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Increased muscle flexibility from static stretching is supported by the literature, but limited research has assessed the duration of maintained flexibility gains in knee joint range of motion after same-day static hamstring stretching. The purpose of our study was to determine the duration of hamstring flexibility gains, as measured by an active knee-extension test, after cessation of an acute static stretching protocol.
All subjects performed 6 active warm-up knee extensions, with the last repetition serving as the baseline comparison measurement. After warm-up, the experimental group performed 4 30-second static stretches separated by 15-second rests.
Thirty male subjects (age = 19.8 ± 5.1 years, ht = 179.4 ± 18.7 cm, wt = 78.5 ± 26.9 kg) with limited hamstring flexibility of the right lower extremity were randomly assigned to control and experimental groups.
Postexercise active knee-extension measurements for both groups were recorded at 1, 3, 6, 9, 15, and 30 minutes.
Tukey post hoc analysis indicated significant improvement of knee-extension range of motion in the experimental group that lasted 3 minutes after cessation of the static stretching protocol. Subsequent measurements after 3 minutes were not statistically different from baseline. A dependent t test revealed a significant increase in knee-extension range of motion when comparing the first to the sixth active warm-up repetition.
Our results suggest that 4 consecutive 30-second static stretches enhanced hamstring flexibility (as determined by increased knee-extension range of motion), but this effect lasted only 3 minutes after cessation of the stretching protocol. Future research should examine the effect of other stretching techniques in maintaining same-day flexibility gains.