Differential strain patterns of the XXXX gastrocnemius aponeurosis and free tendon, in vivo.

@entity1 @entity202 @entity924 @entity6475 @entity717 @entity427
AIM: The mechanical characteristics of the @entity1 free @entity924 , in vivo, remains largely unknown. The present study evaluated the @entity427 of the medial gastrocnemius muscle during voluntary isometric contraction. METHODS: Ultrasonography-obtained @entity924 complex, electromyography of the gastrocnemius, soleus, and dorsiflexor muscles, and @entity717 were recorded during isometric plantarflexion (n = 5). Tendon cross-sectional area, moment arm and segment lengths (L(o)) were measured using magnetic resonance imaging. Tendon force was calculated from joint moments and tendon moment arm, and stress was obtained by dividing force by cross-sectional area. The difference between the free @entity924 complex deformation yielded separate distal aponeurosis deformation. Longitudinal aponeurosis and @entity6475 were obtained from the deformations normalized to segment lengths. RESULTS: At a common tendon force of 2641 +/- 306 N, the respective deformation and Lo were 5.85 +/- 0.85 and 74 +/- 0.8 mm for the free tendon and 2.12 +/- 0.64 and 145 +/- 1.3 mm for the distal aponeurosis, P < 0.05. Longitudinal strain was 8.0 +/- 1.2% for the tendon and 1.4 +/- 0.4% for the aponeurosis, P < 0.01. Stiffness and stored energy was 759 +/- 132 N mm(-1) and 6.14 +/- 1.89 J, respectively, for the free tendon. @entity924 was 73 +/- 4 @entity202 , yielding a stress of 36.5 +/- 4.6 MPa and Young's modulus of 788 +/- 181 MPa. CONCLUSION: The free Achilles tendon demonstrates greater strain compared with that of the distal (deep) aponeurosis during voluntary isometric contraction, which suggests that separate functional roles may exist during in vivo force transmission.
