11/20/09

The physique of Michael Phelps is well documented: 6’ 4” height, 6’ 7” wingspan, narrow hips, paddle-perfect size 14 feet.

Not everyone is lucky enough to have those powerful and ideal genetics for a swimming body. But like Michael, your speed in the water relies upon your unique combination of physical attributes: height, weight, fat, muscle, and buoyancy, to name a few.

While you can’t do much about your height, other factors - specifically weight - are within your control. One way to improve your performance is to understand more about your body’s makeup. Using some basic body mass and body fat tests, you can get a better idea if you need to drop - or maybe add - a few pounds and give yourself a slightly better advantage in the water.

A helpful starting point is your Body Mass Index (BMI). This index is a measure of a person’s weight relative to height. The BMI is often used by physicians and trainers to determine whether an individual is at a healthy weight, overweight, or underweight.

Since BMI is a standard scale, it can be used for anyone, regardless of gender or physical build. For an age group swimmer, BMI will change over time with normal growth patterns. For an adult swimmer, BMI will be remain more steady, but of course fluctuate based on changes in weight.

BMI does not directly measure body fat, such as tests performed with calipers or underwater weighing. But research has proven that BMI correlates to these direct body fat tests. And most importantly, it is inexpensive and easy to perform.

Get Your Score
The National Institutes of Health has an online BMI calculator where you simply input your height and weight, and it generates your number.

The CDC has both an adult and also a child and teen (ages 2-19) BMI calculator online here.

Using those calculators, here’s how a few uber-athletes shape up:

Michael Phelps: 6’ 4”, 195 lbs. BMI: 23.7
Ryan Lochte: 6’ 2”, 185 lbs. BMI: 23.8
Natalie Coughlin: 5’ 8”, 138 lbs. BMI: 21.0
Katie Hoff: 5’ 8”, 141 lbs. BMI: 21.4

A BMI score of 18.6 to 24.9 is considered normal, while experts would categorize a BMI below 18.5 as underweight. A BMI in the range of 25 to 30 is generally considered overweight, while a BMI score over 30 is considered obese.

Gender and the Backstroke Flip
Taking this a bit further, Genadijus Sokolovas, Ph.D. and USA Swimming's director of physiology, tabulated the BMI (along with other body stats) of a set of Olympic Trials qualifiers a few years ago. Those studies revealed that among women, BMI was lowest among freestyle sprinters, who were tallest and lightest. Women backstrokers had higher weights and the highest BMI numbers.

With men, freestyle sprinters had the highest weight and were tallest. Freestyle distance swimmers had the lowest weight. The BMI for male backstrokers was lowest - opposite of the results found among the women. For men, the highest BMI was found among IM swimmers, as they had the lowest height.

Fat vs. Muscle
Keep in mind, however, that while the BMI is a reliable indicator of a person’s total body fat, it is not foolproof. The NIH warns that the index may overestimate body fat in athletes with a muscular build. Similarly, the CDC notes that “highly trained athletes may have a high BMI because of increased muscularity rather than increased body fatness.”

So consider BMI only a reference point in determining your ideal weight for swimming. Worse case is that you’ll know how your body stacks up against the elite.


Melanie McMullen, BaySide Media (www.baysidemedia.com), is a freelance contributor for www.swimnetwork.com and a member of the Downtown Oakland YMCA Master’s swim team. She has a BMI of 22.2.