Newsletter #314: Extreme Exercise & Lifespan 🫀
There is no doubt that aerobic exercise is beneficial for health, and associated with longevity.
Interestingly, we still don’t fully understand the underlying mechanisms that drive this association. For instance, exercise has been shown to be 40% more protective against cardiovascular disease than what would be predicted based on its measurable effects on traditional risk factors (blood lipids, blood pressure, blood glucose).
However, the impact is undeniable, and research that examines the impact of physical activity on mortality suggests that greater benefits continue to be accrued in amounts that are 3-5 times greater than current established guidelines. So, generally speaking, more is better.
But there has been a simmering debate, going on for decades, over whether there is an optimal dose of exercise, beyond which point it actually starts to become harmful. It’s notable that cross-sectional studies that compare people who have engaged in varying amounts of activity sometimes find a so-called “U-shaped curve.” Basically, low and moderate levels of physical activity are shown to lead to significant reductions in risk factors and mortality compared to being sedentary, but very high doses of strenuous and/or prolonged exercise start to move the arrow in the wrong direction. The model looks something like this:
From: https://link.springer.com/article/10.1007/s11936-018-0674-3
And it honestly sounds pretty plausible, right? Most interventions in medicine have a therapeutic dose, beyond which you start to see potential toxicity or deleterious side effects. It’s not hard to imagine that a potent metabolic stimulus like exercise might work the same way. Yet figuring out whether this is indeed the case has proven to be harder than you might think, since most cohorts just don’t contain a ton of heavy exercisers. That’s why I’ve always been deeply interested in studies that follow elite athletes, since these are individuals who must engage in large amounts of vigorous exercise for a substantial portion of their lives, presumably way more than most of us ever could.
This month marks the seventieth anniversary of the first sub-4 minute mile, first run by Roger Bannister in Oxford. That accomplishment was immediately followed by a deluge of middle-distance runners who sought to match his remarkable feat, and many were successful. The mile run is an apt event for examining the potential toll of high volume and high intensity exercise. Training to excel at this distance typically demands far more time and volume than you might expect — as much as 9-12 hours of running per week, accumulating 75-105 miles. Furthermore, a greater percentage of this training is performed at near maximal effort, compared to longer endurance races. So, this is arguably an ideal group for examining the question of whether “extreme exercise” might be harmful.
To that end, a retrospective cohort study of the first 200 men to run a sub-4 minute mile was just published this month. Let’s take a look at their findings, and what we might be able to learn from them.
This Week’s Research Highlight
Running a sub-4 minute mile is associated with extended lifespan.
Canadian researchers retrieved data from a publicly available compendium which lists every athlete who has broken the 4-minute mark for the mile. The team selected the first 200, whose runs occurred from 1954 to 1974. They decided to zero in on these men because they were born between 1928-1954, and thus would have all lived long enough to see a clear effect on longevity. The researchers compared the average difference in life expectancy between these men to male members of the general population of the same age and nationality.
Out of the total, 140 of the men were still alive at the time of the analysis. The researchers determined that sub-4 milers lived an average of 4.7 years longer than counterparts in the general population.
It’s worth noting that when the researchers broke the data down by decade, a generational effect emerged. For instance, those who ran in the 1950s lived an average of nine years longer, while those whose attempt occurred in the 1960s or 1970s experienced an increase in lifespan of 5.5 years and 3 years respectively. This probably reflects improvements in the health of the wider population to whom they were being compared, which could be attributable to medical advances as well as lifestyle (diet, smoking, etc). In other words, the control group was living longer, thus diminishing the relative survival advantage of the athletes. This finding is backed by a mountain of research that has found reductions in mortality in elite athletes, including a systematic review of 54 studies that showed that high-level competitors lived 4-8 years longer than controls from the general population.
So, how do we explain the studies showing increased mortality for “extreme exercise?” Well, one issue that you see in this literature is that the number of people in these cohorts who could be categorized as extreme exercisers is often very very small.
A good illustration of this is an oft-cited analysis of the Copenhagen City Heart Study, which compared joggers to healthy non-joggers. The researchers conclude: "The findings suggest a U-shaped association between all-cause mortality and dose of jogging as calibrated by pace, quantity, and frequency of jogging. Light and moderate joggers have lower mortality than sedentary nonjoggers, whereas strenuous joggers have a mortality rate not statistically different from that of the sedentary group."
But look at the table, and you'll see that out of more than a thousand joggers, only 40 participants fell into the "strenuous jogger" category, and there were only two deaths in that group!
(And since causes of death are not identified, it’s entirely possible that one or both of these deaths were due to some sort of traumatic accident, e.g. a car wreck, or something else wholly unrelated to their exercise habits.)
There probably are some physiological tradeoffs associated with extremely intense and/or prolonged exercise. However, these drawbacks likely occur at levels of activity that very few people can or will ever achieve, and they seem to be largely counterbalanced by tremendous health benefits.
Bottom line: If you are trying to maximize your lifespan and healthspan, an ambitious exercise regimen is arguably the most important and most scientifically validated thing that you can undertake.
Random Trivia & Weird News
🏃♂️ Roger Bannister broke the mile record under less than ideal circumstances.
Bannister was not like most elite athletes nowadays. In 1954, he was a 25-year-old medical doctor in training at St Mary’s Hospital Medical School.
When Bannister took the train to Iffley Road Track in Oxford, he had just worked an early shift at a hospital in London. Needless to say, that’s not what most people would consider ideal physical and mental conditions before attempting a physical feat that many at the time considered impossible and perhaps hazardous.
(And alas, his record did not stand for long — just 46 days later, it was already broken by another athlete!)
Bannister, as the first datapoint in the above analysis, died in 2018 at the age of 88 — himself serving as a nice example of the link between aerobic training and longevity.
Photo credit: British Pathé
Podcasts We Loved This Week
- Simon Hill & Danny Lennon: Coffee and health. Via Sigma Nutrition Radio.
- Saima May Sidik: Why loneliness is bad for your health. Via Nature Podcast.
Products We Like
Now Foods Taurine
Taurine is an amino acid-like molecule that occurs naturally throughout the body. Studies have shown that taurine is linked to remarkable reductions in blood pressure, as well as protection against brain deterioration later in life. However, these kinds of improvements are usually seen with much higher doses than what you would find in a normal diet, which is why supplementation is warranted. I typically take three of these at night before bed.
humanOS Catalog Feature of the Week
Going Slow to Go Fast
This week, I’d like to highlight our course on polarized training, developed by Jeff Rothschild. In this course, Jeff examines how manipulating aspects of exercise and diet can favorably influence adaptations to endurance training. Specifically, he reviews how increasing training volume and intensity influence the number and function of our mitochondria, and then takes a look at the training strategies of elite marathoners and cross-country skiers. As the research above demonstrates, we can learn a lot from the best athletes, in both health and performance.
At the end of the course, he ties it all together and explains how you can apply this science-based info to your own training.
Wishing you the best,
