Strength
Strength is the ability of a muscle to contract which produces tension and a resulting force. To increase strength, resistance must be applied to a muscle during contraction. Resistance can either be manual or mechanical, but must be sufficient enough to increase the size of the muscle fibers (hypertrophy) and increase the recruitment of motor units in the muscle. Manual resistance is a technique used by therapists for weaker muscles that only require mild to moderate resistance. Mechanical resistance is a strengthening technique that uses equipment, such as bands, weights, or machines.A strengthening exercise program gradually increases the resistance over time but maintains a low number of repetitions. There are several types of resistance exercises: isometric, isotonic, and isokinetic. Isometric exercise produces a muscle contraction without noticeable joint movement. Isotonic exercise is more dynamic and causes a muscle to contract during joint movement. Isokinetic exercise occurs at a constant speed and uses various forms of equipment to produce ioskinetic contractions.