Differentiate isotonic and isometric muscle contractions and provide a sport example for each.

• A. Isotonic involves movement with a change in muscle length (e.g., bicep curl); Isometric involves tension with no length change (e.g., holding a plank).
• B. Isotonic involves no movement; Isometric involves constant velocity movement.
• C. Isometric produces external movement; Isotonic produces no movement.
• D. Isotonic contracts with increasing force; Isometric contracts with decreasing force.

Answer: (A)

Muscle contractions can be either isotonic or isometric depending on whether the muscle changes length during the contraction. Isotonic contractions involve a change in muscle length and produce movement. This includes concentric actions where the muscle shortens and eccentric actions where it lengthens while controlling the movement. A sport example would be a vertical jump, where the thigh muscles shorten to extend the knee and push off the ground, producing upward movement (with controlled lengthening when you land). Isometric contractions produce force without changing muscle length, so no joint movement occurs. A sport example is a wrestler maintaining a pin or a defensive hold, where the muscles stay under tension to hold position without any movement of the joints.