Effects Of Frequency On Hamstring Flexibility

The purpose of this study was to determine the optimal frequency of static stretching sessions per day to increase hamstring range of motion. Subjects were randomly assigned to one of four groups. Group 1x stretched once daily, group 2x stretched twice daily, group 3x stretched 3 times daily, and control group did not stretch. Subjects performed a single 30-second static stretch per session. Subjects stretched 5 days per week for 4 weeks. Pre and post measurements were taken. Forty-four college-age males (19.341 plus or minus 1.2 years, 1.793 plus or minus 6.6 cm, 79.594 plus or minus 14.451 kg) with no hamstring or low back injury history nor participation in a stretching program within the past 6 months volunteered for this study. Passive and active knee extension measurements were taken using a PVC apparatus to maintain 90 degree of hip flexion and an inclinometer attached at the tibial shaft below the tibial tuberosity to measure knee flexion. As expected, there were significant differences (p=.0001) between active (58.6 degree plus or minus 1.6) and passive stretches (65.7 degree plus or minus 1.4), and all stretch groups had significant increases (p=.0001) in pre- to post-program flexibility (1x = 11.5%, 2x = 12.7%, 3x = 9.7%). There was also a significant 3-way interaction for groups, type of stretch, and pre- to post measures (p=.05). Tukey post-hoc testing revealed several interesting significant differences in post-stretch results between the groups. For active range of motion there was no difference among 1x (62.96 degree plus or minus 3.1), 2x (61.87 degree plus or minus 2.99) and the control (61.72 degree plus or minus 3.0). However, the control, 1x, and 2x were greater than 3x (57.34 degree plus or minus 3.0). Passive range of motion demonstrated similar results with 1x (72.13 degree plus or minus 2.8), 2x (69.25 degree plus or minus 2.87), and the control (68.49 degree plus or minus 2.8) being greater than 3x (63.55 degree plus or minus 2.8). Additionally, 1x was greater than the control. Finally, an interesting feature of our data is that despite random assignment the treatment groups had significantly less range of motion than the control group at pretest (1x = 7.3%, 2x = 10.9%, 3x 15.6%). Thus, the data patterns suggest that stretching improved range of motion toward the control's level. Stretching once, twice, or three times per day for one 30-second stretch does improve hamstring range of motion. However, a program of stretching 3 times