Acute Static Stretching Results in Muscle-Specific Alterations amongst the Hamstring Muscles

Abstract

This study aimed to explore the acute effects of static stretching on the musculotendinous properties of two hamstring muscles. Twelve male volunteers underwent two testing sessions. One session was dedicated to the evaluation of the semitendinosus muscle before (PRE) and after (POST) static stretching (five sets of 30-s stretching), and the other session similarly explored the long head of biceps femoris muscle. In addition to the displacement of the myotendinous junction (MTJ), passive torque and maximal voluntary isometric torque (MVIT) were evaluated. MVIT (-8.3 ± 10.2%, p = 0.0036, d = 0.497) and passive torque (-28.4 ± 16.9%, p = 0.0003, d = 1.017) were significantly decreased POST stretching. PRE stretching, MTJ displacement was significantly greater for semitendinosus muscle than biceps femoris muscle (27.0 ± 5.2 vs. 18.6 ± 3.6, p = 0.0011, d = 1.975). After the stretching procedure, greater MTJ displacement relative changes were observed for biceps femoris muscle as compared to semitendinosus muscle (22.4 ± 31.6 vs. -8.4 ± 17.9, p = 0.0167, d = 1.252). Because of the smaller MTJ displacement PRE stretching and greater alteration POST stretching in biceps femoris muscles, the present study demonstrated muscle-specific acute responses of hamstring muscles during stretching. Although stretching acutely impairs torque production, the passive torque reduction and alteration of MTJ displacement might impact hamstring injury prevention.

Keywords: biceps femoris; mechanical properties; myotendinous junction; passive torque; semitendinosus.

Figure 1

Timeline of the experimental protocol with the two randomised testing sessions. One session was dedicated to the investigation of the myotendinous junction (MTJ) of the biceps femoris muscle and the other for semitendinosus muscle.

Figure 2

(A) volunteer positioning on the isokinetic dynamometer. (B) Zoomed image illustrating the ultrasonographic (US) probe positioning for the long head of biceps femoris muscle (BF). (C) Example of ultrasound image for the long head of biceps femoris muscle. The vertical dashed line coincides with the echo-intensive wire. The red circle (myotendinous junction, MTJ) corresponds to the junction of the superficial and deep aponeurosis.