What is a possible outcome of a lack of activity according to the Reversibility Principle?

The correct choice highlights the concept of the Reversibility Principle, which states that fitness improvements are not permanent and can be lost over time if activity is not maintained. When an individual reduces or stops their physical activity, the body begins to revert to its baseline state, leading to a gradual decline in fitness levels. This decline can manifest in various ways, such as reductions in cardiovascular endurance, muscular strength, flexibility, and overall functional fitness.

This principle underscores the importance of consistency in physical activity for maintaining health and fitness. It also emphasizes that any gains made through exercise require ongoing effort to sustain, as the body will adapt to a lack of stimulation by decreasing its fitness levels over time.