What best illustrates the fitness training principle of progressive overload in a personal fitness plan?

The principle of progressive overload is fundamental in fitness training, emphasizing the necessity of gradually increasing the demands placed on the body to improve strength, endurance, and overall fitness. This principle is illustrated by the practice of gradually increasing the intensity or duration of exercise sessions. By doing so, individuals push their bodies beyond their current capacities, leading to adaptations that enhance muscle strength, cardiovascular fitness, and stamina.

In a personal fitness plan, this might involve incrementally increasing the amount of weight lifted, the distance run, or the duration of workouts. Such gradual increases help to prevent injury while encouraging continuous improvement and progression in fitness levels. The other choices do not support the principle of progressive overload: maintaining a consistent exercise routine without changes does not challenge the body; focusing exclusively on one type of exercise can lead to plateaus and imbalances; and solely monitoring weight without adjusting exercise does not actively promote overload or improvement in fitness.