normalization values for all three TS muscles, which range from 0°KF to 120°KF (Ball and Scurr, 2010;Ochala et al, 2005;Simoneau et al, 2009). Our results indicate that employing at least two KF angles in standing is more effective and accurate than just using one in standing to determine peak EMG amplitudes of the TS.…”

Changes in muscle and joint elasticity following long-term strength training in old age

“…Only a few experiments have examined the effect of strength training over 14 weeks (Lexell et al 1995;McCartney et al 1996;Ha¨kkinen et al 1998). The authors observed that MVC continuously increases during a 24-week training on knee extensors (Ha¨kkinen et al 1998) and plantar flexors (Ochala et al 2005), or during a 48-week training on elbow flexors and knee extensors (Lexell et al 1995), or during a 96-week training on knee extensors (McCartney et al 1996).…”

“…Nevertheless, since during the quick release experiment, MT release occurs against the resistance of the antagonist muscles, MT stiffness could also be influenced by neural adaptations (Lambertz et al 2001;. Thus, the decrease in SI MT values after the strength training among older men and women may also result from a lower co-activation (Ochala et al 2005). Controversial results have already been observed in the literature concerning co-activation values during maximal contractions as an effect of strength training in elderly people (Ha¨kkinen et al 1998;Reeves et al 2003).…”

“…For that, MT and MA stiffness during plantar flexion have been evaluated by using the quick-release technique and sinusoidal perturbations, respectively. Regarding another experiment using a short-term strength training protocol in older humans (Ochala et al 2005), it can be hypothesized that following the present long-term training program, MT stiffness decreases in both men and women. Concerning MA stiffness, it can be suggested that it remains unaffected in both men and women.…”

Age-Related Changes in Neuromuscular Function and Performance following a High-Intensity Intermittent Task in Endurance-Trained Men

“…One other factor could also affect twitch contractile characteristics and could explain one part of our results. Indeed, a recent study has observed that musculotendinous stiffness decreases following strength training in elderly individuals and could be due to peripheral but also neural adaptations [44] . If we consider this original result along with the fact that more compliant series elastic components in the muscles tend to decrease twitch force [45] and can also partly cause a slowing of the twitch Ct [46] , we can hypothesize that one part of our results in older men could be attributed to a reduction of the musculotendinous stiffness properties.…”