Hamstring flexibility increases the same with 3 or 9 repetitions of stretching held for a total time of 90 s

Abstract Objective To determine if stretching for a constant total time with differing repetition durations and number of repetitions over a 6-week period produced different changes in hamstring flexibility measured by knee extension range of motion (ROM). Design Randomized Control Trial. Setting University laboratory. Subjects 34 volunteers, 18–25 years old with tight hamstrings as determined by a greater than 30° loss of knee extension with hip flexed to 90° participated in the study. Main outcome measures Change in knee extension ROM was assessed in participants who were randomly assigned to a control, or to a stretching group of either 10 s for 9 repetitions or 30 s for 3 repetitions, for a total stretch time of 90 s. Each group stretched 6 days a week for 6 weeks. Results Pre to post stretch comparison indicated both stretching groups were successful in increasing joint ROM (11.6 ± 5.25°–13.4 ± 5.36°) over the control ( F = 19.77, p