Time course of changes in the range of motion and muscle-tendon unit stiffness of the hamstrings after two different intensities of static stretching.

Kosuke Takeuchi,Masatoshi Nakamura,Kazunori Akizuki,Emiliano Cè

doi:10.1371/journal.pone.0257367

Kosuke Takeuchi, Masatoshi Nakamura + Show 2 more

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https://doi.org/10.1371/journal.pone.0257367

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Abstract

ObjectivesThe purpose of this study was to examine the time course of changes in the range of motion and muscle-tendon unit stiffness of the hamstrings after two different intensities of static stretching.MethodsFourteen healthy men (20.9 ± 0.7 years, 169.1 ± 7.5cm, 61.6 ± 6.5kg) received static stretching for 60 seconds at two different intensities based on the point of discomfort (100%POD and 120%POD) of each participant, in random order. To evaluate the time course of changes in the flexibility of the hamstrings, the knee extension range of motion (ROM), passive torque at end ROM, and muscle-tendon unit stiffness were measured pre-stretching, post-stretching, and at both 10 and 20 minutes after static stretching.ResultsFor both intensities, ROM and passive torque at pre-stretching were significantly smaller than those at post-stretching (p < 0.01 in both intensities), 10 minutes (p < 0.01 in both intensities), and 20 minutes (p < 0.01 in both intensities). The muscle-tendon unit stiffness at pre-stretching was significantly higher than that at post-stretching (p < 0.01), 10 minutes (p < 0.01), and 20 minutes (p < 0.01) only in the 120%POD, but it showed no change in the 100%POD.ConclusionThe results showed that ROM and passive torque increased in both intensities, and the effects continued for at least 20 minutes after stretching regardless of stretching intensity. However, the muscle-tendon unit stiffness of the hamstrings decreased only after static stretching at the intensity of 120%POD, and the effects continued for at least 20 minutes after stretching.

Highlights

Static stretching is used to increase flexibility and prevent injuries [1,2], and range of motion (ROM) is often measured as an indicator of flexibility
The passive torque at end ROM increased in both intensities and the change was similar, but the muscle-tendon unit stiffness decreased only in the 120%point of discomfort (POD), not in the 100%POD
It was reported that the knee extension ROM and passive torque at end ROM increased and the muscle-tendon unit stiffness decreased after static stretching at the intensity of 120%POD even if the stretching duration was 20 seconds or less [17,18]

Summary

Introduction

Static stretching is used to increase flexibility and prevent injuries [1,2], and range of motion (ROM) is often measured as an indicator of flexibility. Previous studies pointed out that ROM was affected by both stretching tolerance [3,4,5,6] and muscle-tendon unit stiffness [7,8,9,10]. Previous studies reported that muscle-tendon unit stiffness is involved in the occurrence of sports-related injuries, such as muscle strain [11] and achilleas tendon injury [12]. Static stretching effectively decreases the muscle-tendon unit stiffness [3,13]. A previous systematic review study recommended to use static stretching as part of a fundamental warm-up routine to prevent sports-related injuries [14]

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