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Galen Rupp’s revenge: allergies in marathon runners

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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It’s pretty well established that heavy training — the type you might do to prepare for a marathon — can reduce immune function a bit, leaving you more susceptible to colds. Same thing with the race itself, which can trigger a temporary lowering of immune function: it’s well documented that runners have an elevated risk of catching an upper respiratory tract infection (URTI) in the week or so after a marathon.

Except… are those symptoms (e.g. congestion, cough, watery eyes, sneezing, “nasal discharge”) really the result of URTIs? In a new paper in Medicine & Science in Sports & Exercise, a group of mostly British researchers suggest an alternate explanation: allergies. And they provide some intriguing data to support this claim. They studied 208 runners who ran the 2010 London marathon. Before the race, the runners completed an allergy questionnaire and did a blood test to look for reactions to common inhaled allergens (like pollen). After the race, they filled out questionnaires daily for 15 days describing any possible URTI/allergy symptoms. The key results:

  • 47% of the runners suffered from the symptoms of an apparent URTI after the marathon (i.e. they reported symptoms on at least two days in a three-day period during the 15-day follow-up).
  • The researchers also surveyed non-runners who were living with the runners in the study; only 19% of the non-runners reported URTI symptoms during the period, which (the researchers say) argues against the symptoms being due to an infectious disease like cold or flu.
  • 40% of the runners had some form of allergy, based on either the questionnaire or blood test — and the allergy questionnaire was a “significant predictor” of the whether the runner would suffer URTI symptoms after the race.

So what’s going on here? According to the researchers:

The shifting of breathing during exercise from nose to combined mouth and nasal breathing results in a greater deposition of airborne allergens, and unconditioned air, to the lower airways.

They go on to note that these symptoms may be associated with asthma, but that, “worryingly,” few of the runners were being treated pharmacologically for asthma — which they attribute to the fact that asthma meds are restricted by the World Anti-Doping Association. Given that the average finishing time of their subjects was slower than five hours, I find this an extremely strange argument to make! They go on to recommend that recreational runners should be screened for allergies and consider treatment.

I think this is a really interesting topic. It’s been known for a long time that endurance athletes (particularly winter athletes) are far more likely to suffer from conditions like exercise-induced brochoconstriction (basically exercise-induced asthma symptoms) than the general population. Why is this happening? What makes athletes’ airways more sensitive? Is it the airways being dried out by large volumes of air passing through? Is it particulate matter being inhaled and damaging airways? Or is it allergens that are causing inflammation due to all the deep breathing? It would be great to see more research looking into these questions.

That being said, I think this study has some pretty important limitations. I found the presentation of the data to be a bit lacking — it’s very hard to get a precise sense of just how different the allergy and non-allergy groups were, to see how strong the data really is. But the more fundamental issue is simple: selection bias. The subjects “were recruited randomly during the 4-day registration exhibition before competing in the 2010 London Marathon.” So which people would be more likely to agree to fill out a questionnaire about allergies and give a blood sample for allergy testing? Probably people who have, or believe they have, allergies. So when the results tell us that a very high proportion of runners have some indication of allergies, that doesn’t necessarily hold true for all runners!

Still, a thought-provoking paper: maybe the famous “post-marathon cold” isn’t quite what we thought.

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More on altitude training research

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Yesterday’s post about Carsten Lundby’s altitude study sparked some fantastic discussion in the comments section, on Twitter, and over e-mail. I really appreciate everyone who took time to share their thoughts and expertise, and I’d just like to follow up with a few thoughts of my own.

When a study like this comes along that contradicts the “conventional wisdom,” there are many possible ways to respond. One good response is to look for flaws in the study, to figure out if there’s some logical reason that it contradicts previous findings. At the other end of the spectrum, there are responses like this one, from the comments section of the previous post:

This study has a lot of holes in it, especially since some of the “best” physiologists state that LHTL works. One bogus study cannot change the work that guys like David Martin and the Australia of Sport (AIS) have performed.

With all due respect, the study “has holes in it” if there’s a problem with its methodology or design, not just because someone says it does. One study certainly can refute the work that others have done if the new study is correct and the others are flawed. That’s how science works: it doesn’t care what your name is or where you work. (Speaking of which, it’s no coincidence that this particular commenter works for a company that manufactures and sells altitude tents!)

Another commenter asked about individual (rather than average) responses. This is an excellent question, since it has long been hypothesized that there are “responders” and “non-responders” to altitude training. Here are the individual responses in hemoglobin mass for the altitude group:

On the surface, this looks to be exactly what we see: five “significant” (above the dashed line, which represents the typical error level of the measuring apparatus) responders, three who got significantly worse, and two basically unchanged. But let’s look also at the placebo group:

Once again (though with fewer subjects), we have some individuals responding “significantly” in both directions to the placebo stimulus, and some staying unchanged. Though the small sample size makes comparisons difficult, the scatter of individual results looks pretty similar in both cases (and was statistically indistinguishable).

