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Published on: February 3, 2017
Glycogen utilization in rat respiratory muscles during intense running
H J Green1, M E Ball-Burnett, M A Morrissey
1Department of Kinesiology, University of Waterloo, Ont., Canada.
Heavy exercise significantly depletes muscle glycogen in rat respiratory and locomotor muscles. This indicates broad motor unit recruitment and highlights the role of aerobic metabolism in meeting energy demands during intense activity.
Area of Science:
- Exercise Physiology
- Muscle Metabolism
- Respiratory Physiology
Background:
- Muscle glycogen serves as a crucial energy substrate during physical activity.
- Understanding substrate utilization in respiratory muscles is key to comprehending exercise limitations.
Purpose of the Study:
- To investigate glycogen depletion patterns in rat respiratory and locomotor muscles after strenuous exercise.
- To determine the recruitment strategy of diaphragm and intercostal muscles during hyperpnea.
- To assess the role of glycogen as an energy source for respiratory muscles.
Main Methods:
- Adult rats underwent heavy treadmill exercise at 60 m/min with a 12-degree grade.
- Glycogen concentrations were measured in diaphragm, intercostal, and selected locomotor muscles.
- Lactate concentrations were analyzed to infer metabolic pathways.
Main Results:
- Significant glycogen reduction (39%) was observed in the costal diaphragm and most respiratory muscles.
- Glycogen loss occurred across various muscle fiber types (slow oxidative, fast oxidative glycolytic, fast glycolytic).
- Increased lactate levels in the costal diaphragm suggest a significant contribution of aerobic metabolism.
Conclusions:
- Heavy exercise recruits motor units throughout the diaphragm and intercostal muscles.
- Muscle glycogen is a vital substrate for energy demands during intense exercise in these muscles.
- Aerobic metabolism plays a substantial role in meeting ATP requirements, particularly in the costal diaphragm.
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