Tag: cardio

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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There’s a big new study out in the New England Journal of Medicine that takes a comprehensive look at every case of cardiac arrest during every marathon or half-marathon in the U.S. with more than 100 participants between 2000 and 2010. It’s being widely covered in the press; you can read a good summary in the New York Times or in the Globe and Mail, among other places. The primary message: these events are rare. There 59 cases of cardiac arrest, of which 42 were fatal. That translates to a 1 in 259,000 chance of dying, which is much lower than previous reports and than many other sports.

I’m actually in Houston right now for the U.S. Olympic Marathon Trials, and it happens that Aaron Baggish of Mass General, the senior author of the study, was giving a talk this morning to the members of the World Road Race Medical Society — so I popped in to hear what he had to say. A couple points he made that I found interesting:

Weather wasn’t a factor. The average starting temperature during events where someone suffered a heart attack was almost identical to the 10-year average (55.9 vs. 55.5 F), and the average deviation was just 0.3 degrees.

For 31 of the cases, they were able to track down either the survivor or the next-of-kin and get full medical records, autopsy results, and running history — so this allowed them to really look at the causes of death in detail. One of the surprises is that none of the runners died from a ruptured plaque producing a blood clot, which is (or at least was) thought to be one of the possible mechanisms of sudden death in athletes. The problem with ruptured plaques is that they’re hard to predict in advance. But if underlying coronary artery disease is the real problem (more on that in a sec), then pre-exercise cardiac screening should be able to pick some of that up, Baggish argues.

The average age of the people who survived cardiac events was 53; the average age of the people who died was 34. There are two distinct groups here. One is young people with thick hearts (“hypertrophic cardiomyopathy”), an underlying genetic conditionl; when they collapse, they’re very hard to revive and tend to die. The other is older men with narrowed arteries (coronary artery disease) due to the usual risk factors; when they collapse, they can often be revived if someone gets to them soon enough.

That brings me to one of Baggish’s key point: the absolute best predictor of whether someone would survive cardiac arrest during a race was simple: did a bystander start CPR immediately, before paramedics got there? The lesson is simple: we should all — runners, family members, spectators, heck, everyone in society — have basic CPR training. It could make all the difference to someone, including you.

Baggish’s overall message: running (and by extension, other aerobic activity) is generally safe — but it doesn’t give you immunity from heart disease. That means that everyone, and particularly older males, should be alert for warning signs and not ignore them. Some key ones:

• a burning sensation in the chest (could be confused with acid reflux) that comes on when you start running then gradually fades away, and keeps recurring;
• breathing more heavily than you’d expect given your effort;
• persistent, unusual fatigue.

None of these risk factors necessarily mean something is wrong, but they can be a signal that it’s worth checking in with your doctor to see is you’ve got coronary artery disease that needs to be addressed before racing a marathon.

Last point. Previous studies have shown that most marathon race deaths occur in the final mile or at the finish; this study confirms that. The implication: if you have reason to worry about your heart’s health and want to minimize that risk, think twice about your final sprint. Here’s the data, broken down by race quartile:

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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A new study in Medicine & Science in Sports & Exercise, from the same group in Kansas City that previously found lower fetal heart rates when mothers exercised during pregnancy. This time, they were looking for a dose-response effect — the more exercise, the lower the heart rate — which would strengthen the case for causality rather than correlation. Here’s what they found:

“A” is “active” and “Q” is “quiet (as in whether the fetus is moving around or lying still). The Q results weren’t statistically significant, but for the A results, greater intensity did indeed lead to lower heart rates. But perhaps most significant is what they didn’t find:

Interestingly, maternal factors (i.e. maternal age, maternal resting HR, maternal weight gain, pre-pregnant BMI) did not influence the associations between physical activity and fetal parameters. Fetal cardiac autonomic control was enhanced in mothers who participated in physical activity regardless of the amount of weight they gained, their weight status prior to pregnancy, resting HR or age.

In other words, they’re not saying that fit mothers have fit babies; they’re saying that active mothers have fit babies.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

Anyone remember this Twitter spoof video from back in 2009, when Twitter was just catching on? It’s all about “Flutter,” which “takes microblogging to the next level” by restricting the length of each message to 26 characters instead of 140 characters. Nanoblogging, they call it.

I couldn’t help thinking of this when I read this new study in the European Journal of Applied Physiology about “reduced-exertion high-intensity interval training” (REHIT). Over the last few years, high-intensity interval training (HIT) has gotten a lot of attention as a time-efficient way of getting many of the health benefits of aerobic exercise. There are various protocols — the classic is four to six 30-second sprints with 4:00 easy jogging or cycling to recover between each one; another common one is alternating bouts of 1:00 hard with 1:00 easy. These workouts seem to be highly effective at improving traits like insulin sensitivity. But there’s a catch, according to the authors of the new study:

However, whilst these observations [about HIT] are interesting from a human physiological perspective, their translation into physical activity recommendations for the general population is uncertain for two reasons. First, the relatively high exertion associated with ‘classic’ HIT sessions requires strong motivation and may be perceived as too strenuous for many sedentary individuals. Second, although a typical HIT session requires only 2–3 min of actual sprint exercise, when considered as a feasible exercise session including a warm-up, recovery intervals and cool-down, the total time commitment is more than 20 min [gasp!], reducing the time efficiency. Thus, there is scope for further research to determine whether the current HIT protocol can be modified to reduce the levels of exertion and time-commitment while maintaining the associated health benefits.

