What does isotonic mean?

• A. Exert resistance against the muscle as it moves through a range of motion, at a steady rate of speed.
• B. Combine movement of the joints with contractions of the muscles.
• C. Use muscle tension to improve strength with little or no movement.
• D. Include aerobic rhythmic activities for extended periods.

Answer: (B)

Isotonic contractions involve the muscle changing length as the joint moves. This happens when you perform movements like lifting a weight or doing a curl, where the muscle contracts and shortens (or lengthens during the eccentric portion) while the joint actually moves. The key idea is that there is movement at the joint driven by muscle contraction.

The other descriptions point to different types of contractions: exercising with a constant speed through a range of motion describes isokinetic work, holding a position with muscle tension but no movement describes isometric work, and extended aerobic activity targets cardiovascular endurance rather than a specific muscle-length change.