Daniel Frankl, Ph.D., CSU Los Angeles

Muscular Flexibility I. Flexibility Defined

a. Static flexibility is defined as "the range of motion about a joint."
b. Dynamic flexibility is defined as "the resistance of a joint to motion."

Anatomical Limitations of Flexibility

  • Bony Structures (e.g., elbow, shoulder, knee...).
  • Soft Tissue Structures (e.g., muscles, connective tissue, skin, tendons, adipose tissue).

Physiological Basis of Flexibility

1. Stretch (myotic) Reflex

The myotic reflex results from a stimulation of the muscle spindle, a sensor located inside the muscle that relays information to the CNS concerning the the number of motor units needed to be activated to counter a stretching force acting on the muscle. A dynamic or ballistic stretch triggers the muscle spindle. The myotic reflex is inhibited when the muscle is stretched statically. A second organism, the Golgi Tendon Organ counters the muscle spindle during static stretching and thus protects the muscle from severe injury. Increased core muscle temperatures delay the onset of the myotic reflex and thus act as a protective mechanism against injury. Therefore, (1) always warm-up before engaging in heavy stretching, and (2) engage in static rather than ballistic streching exercises.
2. Reciprocal Inhibition
A neuromuscular function that relaxes (inhibits) the antagonist muscle during contraction of the agonist muscle. The P.N.F. (Proprioceptive Neuromuscular Facilitation) technique of flexibility exercises is based on this principle. A dysfunction of the reciprocal inhibition system leads to a simultaneous contraction of two opposing muscle groups and result in muscle injury.
3. Specificity of Flexibility
  • Different joints exhibit different levels of flexibility.
  • Articulations (flexion, extension, adduction, abduction, rotation...) within a joint exhibit different levels of flexibility.
  • Patterns of flexibility mimic the unique patterns of specific repetitive movements (e.g., typical flexibility as measured on a dancer versus a sprinter).

Factors Affecting Flexibility

  • Heredity
  • Age
  • Gender
  • Mode and level of activity
  • Internal Tissue Temperature
  • Injury (scar tissue, altered bony structure)
  • Pain (increases muscle spasm).
Muscular Flexibility and Health-Related fitness
1. Maintenance of range of motion prevents or relieves joint pain which accompany aging.
2. A greater range of motion prevents injury and soreness.
Muscular Flexibility and Sport Related fitness
1. Increase in range of motion.
2. Flexibility permits ease and grace in movement.
3. Increase in efficiency of movement (saves energy)
Hazards of flexibility
  • Hypermobility and lack of stability in joints (ankle, shoulder, knee...)

II. The Assessment of Flexibility

Health Related Tests

1. Modified Sit-and-Reach Test
2. Total Body Rotation Test
3. Shoulder Rotation Test

Sport Related Tests
III. Methods and Guidelines for Flexibility Prescription
A. The Warm-Up
B. Static or slow-sustained stretching
C. Dynamic or ballistic stretching
D. Proprioceptive neuromuscular facilitation (P.N.F.)
IV. LABS 1. LAB 5-1 -- Assessing Your Current Level of Flexibility (p. 123-128).
2. LAB 5-2 -- Creating a Personalized Program for Developing Flexibility (pp. 129-130).


1. Corbin, C.B. & Noble, L. (1980). Flexibility--A major component of physical fitness, JOPER, June, pp. 23-27.
2. Cornelius, L.W. (1981). Two effective flexibility methods, Athletic Training, Spring, pp. 23-25.
3. PE 150 text.
Copyrightę 1996-99, Daniel Frankl, Ph.D.
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