Extensive activation of which of the following energy systems is associated with lactate accumulation in the muscle?

The extensive activation associated with lactate accumulation in the muscle primarily occurs during fast glycolysis. This energy system is utilized during high-intensity exercise where the demand for energy exceeds the immediate supply available from the phosphagen system. As the rate of energy production increases, glucose is metabolized rapidly through glycolysis, leading to the production of pyruvate.

When exercise intensity is high, the oxygen supply to the muscles may not be sufficient for aerobic metabolism to keep up with energy demands. Consequently, pyruvate is converted to lactate instead of entering the aerobic pathway. This conversion allows for the regeneration of NAD+, which is necessary for glycolysis to continue producing ATP in the absence of sufficient oxygen. The accumulation of lactate occurs as a byproduct of this process, particularly when fast glycolysis is heavily stressed.

In contrast, while other energy systems such as the phosphagen and aerobic metabolism contribute to energy production, they do not lead to significant lactate accumulation under normal circumstances. The phosphagen system operates anaerobically for very short durations, while aerobic metabolism relies on oxygen and does not produce lactate. Slow glycolysis also primarily contributes to energy production without resulting in significant lactate buildup, as it is more efficient and operates at lower intensities where