Progressive overload
Progressive overload is the gradual increase of stress placed upon the body during exercise training.
It was developed by Thomas Delorme, M.D. while he rehabilitated soldiers after World War II. The technique is recognized as a fundamental principle for success in various forms of strength training programs including fitness training, weight lifting, high intensity training and physical therapy programs.
Scientific principles
A common goal for strength-training programs is to increase or to maintain one's physical strength or muscle mass. In order to achieve more strength, as opposed to maintaining current strength capacity, muscles (see skeletal muscles) need to be stressed in such a way that triggers the body's natural, adaptive response to new demands placed on it.
Progressive overload not only stimulates muscle hypertrophy, but it also stimulates the development of stronger and denser bones, ligaments, tendons and cartilage. Progressive overload also incrementally increases blood flow to exercised regions of the body and stimulates more responsive nerve connections between the brain and the muscles involved.