Por Erica Moe

Everything we do has a measurement. In school, grades on tests measure how much we learned. We get annual performance reviews at work. Even for fun, you see how many likes you can get on Facebook. Exercise is no different. We count sets, reps, calories, minutes and miles. All these numbers help us know we’re making progress — right? So you run, you sweat, and you want results. But how do you REALLY know that you are on the right track with your weight loss?

Why not just use the scale?

Stepping on the scale does give you data. It lets you know your current bodyweight. However, it doesn’t distinguish the difference between fat weight and lean weight. If you gain weight, was it muscle or fat? On the scale, there is no way to be sure.

BMI

BMI or body mass index is a measure of body fat based on height and weight. Like the scale, the weight is not categorized into fat or lean. This calculation may inaccurately categorize you. Your doctor uses it because it is fast and free! Calculate yours at www.bmi-calculator.net

Skin fold calipers

This tool is great for measuring some of the fat on your body. Protocols can measure from three to seven different sites on your body. Simply gather the skin and fat that are on top of your muscle and take a measurement. However, that sneaky fat that hides under the muscle layer cannot be measured or estimated. Error can be plus or minus 3 to 5 percentage points.

Hydrostatic weighing

Hydrostatic weighing is a great way to estimate body composition, but a proper laboratory and skill set are needed. Your body is weighed under water and, after many calculations, the lab can estimate your percentage of body fat. The test can be expensive, and not many locations offer it. Error can be plus or minus 1 to 2 percentage points.

Bioelectrical Impedance Analysis (BIA)

Bioelectrical impedance analysis uses a device to send a small electrical current through your body to estimate body composition. Most use two points of contact on the hands or feet. They are inexpensive and fast, but the error can also be up to plus or minus 10 percentage points.

InBody

This intricate machine works similarly to bioelectrical impedance analysis, however, it has an eight-point contact. It gives information about fat weight and lean weight, and it is able to estimate how many pounds of each are in your limbs and torso. That means it can measure muscle growth and fat loss in each of these areas, as well. In addition, it yields more sophisticated data like total body water and basal metabolic rate (the number of calories you need at rest per day). Error for the InBody is plus or minus 3 percentage points. Mission Valley Y offers InBody tests to members.

What else?

In addition to tests that measure body composition, fitness gains can be measured by other tests that give data about other components of physical fitness like flexibility, cardiovascular endurance, muscular endurance and muscular strength.

— Erica Moe is an ACSM certified exercise physiologist who writes on behalf of the Mission Valley YMCA, where she is a fitness director.