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Training induced decrease in oxygen cost of cycling is accompanied by down-regulation of SERCA expression in human
J Majerczak1, J Karasinski, J A Zoladz
1Department of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Krakow, Poland.
Summary
Endurance training improves cycling efficiency by down-regulating sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) pumps, not by altering myosin heavy chain composition. This enhances maximal oxygen uptake and power output.
Area of Science:
- Exercise Physiology
- Muscle Biochemistry
Background:
- Endurance training enhances cycling performance.
- The underlying molecular mechanisms, particularly changes in muscle proteins and efficiency, require further elucidation.
Purpose of the Study:
- To investigate the effects of a 5-week cycling endurance training program on specific muscle proteins and cycling efficiency.
- To determine the relationship between changes in sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) isoforms, myosin heavy chain (MyHC) composition, and the oxygen uptake to power output ratio (VO2/PO).
Main Methods:
- Fifteen untrained men underwent a 5-week moderate-intensity cycling training program.
- Muscle biopsies of the vastus lateralis were analyzed for SERCA1, SERCA2, and MyHC expression before and after training.
- Incremental cycling tests were performed to assess maximal oxygen uptake (VO2max) and VO2/PO ratio.
Main Results:
- Training increased VO2max and the power output at VO2max.
- A significant decrease in the VO2/PO ratio was observed during submaximal and maximal cycling.
- Down-regulation of SERCA2 protein and a trend towards lower SERCA1 were noted, alongside decreased plasma thyroid hormone levels. MyHC composition remained unchanged.
Conclusions:
- The enhanced mechanical efficiency in cycling after initial endurance training is likely attributed to the down-regulation of SERCA pumps.
- Changes in MyHC composition are not the primary driver of improved cycling efficiency in the early stages of training.
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