Key result
Single-leg submaximal cycle training for 10 weeks reduced maximal Ca(2+)-ATPase activity by 19% (156 vs 192 micromol/g/min, P<0.05) compared to the untrained control leg.
Why the study?
Does single-leg submaximal cycle training alter sarcoplasmic reticulum Ca(2+)-regulatory proteins and processes in the vastus lateralis of untrained volunteers?
Does single-leg submaximal cycle training alter sarcoplasmic reticulum Ca(2+)-regulatory proteins and processes in the vastus lateralis of untrained volunteers?
Aerobic-based training downregulates SR Ca(2+) cycling in the vastus lateralis, driven by reductions in Ca(2+)-ATPase activity and SERCA1 protein levels.
Answers are grounded in this paper and cite their sources.
Aerobic training may downregulate SR Ca2+ cycling in untrained muscle; hypothesis-generating and should not yet change practice.
In this study, we employed single-leg submaximal cycle training, conducted over a 10-wk period, to investigate adaptations in sarcoplasmic reticulum (SR) Ca(2+)-regulatory proteins and processes of the vastus lateralis. During the final weeks, the untrained volunteers (age 21.4 +/- 0.3 yr; means +/- SE, n = 10) were exercising 5 times/wk and for 60 min/session. Analyses were performed on tissue extracted by needle biopsy approximately 4 days after the last training session. Compared with the control leg, the trained leg displayed a 19% reduction (P < 0.05) in homogenate maximal Ca(2+)-ATPase activity (192 +/- 11 vs. 156 +/- 18 micromol. g protein(-1). min(-1)), a 4.3% increase (P < 0.05) in pCa(50), defined as the Ca(2+) concentration at half-maximal activity (6.01 +/- 0.05 vs. 6.26 +/- 0.07), and no change in the Hill coefficient (1.75 +/- 0.15 vs. 1.76 +/- 0.21). Western blot analysis using monoclonal antibodies (7E6 and A52) revealed a 13% lower (P < 0.05) sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) 1 in trained vs. control in the absence of differences in SERCA2a. Training also resulted in an 18% lower (P < 0.05) SR Ca(2+) uptake and a 26% lower (P < 0.05) Ca(2+) release. It is concluded that a downregulation in SR Ca(2+) cycling in vastus lateralis occurs with aerobic-based training, which at least in the case of Ca(2+) uptake can be explained by reduction in Ca(2+)-ATPase activity and SERCA1 protein levels.
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Green et al. (2003) studied Healthy untrained volunteers (n=10). Single-leg submaximal cycle training vs. Control leg was evaluated on Homogenate maximal Ca(2+)-ATPase activity (micromol/g protein/min) (19% reduction, p=< 0.05). Single-leg submaximal cycle training for 10 weeks reduced maximal Ca(2+)-ATPase activity by 19% (156 vs 192 micromol/g/min, P<0.05) compared to the untrained control leg.
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