Exercise-induced glycogen utilization by the respiratory muscles.

Area of Science:

• Exercise Physiology
• Muscle Metabolism

Background:

• Controversy exists regarding diaphragmatic glycogen utilization during exercise.
• Previous literature has suggested the diaphragm may not utilize glycogen during physical exertion.

Purpose of the Study:

• To investigate whether prolonged treadmill exercise significantly reduces glycogen concentration in respiratory muscles.
• To determine if the diaphragm, like other muscles, utilizes endogenous glycogen during submaximal endurance exercise.

Main Methods:

• Male Sprague-Dawley rats underwent prolonged treadmill exercise to exhaustion.
• Glycogen concentration in respiratory muscles (diaphragm, intercostals) and other muscles (heart, plantaris) was measured post-exercise.
• Periodic acid-Schiff (PAS) staining was used to assess glycogen in diaphragm fiber types.

Main Results:

• Prolonged exercise led to a significant reduction in glycogen concentration across multiple muscles.
• The diaphragm showed a 43% reduction in glycogen, similar to intercostal muscles (43%).
• Both Type I and Type II fibers in the diaphragm exhibited significant glycogen depletion.

Conclusions:

• Endogenous glycogen is utilized by muscles with diverse aerobic capacities during moderately intense submaximal endurance exercise.
• The costal diaphragm muscle does utilize glycogen during prolonged exercise, challenging recent suggestions otherwise.