DISCUSSION
Our major finding was that statistically significant kneeextension range-of-motion gains of 6.80 and 5.60 were maintained at 1 and 3 minutes poststretching, respectively. The range-of-motion gains returned to the baseline by 6 minutes after stretching. The inability to maintain significant knee-extension angles beyond 3 minutes in our study suggests that a temporary creep effect occurred in which the viscoelastic component of the hamstrings was not deformed enough to produce a permanent change. With respect to the contractile component of muscle, Bohannon proposed that the inability of the hip joint to maintain significant flexion angles after hamstring stretching was due to temporary sarcomere lengthening. Temporary sarcomere lengthening may have occurred with our hamstring stretch subjects. Bohannon recorded 1 of 2 follow-up measurements in an elapsed time frame similar to that incorporated in our study. Over the course of 3 consecutive days of 8-minute passive loading, Bohannon recorded statistically significant (P < .01) maintained angles of hip flexion of 3.00 (day 1), 3.30 (day 2), and 2.90 (day 3) at 10 minutes postloading. Ten minutes after cessation of an 8-minute static stretch, Bohannon recorded a statistically significant (P < .01) maintained angle of hip flexion of 3.00. The return of knee extension in our study to baseline at 6 minutes is similar to the inability of the hip joint in Bohannon's study to maintain any significant increase 10 minutes after cessation of the stretch. Although the 2 studies differed in procedure, the results suggest that the hamstring complex (including the hip and knee joints) may require greater durations of stretch or increased stretching repetitions in order to create more permanent changes in its contractile and noncontractile components. The ability of the stretching protocol to increase the angle of knee extension 6.80 (at 1 minute) was slightly less than the 8.00 and 9.20 reported by Worrell et al, and Sullivan et al, respectively. However, our study reported similar results with fewer stretches. All 3 studies incorporated a prebaseline warm-up, used the AKE test to measure knee joint range of motion, and had subjects perform a static stretching protocol in an upright position. The differences in the angle of knee extension at 1 minute recorded by Worrell et al and Sullivan et al may be the result of the number of stretches: 48 total stretches (15 stretching sessions performed over a 3-week period) and 48 total stretches (8 stretching sessions performed over a 2-week period), respectively. The effect of the repeated AKEs produced a 6.0° increase in the angle of knee extension when comparing the first (129.20 + 12.30) with the sixth (135.10 12.40) extension. This increase in the angle of knee extension may be due to reciprocal inhibition of the hamstrings, resulting in their relaxation and subsequent stretch from the quadriceps contraction used to extend the lower leg. Postbaseline measurements of the control group suggest that this knee-extension angle increase was only temporary, which may reflect a temporary increase in sarcomere lengthening and a temporary creep effect. Finally, the control group had decreased knee extension 6 minutes after the baseline measure (3-minute measurement interval plus 3 minutes of lying quietly) and continued to decline through the 30-minute measure. This phenomenon also occurred in the stretch group. The Table reveals that the knee extension had decreased to baseline 6 minutes poststretching and continued to decrease. We speculate that, had the measurements continued beyond 30 minutes, the stretch group's knee extension also would have decreased below baseline. The exact reason for this is not known. However, it may represent an increase in muscle viscosity produced during the quiet lying. Most likely, if muscle viscosity had increased, it was due to a decrease in muscle temperature. We placed no restrictions on a subject's activity before beginning data collection, nor did we wait a specified time before taking measures. Thus, it is likely that the muscle was in a relatively warm state at the beginning of data collection and cooled as the expe iment progressed.