What are the facts behind these common exercise claims?

Caloric Expenditure and Exercise
A calorie is a measure of heat energy. The energy is given off when oxygen and fuel are combined to form the energy that powers our bodies. A calorie also refers to the energy stored in food. The long-term balance between energy intake and energy expenditure is the most important factor in maintaining weight and body fat.

Caloric expenditure during exercise depends on two things: Body mass (weight) and Intensity.

As long as intensity is similar between different activities, caloric expenditure will also be similar. Intensity levels might feel different because of differences in specific muscle strength or because of the amount of movement involved. For example, walking requires relatively fast limb movement to increase intensity because it is a very low resistance activity. Cross-country skiing or rowing involve more muscle groups and greater resistance, so they will require less movement to reach the same intensity level as walking. It may feel as though skiing and rowing are harder workouts, but that is because most people do not walk fast enough to reach the same level of exertion. If you make the intensity levels similar, the caloric expenditure will be roughly the same.

Fat Burning
The biggest trend in exercise during the past few years has been the idea that lower-intensity, longer duration exercise somehow burns more body fat than higher intensity workouts. This has led to a surge in sales of heart rate monitors, books, videos and HealthRiders.

The "fat burning" hypothesis was based on the fact that during moderate intensity exercise, as duration increases, the percentage of energy derived from fat (as opposed to carbohydrates) increases. The conclusion was drawn that fat used during exercise would directly reduce body fat stores. In fact, this theory was never empirically studied before it was publicized as "truth," and has been discounted by most reputable exercise authorities. The few studies that have tried to investigate this issue have found that over time, groups that engaged in higher intensity exercise lost more body fat than lower intensity exercisers, although the numbers were too small to conclude that this is the best approach for everyone.

The most important factor in controlling weight and body fat is the long-term balance between energy expenditure and energy (food) intake. There is no machine or exercise that can "burn fat" any better than any other.

Muscle Toning and Muscle Mass
Muscle "tone" refers to an increased tightness and firmer shape, as opposed to "flabby" and "hanging." Equipment manufacturers often claim that their machines will "firm and tone muscle groups" and even "increase muscle mass so you will burn more fat at rest."

Increased muscle strength and muscle mass occurs in two stages. The first is called neuromuscular adaptation. This basically means that the brain learns to recruit muscle fibers in a more efficient and coordinated pattern, resulting in the generation of greater muscle force, without much of an increase in muscle size. After several months of sufficient training, the actual size of the muscle will start to become larger. How large the muscle becomes is based on genetic background, volume and intensity of training and diet.

Building muscle strength and size requires that the muscles work against a certain level of resistance. This usually means lifting a weight that is at least heavy enough to cause muscle fatigue in 8-12 repetitions.

For the most part, cardiovascular exercises do not involve enough resistance to substantially increase muscle strength and size. Cardiovascular exercise consists of rhythmic movements repeated hundreds of times.

Beginning exercisers will see an initial increase in muscle strength and firmness as the body adapts to the new activity demands placed upon it. If enough volume is performed, in time a certain amount of muscle "tone" will develop in the muscle groups worked by the exercise. This is especially true if the overlaying layers of fat are reduced. These effects will be more pronounced if the exercise has a relatively higher resistive component or if it is performed at higher intensities. You should not, however, expect to achieve large increases in muscle size from cardiovascular exercise.

Some manufacturers have begun to add upper-body components to such traditionally legs-only exercises as treadmills and stairclimbers. Ads emphasize the superiority of a "total body workout." If you find that you enjoy the feeling of the additional upper body activity, then consider these options. Do not be swayed by the idea that this is a "better workout." Any physical advantages of combined upper and lower body are modest at best and are easily eclipsed by consistently performing an activity you enjoy. "Total-body workout" and the "muscle toning" capabilities of the exercise should not be major factors in your choice of equipment.

Easy Workouts and Less Time
Many equipment manufacturers promise that their machines will "make exercise effortless" or will provide "benefits in half the time of ordinary machines." It should be clear by now that fitness results cannot be achieved with no effort. It takes a certain level of intensity, frequency and duration to see results. The intensity does not have to be strenuous or uncomfortable, but it must be sufficient to stimulate changes. There is no exercise or piece of equipment that can circumvent the laws of physiology and provide increased fitness without effort.

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