High- versus low-volume static stretching and eccentric exercise: a randomized controlled trial in older adults with hamstring tightness and possible sarcopenia

Purpose: This study examined the effects of home-based high-volume static stretching on range of motion (ROM), musculotendinous unit (MTU) stiffness, muscle morphology, strength, balance, and physical function in older adults with hamstring tightness and possible sarcopenia. Methods: Sixty-eight community-dwelling older adults (67.2 ± 4.5 years) were randomly assigned to high-volume static stretching (30 min/day), low-volume static stretching (3 min/day, 3 days/week), eccentric exercise (ECC), or non-intervention control (CON) for 6 weeks. Assessments conducted at baseline, post-intervention, and 3-month follow-up included muscle thickness (MT), ROM, MTU stiffness, isometric knee flexor strength, cross-education effects on contralateral strength, Y-Balance performance, and function outcomes. Results: Significant group × time interaction effects were observed for ROM and isometric strength (p < 0.05). ROM increased after both stretching interventions (12.4° high-volume; 10.3° low-volume; d = 1.27–1.48), with no statistically detectable between-group difference. Isometric knee flexor strength improved after ECC (≈ 7.0 Nm; d = 1.53), with no contralateral strength transfer. No consistent intervention-related improvements were observed in MTU stiffness, muscle thickness, Y-Balance, or physical function. At the 3-month follow-up, knee flexor strength differed from baseline in the ECC group, although this was an uncontrolled follow-up observation. Conclusions: No statistically detectable difference in ROM was identified between high- and low-volume stretching. Exploratory analyses indicated that ECC improved strength more than control, whereas stretching-related changes remained below the minimal detectable change. Low-volume stretching required substantially less weekly exercise time than high-volume stretching; however, equivalence was not established. Stretching and eccentric exercise may therefore produce distinct flexibility and strength adaptations in older adults. Clinical registration: The study protocol has been registered with the Thai Clinical Trials Registry (TCTR20251222012).