What substance is produced when athletes push their cells to use up O2?

When athletes push their cells to utilize oxygen during intense exercise, they may quickly reach a state where the demand for energy exceeds the oxygen supply available for aerobic respiration. Under these conditions, cells switch to anaerobic respiration, which occurs in the absence or insufficient level of oxygen.

In anaerobic respiration, glucose is partially broken down to produce energy. This process yields lactate (or lactic acid) as a byproduct. The production of lactate is a way for cells to continue to generate energy quickly when oxygen is limited. It effectively allows athletes to sustain performance for a short period, though the accumulation of lactate can lead to muscle fatigue and discomfort.

Understanding this biochemical pathway is essential in sports biology as it explains how athletes manage energy under physically demanding conditions and the physiological responses that accompany intense exercise.