What principle suggests that improvements in fitness and performance come from gradually increasing the stress placed on the body?

The principle of progressive overload is fundamental to improving fitness and performance in any exercise regimen. It entails the concept that for the body to continue making gains in strength, endurance, or overall fitness, the intensity, volume, or frequency of exercise must be gradually increased over time. This gradual increase forces the body to adapt to higher levels of stress, leading to improvements in physical capabilities.

When new stress is introduced, such as lifting heavier weights or increasing the duration of aerobic activities, the body responds by adapting to these challenges. This process can involve muscle hypertrophy (growth), increased cardiovascular efficiency, and improved neuromuscular coordination. The consistent application of progressive overload ensures that the body does not plateau and continues to enhance its fitness levels.

Other principles, such as specificity, refer to the idea that training adaptations are specific to the type of exercise performed, and adaptation describes the body's response to exercise in general. Reversibility indicates that fitness gains can be lost if training ceases. While these concepts are important in understanding training, they do not focus specifically on the need to continuously increase exercise stress like progressive overload does. Hence, the principle of progressive overload is crucial for sustained improvements in physical performance and fitness.