The total amount of effort expended in training. According to the overload principle of training, to improve physical fitness exercise must require more effort than usual. Improvements in flexibility are obtained only if muscles are stretched beyond their normal length; cardiovascular or aerobic fitness is gained only by elevating the heart rate above the normal range; and strength is increased only after training against resistances greater than normal (see repetition maximum). Although it is essential to ensure that the training intensity is high enough, it is equally important that the intensity is not so high there is a great risk of overuse injuries and overtraining (see progression). A number of methods are used to establish the training intensities which give maximum benefits (see training heart rate).
Subjects: Medicine and Health.