NSCF Personal Trainer Complete Practice Exam

The protein-sparing mechanism is primarily dependent on the availability of carbohydrates to provide energy during exercise. When carbohydrate stores (glycogen) in the body are insufficient, the body begins to utilize protein for energy instead of sparing it for tissue repair or muscle building. This process occurs as the body seeks alternative fuel sources when its preferred source—carbohydrates—is not available.

During exercise, particularly when vigorous or prolonged, having adequate carbohydrates is crucial. If carbohydrate intake is inadequate, the body will start breaking down amino acids from protein to meet energy demands, effectively shutting off the protein-sparing mechanism. Hence, ensuring sufficient carbohydrate intake is essential for preserving muscle protein during physical activity.