Muscles

When muscle strength is obtained trough resistance exercises that do not use the full range of motion, the muscle tissue shortens and limits flexibility.

Connective Tissues

• joint capsule
• ligaments
• tendons
• skin
• adipose tissue (fat)

Physiological basis of flexibility

Stretch (myotic) reflex

The myotic reflex is a direct result of stimulation of the muscle spindle, which sends information to the central nervous system concerning the degree of stretch upon the involved muscle and the exact number of motor units needed to contract in order to overcome stretch. When a muscle is ballistically stretched, it responds with a contraction whose amount and rate vary directly with those of the causative stretch. When a muscle is statically stretched, this reflex is inhibited. This inhibition is initiated by the Golgi Tendon Organ, as a protective mechanism to avoid injury. (Image source: www.accessexcellence.com/AB/GG/collagen_Elastin.html; cited from: essentialcellbiology.com)

Reciprocal inhibition

This is a neuromuscular function that inhibits (relaxes) one set of muscles when the antagonist (opposing muscles) are contracting (proprioceptive neuromuscular facilitation--P.N.F--is based on this function). When this mechanism dysfunctions, with both agonists and antagonists contracting simultaneously a muscle strain (torn fibers and spasm) result.

Specificity of flexibility

• Flexibility varies considerably between the different joints of the body.
• Flexibility varies considerably between articulations within the same joint (articulations are the different movements of the joint: flexion, extension, adduction, abduction, rotation).
• c. Continuous participation in a particular activity will result in a unique pattern of flexibility, due to the mechanics of joint and tissue stress inherent in the activity. In other words, most goalies or most defenders (etc.) will tend to be flexible in the same ways.

• Age -- decrease in the extensibility of soft tissue with aging is related to diminished range of movement as we grow older, independent of gender (decrease in flexibility can be significantly slowed down if we keep active).
• Gender -- females exhibit a greater range of movement, independent of age.
• Activity -- active individuals exhibit a greater range of movement than sedentary individuals (so keep active!). Also, inactivity is strongly associated with increased adipose tissue which decreases flexibility.
• Internal Tissue Temperature -- changes in internal muscular temperature may increase or decrease the range of motion by as much as 20 percent (so always "warm-up" first!).
• Heredity -- appears to be joint specific (this notion needs more scientific proof, however).
• Injury -- scar tissue resulting from injury hinders the range of motion in a joint.
• Pain -- as pain increases, muscle spasm results and, therefore, flexibility is decreased. * Strength training does not decrease flexibility unless you do the exercise unproperly and not in the full range of motion.

• Maintenance of range of motion prevents or relieves joint pain which accompany aging.
• A greater range of motion prevents injury and saves energy.
• Flexibility permits ease and grace in movement.

• Static or slow-sustained stretching -- a steady position which elongates, muscles, tendons, ligaments, and fasciae.
• Dynamic or ballistic stretching -- a bobbing, bouncing movement, involving muscular contraction, which moves into and out of an elongated position.
• Proprioceptive Neuromuscular Facilitation (P.N.F.) a maximal contraction of the muscles to be stretched followed by relaxation of that same muscle and progressive stretching of it. The maximal isometric contraction helps in the relaxation of the muscle to be stretched which allows for more lengthening of the muscle. While the P.N.F. is believed to be the most effective flexibility development method, its drawbacks are a need of a helper, a longer period of time, and a higher degree of pain for success.

• In ballistic movement, there is a danger of exceeding the extensibility limits of involved tissue, thereby causing injury.
• Static stretching promotes muscle relaxation by reducing sensory activity and muscle spindle tension.
• Ballistic stretching tends to elicit pain and soreness both during and after exercise.
• Static stretching is just as effective as ballistic stretching in producing gains in range of motion.
• Ballistic stretching elicits the stretch reflex, which contracts the muscle. SO DON'T BOUNCE--JUST "HANG" AND RELAX IN A STRETCHED POSITION.

Why should one always first warm-up before stretching?