You May not Be Working Out as Hard as You Thought
Credit: Mike Tittel / Getty Images

Regular, moderate-intensity exercise, like walking or mowing the lawn, is essential for good health. And vigorous exercise, such as intervals or a morning run can be even more beneficial, keeping your heart healthy and your waistline trim. But what do moderate and vigorous intensity actually mean? According to a new study, most people don't really know – and you likely aren't working out as hard as you think.

A team of Canadian researchers wanted to find out whether people who assume they're meeting recommended guidelines for physical activity truly are. In the U.S., the federal government suggests 75 minutes of vigorous or 150 minutes of moderate aerobic exercise per week to achieve the maximum health benefits. For this study, the researchers rounded up 129 sedentary adults and familiarized them with Canada's physical activity guidelines, which are similar to the U.S.'s. Most of the volunteers said they understood these parameters and felt they could achieve them; some said they believed they already met the guidelines in their everyday lives.

But a round of treadmill tests told the true story. Participants were asked to walk or jog at "light," "moderate," and "vigorous" efforts in varying orders while the researchers monitored their heart rates and peak oxygen uptakes (a measure of aerobic capacity). Overall, the volunteers nailed the light exercise portion of the test. Their interpretations of light effort were spot-on with the definition they'd been given. But when it came to doing moderate and vigorous exercise, a vast majority of these people weren't exerting as much physical effort as they thought they were — and falling short of what constitutes moderate and vigorous intensity.

RELATED: Fast Fitness: A High-Intensity Workout Plan

The men in the study fared worse than the women. A whopping 87 percent of these guys overestimated their execution of moderate intensity exercise. On average, their heart rates fell 5 percent short of the range considered to be moderate effort. For vigorous intensity, 72 percent of the men missed the mark, although not by as much as they did for the moderate test. Their average heart rate was 2 percent less that it would have to be to hit the vigorous range.

Why do so many people underestimate moderate and vigorous intensity? "It may be that they are not familiar enough with exercise, particularly more strenuous exercise, so they underestimate what they are capable of," says lead researcher Jennifer Kuk, a kinesiology professor at York University, where the study was conducted. "Alternatively, all of the health-promotion messages we receive that call exercise 'fun' and say it's 'easier than you think' may be leading people to think that moderate and vigorous are easier than they actually are."

The best way to do get a handle on what both moderate and vigorous intensity actually feel like, says Kuk, is to determine your maximum heart rate by subtracting your age from 220. So if you're 30 years old, your max heart rate should be 190 beats per minute. Next, measure your heart rate while exercising with an electric monitor, which sport watches often have as a feature. Kuk says light intensity will be 50 to 63 percent, moderate intensity will be 64 to 76 percent, and vigorous intensity will be 77 to 93 percent of your maximum heart rate. If you're not hitting these numbers, it's time to start pushing yourself a little harder.

"The second way to determine intensity is with the talk test," Kuk says. "This is more subjective, but in general, while doing moderate exercise, you should be able to talk but not sing. When doing vigorous exercise, you will not be able to talk. Engaging in moderate- and vigorous-intensity activity is essential for health, so it is important that people really understand what those mean so they can obtain a sufficient level of intensity."