Passive Stiffness and Maximal and Explosive Strength Responses After an Acute Bout of Constant-Tension Stretching.

CONTEXT

Constant-tension (CT) stretching has been used to reduce hamstrings passive stiffness; however, the time course of hamstrings stiffness responses during a short bout of this type of stretching and the effects on maximal and explosive strength remain unclear.

OBJECTIVE

To examine the time course of hamstrings passive-stiffness responses during a short, practical bout of manual straight-legged-raise (SLR) CT passive stretches and their effects on maximal and explosive strength in healthy young women.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Eleven healthy women (age = 24 ± 4 years, height = 167 ± 4 cm, mass = 65 ± 8 kg) participated.

INTERVENTION(S): Participants underwent four 15-second SLR CT passive stretches of the hamstrings.

MAIN OUTCOME MEASUREMENT(S): Hamstrings passive stiffness was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curves generated before and after the stretching intervention and at the beginning of each 15-second stretch. Hamstrings peak torque and rate of torque development were derived from maximal voluntary isometric contractions performed before and after the stretching intervention.

RESULTS

The slope coefficients (collapsed across phase) for the third and fourth stretches and the poststretching assessment were lower than the prestretching assessment ( range = .004-.04), but they were not different from each other ( > .99). In addition, no differences in peak torque ( = -0.375, = .72) or rate of torque development ( = -0.423, = .68) were observed between prestretching and poststretching.

CONCLUSIONS

A short bout of SLR CT passive stretching may effectively reduce hamstrings stiffness without negatively influencing maximal and explosive strength.