Isotonic contractions are made up of which two phases?

Isotonic contractions are characterized by the muscle changing length while generating a constant force, which occurs in two distinct phases: concentric and eccentric.

During the concentric phase, the muscle shortens as it contracts, which typically occurs when lifting an object. This phase is crucial for overcoming resistance, such as when performing a bicep curl where the bicep muscle shortens to lift the weight upward.

In the eccentric phase, the muscle lengthens while still generating force, such as when lowering a weight back down. This phase is essential for controlling the movement and preventing injury, as it provides stability and strength in the downward motion.

The combination of these two phases defines isotonic contractions, highlighting how muscles perform work through both shortening and lengthening movements. Thus, the correct answer accurately reflects the two phases that constitute isotonic contractions.