Effect of heel drop static stretching on triceps surae stiffness through shear wave elastography

The heel drop static stretching is a stretching posture where the forefoot is placed on a step and the heel is dropped to maximum dorsiflexion and held in that position for the duration of the stretch. Heel drop static stretching is widely used in training and rehabilitation programs. However, to our knowledge, no previous studies have investigated the acute effect this stretching posture has on the mechanical properties of the triceps surae.

A total of 29 healthy young adults participated in the study. The range of motion, the maximum isometric voluntary contraction and the stiffness of gastrocnemius lateralis, gastrocnemius medialis and Achilles tendons were measured before and after 3x 60-s series of heel drop static stretching. High-density surface electromyography was acquired during the maximum voluntary contraction and stretching protocols.

The main findings of the present study were: (1) the immediate effect of a series of heel drop static stretches was a significant increase in shear modulus of the lateral and medial gastrocnemius; there was no statistically significant change in Achillies tendon shear modulus; (2) there was no correlation between muscle activation and stiffness levels in triceps surae structures; (3) there was no change in maximum voluntary contraction pre-and post-stretching and (4) there was statistically significant increase in dorsiflexion range of motion pre- and post-stretching.

The results show that heel drop static stretching should not be viewed as a method to acutely reduce gastrocnemius muscle stiffness.