overload principle

A fundamental training principle which states that fitness improves only when workloads are greater than those normally encountered. The workload can be quantified in terms of training intensity (rate of doing work) or training volume (the total amount of work done). The principle applies to all aspects of fitness including strength, speed, and endurance of muscle contractions. It also applies to improvements in flexibility and the strength of bones, joints, and ligaments.

The overload principle is most easily demonstrated in weight training; the best results occur when a muscle performs at the maximal limits of its strength and endurance. See also progression.