The document outlines several principles of physical activity and training:
1. The overload principle specifies that one must perform physical activity in greater than normal amounts to improve fitness or health.
2. The principle of progression indicates the need to gradually increase overload over time to achieve optimal benefits.
3. The principle of specificity states the need for specific exercises to improve specific fitness components or parts of the body.
4. The principle of reversibility notes that benefits from training are lost if overload is reduced through inactivity or injury.