Abstract
The purpose of this study was to compare the duration of high-intensity static stretching on flexibility and strength in the hamstrings. Fourteen healthy males (20.8 ± 0.6 years, 170.7 ± 6.5 cm, 66.4 ± 9.9 kg) underwent high-intensity static stretching for three different durations (10, 15, and 20 seconds). The intensity of static stretching was set at the maximum point of discomfort. To examine the change in flexibility and strength, range of motion, peak passive torque, relative passive torque, muscle-tendon unit stiffness, peak torque of isokinetic knee flexion, and knee angle at peak torque of isokinetic knee flexion were measured. To evaluate a time course of pain, a numerical rating scale was described. Range of motion (P < 0.01), peak passive torque (P < 0.01), and knee angle at peak torque were increased at all interventions. Relative passive torque (P < 0.01) and muscle-tendon unit stiffness (P < 0.01) were decreased at all interventions. Peak torque decreased after 10 seconds of stretching (P < 0.05). Numerical rating scale during stretching was 8-9 levels in all interventions, the pain disappeared immediately after the post-measurements (median = 0). The results suggested that muscle-tendon unit stiffness decreased regardless of duration of high-intensity static stretching. However, peak torque of isokinetic knee flexion decreased after 10 seconds of high-intensity static stretching, though it was no change after for more than 15 seconds of stretching.
Highlights
Static stretching (SS) is commonly used as a part of a warm-up routine in order to increase range of motion (ROM) and potentially prevent injuries [1]
Range of motion (P < 0.01), peak passive torque (P < 0.01), and knee angle at peak torque were increased at all interventions
The passive property of the muscle-tendon unit is measured by using muscle-tendon unit stiffness, which is calculated from the slope of the torque-angle curve during passive joint movement [8,9,10]
Summary
Static stretching (SS) is commonly used as a part of a warm-up routine in order to increase range of motion (ROM) and potentially prevent injuries [1]. It is pointed out that the passive property of the muscle-tendon unit and tolerance for stretching influences ROM [5,6,7]. The passive property of the muscle-tendon unit is measured by using muscle-tendon unit stiffness, which is calculated from the slope of the torque-angle curve during passive joint movement [8,9,10]. Tolerance for stretching is measured by peak passive torque during passive joint movement [10,11,12]. ROM is defined as one at which the subject is able to have a maximally tolerable angle without pain. An increase in the passive torque during the passive joint movement indicated that the subjects received higher force without pain, which indicates that an increase of tolerance is obtained
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