Acute local and non-local morphological, sensory and fluid responses to stretching and foam rolling in young females

Background: This study aimed to compare and examine the local and non-local effects of a foam rolling (FR) and static stretching (SS) intervention applied to the plantar flexor (PF). Methods: Fourteen female participants were investigated. Each participant underwent three conditions in a random order at least 48h apart and at the same time of the day: Control (CC), SS, and FR. Each condition was performed unilaterally in the dominant PF for 4 sets (apart from CC). SS was performed for 30 s. The FR included 30 rolls (15 in each direction) over a period of 30 s. A rest of 30 s was provided between each set for all conditions. Outcome variables were ankle dorsiflexion range of movement (ROM), tissue hardness, localized bioimpedance analysis at 50 kHz (L-BIA), and pain pressure thresholds (PPT). Tissue hardness, L-BIA, and PPT were measured in the lower leg and thigh. Measures were assessed pre (T0), immediately post (T1), and 10-min after (T2) the intervention. Results: No differences were found for time for the CC or between the T0 of each condition. Concerning the lower leg, ROM improved for SS and FR from T0 to T1 while returning to baseline in T2. A significant increase in PPT was observed only for SS in T1. L-BIA showed a significant increase for both phase angle and impedance only for FR in T1. Tissue hardness did not change for any group at any time-point. Concerning the thigh, no measure at any time point showed significant differences. Conclusion: Both, FR and SS were able to acutely improve ankle ROM. The observed changes were probably caused by a change in viscoelastic properties and local pain perception, without any variation in tissue morphology. FR was the only intervention to improve the intracellular-to-extracellular ratio and decrease fluids. Non-local effects were not observed.