I tend to view skeptically science reporting that leans heavily on simplistic concepts and flashy titles. However, “skeptical” does not mean “dismissive”. Mainstream reporting may focus on click-bait terms but that does not necessarily mean anything about the underlying science.
I have seen lots of recent headlines about the benefits of being a “weekend warrior” and decided to look at the primary research. The net benefits of getting most of your physical activity over the weekend, rather than spread throughout the week, are not intuitive. Being relatively inactive for 5 days a week may have it’s own negative health impacts. Also, trying to compensate for lack of time with increased intensity can have its risks. But at the same time, a “week” is an artificial construct, not a biological concept, and so perhaps averaging physical activity over this timeframe may be just fine.
Let’s look at the recent study prompting those headlines – Associations of “Weekend Warrior” Physical Activity With Incident Disease and Cardiometabolic Health. First I note that the “weekend warrior” meme comes from the researchers and is not an invention of the media. This does not mean it’s automatically a good thing – often researchers or press offices will use techniques to increase the visibility of their research and the media happily comply. But in this case I think it’s a benign shorthand for people who get most of their exercise on the weekend.
The study looks at “89,573 participants (62±8 years of age; 56% women) of the UK Biobank prospective cohort study who wore an accelerometer for 1 week between June 2013 and December 2015.” So this is a retrospective correlational study (even though the data comes from a prospective cohort study). It is not controlled or blinded. The advantage of these kinds of studies is that you can look at large numbers of subjects. The downside is that it is difficult to account for every possible confounding factor.
One apparent weakness is that subjects only had to wear an accelerometer (like a FitBit) for one week. We cannot assume this one week is representative of their long term activity.
They broke the subjects into three groups – <150 minutes of moderate or greater physical activity per week, >150 minutes per week but with 50% or more concentrated in two days on the weekend, and >150 minutes but spread out more evenly throughout the week. When compared to the inactive group, the weekend warrior group and the regular exercise group both showed a significant decrease in risk for >200 conditions assessed. The associations were strongest for cardiovascular disease. When compared directly to each other, there was no difference between weekend warriors and regular exercisers. There was also no difference when compared to those who got >230 minutes of exercise per week.
Taken at face value, this can be seen as good news. I think what this data is telling us is that being inactive is extremely unhealthy, and that any exercise is better than no exercise. First, moderate exercise is sufficient to see the health gains demonstrated in this study. This can include walking, doing housework, or pretty much anything where you are standing and moving around.
Further, the bulk of the benefits are seen with 150 minutes of exercise per week, regardless of how it is distributed. So if you can get out for a two-hour walk on a Saturday to supplement your daily physical activity of just going about your business, that can get you to the threshold. Or you can take a 30 minute walk in the evenings. This kind of physical activity can be achievable for most, even older, people.
It’s important that when making public health recommendations that we don’t make the perfect the enemy of the good enough. The notion of “regular exercise” may seem intimidating to many people, either because of their busy schedule, or because they have physical limitations. Often the concept of “exercise” is paired with imagery of people in their 20’s engaging in vigorous exercise. So it’s important to get the message out there that even modest amounts of moderate exercise (equivalent to walking) has demonstrable health benefits. Again, this can be framed as, an extreme sedentary lifestyle has health risks.
On the other hand, this research is not saying that there are no benefits to exercise beyond this minimum threshold. Resistance exercise can build bone and muscle, or maintain bone and muscle, which has huge impacts on quality of life for older adults. There are also aspects of “fitness” that go beyond disease prevention, which was the focus of this study.
One other general point to pull out of this study is that the benefits of lifestyle factors are often not linear. It is a cognitive bias in humans that we tend to default to linear assumptions (the so-called linearity bias). But the world is often not linear. In medicine this often manifests as the assumption that if a little is good, then more is better, and extreme amounts will have extreme benefits. This is the faulty logic behind megadosing vitamins.
Here we are seeing massive benefits when going from little to no exercise to moderate exercise, and then a relative plateauing of benefits beyond 150 minutes of moderate exercise per week. Other research shows continued increase in benefits (depending on the outcomes followed), such as this study of A-fib which found the benefits of exercise continued even to the >300 minutes per week group. But still, the steep part of the curve is at the low end.
This is often the case, and a good general approach to health – avoid extreme unhealthy lifestyles, pick the low-hanging fruit wherever possible. Most of the health benefits are likely to be found with just moderate good lifestyle choices, without the need for extreme routines or diets.
We can also take an “intention to treat” approach to lifestyle recommendations. Emphasizing extreme or difficult choices may cause many people to throw up their arms in defeat and do nothing. But emphasizing the benefits of just moderate choices are more likely to change behavior.
