On Hamstring Flexibility Using Consistent Stretching Parameters

Davis, D.S., P.E. Ashby, K.L. McCale, J.A. McQuain, and J.M. Wine. The effectiveness of 3 stretching techniques on hamstring flexibility using consistent stretching parameters. J. Strength Cond. Res. 19(1):27–32. 2005.—This study compares the effects of 3 common stretching techniques on the length of the hamstring muscle group during a 4-week training program. Subjects were 19 young adults between the ages of 21 and 35. The criterion for subject inclusion was tight hamstrings as defined by a knee extension angle greater than 208 while supine with the hip flexed 908. The participants were randomly assigned to 1 of 4 groups. Group 1 (n 5 5) was self-stretching, group 2 (n 5 5) was static stretching, group 3 (n 5 5) was proprioceptive neuromuscular facilitation incorporating the theory of reciprocal inhibition (PNF-R), and group 4 (n 5 4) was control. Each group received the same stretching dose of a single 30second stretch 3 days per week for 4 weeks. Knee extension angle was measured before the start of the stretching program, at 2 weeks, and at 4 weeks. Statistical analysis (p # 0.05) revealed a significant interaction of stretching technique and duration of stretch. Post hoc analysis showed that all 3 stretching techniques increase hamstring length from the baseline value during a 4-week training program; however, only group 2 (static stretching) was found to be significantly greater than the control at 4 weeks. These data indicate that static stretching 1 repetition for 30 seconds 3 days per week increased hamstring length in young healthy subjects. These data also suggest that active self-stretching and PNF-R stretching 1 repetition for 30 seconds 3 days per week is not sufficient to significantly increase hamstring length in this population.