Final answer:
In weightlifting and strength training, the most common method used to enhance motor performance skills and sports performance is the use of isotonic contractions consisting of concentric and eccentric contractions.
Step-by-step explanation:
In weightlifting and strength training, the most common method used to enhance motor performance skills and sports performance is the use of isotonic contractions. Isotonic contractions involve the muscle tension staying constant while the length of the muscle changes. There are two types of isotonic contractions: concentric and eccentric.
In a concentric contraction, the muscle shortens to move a load. For example, when you bring a hand weight upward, the biceps brachii muscle contracts and the angle of the elbow joint decreases.
In an eccentric contraction, the muscle tension diminishes and the muscle lengthens. For example, when you lower a hand weight in a slow and controlled manner, the biceps brachii muscle releases tension and the angle of the elbow joint increases.