Exercise can help with mental health, cognitive health, sleep quality, cancer prevention, immune function, high blood pressure, and lifespan extension. So ideally, how much should we exercise? The latest official physical activity guidelines recommend adults get at least 150 minutes a week of moderate aerobic exercise, which comes out to be a little more than 20 minutes a day.
It is true that walking 150 minutes a week is better than walking 60 minutes a week. Following the current recommendations for 150 minutes appears to reduce your overall mortality rate by 7 percent, compared to being sedentary. Walking for only 60 minutes a week only drops your mortality rate about 3 percent. But, walking 300 minutes a week drops overall mortality by 14 percent. So, walking twice as long—40 minutes a day, compared to the recommended 20—yields twice the benefit. And, an hour-long walk each day may reduce mortality by 24 percent! (I use walking as an example, because it’s an exercise nearly everyone can do, but the same goes for other moderate-intensity activities, such as gardening or cycling.)
This meta-analysis of physical activity dose and longevity found that the equivalent of about an hour a day of brisk, four-miles-per-hour walking was good, but 90 minutes was even better. What about more than 90 minutes? Unfortunately, so few people exercise that much every day that there weren’t enough studies to compile a higher category.
Okay, but if we know 90 minutes of exercise a day is better than 60 minutes, is better than 30 minutes, why is the recommendation only 20 minutes? I understand that only about half of the population even make the recommended 20 minutes a day. So, the authorities are just hoping to nudge people in the right direction.
