Which contraction occurs when the muscle generates tension but does not shorten because the external load is greater than the force produced?

Which contraction occurs when the muscle generates tension but does not shorten because the external load is greater than the force produced?

• A. Isometric contractions
• B. Isotonic contractions
• C. Treppe
• D. Fused tetanus

Answer: (A)

When a muscle can generate tension but does not shorten because the external load is greater than the force produced, the fibers are activated yet the overall length stays the same. This is an isometric contraction. In this situation, the sarcomeres don’t shorten—the joint angle doesn’t move—even though cross-bridges are forming and force is being developed to try to overcome the load. The key point is that the load prevents movement, so length remains constant while tension rises. This differs from isotonic contractions, where the muscle changes length as it moves a load—shortening during a concentric action or lengthening during an eccentric action—because the tension is enough to move the resistance. Other options describe different phenomena: Treppe is the gradual increase in force with successive stimuli due to calcium buildup, and fused tetanus is a smooth, continuous contraction from high-frequency stimulation, not specifically about maintaining length under a heavy load.

When a muscle can generate tension but does not shorten because the external load is greater than the force produced, the fibers are activated yet the overall length stays the same. This is an isometric contraction. In this situation, the sarcomeres don’t shorten—the joint angle doesn’t move—even though cross-bridges are forming and force is being developed to try to overcome the load. The key point is that the load prevents movement, so length remains constant while tension rises.

This differs from isotonic contractions, where the muscle changes length as it moves a load—shortening during a concentric action or lengthening during an eccentric action—because the tension is enough to move the resistance. Other options describe different phenomena: Treppe is the gradual increase in force with successive stimuli due to calcium buildup, and fused tetanus is a smooth, continuous contraction from high-frequency stimulation, not specifically about maintaining length under a heavy load.