In fitness, what does the term "overload" refer to?

The term "overload" in the context of fitness refers to the principle of applying more stress than the body is accustomed to in order to promote adaptation and improvement in performance. When athletes or individuals engage in training that exceeds their current physical capabilities, it compels the body to adapt by increasing strength, endurance, or overall fitness levels. This is foundational in program design, as progressively increasing the demands on the body—through greater weight, longer durations, or higher intensity—stimulates physiological changes necessary for improvement.

The concept emphasizes that to see gains in fitness, one must consistently challenge the body beyond its current limits. Sticking to the same routine or training less than required does not provide the necessary stimulus for adaptation, while training at a high intensity alone doesn’t encompass the full scope of the overload principle, which focuses on systematically increasing stress over time.