Q: What do the “METs” and “watts” numbers mean on gym machines?
A: Found on stationary bikes, stair steppers, and other aerobic gym machines, METs (metabolic equivalents) indicate the intensity of your workout. Consider that 1 MET represents the amount of oxygen you consume and the number of calories you burn at rest. Thus, if you have been pedaling, cycling, or running at an intensity of, say, 5 METs, you have been burning five times as much oxygen and calories as you would while simply sitting in a chair.
The government’s Physical Activity Guidelines for Americans recommend that adults exercise at moderate intensity (3 to 5.9 METs) for a minimum of 150 minutes (2½ hours) a week, or at vigorous intensity (6 METs and above) for at least 75 minutes a week. Walking at 3 miles per hour has an intensity of about 3 to 4 METs. Running at 6 miles per hour (a 10-minute mile) is equivalent to 10 METs.
Watts, for their part, are a measure of power output during exercise. It’s the same as the power (measured in watts) that lights a bulb. The best way to explain this power is through calories: The more watts, the more calories burned, says the National Academy of Sports Medicine.
There are no specific exercise recommendations for watts, and if you use the watts indicator on exercise machines to measure your progress, the number to aim for will vary depending on your training goals. Watts tend to be more important to athletes than to people who simply are trying to keep fit. To get a sense of where your watts will fall, a beginner cyclist, for instance, may average 70 to 75 watts in a 30-minute workout. A fit cyclist will average more than 100 watts. A professional cyclist can reach 300 to 400 watts.
Your body weight factors into wattage (the heavier you are, the more power needed to move you), which is why you have to enter this information into the exercise machine (it’s also needed to determine the calories burned).
So should you pay attention to these numbers?
It’s up to you. Using METs and watts to gauge if you are meeting your exercise goals and your progress is a motivator for some people—but keep in mind that they are not necessarily 100 percent accurate, and you can also get a good sense of the intensity of your workout by observing your overall heart rate for the exercise session, whether or not you are sweating, the number of calories burned, and how “spent” you feel at the end.