Aerobic Exercise

A teen’s fitness program should include aerobic exercise such as brisk walking, basketball, bicycling, swimming, in-line skating, soccer, jogging—any continuous activity that increases heart rate and breathing. Regular workouts improve the efficiency of the cardiorespiratory system, so that the heart and lungs don’t have to work as hard to meet the body’s increased demands for freshly oxygenated blood.

Aerobic exercise also affects body weight composition, by burning excess calories that would otherwise get converted to fat. In general, the more aerobic an activity, the more calories are expended. For instance, if a teenager weighing 132 pounds walks at a moderate pace for ten minutes, he burns forty-three calories. Running instead of walking more than doubles the amount of energy spent, to ninety calories.

Low-intensity workouts burn a higher percentage of calories from fat than high-intensity workouts do. However, the more taxing aerobic exercises ultimately burn more fat calories overall. One study compared the burn rates for a thirty-minute walk at three and a half miles per hour and a thirty-minute run at seven miles per hour. The walking group expended an average of 240 calories. Two-fifths came from fat, and three-fifths came from carbohydrates, for a total of ninety-six fat calories. In the running group, the ratio of fat energy burned versus carbohydrate energy burned was significantly less: one to four. Yet overall, the runners consumed 450 calories. Total number of fat calories burned: 108.

Weight Training

Under the guidance of well-trained adults, children aged eight or older can safely incorporate weight training (also called strength training and resistance training) into their workouts to increase muscle strength and muscle endurance. Muscle strength refers to the ability to displace a given load or resistance, while muscle endurance is the ability to sustain less-intense force over an extended period of time. Males will not be able to develop large muscles until after puberty. Females generally are not able to develop large muscle mass. They do not have to worry about getting too muscular.