Many exercisers wonder about the veracity of the calorie-counting functions on cardio exercise machines. Your suspicion is well-founded.
Treadmills, ellipticals, stationary cycles and similar units display two types of performance metrics, says Jim Zahniser, public relations manager of Precor, an equipment maker. The displays of heart rate, speed and distance are “straightforward and fairly accurate,” Zahniser says. But the calorie counter is crafted to reflect the burn of an average exerciser, not you in particular, he says.
Caloric expenditure is mostly a function of distance covered and body weight, plus a variety of other factors, though there is some disagreement about what those factors are (heart rate? sex? hair color?) and how much they matter. The machine can account for body weight and distance but not all other factors, so it uses averages.
For all their shortcomings, the machines' calculations are based on sound science, says Conrad Earnest, chief exercise physiologist at the Cooper Institute in Dallas.
“It is possible to calculate energy expenditure ... with reasonable accuracy,” he says, using just body weight and treadmill running distance. “It will never be 100 percent accurate. But the equations ... have been validated.”
Say you hit the treadmill for 30 minutes today and, according to the machine, use 400 calories. You might really have burned 323 or 491. But if you work out on the same machine on Thursday, you can see whether you're meeting, beating or falling short of your prior performance.
Calorie counts on elliptical machines are invariably higher than those for similar sessions on treadmills. Should you ellipticize to burn more calories?
Perhaps, particularly if the machine also has moving handles that engage the arms and shoulders, says William J. Kraemer, a kinesiology professor at the University of Connecticut.