In other words, the “140 character” version of exercise is still too damn long, so we need to shorten it to 26 characters!

So here’s the protocol they used. The subjects (29 sedentary young men and women) did three workouts a week for six weeks. Each of these workouts was exactly 10 minutes long, and consisted almost exclusively of “low intensity” cycling, at 60 W. This is very easy. During each 10-minute workout, the subjects incorporated two 10- to 20-second hard sprints. That’s it. Lo and behold, the men in the REHIT group increased their insulin sensitivity by 28%. Strangely, the women didn’t improve — it’s not clear why there was a gender difference. It may be that the very short sprints are most useful for men, who tend to be more powerful and thus are able to burn through more glycogen in a short time.

Anyway, there you have it: REHIT, the Flutter of exercise. I have to admit, part of me finds this a little funny. Soon we’ll be doing studies to show that, if you’re really and truly unfit, just blinking your eyes will allow you to make “measurable gains” in fitness parameters. On the other hand, the barriers to getting people to exercise really are tough to beat. I’m always encouraging my parents to do a little HIT rather than just stick to low-intensity activity — and they do, but they’re rarely motivated to spend more than 10 minutes in total. So it’s encouraging — and useful — to know that even a very minimal bout of high intensity will help. In the end, though, the message is pretty much what we already knew: every little bit helps — but more is better.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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Is marathon running good or bad for your heart? That question has become a hot topic over the past few years thanks to a few studies showing negative effects like heart scarring and artery hardening in veteran marathon runners. One of those studies was a conference presentation last year that looked at 25 male runners who had each completed the Twin Cities marathon 25 years in a row. Compared to matched controls, the runners had greater plaque volume in their coronary arteries.

Now the same group of researchers has followed up with a similar study of 25 female runners who have run a marathon each year for the past 10 years. In this case, the result (as presented at the American Health Association conference) is exactly the opposite: the runners have fewer coronary plaques than matched controls.

So what to make of this? Neither study has been published in a journal yet, so it’s difficult to analyze the results in detail. It’s possible that the conflicting results are simply a result of the fact that the male marathoners were older, on average, that the female marathoners. Or it may be a physiological gender difference. Or it may have something to do with training history. Or it may be a complete fluke: in the male group, the key difference in the plaque volume was 274±176 vs. 169±170. Those are rather large ranges of uncertainty.

But the real question is none of the above: it’s whether these findings about elevated risk factors translate into compromised health. So far, I’m not aware of any study that links marathon running, or any form of endurance exercise, to elevated risk of death (or any other serious ailment) from any cause. That doesn’t mean such risks don’t exist (they could easily be hidden by the overall positive effect of exercise’s other health benefits). Still, as I wrote in the Globe and Mail a few months ago (and probably reflecting my “wishful thinking” bias), I can’t bring myself to get too worried about these apparent risks in the absence of any direct evidence. As Amby Burfoot wrote, “show me the bodies in the streets.”

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

Here’s an interesting graph from a new paper from the Cooper Institute, the famous fitness institute founded by Kenneth Cooper, the “inventor” of aerobics:

The paper appears in this month’s issue of Medicine & Science in Sports & Exercise, and it shows the results of 52,785 fitness tests performed on men at the Cooper Institute between 1970 and 2009. Each patient appears only once in the data, so it’s not a longitudinal study of how individuals got more or less fit; it’s a cross-sectional study showing how the initial fitness of patients at the institute has changed over the years. The trend is pretty straightforward: a big jump from the 1970s to the 1980s, then levelling off to the 1990s, then a slight decline into the most recent decade.

So… at first glance, I found this data pretty surprising. My naive guess would have been that fitness (as represented in this graph by VO2max determined in an incremental treadmill test) would have declined steadily from the 1970s to the present. After all, we’re always hearing about how society has never been less fit. Instead, it seems that we’re fitter than we were 30 years ago, and other data in the paper suggests that we’re more active too. So does this mean that our current health woes have nothing to do with physical activity level? After all, the data also shows that average weight in the subjects has increased by 8 kg since 1970, while height has stayed the same. So we’re more active, but fatter — a pretty good indicator that diet, rather than exercise, is driving the rise in obesity.

Of course, there are a few caveats. For one thing:

Cooper Clinic patients are self-referred or referred by their employers and are primarily healthy college educated middle to upper income non- Hispanic whites who have access to medical care.

So there’s really no way of knowing whether the average patient who decides to go to the Cooper Clinic is comparable to the average patient from the 1970s. It could be, for example, that the clinic’s clientele has changed as it became famous, so that it now attracts people who are already a bit more serious about fitness. But that’s just speculation. The data may well be a fair representation of societal trends — and if so, I need to revise some of my assumptions.