Worked Up, Working Out

It’s been a frightening week to work out, or so it seems. Exercising too hard can make your muscles break and kill you, and likewise, thinking you aren’t exercising as hard as you should be can apparently kill you too. So, dead either way? At least if you go off running with the latest headlines, that’s what one could think.


It’s an important finding that going too hard in spin classes can lead to rhabdomyolisis, which if you haven’t heard of it, is the breakdown of muscle tissue that leads to muscle fiber contents being released into blood [here]. Doctors highlighted cases of spin class-induced rhabdomyolysis in a recent article, pointing out that in 42 of 46 cases of spin-induced rhabdo, it occurred after their first class [here]. Now let me be clear; it’s no joke. Urine turning brown, decreased kidney function, potential death. Not stuff to fuck around with. At the same time, it’s important to think about how often it actually occurs.

Though the doctors said it’s “on the increase”, there wasn’t a specific number of cases. That makes sense in large part because it’s complex to count rare events in the population that only get measured when people go to the hospital. One study of military recruits counted 22.2 cases per 100,000 soldier-years [here]. For reference, there are about 200 heart attacks per 100,000 person-years in the U.S. [here]. Another study from 1997 estimated 26,000 cases of rhabdomyolysis are reported in the United States every year [here]. The main point to consider here is that rhabdomyolysis is a rare event, but counting exactly how many cases is “more” in a challenge. It’s also worth mentioning that rhabdomyolysis is more common in statin users [here], since 28 percent of Americans over 40 take them as of 2012 [here]. With hip pain following high intensity workouts also increasingly common, the high-intensity workouts du jour are no joke.

Then we have the finding that people who believe they are less active than their peers are more likely to die earlier than those who think they are as active or more active, regardless of their body composition, actual exercise habits, and health [here]. What is important about this finding is that while it was one study, it was one study conducted with three different samples, each of which had several thousand people. The authors measured perceived activity with self-report and actual physical activity with either self-reported measures of types of activity, or objective measures with instruments called accelerometers, and verified mortality using vital statistics (aka death certificates). There was a gap of up to 21 years between collecting the exercise data and the death data (records through 2011), which doesn’t allow causal inference, but at least prevents reverse causality (although arguably, would dead people really report they are more active than their peers??).

What I find interesting about this study is the set of questions it leads to. Is it a placebo effect? Is it mind over matter? Why would thinking you are less active than your peers be associated with earlier mortality (is it about the exercising at all)? That leads to a few questions I would have for future research. If the authors had a variety of social comparisons (how much money do you make, how active are you, how good is your sex life, how happy are you, etc.), would they find the same thing? Does thinking you are active really make health better? Some studies have found optimists have better health, perhaps because of lesser stress [here]. And more importantly, if this were a causal relationship, would changing people’s perceptions actually prolong (and perhaps along the way, improve) their lives?

These are fascinating findings in the context that 80 percent of Americans don’t meet exercise recommendations from the CDC [here]. For the record, for adults, it’s 2 hours and 30 minutes a week of moderate-intensity, or 1 hour and 15 minutes a week of vigorous-intensity aerobic activity, and resistance training two days per week [here]. So questions this raise for me are: what role can and should exercise play in health, who are the people we compare ourselves to, and why are we exercising so hard? These highlight the importance of moderation, and in paying attention to your own body, and for coaches/instructors/teachers, the importance of letting athletes slow down when needed. It’s also important to remember the severe outcomes are rare, and total fear isn’t the way to go either. Now if you’ll excuse me, it’s time for me to get after it.