Transverse forces in skeletal muscle with massage-like loading in a rabbit model

BACKGROUND The objective of this study was to quantify the transverse forces in skeletal muscle subjected to constant compressive massage-like loading (MLL) following eccentric exercise (ECC). METHODS Twenty-eight New Zealand White rabbits were used for this two-part study. For all testing, a customized electromechanical device was utilized to apply a constant compressive force MLL to the tibialis anterior (TA) muscle and the resultant transverse forces were quantified. The device consisted of two stepper motors that were positioned orthogonally to each other and connected to separate sliding tracks. A stainless steel cylindrical massage tip was mounted to a customized two-axis sensor consisting of two strain gauges with which forces along the two axes were measured. First, we determined the effects of tissue loading frequency and compression magnitude on transverse forces in the TA. Following a bout of ECC, sixteen rabbits were randomly assigned to a protocol with MLL frequency of 0.25 Hz or 0.5 Hz at a constant compressive force of 5 N or 10 N. Secondly, we utilized a protocol of 0.5 Hz, 10 N, 15 min MLL that was performed on 4 consecutive days commencing immediately post ECC (n = 6 animals) or 48 hours following ECC (n = 6 animals). Transverse forces were measured during all 4 MLL sessions for the entire 15 min duration for both the immediate and the delayed groups. RESULTS Both frequency and magnitude of compressive force due to MLL showed an effect on the magnitude of transverse force (p < 0.05 for each parameter). Furthermore, MLL beginning immediately following ECC produced higher transverse forces than MLL delayed by 48 hours with an average 20% difference between the two MLL groups over the four day protocol. Forces were higher in the middle 5 minutes compared to the first 5 minutes for all MLL bouts in both groups. CONCLUSIONS Frequency and magnitude of MLL and timing for delivery of MLL following ECC affect resultant transverse force values for exercised muscle. The application of our findings to humans receiving massage following exercise remains unknown at this time.