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EFFECTS OF 15 MINUTES OF DORSIFLEXION STRETCH ON RANGE OF MOTION, STIFFNESS, AND HYSTERESIS AREA

P Kis
L Li

Abstract

Petra Kis, Li Li, FACSM. Georgia Southern University, Statesboro, GA.

BACKGROUND: Stretching effects on the human body have been studied by many. However, studies related to the hysteresis area (Area) are few. Hysteresis depicts the differential loading-unloading curves of the viscoelastic material (1). The relationship between stress and strain is not constant but depends on the history of the loading process. There are three major characteristics of a viscoelastic material of ligaments and tendons: creep, stress relaxation, and hysteresis or energy dissipation (1). This study aimed to investigate the effect of 15 minutes of static stretching on range of motion (ROM), stiffness, and Area. METHODS: 16 healthy college students participated in the experiment. The study consisted of a 15-minute ankle dorsiflexion stretch while standing on an elevated surface. Angle (degrees) and force (Newton) was recorded throughout the maximal pre- and post-tests of the ankle dorsiflexion to determine ROM, stiffness, and Area. In this study, stiffness was estimated by (MaxF-MinF)/(MaxA-MinA), ROM was the greatest angle value recorded, and the Area was calculated by the difference of areas under the loading and unloading curves. A paired student t-test was performed to examine the potential difference before and after the stretch. RESULTS: Significant Area differences between the pre- and post-tests were detected (pre: 1018.16±394.92, post: 1044.63±410.40, p=0.00002). In contrast, no significant difference was observed from Stiffness (pre: 0.9969±0.2012, post: 0.9977±0.2034) and ROM (pre: 18.25±4.79, post: 19.01±5.03), although increasing trends were seen in both after the 15 minutes stretching. CONCLUSION: Increase trends observed in ROM and stiffness, although not statistically significant. The hysteresis area was increased significantly, which suggests that the Area was more sensitive to stretch-induced change than the other two variables. Increased hysteresis area represents more energy that has been dissipated or lost during the loading/unloading process. Reference: Robi, K., Jakob, N., Matevz, K., & Matjaz, V. (2013). The physiology of sports injuries and repair processes. Current issues in sports and exercise medicine, 43-86.

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