While the term "strength training" may elicit images of a Speedo-clad Arnold Schwarzenegger, bodybuilders encompass only a fraction of strength-training enthusiasts. In fact, from marathoners to moms, everyone can benefit from increasing their muscle mass.

Strength training is recommended as one of the key components of overall fitness. It involves working your muscles against weight or resistance to increase strength. Weight training can include the use of free weights such as dumbbells, weighted machines or your own body mass (think push-ups and squats). Resistance training, on the other hand, employs anything from elastic bands to a swimming pool full of water to create tension to oppose your bodys natural muscle contraction.

Without exercise, most adults lose about one-half pound of muscle per year, according to the American Council on Exercise. Because muscle helps burn additional calories - even at rest - the decrease in muscle mass as we age can reduce our calorie needs and increase our tendency to gain weight. But strength training can counteract this natural decline. According to some studies, strength training can increase metabolic rate by up to 95 calories a day. The amount of muscle change (and metabolic change) is highly variable, however, as it depends on technique, amount of weight or resistance, frequency, proper rest between sessions, diet and individual genetics.

Men who strength train regularly can build significant muscle mass, but muscles don't have to bulge for you to enjoy the benefits of strength training. In fact, due to a lower testosterone level, women who strength train rarely show bulging biceps despite dramatic strength increases. Moreover, studies have reported benefits for even the most modest levels of strength training. Research conducted with elderly populations has shown that modified strength training can help improve nursing home residents ability to walk, to get up from chairs and to climb stairs.

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Strength training is also an important factor in combating excess body weight. Although the American Heart Association cites aerobic exercise as most effective in promoting loss of excess body fat, some research suggests that fat loss is greater when aerobic and strength training are combined.

Abdominal fat the fat most strongly linked to development of heart disease, diabetes and cancer - seems most affected by strength training efforts. In several studies, strength training (or a combination of aerobic and strength training) decreased total body fat by one to two percent and reduced abdominal fat by up to twelve percent. It also helped normalize high insulin levels and improved insulin resistance in study subjects.

Another benefit of strength training is the role it plays in strengthening bones. Even forms of strength training that are not technically weight bearing exercise place a load on your musculoskeletal system. This stimulates bone-building cells called osteoblasts and increases bone density. In fact, a Tufts University study published in the Journal of the American Medical Association reported reduced fracture risk among post-menopausal women who strength trained.

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The American College of Sports Medicine has developed age - and ability-specific recommendations to ensure that those who practice strength training do so safely. Yet, despite all of the reported benefits, experts emphasize that strength training is still just one piece of the fitness puzzle. Combining aerobic, strength training and flexibility exercise can yield improved fitness, increased strength and decreased abdominal fat. As always, be sure to speak with your doctor before beginning any new exercise program.

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