Final answer:
Examples of active-isolated stretching include repeating a stretch for 2-3 sets and contracting a muscle before stretching. It focuses on contracting one muscle to stretch another and differs from static stretching or isometric and isotonic contractions.b) Repeating a stretch for 2-3 sets
Step-by-step explanation:
Active-isolated stretching involves the contraction of one muscle while stretching the opposing muscle, usually involving movements that actively stretch the targeted muscles for 2 to 5 seconds. So, to answer the question, some examples of active-isolated stretching are repeating a stretch for 2-3 sets (option b) and contracting a muscle before stretching (option d). Holding a stretch for 30 seconds (option a) and using a foam roller (option c) are not examples of active-isolated stretching but are rather static stretching and myofascial release techniques, respectively.
To further explain, flexibility exercises such as active-isolated stretching help in increasing muscle flexibility and joint range of motion. This form of stretching is distinct from isometric contractions where the muscle tension increases but the muscle length does not change. It's also important to differentiate active-isolated stretching from isotonic contractions, which include both concentric contractions (muscle shortens) and eccentric contractions (muscle lengthens), as the muscle goes through different movements during these exercises.