Investigating the Mechanisms Underlying Remote Myofascial Release on Hamstring Flexibility

Fascia connects adjacent muscles to create a body-wide network, allowing manipulation of one segment to affect a distal body segment. Research has shown that performing a bout of self-myofascial release (SMR) on the plantar fascia with a foam rolling device acutely increases hamstring flexibility. Thus far, there has been no research examining the mechanism of action underlying this effect, although it is hypothesized to occur due to an interaction of mechanical, neural, and physiological factors. The purpose of this study is to examine the acute effects of a bout of SMR on the plantar fascia on hamstring stiffness, flexibility, hydration, and joint position sense (JPS). Seventeen healthy postmenopausal participants were recruited for this repeated measures study. A myotonometer measured biceps femoris stiffness, bioelectrical impedance (BIA) was used to estimate total body water concentrations, a JPS test was administered to assess proprioception, and a passive straight leg raise (PSLR) test measured hamstring flexibility in a foam rolling condition (FR) and a no-foam rolling condition (NFR). Results from separate repeated-measures ANOVA tests revealed a significant interaction for condition and time for both stiffness (p < 0.001, η2p = 0.543) and flexibility (p < 0.001, η2p = 0.564). There were no significant interactions or main effects for JPS and BIA measurements. The increase in hamstring flexibility aligns with previous findings. The significant increase in hamstring stiffness was unexpected, warranting further research into the contractile activity of myofibroblasts.