HHN: How much exercise should adults get each week to stay healthy?
CG: Most people will significantly improve their health and fitness by doing 150 minutes, or 2 ½ hours, of moderate exercise every week.
This doesn’t mean that if you exercise less, you aren’t going to get healthful benefits. You’ll still get benefits, but not as much benefit as you would if you reached the target amount.
Why 150-Minute Movement Matters
HHN: How do we know that 150 minutes per week is the right target for health benefits?
CG: Hundreds of large population studies worldwide have compared people’s self-reported [pullquote-right] "People all over the globe who exercise about 150 minutes/week or more have a 25%-50% reduced risk of heart disease, diabetes, and some cancers." [/pullquote-right] exercise habits and various health outcomes. Consistently, active people all over the globe who exercise about 150 minutes/week or more have a 25%-50% reduced risk of heart disease, diabetes, and some cancers: breast cancer, colon cancer, and prostate cancer.
HHN: A 25% - 50% reduced risk is quite a range.
CG: That’s the range we see in the research. A reduced risk of 30% - 40% is most often found, but sometimes it’s lower and other times higher. In all likelihood this variability largely reflects individual differences in people’s responsiveness to exercise.
It’s interesting that this range is similar for most chronic diseases we’ve studied. An equivalent reduction in risk may hold true for other cancers as well; we just don’t have enough data to say yet. Since many cancers have common risk factors, such as being overweight, I think it’s very likely that the 25−50% lowered risk holds true across the board.
HHN: How does exercise effect longevity?
CG: On average, people who exercise 150 minutes per week live about two years longer than those who don’t. In other words, for every minute you spend exercising, you add 7 minutes to your life expectancy—not bad odds!
Cynics who don’t like exercise might say, "I'd rather die two years earlier than spend those years doing something I hate," but [pullquote-right] "For every minute you spend exercising, you add 7 minutes to your life expectancy." [/pullquote-right] the larger reality is, people who stay active age more healthfully, and as such have a higher overall quality of life. In later years they’re less frail, more independent, and better able to do activities of daily living than their sedentary counterparts.
Basically, physical activity enables people to do what they like to do for much longer in their lives.
HHN: Are there other vital health benefits associated with exercise?
CG: Most randomized controlled trials of people who are depressed or anxious show starting an exercise program in the recommended range reduces feelings of depression/anxiety. [pullquote-right] "One study found that exercise could be as effective as medication or other therapies for depression." [/pullquote-right] One very nicely conducted study of 156 men and women aged 50+ conducted by James Blumenthal of Duke University found that exercise could be as effective as medication or other therapies for depression. We’ll need a lot more data, though, before we tell people to throw away their medicines.
Consistent with this finding, in a two-year intervention study I oversaw, 904 men and women aged 60+ were randomly assigned to one of four intervention groups—physical activity, diet, physical activity and diet, [pullquote-right] "In an intervention study, the older adults who exercised about 150 minutes a week reported being in a better emotional state than the control group of non-exercisers." [/pullquote-right] and a control group—and the older adults who exercised about 150 minutes a week reported being in a better emotional state than the non-exercisers. What did surprise us was the very large increase in depression and anxiety seen among those who exercised considerably more than the recommended minutes. Now, these are association data, so we can’t say that over-exertion leads to depression or anxiety, or any other cause and effect. It’s possible that some people who are anxious tend to exercise more. Some literature associates more excessive amounts of exercise with obsessive-compulsive behavior and eating disorders.
Overall, then, there’s no question that making a habit of moderate exercise can reduce your risk of heart disease, diabetes, and some cancers by up to half, alleviate depression and anxiety, increase longevity, and contribute to healthy aging. These are powerful effects. No drug can match these benefits. Exercise is truly the best medicine we have.
HHN: Since people who exercise regularly may have other healthy lifestyle habits, how do we know that exercise and not other confounding factors is responsible for these outcomes?
CG: All the data from these population studies adjusts for other potential factors, such as age, preexisting conditions, smoking habits, gender, and nutrition, as well as that can be measured. We are confident that the 25−50% risk reduction for cardiovascular disease, diabetes, and some cancers is an independent effect of being more active.
