Making Physiology Happen


March 2018: Antagonistic Muscles and Range of Motion ~ Flexibility Training

iWorx Systems, Inc.
First Name:
Last Name:
Featured Experiment

Antagonistic Muscles and Range of Motion ~ Flexibility Training

Body parts are moved in different directions by muscles that act on the same bone from different directions. A simple example is the movement of the forearm. When the biceps muscle contracts, the forearm and the hand move toward the shoulder in a motion called flexion. When the triceps muscle contracts, the forearm and hand move away from the shoulder in a motion called extension. Since these two muscles move the forearm in different directions, they are antagonistic muscles.

Range of motion (ROM), or flexibility, is the ability to move body parts through their normal range of motion on an axis. Movement can be limited by the connective tissue covering the muscles and by the tendons that link the muscles to bone. The American College of Sports Medicine has specific guidelines for flexibility training and the ability to increase the range of motion in joints for the general public. These guidelines state:
  • Stretch at least twice a week, preferably after warming up.
  • Do 1-3 stretches for each muscle group and hold each stretch position for 15 to 30 seconds.
  • Avoid “bounce stretching” because it can increase stiffness and is potentially harmful (it can lead to tearing of ligaments or tendons).
However, maximal flexibility of a moveable joint may NOT be best. Many researchers use the term "optimal" flexibility, implying that too much or too little flexibility are both potentially harmful. There is a “window” of flexibility at which the joint is functioning optimally. Physical therapists and athletic trainers use “optimal” flexibility data to determine range of motion and flexibility in a specific joint.

Also, as individuals age there is usually a decrease in physical activity which causes tissues to lose their elasticity. Connective tissues increase around skeletal muscles (fibrosis) and they develop more cross-linkages. These changes in connective tissue make older individuals more prone to stiffness. In these cases, stretching and flexibility exercises may reduce pain & discomfort and extend or maintain a person's normal, comfortable range of motion. Maintaining flexibility becomes more challenging with age, but loss of flexibility can severely impair normal range of motion in older individuals, leading to disability.
Download the Lab

View Lab (.pdf)