So what do we conclude from this study? As I said in the previous post, this was an exquisitely careful study with an excellent design. That means we can place very high confidence (relative to previous altitude studies) in its evaluation of the specific conditions it tested. And this is the rub. They held certain conditions constant, such as oxygen levels, time exposed to hypoxia, and training stimulus. But what if the training stimulus was inappropriate (too hard? too easy?). What if the athletes had insufficiently high iron (despite being given daily iron supplements)? What if being confined to their rooms for 16 hours a day caused negative adaptations?

These are all possibilities — and they’re all possibilities considered by the researchers themselves in their discussion in the paper. No one — not me, not the researchers — is saying “altitude training is a scam.” But what they (and I) are saying is that, if you take a fairly conventional live-high-train-low paradigm as executed in the study (4 weeks, 3,000m/1,000m, continuing essentially the same training plan that you were doing at sea level, etc.), don’t assume that you’re automatically going to get the results you’re looking for. There are clearly some other variables at play that need to be controlled. Elite coaches and athletes have some pretty strong ideas about what these additional variables are. And if I worked for an altitude tent company, I’d spend a little less time mouthing off about “bogus studies,” and a little more time trying to nail down exactly what those variables are.

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A reality check for altitude tents and houses

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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[UPDATE 11/30: Lots of great discussion of this post below and on Twitter. I’ve added a new post with some responses, more data, and further thoughts HERE.]

A recurring theme on this blog is that not all studies are created equal. The quality of the study design makes a huge difference in the amount of faith that we can place in the results. So it’s always a big pleasure to see awesomely painstaking studies like the new one in Journal of Applied Physiology by Carsten Lundby’s group in Zurich. The topic: the “live high, train low” (LHTL) paradigm used by endurance athletes, in which they spend as much time at high altitude as possible to stimulate adaptations to low oxygen, while descending to lower altitude each day for training so that their actual workout pace isn’t compromised by the lack of oxygen.

There have been a bunch of LHTL studies since the 1990s that found performance benefits — but it’s really difficult to exclude the possibility of placebo effect, since athletes know they’re supposed to get faster under the LHTL strategy (and, conversely, athletes who get stuck in the control group know they’re not supposed to get faster). But Lundby and his colleagues managed to put together a double-blinded, placebo-controlled study of LHTL. The main features:

  • 16 trained cyclists spent eight weeks at the Centre National de Ski Nordique in Premanon, France. For four of those weeks, they spent 16 hours a day confined to their altitude-controlled rooms. Ten of the subjects were kept at altitude (3,000 m), and six were at ambient (~1,000 m) altitude.
  • Neither the subjects nor the scientists taking the measurements knew which cyclists were “living high.” Questionnaires during and after the study showed that the subjects hadn’t been able to guess which group they were in.
  • On five occasions before, during and after the four weeks, the subjects underwent a whole series of performance and physiological tests.

So, after going to all this trouble, what were the results?

Hemoglobin mass, maximal O2-uptake in normoxia and at a simulated altitude of 2,500 m and mean power output in a simulated 26.15 km time-trial remained unchanged in both groups throughout the study. Exercise economy (i.e. O2-uptake measured at 200 Watt) did not change during the LHTL-intervention and was never significantly different between groups. In conclusion, four weeks of LHTL using 16 hours per day of normobaric hypoxia did not improve endurance performance or any of the measured associated physiological variables.

This is, frankly, a surprising result, and the paper goes into great detail discussing possible explanations and caveats — especially considering the study didn’t find the same physiological changes (like increased hemoglobin mass, which you’d expect would be placebo-proof) that previous studies have found. Two points worth noting:

(1) The subjects were very well-trained compared to previous studies, with VO2max around 70 ml/kg/min and high initial hemoglobin mass. It’s possible that the beneficial effects of LHTL show up only in less-trained subjects.

(2) There’s a difference between living at 3,000 m and living in a room or tent kept at oxygen levels comparable to 3,000 m: pressure. “Real-world” altitude has lower pressure as well as lower oxygen; this study lowered oxygen but not atmospheric pressure. Apparently a few recent studies have hinted at the possibility that pressure as well as oxygen could play a role in the body’s response to altitude, though this remains highly speculative.

