Diurnal variation of hamstring and lumbar flexibility.

This study assessed diurnal variation of hamstring and lumbar flexibility and also measured flexibility differences between men and women. Sixty-seven healthy, recreationally active college students (M=31 and F=36; age, M=22.9+/-3.5 and F=21.7+/-2.8 years old) participated. Hamstring and lumbar flexibility measurements were taken at waking (baseline measure) and every 2 hours through a 12-hour period using the active knee extension test and modified-modified Schober test. Hamstring flexibility (M: -53.1+/-2.3 degrees, F: -46.7+/-2.8 degrees) and lumbar flexion (M: 6.9+/-1.4 cm, F: 6.0+/-1.4 cm) were lowest at baseline. Hamstring flexibility was highest at the 12-hour time point (M: -48.6+/-2.7 degrees, F: -37.4+/-2.9 degrees), whereas lumbar flexion was highest at the 10-hour time point (M: 7.5+/-0.9 cm, F: 6.9+/-1.3 cm). Hamstring flexibility of the women was significantly greater at every time point than the men's (p<0.05). Lumbar flexibility for the men was significantly greater at every time point than women (p<0.05). Both sexes experienced similar increases in flexibility for hamstrings and lumbar spine over 12 hours. Findings of this study indicate that diurnal variation and gender differences in lumbar and hamstring flexibility should be considered and controlled for in flexibility testing, training, and research.