Daily wisdom: the Truth about intensity

A study out of Brigham Young University has understandably generated a lot of buzz in the fitness community. It found that adults who were highly active five days per week were younger biologically by nine years when compared to their sedentary or even moderately active counterparts. “This is represented through the length of their telomeres, which shorten as cells turn over and die,” explains Berenc. “Shortening of telomeres is often linked to stress on the cell and inflammation. Exercise has been shown to help reduce both of those factors potentially leading to the longer length.” In short, exercise can keep you biologically younger even as you age.

But perhaps more interesting to high performers than the study’s conclusion: how the study authors define high levels of exercise. To be highly active, women had to engage in 30 minutes of jogging per day (40 minutes for men), five days a week. To some athletes, this seems pretty moderate.

The authors of this study likely based their methodology on The Office of Disease Prevention and Health Promotion’s definitions of exercise. The Office defines moderate intensity activity as one that expends at least three times the amount of energy expended at rest (i.e. brisk walking, house cleaning, gardening, biking slower than 10 mph, and even some office work). To qualify as vigorous exercise, you must expend six times the amount of energy you would at rest. This could be jogging, jumping rope, swimming laps, hiking uphill, or biking faster than 10 mph.

In terms of frequency, training three to five times per week for a minimum of 30 to 40 minutes is indeed technically highly active, per Berenc. "As is shown in the study, there are significant health benefits found with this type of training, with more coming at the higher frequency," he says. If you’re thinking, “that doesn’t seem so intense,” you’re not alone. “What we need to keep in mind is that these guidelines apply to all Americans, regardless of fitness level,” Berenc notes. In other words, what may be easy for you could be seriously tough for others who aren’t regular gym-goers.

“This is where relative intensity, or how intense an activity (or duration of an activity) is to you, is likely a better option to use in determining how hard, for how long, and how frequently you should work out,” says Berenc. Also known as a rating of perceived exertion, relative intensity has you rank the difficulty of an exercise on a scale of one to 10 (with 10 being your max effort). As it relates to this study, we can define moderate activity as a five or six out of 10 and vigorous activity as seven or higher out of 10, per Berenc. “The benefit of using this scale is as you become more fit and can perform at a higher level, it retains its accuracy,” says Berenc.