As always, one new study doesn’t erase all previous studies, nor does it override the practical experience of elite athletes. But it suggests that we should think carefully about whether altitude really works the way we’ve been assuming it works. As the researchers conclude:

In summary, our study provides no indication for LHTL, using normobaric hypoxia, to improve time trial performance or VO2max of highly trained endurance cyclists more than conventional training. Given the considerable financial and logistic effort of performing a LHTL camp, this should be taken into consideration before recommending LHTL to elite endurance athletes.

 

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Which “rules of running” should you break?

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Forgot to mention this earlier — I have an article in this month’s Runner’s World called “Breaking All the Rules,” which is now available online. Basically, I had a chance to chat with a bunch of veteran coaches — Jack Daniels, Frank “Gags” Gagliano, Roy Benson, Jeff Galloway, Hal Higdon and Pete Pfitzinger — and ask them which “rules of running” they’d recommend not following blindly. Here’s one example:

THE RULE: Do prerace strides
For generations, runners have followed the same rituals to warm up before races or workouts: Start with some jogging, move on to a little bit of stretching, then perform a series of “strides”—short sprints lasting about 10 seconds that get your heart pumping and kick-start the delivery of oxygen to your running muscles. But do these timeworn rituals really help us perform better? Jack Daniels, Ph.D., isn’t convinced. “What I most often see at races is a bunch of runners striding up and down at a speed that is clearly faster than the coming race pace,” he says. Since these strides are the last thing runners do before starting the event, that inappropriate pace is fresh in their minds. “And when the gun finally sounds, they ‘stride’ or sprint right out.” The result: a way-too-fast start followed by an inevitable crash.
HOW TO BREAK IT: For shorter events like 5-K and 10-K races, jogging just long enough to get a good sweat going is all you need to do, says Daniels. (For longer races, you can get away with even less: Run the first mile of a half or full marathon as your warmup.) To get the oxygen-boosting benefits of strides without skewing your pace judgment—and screwing up your race result—try a sustained two-to three-minute effort 10 minutes before starting the race or workout. Run it slightly faster than your half-marathon pace, or at a speed that feels moderately hard. You should not be sprinting.

Other topics covered include stretching, the length and pace of your long run, having a recurring weekly training structure, back-to-back hard days, cross-training during injuries, and so on. I should emphasize: none of the coaches are suggesting that existing rules-of-thumb are 100-percent bad. They’re just worth thinking about to make sure that they really do make sense for your personal situation and goals. For example, Higdon questions the wisdom of the 10-percent rule — he’s not saying that you should never increase your mileage by 10 percent; he’s just saying that sometimes it might make sense to increase it by more, sometimes by less, so you shouldn’t follow the rule blindly.

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Can you “train” your fingers and toes to withstand cold?

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Winter’s coming, so here’s a topical study just published in the European Journal of Applied Physiology. Do your fingers and toes gradually adapt to being exposed to cold temperatures? There are three questions we can ask:

  1. Are the digits able to maintain a higher temperature when they’re exposed to cold?
  2. Are the digits quicker to experience “cold-induced vasodilation” (COVD)? (When you get cold, your blood vessels contract; but after a certain point, the vessel walls get so cold that they can’t stay contracted, so you get a sudden rush of blood that helps to warm up your fingers and toes — which turns out to be a very useful response to avoid frostbite.)
  3. Do your digits hurt less?

Over the years, many researchers have tested whether our digits adapt to cold, and the results are all over the map — some see a positive effect, some see a negative effect, some see no effect. Into the breach come researchers from the Netherlands and from Brock University in Canada. They took 16 suckers volunteers and had them dip their right hand and foot in 8 C water for 30 minutes at a time for 15 consecutive days. At the beginning and end of the experiment, the “trained” hand/foot was compared to the “untrained” hand/foot.

Here’s how skin temperature changed over the 15 days:

The data kind of meanders around, but there’s not much of a clear trend. Unfortunately, there was a clear trend for CIVD: during the pre-training test, 52% of subjects experienced CIVD; during the post-training test, only 24% experienced it.

And finally, the pain score:

On the surface, this might seem like good news: it hurts less as you gradually become accustomed to the unpleasant sensation of being cold. In fact, though, this is bad news. As your body gets used to the cold, you notice it less, but you also are less likely to get the warming effects of CIVD. Combine these two factors, and you become increasingly likely to get frostbite without realizing it.

So what does this mean? Well, it probably ends my dreams of being a polar explorer. I have extremely poor circulation in my fingers, and this suggests that this is unlikely to improve no matter how often I freeze my fingers off. So, despite the odd looks I get, I’m going to continue to run in my big puffy mittens whenever it gets close to freezing, because I won’t get any long-term “training” benefit from suffering.