The Body Composition of Athletes

By Candace Chemtob, B.S. and M.S. in Human Nutrition

If looking solely at BMI to determine health of an athlete, Nick Matthew would be at the very high end of the “normal” scale. His 6’ 0” and 172lbs gives a BMI of 23.2. At 25 he’d be considered overweight.
If looking solely at BMI to determine health of an athlete, Nick Matthew would be at the very high end of the “normal” scale. His 6’ 0” and 172lbs gives a BMI of 23.2. At 25 he’d be considered overweight.

In most sports, it is obvious that body size and body composition contribute to optimal athletic performance. A NBA basketball player is never going to excel in gymnastics and vice versa. Body size and composition exert a strong influence on an athlete’s speed, strength, agility, and power. In general, sports that require speed and agility, like squash, favor leaner bodies with a higher muscle to fat ratio. In last month’s article, sports nutrition strategies to increase the ratio of muscle to fat was discussed. This month, we will review methods to measure body composition, their usefulness, and limitations.

When it comes to the “ideal” body size or composition for athletic performance, there is no “one size fits all.” Studies show that athletes have lower percent body fat than the average American. Athletic men fall into the range of 6 to 13 % body fat when compared to the average American male with a range of 18 to 24% body fat. Women have a higher amount of “essential fat” stores. If a female athlete’s percent body fat falls below a critical level (near 16 to 17%), they can develop a series of health related problems referred to as the female triad (reproductive function and bone strength are amongst some of the affected body systems). For this reason, the female athlete should have a significantly higher average % body fat (typically in the range of 16 to 21 % body fat), than the athletic male. The average American female has a % body fat of 25 to 31% .

It is important to point out that percent body fat or muscle mass is not predictive of optimal athletic performance. The American College of Sports Medicine recommends “individualized assessments of an athlete’s body composition…An optimal competitive body weight and relative body fatness should be determined when an athlete is healthy and performing at his or her best.” Individual assessments should be done by qualified health professionals, such as registered dietitians, sports medicine physicians, or exercise physiologists.

There are several ways to classify body size and measure body composition. The simplest method is calculating body mass index (BMI), which is weight (kg)/height (m2). BMI is not a useful measurement in athletes for it does not take into account varying degrees of fat mass, and lean body mass. An example of the limitations of using BMI in athletes is Dwight Howard’s (NBA All-Star) BMI. He has a BMI of 27, which places him in the “overweight” category. Even if you are not an Orlando Magic fan, you probably would not call Dwight “fat.”

The most commonly used methods to measure body composition (% body fat) are skin fold measurements using calipers and bioelectrical impedance. Skin fold thickness measurements are taken using calipers in several locations—thigh, arm, and waist are common. The assumption is that the thicker the skin fold, the higher the % body fat. Bioelectrical impedance uses an electric current to measure body composition and is based on the fact that fat and lean body mass conduct electricity differently. These methods are widely used because the equipment is inexpensive ($100 to $200) and an untrained person can administer these tests. Unfortunately, these techniques do not provide reliable measurements of body composition, with a high error rate of +/- 4%.

For example, a measurement of 12% body fat means that actual % body fat could be as low as 8% and as high as 16%! Caliper and bioelectrical impedance assessments of body composition are also not sensitive enough to track changes in the body composition of an athlete over time.

There are two recommended methods to measure body composition, underwater weighing and DEXA. Underwater weighing has been long considered the “gold standard” and is based on the fact that the density of fat is less than the density of lean body mass (which includes muscle mass). It has an error rate of +/- 1.5%. The other method is dual-energy x-ray absorptiometry (DEXA). DEXA machines are most commonly used to measure bone mass and assess risk for osteopenia/osteoporosis, and are available in most communities. DEXA is considered the most accurate measurement on body composition, however, the cost can be prohibitive.

Most athletes are “number” oriented, after all performance is measured in seconds, wins/losses, rankings and skill levels. If you are interested in measuring and tracking your body composition, please don’t get stuck on a number. The American College of Sports Medicine states: “athletes and coaches should know that there are errors associated with all body composition techniques and that it is not appropriate to set a specific body fat percentage goal for individual athletes. Rather, a range of target percentages of body fat should be recommended” at which the athlete is performing their best.

To conclude, with an observation about the top 10 PSA pros (July 2011 rankings). Although the top PSA players appear lean (with a high muscle to fat ratio), their body size ranges from a height of 5’8 (30 percentile for height) to almost 6’3” (greater than 95 percentile for height) and body weights from 158 to 200 pounds. This is a visual that most squash fans have probably already realized. Unlike other sports, including the examples of basketball and gymnastics, body size may not limit the success of a squash player. So big or small, you can shoot for the stars, keep your feet on the court, and strive to reach your optimal performance.