As we've said, it's not how much you weigh, it's how much of that weight is fat and muscle that really matters. The only way to really know is to use one of the several techniques that have been developed to measure body composition.
These days, health clubs, sports expos, hospitals, and performance labs across the country offer high-tech ways to get your percentage of body fat calculated. Here is a look at each method and how reliable the results are. In general, we recommend using one of the easier techniques, such as bioelectric impedance or skinfold calipers (with a well-trained technician), because you'll be more likely to get retested. It's not good enough to get tested once; you want to repeat your body composition three to four times per year: preseason, midseason, and postseason. This will help track how your body composition is throughout the year and whether you are getting too lean or not lean enough when it really matters the most.
Hydrodensitometry (Underwater Weighing)
Long considered the gold standard for body composition testing, this technique is based on the fact that fat is less dense than fat-free tissue. It requires submerging the athlete in a tank to measure the water and air dis placement. Newer techniques, such as DEXA body scans, are now generally used instead of underwater weighing.
Dual-Energy X-ray Absorptiometry (DEXA) Scans
DEXA is generally available only at research facilities and is the most precise technique to measure body fat. DEXA uses a whole body scanner to detect bone and soft tissue mass. It can take less than ten minutes and is about the most accurate way of testing your true body fat. Bonus: you'll get the health of your bones at the same time. The only downsides are that the test can be expensive and it can be hard to find a facility that has the equipment.
Bioelectric Impedance Analysis (BIA) Scales
These scales have gotten better and less expensive over the years. They use a low-level electrical current to travel through the body to determine the amount of muscle and fat. The fat impedes an electrical current and water; this is an indirect way of measuring muscle mass.
BIA scales are available from Tanita, Homedics, and Health O Meter, all of which have been found to be well correlated to underwater weighing. They have about a 4 percent margin of error. One problem with BIA scales is that hydration status, skin temperature, and food intake impact the readings. It's best to test at the same time of day and when you are adequately hydrated.
Skinfold caliper readers measure the thickness of the fat layer on specific body sites (arms, thighs, abdomen, chest, and back). The reliability of the results of calipers is dependent on who is taking the measurements and the calibration of the calipers. Use calipers to monitor changes in your body fat over time. It's also important to always use the same technician.
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