One of the five health related components of fitness is flexibility. Flexibility relates to the ability to move a joint through it’s full range of motion (ROM). To develop a complete fitness program, you should take time to emphasize this component in your routine by stretching. Unfortunately, “...most people neglect flexibility training, limiting freedom of movement, physical and mental relaxation, release of muscle tension and soreness, and injury prevention.” (American Council on Exercise)
Flexibility is classified into two types: static and dynamic. Static flexibility is a measure of the limits of a joints overall range of motion. It’s measured by stretching and holding a joint in the position of it’s maximum range while using a measuring instrument to quantify that range. To achieve the maximum range, passive forces are required (force generated from an external source). Dynamic flexibility is a measure of overall joint stiffness during movement. Unlike static flexibility, dynamic flexibility requires active force production (your own muscles contracting). Because it’s difficult to quantify “stiffness,” dynamic flexibility is measured more subjectively. For example, how easy is it to swing a tennis racket, climb steps, or get in and out of a car? The target of any good stretching program is to improve static and dynamic flexibility so that normal ROM can be achieved. The term “normal” relates to population studies that have measured various areas of the body and established an average degree of movement for a particular joint.