At what point does cardiovascular endurance begin to reduce after cessation of training?

Cardiovascular endurance begins to diminish after a period of inactivity due to the body's physiological adaptations to aerobic training. Research indicates that after about two weeks of reduced or no training, significant declines in cardiovascular fitness can be observed. This decline is associated with a decrease in blood plasma volume, reduced cardiac output, and a decline in the efficiency of the cardiovascular system.

During the initial days of ceasing exercise, while some performance decreases may be noticed, the more pronounced reductions in endurance typically commence after approximately two weeks. This is because the body starts to revert to its pre-training state as the adaptations gained from regular cardiovascular exercise begin to regress. Consequently, two weeks serves as a significant marker in the timeline of cardiovascular endurance loss following the cessation of training.