A Better Way of Measuring Body Composition: Air Displacement Plethysmograph

It looks a little like a futuristic spaceship, but the air displacement plethysmograph (ADP) actually provides down-to-earth data. The body composition testing device is shaped like a human-sized pod and uses air displacement to measure an individual’s body fat and lean body mass. This can be useful for anyone, but especially for:

• Those who want to monitor the effectiveness of their exercise and nutrition programs
• Athletes who are tweaking their training
• Anyone who wants to track the progression of certain conditions, such as obesity

Some businesses and fitness centers use ADP as one of their assessment tools. Experts consider this technology the gold standard in assessing body mass and more accurate than other methods such as underwater weighing and skinfold calipers.

How ADP Works

To get a measurement, you enter the device and sit down on the small molded seat. You will wear a close-fitting swimsuit and swim cap so the ADP can get the best reading of the mass of your body. The technician will set up the machine and close the door to the pod for two 50-second periods. During that time, you’ll be able to see outside of the pod, looking through the window.

You’ll be in the ADP about three minutes, with the entire testing process lasting 10 to 15 minutes. The results are immediately available, and the ADP can provide detailed information on body composition, resting metabolic rate and total energy expenditure.

What the ADP Measures

The ADP measures body composition, including percentage of fat, percentage of fat free (lean) mass, fat, lean and body mass in kilograms, body volume, body density, energy expenditure and, if also tested, thoracic gas volume.

Fat and lean measurements are useful because a person’s weight is not always the best indication of their fitness. Two people could have the same height and weight, and even have the same body mass index (BMI), but have very different body compositions.

BMI is a way to figure out an individual’s classification (i.e. underweight, normal, overweight or obese). BMI may not be the best form of measurement, scientists say, because when it looks at weight, it doesn’t distinguish between fat and muscle. Having a more accurate measurement of fat to lean provides a better assessment of health.

With nearly 40 percent of Americans classified as obese, understanding body composition becomes even more important. In weight loss, for example, the scale may not show a decrease, even though a person has been eating a healthier diet and exercising. That might be because as the person decreases fat mass, they are increasing lean muscle mass. The weight may remain the same, but the body composition has improved. Understanding this difference can be instrumental in assessing weight-loss efforts.

Additional measurements, such as energy expenditure, help determine metabolism rates and fuel needs, which is particularly helpful for elite athletes. Thoracic gas volume measures lung capacity and can be useful regardless of how athletic you are.

If you think you could benefit from a better understanding of your body composition, ask your doctor or area fitness clubs if they offer ADP testing. You also can make an appointment for ADP testing by emailing [email protected] or by calling (407) 237-6351.