In addition, hundreds of randomized clinical trials have randomized a group of people to different exercise programs or no exercise, and here too, we find that 150 minutes [pullquote-right] "We are confident that the 25−50% risk reduction for cardiovascular disease, diabetes, and some cancers is an independent effect of being more active." [/pullquote-right] of moderate exercise weekly generally helps people improve their aerobic fitness, muscular fitness, and/or body composition. In addition, this exercise regimen leads to improvements in risk factors or biomarkers— e.g., lowering of high blood lipids/cholesterol, high blood pressure, abdominal body fat, insulin resistance levels, blood glucose levels—associated with chronic diseases such as cancer, heart disease, and diabetes.
HHN: You said that 150 minutes per week "generally" helps people improve their fitness. In other words, this isn’t necessarily true for everyone.
CG: Right. There’s variability among individuals. Some people who exercise a lot less do well, and some people need a lot more to receive the same benefits.
HHN: How much individual variability is there, and why do some people progress more quickly than others?
CG: Most people will experience an average or near average response to aerobic training. So, for example, after 3 months of training, about 60% will increase their VO2 max, [pullquote-right] "Some people who exercise a lot less do well, and some people need a lot more to receive the same health benefits." [/pullquote-right] the maximum rate they are consuming oxygen during exercise, by about 10% - 20%. Approximately 3% will be at the very high and another 3% at the very low end of the response curve. Many people who don’t progress at the average pace catch up later. Even those who don’t are still likely to get a multitude of benefits from the exercise.
We’re just starting to crack the nut as to why this happens. Some of the differences are genetics, but we haven’t identified the genes that would enable us to say to someone, "You might need to do a little more exercise to get the same benefits," or "You could get away with doing a lot less."
Measuring Moderate Exercise
HHN: Let’s talk about the "moderate intensity" part of the 150-minute exercise equation. How does the American College of Sports Medicine define moderate?
CG: There are a number of ways.
One is percentage of maximum heart rate. You figure your rate by starting with the number 220 and deducting your age. So if you’re 50 years old, your maximal heart rate would be 220 — 50 = 170 beats per minute.
ACSM considers moderate intensity to be 64% - 76% of maximum heart rate. [pullquote-right] "Determining your maximum heart rate with the 220 — your age formula isn’t terribly accurate." [/pullquote-right] So, again, if you’re 50 years old, your heart rate during moderate exercise should be approximately 109 to 129 beats per minute (that's 170 x .64 = 109 and 170 x .76 = 129).
While you can use this method, it may not be practical for the average person, and determining your maximum heart rate with the 220 — your age formula isn’t terribly accurate either.
For most people a better way is rating their perceived exertion: how hard the exercise feels.
HHN: Is there a scale that measures perceived exertion?
CG: Yes. The ACSM uses a Rating of Perceived Exertion scale which goes from 6 to 20. Moderate intensity is a self-report of about 12 to 13.
If you’re wondering why 6 to 20 is the range, back when the scale was developed, it was highly correlated with heart rate, with 6 being equivalent to a heart rate of 60 and 20 to about 200. It turns out this relationship hasn’t held up perfectly, but the measurement still works well for assessing the perception of effort.
All this said, for most individuals, neither of these ratings is ideal. [pullquote-right] "When you’re exercising, ask yourself: Does this feel fairly light to somewhat hard?" [/pullquote-right] There’s a much easier solution that we recommend everyone use: Moderate exercise should feel "fairly light to somewhat hard." When you’re exercising, ask yourself, "Does this feel fairly light to somewhat hard?"
HHN: What about people who use heart rate monitors and apps?
CG: I think they’re great if they help you track and keep up your exercise program. [pullquote-right] "Sometimes heart rate monitors don’t give accurate readouts whatsoever." [/pullquote-right] But make sure you also think about how you feel. Those devices don’t work perfectly. Sometimes they don’t give accurate readouts whatsoever.
Trust your gut. If you’re feeling, "I am working super hard," you probably are.
HHN: Let’s dive into "fairly light to somewhat hard, "because that itself encompasses quite a range. Is the goal to move from "fairly light" to the "somewhat hard" area of the spectrum over time?
CG: The two relevant questions here are: "What does somebody want to do?" and "What will s/he continue to do?"
In general, a goal would be to try to increase intensity. If you start out "fairly light," in time you might want to gradually increase intensity until it feels somewhat harder. Higher intensity exercise does improve fitness. And reduction of heart disease, diabetes, and cancer risk is also dose responsive; more intense exercise over time is beneficial.
