The Skeletal Muscle MMP/TIMP System is Affected in Response to an Acute Bout of Plyometric Exercise and 12-weeks of Plyometric Exercise Training

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INTRODUCTION: Matrix metalloproteases (MMPs) play a critical role in skeletal muscle remodeling and adaptation through modulation of the inflammatory response, proteolysis of the extracellular matrix, and satellite cell activation. MMPs are regulated at several levels to include transcription and are inhibited by tissue inhibitors of metalloproteases (TIMPs). It is not known if training-induced skeletal muscle adaptation alters the response of the MMP/TIMP system to an acute bout of exercise. Furthermore, exercise training 2× vs. 1×/d may enhance skeletal muscle adaptation, subsequently altering the MMP/TIMP response. PURPOSE: To test the hypothesis that the MMP/TIMP system is responsive to exercise training and indicative of skeletal muscle adaptation, we assessed the impact of an acute bout of plyometric exercise on the MMP/TIMP system pre- and post- 12-weeks of plyometric training 2× vs. 1×/d. METHODS: Volunteers (9 men/9 women, 22±1 y) performed an acute exercise test (AET: 10 sets of 10 plyometric jumps, 40% 1RM). Muscle biopsies were obtained pre- and 10 and 120 min post-AET. Participants completed 12-weeks of non-linear periodized training of either 1×/d (n=8) or 2×/d (n=6) power exercise sessions (total volume equated) or were in a non-exercise control group (CON; n=4). Total RNA was isolated from muscle and analyzed for MMP-2, -3, -9, and TIMP-1 and -2 mRNA. RESULTS: Table 1 provides mRNA fold changes for MMPs and TIMPs post-AET at Baseline and after 12-weeks of training (or CON). At Baseline, the AET increased mRNA in all MMPs and TIMPs 120 min post- AET. After 12-weeks of training, in response to the AET, there was an attenuated MMP response in the exercise-trained groups, and a reduction in the TIMP response in all groups with the frequency of training affecting the magnitude of reduction. CONCLUSIONS: Plyometric exercise training for 12-weeks attenuates mRNA expression of the MMPs in response to an AET, indicating skeletal muscle adaptation. Further, a prior AET modulates mRNA expression of TIMP-2 120 min post-AET, suggesting TIMP-2 serves a role in adaptation to a novel acute exercise bout. Interestingly, TIMP-1 and TIMP-2 are affected by the frequency of exercise training, as is evident by the significant down regulation of mRNA expression 120 min post-AET in the 2×/d group after 12-weeks of training. These data support a role for the MMP/TIMP system in skeletal muscle adaptation to plyometric exercise training.Table 1: The MMP/TIMP mRNA Response to an AET pre- and post- Plyometric Exercise Training