During which phase of isotonic muscle action is the external load being lowered?

The correct phase during which the external load is being lowered is the eccentric phase. In this phase, the muscle lengthens as it contracts while controlling the movement of the load. For instance, when performing a bicep curl, as the weights are lowered back down after being lifted, the biceps are in an eccentric contraction, which allows the muscle to control the descent of the weight in a controlled manner.

This process is vital for various aspects of fitness, including strength training and injury prevention, as it emphasizes muscle control and stability while managing external forces. Understanding this phase helps instructors design better workout programs that incorporate both lifting and lowering movements, contributing to overall strength development.