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Related Experiment Video

Updated: Jul 25, 2026

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling

Assessment of Myofilament Ca²⁺ Sensitivity Underlying Cardiac Excitation-contraction Coupling

Published on: August 1, 2016

Altered sarcoplasmic reticulum function in rat diaphragm after high-intensity exercise.

S Matsunaga¹, S Inashima, H Tsuchimochi

¹Institute of Health Sciences and Physical Education, Osaka City University, Osaka-shi, Osaka, Japan.

Acta Physiologica Scandinavica

|October 24, 2002

Summary

Acute high-intensity exercise impairs sarcoplasmic reticulum (SR) function in the diaphragm. This reduced SR Ca(2+) handling and Ca(2+)-ATPase activity may decrease exercise tolerance.

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Area of Science:

Exercise Physiology
Skeletal Muscle Biology
Cellular Physiology

Background:

Sarcoplasmic reticulum (SR) plays a crucial role in skeletal muscle excitation-contraction coupling by regulating intracellular calcium (Ca2+).
Previous studies have indicated that high-intensity exercise affects SR function in locomotor muscles.

Purpose of the Study:

To investigate the impact of acute high-intensity exercise on Ca2+ handling and Ca2+-adenosine triphosphatase (ATPase) activity of the SR in the rat costal diaphragm.
To determine if diaphragm SR function is similarly affected by exhaustive exercise as observed in limb muscles.

Main Methods:

Rats underwent treadmill exercise at 100% maximal O2 consumption until fatigue.
Sarcoplasmic reticulum (SR) Ca2+ uptake and release rates were measured using the Ca2+ fluorescent dye indo-1.
SR Ca2+-ATPase activity was assessed in muscle homogenates.

Main Results:

Exercise significantly increased muscle lactate and inorganic phosphate levels.
SR Ca2+ uptake and release rates were significantly reduced by 24% and 22%, respectively.
SR Ca2+-ATPase activity decreased, correlating with the reduced Ca2+ uptake.

Conclusions:

Acute high-intensity exercise attenuates SR function in the diaphragm, similar to findings in locomotor muscles.
Impaired SR function in the diaphragm may contribute to reduced exercise tolerance and performance during strenuous physical activity.