Effect of stretch frequency and sex on the rate of gain and rate of loss in muscle flexibility during a hamstring-stretching program: A randomized single-blind longitudinal study

Abstract

This study evaluated the effects of 4 different weekly stretching protocols on the rate of gain and decline in hamstring flexibility over an 8-week period, across sex. Using a randomized single-blind design, 53 healthy subjects aged 18-46 years were assigned to 1 of 4 stretching protocols or a control group. The stretching protocols consisted of either daily or 3 times per week stretching and performed once or twice each day. These protocols differed in terms of frequency and total weekly stretching time. All the subjects stretched their hamstring muscles for 4 weeks and were measured weekly for their hip range of motion (ROM). Stretching ceased the final 4 weeks as the weekly measurements continued. The results revealed no significant differences in the rate of gain or the rate of loss between the different stretching protocols (2-way analysis of variance, F = 2.60, p> 0.05). All the stretching groups gained in hip ROM from pre to week 4 (F = 269.24, p< , 0.001). After cessation, the rate of loss was similar for all the 4 stretching groups (F = 102.86, . 0.05). Stretching appears to be equally effective, whether performed daily or 3 times per week, provided individuals stretch at least 2 times each day. Moreover, although women are more flexible than men are, there was no sex difference in terms of stretching response. © 2012 National Strength and Conditioning Association.