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.
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.
Conversely, decreased use of the muscle results in incremental loss of mass and strength, known as muscular atrophy (see atrophy and muscle atrophy). Sedentary people often lose a pound or more of muscle annually.
The loss of 10 pounds of muscle per decade is one consequence of a sedentary lifestyle. The adaptive processes of the human body will only respond if continually called upon to exert greater force to meet higher physiological demands.
In order to minimize injury and maximize results, the novice begins at a comfortable level of muscular intensity and advances towards overload of the muscles over the course of the exercise program. Progressive overload requires a gradual increase in volume, intensity, frequency or time in order to achieve the targeted goal of the user. In this context, volume and intensity are defined as follows:
- Volume is the total number of repetitions multiplied by the resistance used as performed in specific periods of time.
- Intensity is the percent value of maximal functional capacity, or expressed as percent repetition maximum.
This technique results in greater gains in physical strength and muscular growth, but there are limits. An excess of training stimuli can lead to the problem of overtraining. Overtraining is the decline in training performance over the course of a training program, often increasing the risk of illness or injury or decreased desire to exercise. In order to help avoid this problem, the technique of periodization is applied. Periodization in the context of fitness or strength training programs is the scheduling of provisions for adequate recovery time between training sessions, variety over the course of a long-term program and motivation - avoiding monotony when repeating identical exercise routines.
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