![]() ![]() 50 A decrease in the size of a muscle is referred to as atrophy.įigure 9-1. This increase in muscle size is referred to as hypertrophy. ![]() The size of a muscle tends to increase in cross-sectional diameter with resistance training. The greater the cross-sectional diameter or the bigger a particular muscle, the stronger it is, and thus the more force it is capable of generating. Muscular strength is proportional to the cross-sectional diameter of the muscle fibers. 12įACTORS THAT DETERMINE LEVELS OF MUSCLE STRENGTH, ENDURANCE, AND POWER However, because all muscles function concentrically, eccentrically, and isometrically in 3 planes of motion, a strengthening program should be multiplanar, concentrating on all 3 types of contraction. Traditional strength-training programs have been designed to develop strength in individual muscles in a single plane of motion. Consequently, it has been recommended that the strengthening program includes exercises that strengthen the muscle in the manner in which it contracts functionally. Rehabilitation exercises have traditionally concentrated on strengthening isolated single-joint motions, despite the fact that the same muscle is functioning at a second joint simultaneously. The hamstrings contract concentrically to flex the knee, while the hip tends to flex eccentrically, lengthening the hamstring. An example of an econcentric contraction is a prone, open kinetic chain hamstring curl. 16 An econcentric contraction is possible only in muscles that cross at least 2 joints. 47Īn econcentric contraction combines both a controlled concentric and a concurrent eccentric contraction of the same muscle over 2 separate joints. Concentric and eccentric contractions are considered dynamic movements. ![]() In an eccentric contraction, the resistance is greater than the muscular force being produced, and the muscle lengthens while producing tension. In a concentric contraction, the muscle shortens in length while tension increases to overcome or move some resistance. Considerable force can be generated against some immovable resistance even though no movement occurs. 21 An isometric contraction occurs when the muscle contracts to produce tension, but there is no change in muscle length. Skeletal muscle is capable of 3 different types of contraction: isometric, concentric, and eccentric. Why is it important that she regain all 3 aspects of muscular fitness? This statement becomes increasingly true with age.Ī softball pitcher was out for a whole season for rehabilitation following shoulder surgery. For the average person in the population, developing muscular endurance is likely more important than developing muscular strength because muscular endurance is probably more critical in carrying out the everyday activities of living. As we will see later, as muscular strength increases, there tends to be a corresponding increase in endurance. Muscular endurance is the ability to perform repetitive muscular contractions against some resistance for an extended period. Muscular strength is closely associated with muscular endurance. Resistance training plays a critical role in injury rehabilitation. Muscle weakness or imbalance can result in abnormal movement or gait and can impair normal functional movement. Maintenance of at least a normal level of strength in a given muscle or muscle group is important for normal healthy living. For the athletic trainer supervising a rehabilitation program, regaining and, in many instances, improving levels of strength and endurance are critical for discharging and returning the patient to a functional level following injury.īy definition, muscular strength is the ability of a muscle to generate force against some resistance. Discuss differences between males and females in terms of strength development.įollowing all musculoskeletal injuries, there will be some degree of impairment in muscular strength and endurance.Differentiate between muscle strength and muscle endurance.Describe specific methods for improving muscular strength.Discuss the physiology of strength development and factors that determine strength.Discuss the anatomy and physiology of skeletal muscle.Define muscular strength, endurance, and power, and discuss their importance in a program of rehabilitation following injury.The athletic training student should be able to: ![]()
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