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Featured Experiment

AntagonisticMuscles and Range of Motion ~ Flexibility Training

Bodyparts are moved in different directions by muscles that act on the samebone from different directions. A simple example is the movement of theforearm. When the biceps muscle contracts, the forearm and the handmove toward the shoulder in a motion called flexion. When the tricepsmuscle contracts, the forearm and hand move away from the shoulder in amotion called extension. Since these two muscles move the forearm indifferent directions, they are antagonistic muscles.

Range of motion (ROM), or flexibility, is the ability to move bodyparts through their normal range of motion on an axis. Movement can belimited by the connective tissue covering the muscles and by thetendons that link the muscles to bone. The American College of SportsMedicine has specific guidelines for flexibility training and theability to increase the range of motion in joints for the generalpublic. These guidelines state:
  • Stretch at least twice a week,preferably after warming up.
  • Do 1-3 stretches for eachmuscle group and hold each stretch position for 15 to 30 seconds.
  • Avoid“bounce stretching” because it can increasestiffness andis potentially harmful (it can lead to tearing of ligaments ortendons).
However,maximal flexibility of a moveable joint may NOT be best. Manyresearchers use the term "optimal" flexibility, implying that too muchor too little flexibility are both potentially harmful. There is a“window” of flexibility at which the joint isfunctioningoptimally. Physical therapists and athletic trainers use“optimal” flexibility data to determine range ofmotion andflexibility in a specific joint.

Also, as individuals age there is usually a decrease in physicalactivity which causes tissues to lose their elasticity. Connectivetissues increase around skeletal muscles (fibrosis) and they developmore cross-linkages. These changes in connective tissue make olderindividuals more prone to stiffness. In these cases, stretching andflexibility exercises may reduce pain & discomfort and extendormaintain a person's normal, comfortable range of motion. Maintainingflexibility becomes more challenging with age, but loss of flexibilitycan severely impair normal range of motion in older individuals,leading to disability.
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