Title: “Resistance Exercise as a Stimulus for the Repeated Bout Effect and the Contribution of the Extracellular Matrix”
Supervisor: Dr. Cameron Mitchell
Committee members: Dr. Don McKenzie, Dr. James Markworth
Abstract: Skeletal muscles responds to unaccustomed exercise by orchestrating an adaptive response to attenuate damage by future bouts of same or similar exercise. This intrinsic protective phenomenon is known as the repeated bout effect (RBE). Currently, the mechanisms underlying RBE has yet to be elucidated. There is evidence to suggest that the protective effect can be elicited by submaximal, nondamaging exercises. However, to our knowledge, no study has identified whether conventional resistance exercise training (RET) can confer a similar magnitude of protective effect. Moreover, the role of extracellular matrix (ECM) remodeling has been identified as one potential mechanism in the adaptation of the musculature and its microenvironment to mechanical stimuli. Considering the lack of knowledge underpinning the mechanisms behind RBE and recent discoveries emphasizing the importance of ECM dynamics in dictating this niche muscle environment, we hypothesize that RET preceding a damaging bout of exercise will mitigate indirect damage markers (e.g., Soreness and strength) and induce a RBE. Importantly, markers of ECM adaptations will be evident with an increase in growth factors (e.g., TGFb), collagen synthesis and degradation (e.g., MMPs), as well as glycoprotein levels (e.g., TN, FN). Using a unilateral design, 215 young healthy subjects will complete: 3 weeks of RET on the training leg (RET) [3 sets of 12 rep leg extensions twice a week, totaling 6 sessions], followed by two eccentric bouts separated by 21 days on both the trained and untrained (control) leg. The RET and control leg will be randomized. Following exercise, immunohistochemistry (e.g., FN, TN), magnetic bead multiplex (e.g., TGFb) and qPCR (e.g., Collagen, MMP-2 and -9) will be used to characterize differences in ECM expression. These findings will provide insights into how the ECM interacts to manifest RBE following exercise.