Changes in force and stiffness after static stretching of eccentrically-damaged hamstrings.

PURPOSE

This study compared responses to static stretching between eccentrically damaged and non-damaged muscles.

METHODS

Twelve young men performed 60 maximum knee flexor eccentric contractions of one leg, and received a 300-s continuous passive static stretching at tolerable intensity without pain to both knee flexors at 2 and 4 days after the eccentric exercise. Range of motion (ROM) and passive stiffness during knee extension, passive torque at onset of pain (PT), maximum voluntary isometric (MVC-ISO) and isokinetic concentric contraction torque (MVC-CON), and visual analogue scale (VAS) for muscle soreness were measured before, immediately after, 60 min, 2 and 4 days after exercise as well as before, immediately after, 20 and 60 min after the stretching. Changes in these variables after eccentric exercise and stretching were compared between limbs.

RESULTS

The eccentric exercise decreased MVC-ISO, MVC-CON, ROM and PT, and increased passive stiffness and VAS (p < 0.05), suggesting that muscle damage was induced to the knee flexors. ROM and PT increased after stretching for both limbs; however, the magnitude of the increase was greater (p < 0.05) for the damaged than non-damaged limb. Passive stiffness decreased for both limbs similarly (4-7 %) at immediately after stretching (p < 0.05). Significant decreases in MVC-ISO torque (7-11 %) after stretching were observed only for the non-damaged limb (p < 0.05), but MVC-CON torque did not change after stretching for both limbs. VAS decreased for the exercised limb after stretching (p < 0.05).

CONCLUSIONS

These results suggest that the static stretching at tolerable intensity without pain produced greater positive effects on damaged than non-damaged muscles.