Resistance training is a type of exercise that uses external resistance to cause muscle contractions with the intent to strengthen and tone, build mass and expand endurance. Dumbbells, resistance bands, water bottles or body weight are all examples of external resistance, as defined by WebMD.
Resistance training works because it breaks down muscle cells through catabolism, which prepares the body to respond with anabolism, a process that repairs and strengthens muscles. Resistance training helps lower moderate blood pressure levels, decreases the effects of falls in the elderly and increases the rate at which the body burns calories. WebMD recommends that resistance exercise be undertaken in stages, be suited to the individual and stimulate the major muscle groups, such as chest, back, shoulders, arms, abdominals and legs.