Effect of an 8-Week Functional Hopping Training Program on Pain, Muscle Strength, and Lower Extremity Function in Male Volleyball Players Following ACL Reconstruction: A Controlled Intervention Study

Abstract

Background: Anterior cruciate ligament reconstruction (ACLR) is common among volleyball players; however, pain, strength deficits, and functional limitations often persist during the late stage of rehabilitation. Functional hopping protocols have been proposed to address these deficits and facilitate readiness for return to sport. Objectives: This study primarily aimed to evaluate the effects of an 8-week functional hopping program on pain and lower-extremity muscle strength in male volleyball players after ACLR. A secondary objective was to assess improvements in sport-specific functional performance. Methods: This randomized controlled trial included 30 male volleyball players aged 20 - 35 years who were 6 - 12 months post-ACLR and were recruited from rehabilitation centers in Iran. Participants were randomized to an intervention group (n = 15; a supervised functional hopping program, 3 sessions/week, 40 minutes/session) or a control group (n = 15; standard-of-care rehabilitation, including resistance training, neuromuscular drills, and balance exercises, 2 - 3 sessions/week, 45 - 60 minutes/session). Outcomes included pain during squatting, assessed using the Visual Analog Scale; isometric hip, knee, and ankle strength, assessed using hand-held dynamometry; and functional performance, assessed using the Triple Hop and Figure-8 Hop tests. Data were analyzed using ANCOVA, adjusted for baseline scores (alpha = 0.05). Results: After the intervention, the hopping group demonstrated significantly greater improvements than the control group, including reduced pain (P = 0.002, η2 = 0.29), enhanced multi-joint strength (P ≤ 0.019, η2 = 0.19 - 0.68), and superior agility/power on hop tests (P < 0.001, η2 = 0.67). The control group showed no significant within-group changes (P > 0.05). All effect sizes indicated moderate-to-large practical significance. Conclusions: The functional hopping program was not associated with adverse events and significantly improved pain, strength, and sport-specific function. These findings support integrating progressive, quality-focused hopping into late-stage ACLR rehabilitation to improve pain, strength, and hopping performance. Whether these short-term gains translate into reduced reinjury risk or improved return-to-sport rates requires validation in prospective studies.