Specific training improves skeletal muscle mitochondrial calcium homeostasis after eccentric exercise

Area of Science:

• Exercise Physiology
• Mitochondrial Biology
• Muscle Adaptation

Background:

• The repeat bout effect describes muscle adaptation to exercise, but mitochondrial responses remain unclear.
• Eccentric exercise can disrupt mitochondrial calcium homeostasis and respiratory function.
• Understanding these adaptations is crucial for optimizing training protocols.

Purpose of the Study:

• To investigate the effects of downhill exercise training on mitochondrial calcium content (MCC) and respiratory function after acute eccentric exercise.
• To examine the role of calpain activity and heat shock protein 72 (HSP72) in mediating these adaptations.
• To determine if prior training mitigates exercise-induced mitochondrial dysfunction.

Main Methods:

• Thirty-four rats were divided into control and trained groups, subjected to downhill treadmill running.
• An acute bout of eccentric exercise was performed two weeks post-training.
• Mitochondrial respiratory function, MCC, calpain activity, and HSP72 expression were measured post-exercise.

Main Results:

• Acute eccentric exercise significantly increased MCC in untrained rats but not in trained rats.
• Mitochondrial respiratory function was slightly depressed in untrained rats post-exercise, but remained stable in trained rats.
• Prior training reduced calpain activity and HSP72 upregulation following eccentric exercise.

Conclusions:

• Downhill exercise training improves mitochondrial calcium homeostasis and stabilizes respiratory function after prolonged eccentric exercise.
• These protective effects are associated with attenuated calpain activity and HSP72 response.
• The findings highlight the benefits of training for mitigating exercise-induced mitochondrial stress.