Muscular Strength

Defined most simply as the ability to produce muscular force, muscular strength is often divided into muscular strength and muscular endurance. Muscular endurance is the ability of a muscle to contract repeatedly or continuously (as when carrying a child), whereas pure strength is the amount of force produced for one contraction (as when standing up from a chair). Most of us need a combination of the two—muscular endurance for posture muscles, and muscular strength in the trunk, legs, and arms for lifting.

Many people start losing strength as they age or become inactive, although the loss is not irreversible (Rogers and Evans 1993). In addition, women lose more strength than men do, especially from the upper body (perhaps because they may be less active when they are younger). Muscular strength allows you to perform many tasks at home and at work and, more important, helps to reduce the stress on joints. Hurley and Hagberg (1998) state,". . . muscular strength is a major determinant of an older person's ability to maintain an active, high-quality lifestyle. . . ."

A top bodybuilder in the 70s age group reported that she started lifting weights because she had problems lifting grocery bags and doing other household chores. Amazingly, she did not start lifting weights until she was in her 70s. She is now in her 80s and looks great. I show her picture to my students and ask them to guess her age; they are always a couple of decades low.

Nervous system control of a muscle and the condition of the muscle itself combine to produce the muscular control and strength that various activities require. In fact, much of the initial gain from strength training is a fine-tuning of the amount of neural input that is required to contract a muscle. An example is the process by which toddlers learn to stand. Through repeated attempts, their movements become smoother and they are able to stand for longer periods. The amount of muscle contraction necessary for the activity has been refined, as has the strength in the muscle itself.

When there is pain around a joint such as your knee, the nervous system can also inhibit muscle contraction. Many patients have told me about a knee buckling unexpectedly, usually secondary to pain. After starting a strengthening routine, they have less pain and fewer problems with their knees giving way. Postsurgery joint replacement patients also illustrate the inhibition of muscle contraction because of pain. I see many patients the day after surgery who cannot lift their legs off the bed, even though they had no problem doing so before the surgery. As the pain around the surgical site decreases and they practice movements, these patients are able to lift the surgical leg again, even though there is no real change in strength. Most strengthening programs produce both neural and muscular changes that improve one's muscular control and strength (Sale 1988).