What causes muscle burn during intense exercise?

The sensation of muscle burn during intense exercise is primarily caused by the buildup of acidity in muscle cells, which occurs as a result of anaerobic metabolism. When the body is subjected to high-intensity activities, it may require energy at a pace faster than oxygen can be delivered to the muscles. To meet these energy demands, muscles often resort to anaerobic glycolysis, which breaks down glucose without oxygen and produces lactic acid as a byproduct.

As lactic acid accumulates, it dissociates into lactate and hydrogen ions, leading to an increase in hydrogen ion concentration. This rise in acidity can lower the pH in muscle cells, contributing to that burning sensation. This physiological response is a signal that the muscles are under stress and working hard, indicating that they are nearing their capacity. Thus, the burning sensation serves as a reminder that the muscles are feeling the effects of fatigue due to increased acidity.

In contrast, while increased blood flow typically occurs during exercise to supply nutrients and oxygen to working muscles, it does not directly cause the burning sensation. Similarly, a decrease in oxygen supply can lead to anaerobic metabolism, but it is the resultant increase in acidity that specifically triggers the burn. Overstretching of muscles may lead to injury or