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Enhanced sarcoplasmic reticulum Ca(2+) release following intermittent sprint training
N Ortenblad1, P K Lunde, K Levin
1Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense University, 5230 Odense M, Denmark. niels.ortenblad@agrsci.dk
Summary
High-intensity intermittent sprint training enhances peak calcium release from the sarcoplasmic reticulum (SR) in muscles. This occurs due to increased SR volume, not altered muscle calcium uptake or ATPase capacity.
Area of Science:
- Exercise Physiology
- Muscle Biology
- Cellular Physiology
Background:
- Sarcoplasmic reticulum (SR) plays a crucial role in muscle contraction and relaxation by regulating intracellular calcium (Ca2+).
- Understanding how exercise training affects SR function is vital for optimizing athletic performance and muscle adaptation.
Purpose of the Study:
- To investigate the impact of high-intensity intermittent sprint training on the function of the sarcoplasmic reticulum in young men.
- To determine changes in Ca2+ release, uptake, and Ca2+-ATPase activity within the SR following a 5-week training intervention.
Main Methods:
- Nine young men underwent a 5-week high-intensity intermittent bicycle training program, with six participants serving as controls.
- Muscle biopsies from the vastus lateralis were analyzed before and after the training period to assess SR function, including Ca2+ release rates and Ca2+-ATPase activity.
Main Results:
- Intermittent sprint performance improved by 12% post-training.
- Peak Ca2+ release rate from the SR significantly increased by approximately 9% after training (P < 0.05).
- While the relative density of ryanodine receptors (RyR) remained unchanged, the total number of RyR increased by 48% (P < 0.05), suggesting an increased SR volume. Ca2+ uptake and Ca2+-ATPase capacity showed no significant changes, despite increased SERCA1 and SERCA2 isoform density.
Conclusions:
- High-intensity intermittent training enhances peak SR Ca2+ release, primarily due to an expansion of the SR volume.
- The capacity for SR Ca2+ sequestration and the activity of Ca2+-ATPase are not significantly altered by this type of training.
- These findings suggest a specific adaptation of SR Ca2+ handling mechanisms that favors release rather than uptake following intense sprint exercise.