Flexibility is defined by Gummerson as "the absolute range of movement in a joint or series of joints that is attainable in a momentary effort with the help of a partner or a piece of equipment." This definition tells us that flexibility is not something general but is specific to a particular joint or set of joints. In other words, it is a myth that some people are innately flexible throughout their entire body. Being flexible in one particular area or joint does not necessarily imply being flexible in another. Being "loose" in the upper body does not mean you will have a "loose" lower body. Furthermore, according to SynerStretch, flexibility in a joint is also "specific to the action performed at the joint (the ability to do front splits doesn't imply the ability to do side splits even though both actions occur at the hip)."

• Types of Flexibility
• Factors Limiting Flexibility
• Strength and Flexibility
• Overflexibility

Types of Flexibility

Many people are unaware of the fact that there are different types of flexibility. These different types of flexibility are grouped according to the various types of activities involved in athletic training. The ones which involve motion are called dynamic and the ones which do not are called static. The different types of flexibility (according to Kurz) are:

dynamic flexibility

 (also called kinetic flexibility)

static-active flexibility

 (also called active flexibility)

static-passive flexibility

(also called passive flexibility)

Research has shown that active flexibility is more closely related to the level of sports achievement than is passive flexibility. Active flexibility is harder to develop than passive flexibility (which is what most people think of as "flexibility"); not only does active flexibility require passive flexibility in order to assume an initial extended position, it also requires muscle strength to be able to hold and maintain that position.

Factors Limiting Flexibility

According to Gummerson, flexibility (he uses the term mobility) is affected by the following factors:

• Internal influences
  • the type of joint (some joints simply aren't meant to be flexible)
  • the internal resistance within a joint
  • bony structures which limit movement
  • the elasticity of muscle tissue (muscle tissue that is scarred due to a previous injury is not very elastic)
  • the elasticity of tendons and ligaments (ligaments do not stretch much and tendons should not stretch at all)
  • the elasticity of skin (skin actually has some degree of elasticity, but not much)
  • the ability of a muscle to relax and contract to achieve the greatest range of movement
  • the temperature of the joint and associated tissues (joints and muscles offer better flexibility at body temperatures that are 1 to 2 degrees higher than normal)
• External influences
  • the temperature of the place where one is training (a warmer temperature is more conducive to increased flexibility)
  • the time of day (most people are more flexible in the afternoon than in the morning, peaking from about 2:30pm-4pm)
  • the stage in the recovery process of a joint (or muscle) after injury (injured joints and muscles will usually offer a lesser degree of flexibility than healthy ones)
  • age (pre-adolescents are generally more flexible than adults)
  • gender (females are generally more flexible than males)
  • one's ability to perform a particular exercise (practice makes perfect)
  • one's commitment to achieving flexibility
  • the restrictions of any clothing or equipment

Some sources also the suggest that water is an important dietary element with regard to flexibility. Increased water intake is believed to contribute to increased mobility, as well as increased total body relaxation.

Rather than discuss each of these factors in significant detail as Gummerson does, I will attempt to focus on some of the more common factors which limit one's flexibility. According to SynerStretch, the most common factors are: bone structure, muscle mass, excess fatty tissue, and connective tissue (and, of course, physical injury or disability).

Depending on the type of joint involved and its present condition (is it healthy?), the bone structure of a particular joint places very noticeable limits on flexibility. This is a common way in which age can be a factor limiting flexibility since older joints tend not to be as healthy as younger ones.

Muscle mass can be a factor when the muscle is so heavily developed that it interferes with the ability to take the adjacent joints through their complete range of motion (for example, large hamstrings limit the ability to fully bend the knees). Excess fatty tissue imposes a similar restriction.

The majority of "flexibility" work should involve performing exercises designed to reduce the internal resistance offered by soft connective tissues (see section Connective Tissue). Most stretching exercises attempt to accomplish this goal and can be performed by almost anyone, regardless of age or gender