Which principle of training involves a gradual increase in training load?

The principle of training that involves a gradual increase in training load is known as progressive overload. This principle is fundamental in exercise training because it is essential for continued improvement in strength, endurance, and overall performance. By systematically increasing the demands placed on the body, such as increasing weights, duration, or intensity, athletes and individuals can stimulate adaptations that lead to improved physical fitness.

Progressive overload ensures that the body is constantly challenged, which promotes growth and adaptation of muscles, cardiovascular systems, and overall athletic performance. Without this gradual increase, the body can plateau in its performance, leading to stagnation. Thus, applying this principle appropriately allows for ongoing development and prevents the risk of injury that might occur from sudden increases in training intensity or volume.

In contrast, the other principles presented do not specifically focus on this systematic increment in training load. Specificity relates to training directly relevant to the desired outcome, variance involves changing up exercises to prevent boredom or plateaus, and maintenance refers to the level of training needed to maintain a certain level of fitness once it has been achieved.