On the other hand, people tend to stick with exercise that feels fairly pleasant. [pullquote-right] "Doing a light amount of exercise regularly is way better than pushing yourself for additional improvement and then not exercising at all." [/pullquote-right] Some people don’t enjoy exercising at the higher range of the moderate scale and then stop. If you might be one of those people, doing a light amount of exercise regularly is way better than pushing yourself for additional improvement and then not exercising at all.
Mixing Up Your Minutes
HHN: For great health outcomes, does it matter how you reach your 150 weekly minutes?
CG: There are lots of ways to approach your minutes. You might exercise anywhere from 2 to 6 times a week. The one option we typically don’t recommend is doing all 150 minutes in one day.
HHN: Is it problematic to get all your exercise in a single day, such as on a long weekend bike ride?
CG: There’s very little data on this. One good study at the Harvard School of Public Health looked at Weekend Warriors who exercised 1x -2x weekly. For those with a chronic disease, the exercise showed adverse impact, but for healthy individuals, it postponed their mortality. So, if you’re healthy and too busy during the week, you can do your 150 minutes on the weekend and probably get similar positive health results.
Just keep in mind that there’s a risk of overuse injury. Studies of injuries show that they are more common with longer duration and more vigorous exercise.
HHN: Exercising for 2 ½ hours even on a weekend might not be practical for very busy people. Are there other effective options?
CG: Yes. People pressed for time can exercise harder in fewer minutes. Instead of 150 minutes at moderate intensity, experienced exercisers can do 60+ minutes weekly at vigorous intensity, perhaps 20 minutes three days a week.
Vigorous exercise disperses more calories or uses more energy more quickly, so in terms of total energy expenditure, one of the most important determinants of health benefits, the 150 moderate and 60 vigorous minutes guidelines appear fairly equivalent. That’s likely why we see similar health outcomes.
Vitals of Vigorous Exercise
HHN: How does the American College of Sports Medicine define "vigorous" exercise?
CG: The three definitions would be:
- 77% to 95% of your maximal heart rate. Again, to get your maximum heart rate start with 220 and subtract your age. Then to get your vigorous range, multiply the maximum heart rate number by .77 and by .95.
- A 14 — 17 Rating of Perceived Exertion on the 6 — 20 scale.
- Your personal feeling that the exertion is "somewhat hard to very hard."
You can also accomplish more in a shorter period of time by using an interval approach: exercising for a couple of minutes [pullquote-right] "A body of research shows that interval training can expedite fitness improvements." [/pullquote-right] at the "somewhat hard to very hard" range and then alternating with a "fairly light to somewhat hard" intensity. A body of research shows that this kind of interval training can expedite fitness improvements such as maximal oxygen uptake. This may be because intervals allow you to spend more time in high-intensity exercise than you might be able to do otherwise, stimulating changes in cells that result in improvements in cardiorespiratory, metabolic, and muscle function.
Staying Sedentary isn’t Smart
HHN: Have there been any brand-new exercise discoveries with important health implications?
CG: A new finding is that what you do when you’re not exercising can influence your overall health. [pullquote-right] "Just one day of sitting can turn off fitness-related proteins involved in glucose and fat metabolism." [/pullquote-right] Just one day of sitting can turn off fitness-related proteins involved in glucose and fat metabolism. So, even if you meet the recommended activity guidelines, if you’re spending many hours sitting, it reduces the health benefits of your exercise. The percentage of reduction in benefit isn’t yet known, but it clearly has an attenuating effect.
In short, acute changes are happening to us that aren’t necessarily observable by us. The good news is that if we just move around, say for a couple of minutes every hour, we can easily change the outcome.
HHN: Why does a long period of sedentary activity make such a difference?
CG: We now know that changes in blood flow and metabolic activity happen quickly and quite acutely in the body. Our body adapts to whatever we’re doing. So, just as exercise induces an increase in our body’s use of glucose, spending a lot of time sitting can induce a shift to a less efficient metabolic state in in our muscles.
HHN: So, to get great health outcomes, stay moderately or vigorously active in moderation and keep moving even when you’re not exercising.
CG: Exactly. There are so many activities that can build and maintain physical fitness, and a variety of time and intensity options to meet different people’s schedules and abilities and result in similar health outcomes. I hope you’ll give 150 weekly minutes of moderate exercise or 60 weekly minutes of vigorous exercise a try.What Every Adult Should Know About Exercising for Health. Click To Tweetby