Body Composition and its Relation to Sports

In sports medicine, we often focus on the more severe and “down time” injuries and neglect the smaller, yet still important injuries. Many of these injuries are evaluated and managed not by sports doctors but by coaches and trainers in the training rooms, locker rooms and field houses. Although this is often appropriate more complicated or refractory cases demand the attention of a physician.

In sports medicine we are often concerned about the optimum body composition for different people. Gymnasts should have drastically different proportions of muscle, fat and bone than football linebackers. Furthermore, we are interested in what is healthy for fitness enthusiasts, weekend warriors and non-athletes as well.

Many people determine their body composition status by body weight alone. While this is indeed an important parameter, it is by no means a complete way to determine whether or not you have the correct body composition. Consider the examples of a 300 pound football linebacker with 15 percent body fact and the 5-feet, 2 inch small framed woman who has 35 percent body fat.

Over the years, several methods of determining body fat percentages have evolved. These range from the very simple to the extremely exotic; For the most part there are three practical accepted methods of determining body fat.

The first is probably the least used and most complicated. It’s called the hydrostatic weighing. This method is based on the principle that fat is less dense than water and will tend to float. Bone and muscle are both denser than water and will sink. In order to determine the percentage of body fat, an examiner must know the patient’s weight in air and his or her weigh in water. Then, using a simple mathematic formula, it is possible to determine the percentage of body weight that is fat.

A second method that is becoming both more practical and more popular recently is bioimpedance. This technique makes use of the observation that body tissue that does not contain fat conducts electricity much faster than fatty tissue. Early bioimpedance techniques involved inserting needles into the muscle tissue. Needless to say, this wasn’t particularly popular. However, today’s methods use skin electrodes and is completely painless. Companies from Sharper Image to Wal-Mart are now offering fairly low cost devices that will measure bioimpedance.

Although this quick and repeatable method of measuring body fat is very attractive, there is evidence to suggest that it may be one of the least accurate and precise methods of measurement. The data may be affected by several factors including hydration status and young lean males may have their body fat percentage over predicted.

The most tried and true method of measuring body fat is called anthropometry or skin fold measurement. This uses the measurement of folds of skin to estimate total body fat composition. It requires a trained examiner to take one or more skin fold measurements (depending on the method) and the use of a table to estimate body fat. This method is both accurate and repeatable when performed by a skilled examiner.

Many organizations have published recommendations regarding the optimum percentages of body fat for different people. For example, the American College of Sports Medicine has said that 16-18 percent is acceptable for men of all ages and 22-26 percent for women. Various studies have looked at ideal composition for specific sports or specific positions. However, like the measurements for lay people, there is not general agreement in this area.

Aside form being aware of their body composition, people often would like to change their percentage of muscle or fat or at least redistribute their proportions. One could argue whether this national obsession is healthy or not but it is well established that the trend exists.

For athletes trying to gain weight it is important (for the most part) that they try to gain muscle rather than fat. This is done with a combination of increasing their caloric intake and using strength training exercises to increase their lean mass.

Weight loss (a more common goal) should be viewed in the context of body composition as well. It is unhealthy to lose lean mass in order to drop total body weight. As with weight gain, exercise is an important factor as well. Exercise for weight loss should emphasize not only lean mass expansion but fat loss too.

With either weight loss or weight gain, a healthy diet is key. It should be mentioned that in today’s aesthetics-driven society, eating disorders are becoming ever more common. People with eating disorders have complex problems that go beyond the scope of this article. However, it should be said that if you believe that you or someone you know has an eating disorder, it is vitally important that professional help is sought. These problems are extremely unhealthy and may require aggressive treatment.

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