Final answer:
Isotonic contractions involve muscle length changes, with examples of concentric and eccentric contractions. Series elastic elements store and release energy in muscle contraction.
Step-by-step explanation:
In biology, isotonic contractions occur when the tension in a muscle stays constant while the muscle length changes. There are two types of isotonic contractions: concentric and eccentric. During a concentric contraction, the muscle shortens to move a load. An example of this is when the biceps brachii muscle contracts to lift a hand weight upwards. In contrast, an eccentric contraction occurs when the muscle lengthens as the tension diminishes. An example of this is when the hand weight is slowly lowered down.
The role of series elastic elements in muscle contraction is to store and release energy. These elements, such as the tendons, act as springs that stretch and store energy during eccentric contractions. This stored energy is then released during the subsequent concentric contraction, aiding in the movement.