The acute effect of stretching on eccentrically-damaged muscle: Analysis of differences between Hold relax stretching and modified PNF stretching

Abstract

It is well known that eccentric exercise induces muscle damage that is characterized by a prolonged decrease in muscle strength and range of motion, development of delayed onset muscle soreness. The previous studies showed that hold-relax stretching (HRS) was effective for improving the decreases in range of motion and muscle soreness. In addition, modified proprioceptive neuromuscular facilitation stretching (mPNF) was an equally effective for HRS. However, it was unclear whether there are differences between acute effects of HRS and mPNF on muscle strength and muscle soreness in eccentrically damaged muscle. Therefore, the present study aimed to compare the acute effects of HRS with those of mPNF on muscle strength and soreness in eccentrically damaged muscle. The participants comprised 40 volunteers randomly assigned to either the HRS group (N = 20) or the mPNF group (N = 20). Initially, the participants of both groups performed 60 maximal eccentric contractions of the knee extensors. Two days after this exercise, each group performed either HRS or mPNF for 60 s at a time and repeated them six times for a total of 360 s. Muscle strength and soreness during stretching and contraction were measured before and immediately after HRS and mPNF. The results showed that the muscle soreness observed after eccentric contraction significantly decreased immediately after both HRS and mPNF. In addition, there were no significant changes in muscle strength immediately after both HRS and mPNF. These results suggest that while both HRS and mPNF can effectively decrease muscle soreness without reducing performance.