Six years have passed since the Office of Disease Prevention and Health Promotion published Physical Activity Guidelines for Americans (PAG). Researchers funded in part by a grant from the Heart and Stroke Foundation and the Faculty of Health at York University, Canada, responded a few weeks ago. Their findings were published in PLOS ONE: Adults underestimate the intensity level at which they work out.
The PAG report differentiates absolute intensity—the amount of energy expended per minute of activity—from relative intensity, the level of effort required to do an activity. "A general rule of thumb is that two minutes of moderate-intensity activity counts the same as one minute of vigorous-intensity activity," according to the PAG. Although the absolute-intensity levels might reflect similar energy expenditures, the relative-intensity levels are not the same, and overcompensating with vigorous-intensity workouts so you can get out the door faster in the morning or make it back to work in time can hurt you.
And the more recent study? Researchers started by asking participants if they were familiar with the national exercise guidelines. Most were not, but when they were handed a copy, participants felt they could follow or already were following the guidelines, the New York Times reported.
Then they took to the treadmill and were asked to maintain a vigorous-, moderate-, and light-intensity level for three minutes. "Few" ran at 65 percent (desired) of their maximum heart rate when running "moderately," and "even fewer" ran at 75 percent during their vigorous-intensity stint. When participants ran at "the slowest pace that they felt would qualify as moderate [or] the slowest pace at which someone could expect to gain significant health benefits from the exercise," about 25 percent of participants met the pace.
Worse: Current reports on U.S. and Canadian adults say that only 15 to 25 percent work out at levels intense enough to meet national guidelines. If participants played up their intensity levels, "the problem of physical inactivity may be even larger," Dr. Jennifer Kuk, who oversaw the runners, told the New York Times.