A new study has changed the exercise advice I give to my patients in the clinic.
The standard recommendations are to get at least 150 minutes a week of moderate intensity exercise or 75 minutes a week of vigorous exercise (which is useful if you’re short on time).
This assumes vigorous exercise is about twice as effective as moderate. But a new study blows that assumption out of the water. And this has some important implications for how we approach exercise to maximize our health.
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The Study
The new study draws on data from the massive UK Biobank, which collects comprehensive health and lifestyle data on over half a million participants. The study authors looked at information about activity levels and health outcomes for a subset of this group. Their goal? To see how the impacts of light, moderate, and vigorous physical activity compare. They wondered: Is it really true that 1 minute of vigorous activity has the same effect as 2 minutes of moderate activity? [1]
In the past, this would have been difficult to answer. Previous studies exploring links between exercise and health typically rely on self-reported data, where participants answer questions about their exercise. That method is fraught with potential bias, meaning we haven’t had much confidence in the results.
But this new study draws on a novel kind of data to fill in the picture in a way we haven’t been able to do in the past. A portion of the participants in the UK Biobank wore devices — like a smart watch — that measured and recorded activity levels. This gives us access to much more accurate data.
So what did the researchers discover when they sifted through this new data?
Shockingly, vigorous physical activity wasn’t found to have double the impact of moderate physical activity. Instead, it had 4 to 9 times the impact [1].
There’s a range here because the relationship between exercise type and health benefit varies depending on which health outcome you're looking at. For all-cause mortality, it was 4.1 minutes. For heart-disease-related mortality, it was 7.8. The highest number was 9.4 for type 2 diabetes [1].
And this study also looked at something that’s much less talked about: light intensity activity, like leisurely walking. Here, as you’d expect, we need a much greater volume to see the same impact as 1 minute of vigorous activity. The researchers found it ranged from 53 minutes with all-cause mortality to 94 minutes with type 2 diabetes risk [1].
Think about this for a moment. The data shows that it takes almost 10 times as much moderate activity to see the same benefits as 1 minute of vigorous activity when it comes to the risk of developing type 2 diabetes. If we stick to light physical activity, we need about 100 times as much.
The implications are huge. The standard advice that says 75 minutes of vigorous activity is about as helpful as 150 minutes of moderate activity looks way off. If this study is right, we’re going to need at least 300 minutes of moderate activity to gain the same benefits for all-cause mortality.
How Low? Other Biobank Studies
But practically speaking, what does this all mean in terms of the exercise advice that I give to my patients?
This is best explained if I give you two patient examples.
Let’s start with Simon. Simon is short on time, so he wants to know what the minimum amount of exercise he should do is and still get most of the benefits of exercise.
A separate, recent study has changed our understanding.
In the past, studies generally focused on structured exercise. In other words, they tended to measure activities like going for a walk, lifting weights, and so forth. The reason is that we’re much better at accurately recalling our activity when it comes in this form. If I ask you how much exercise you got in the past week, it is these kinds of activities that will come to mind.
But we often engage in physical activity that isn’t structured in this way. For example, you might go up and down the stairs in your house several times a day. And maybe you recently carried out several heavy boxes to the trash and raked up grass clippings in your yard. For me, jumping on the trampoline with my kids is something that I wouldn’t necessarily think to count as exercise. These kinds of activities are hard to accurately recall. So they’ve also been difficult to measure and include in studies.
Wearable motion trackers give us a way to objectively measure these kinds of activities without relying on memory. And that unlocks an entirely new stream of data.
Researchers recently took advantage of this data to make a startling discovery. They were looking at the UK Biobank cohort. But this time, they focused their attention on “nonexercisers.” These were people who reported no leisure-time exercise and no more than one recreational walk per week [2].
Even though they didn’t participate in structured exercise, researchers were curious about their physical activity throughout the week. In particular, they looked for how often they performed vigorous activity as they went about daily life. They call this type of activity Vigorous Intermittent Lifestyle Physical Activity, or VILPA. And then they analyzed how levels of VILPA are associated with all-cause, heart disease, and cancer mortality [2].
This is the kind of exercise that would be invisible to traditional study methods.
So here’s what they discovered. Let’s start with the median number of times a person engaged in VILPA each day. This is the amount of activity where half the people in the sample are doing more, and half less. The median was 3 bouts of activity a day lasting 1 to 2 minutes each [2].
Remember, these are nonexercisers. So this is all the vigorous activity they’re getting in a typical week. It amounts to about 6 minutes a day at most, so just 42 minutes a week. What difference did it make? Well, compared to those with no VILPA, the median frequency was associated with an incredible 38–40% reduction in all-cause and cancer mortality risk. And there was a 48–49% reduction in heart disease mortality risk [2].
At a minimum total daily time of VILPA of 3.4–4.1 minutes, researchers saw an average mortality risk drop of 22–28% [2].
This study showed exercise has a strong dose response that fades the more of it we get. In other words, the first chunk of exercise appears to be more beneficial than the second, and the second is more beneficial than the third, and so on until we reach a point where it makes little difference.
When we go from no bouts of VILPA to 1 bout a day, the mortality risk drops sharply. But by the time we go from 4 to 5, the drop is barely perceptible.
This tells us that simply going from sedentary to a little activity captures a large share of the benefits we’ll get from exercise in terms of mortality risk. So someone who works in a bit of VILPA and someone who exercises regularly are both going to see massive gains compared to someone who is totally inactive.
So for Simon, since he’s so short on time, I encourage him to focus on exercise snacks. Walk up 1–3 flights of stairs instead of taking the elevator, for example. Personally, I’ll do some sets of push-ups or wall squats during my breaks while I’m in between patients at the clinic. I can easily do a 1–2-minute bout of activity 3–5 times a day. On clinic days, I don’t have to head to the gym, I don’t need special equipment, and I don’t have to shower afterward because the duration of each exercise snack is small enough that I don’t work up a sweat. And by pursuing this strategy consistently, we can reap the lion’s share of the benefits of exercise.
If Simon can manage to get some time to dedicate to exercise, though, he should add some vigorous forms. Done safely, this will give him the most bang for the buck, as we saw with the new study we reviewed earlier in this article.
Henry
Then there’s Henry, another patient at the clinic. He’s in a season of life where he has heaps of time to exercise. So what advice would I give him?
Well, the research we’ve been looking at makes one thing clear: vigorous physical activity is far superior to moderate or light activity in terms of its payoff. So I would advise Henry, also, to include it in his weekly routine. But we mustn’t overdo it and risk injury. So I’d advise Henry not to do more than 2 high-intensity workouts per week.
Instead, I’d advise Henry to add some zone 2 training. Zone 2 training is when we’re working at an intensity where we can still carry on a conversation.
How much more does it make sense to add? One long-term cohort study found a measurable health impact from getting up to 600 minutes of moderate activity [3].
So if Henry really had that much time to dedicate to his fitness, including lots of Zone 2 training would be required — in addition, of course, to resistance training and power training.
But the point I want to emphasize in this article is that we can do a lot of good for our health even at a much lower volume of exercise, particularly when it’s high intensity. And all of us can add exercise snacks to our schedule, no matter how busy we are.
