Crossover Effects of Unilateral Static Stretching and Foam Rolling on Contralateral Hamstring Flexibility and Strength

CONTEXT: Static stretching (SS) and self-administered foam rolling (SAFR) are both effective techniques often used in rehabilitation settings to improve one's range of motion (ROM). However, their effects on nonintervened contralateral limb's performance remain equivocal. OBJECTIVE: To examine the acute effects of unilateral hamstring's SS and SAFR on the contralateral hip-flexion passive ROM and the strength performance. DESIGN: Randomized crossover trial. SETTING: Controlled laboratory. PARTICIPANTS: A total of 23 healthy young adults (13 males and 10 females) participated in this investigation. INTERVENTIONS: Ten sets of 30-second SS or SAFR were performed on the participants' dominant hamstring muscles. MAIN OUTCOME MEASURES: Before (pre) and after (post) the interventions, the contralateral hip-flexion passive ROM, the isometric strength of the contralateral hamstrings, and surface electromyography amplitude were measured. Separate 2-way (time × intervention) repeated measures analyses of variance were used to examine the changes in the dependent variables. RESULTS: Both interventions significantly increased the contralateral hip-flexion passive ROM. In addition, the post-ROM value was significantly greater (P = .03) for the SS (mean ± SE = 73.5° ± 4.7°) than that for the SAFR (mean ± SE = 70.3° ± 4.5°). There were also main effects for time (P = .03) and intervention (P = .02) for the contralateral hamstring strength. However, no significant interaction or main effects were found for the normalized electromyography amplitude of the knee flexor muscles. CONCLUSIONS: The increased contralateral hip-flexion passive ROM following both interventions was likely due to the enhanced stretch tolerance. However, the differential strength performance responses might be due to different neural mechanisms, which are proposed and discussed.