During which type of muscle action is there a reduction in muscle tension?

The correct answer is the eccentric muscle action. During eccentric actions, the muscle lengthens under tension as it controls the descent of weight or resistance. This type of muscle action involves a reduction in muscle tension relative to the load being applied. Although the muscle is still under tension to control the movement, it does not contract as forcefully as it does during a concentric contraction, where the muscle shortens while generating force.

In considering the other types of muscle action for context, isometric actions occur when the muscle generates tension without changing length, thus maintaining muscle tension throughout the contraction. Concentric actions involve the muscle shortening while generating tension, leading to an increase in muscle tension as it works against resistance. Plyometric actions combine an eccentric stretch followed by a rapid concentric contraction, which also suggests an initial increase in tension during the stretch phase before the explosive contraction occurs. Therefore, eccentric muscle action is uniquely characterized by a reduction in tension as the muscle elongates.