Changes in Muscle Mechanical Properties and Muscle Activation During Low-intensity Contraction After Static Stretching

Abstract

Purpose

The effects of static stretching (SS) on muscle behavior during low-intensity contraction remain unclear. This study investigated changes in muscle shear modulus and muscle activation of the synergist muscles during low-intensity contraction after SS.

Methods

Thirteen healthy males with no regular exercise habits and no history of lower limb pathology participated in this study. Before and after static stretching targeting the gastrocnemii (a total of 5 min at the maximal dorsiflexion angle), participants exerted 20% of their maximal voluntary torque, which was held constant. Shear modulus, an index of total muscle force, and muscle activation of the triceps surae [gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and soleus (SOL)] were measured during the low-intensity contraction.

Results

A decrease in shear modulus at rest was observed in the GM and GL but not in the SOL. Moreover, during low-intensity contraction, the shear modulus of the GL decreased significantly. In addition, the change in the shear modulus of the SOL was positively correlated with the ratio of GL muscle activation among the triceps surae.

Conclusion

These results suggest that SS can transiently reduce the shear modulus of the gastrocnemii during low-intensity contraction, potentially modulated by baseline activation patterns, providing hypothesis-generating insight for task-specific warm-up and rehabilitation strategies.

Keywords

Shear modulus / Muscle activation / Triceps surae / Shear wave elastography / Static stretching

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