Comparative Effects of a 6-Week Instrument-Assisted Soft Tissue Mobilization and Static Stretching Program on Joint Range of Motion and Muscle Strength in Individuals with Hamstring Tightness: A Randomized Controlled Trial

This randomized controlled trial aimed to investigate the effects of a 6-week instrument-assisted soft tissue mobilization (IASTM) and static stretching program on hamstring flexibility, knee extension range of motion (ROM), and muscle strength in individuals with hamstring tightness. Forty-five healthy adults with hamstring tightness were randomly assigned to IASTM, static stretching, or control groups (n=15 each) using a computer-generated randomization sequence with allocation concealment. Active and passive knee extension ROM were measured using a digital inclinometer, and isometric hamstring and quadriceps strength were assessed with a hand-held dynamometer. The intervention groups received treatment three times per week for six weeks, while the control group performed only a standardized 3-minute warm-up. Assessments were conducted at baseline and three days post-intervention. Data were analyzed using mixed ANOVA. A significant main effect of time was observed for knee extension ROM (p < 0.001). Both IASTM and static stretching groups showed significant improvements in active and passive ROM compared to baseline (p < 0.05), whereas no significant changes were observed in the control group (p > 0.05). No significant differences were found between the intervention groups in terms of ROM gains (p > 0.05). A significant group × time interaction effect was observed for hamstring muscle strength (p < 0.05), with a significant increase only in the IASTM group (p < 0.05). Quadriceps muscle strength did not change significantly in any group (p > 0.05). Both IASTM and static stretching effectively improved hamstring flexibility following a 6-week intervention, with no superiority between techniques. However, IASTM demonstrated an additional benefit by enhancing hamstring muscle strength. These findings suggest that IASTM may be preferable when both flexibility and muscle performance improvements are targeted.