An interesting study just appeared in the Journal of Clinical Endocrinology & Metabolism that adds to two earlier posts my blog — one about circadian rhythms and the role of melatonin in regulating sleep and overcoming jet lag, the other about the use of “light visors” at appropriate times to help reset sleep cycles. The new study, from Harvard, found that ordinary electric light before bedtime strongly suppresses melatonin production.
Backtracking for a moment:
Melatonin is a hormone produced at night by the pineal gland in the brain. In addition to its role in regulating the sleep-wake cycle, melatonin has been shown to lower blood pressure and body temperature and has also been explored as a treatment option for insomnia, hypertension and cancer.
As a result, many people take melatonin at bedtime after flying from west to east, to help move their sleep cycle forward. And some people, including top athletes at the Commonwealth Games, use the light visors I discussed in that previous post to suppress melatonin in the morning (if they flew west to east) or the evening (if they flew east to west).
This all makes intuitive sense, but as far as I know most people had assumed that ordinary room lights wouldn’t have a significant effect on melatonin — otherwise, no one would shell out the big bucks for a light visor! So what does this mean? Well, if you have trouble getting to sleep, you might want to start paying more attention to your lighting environment in the hours before bedtime. And, on the plus side, if you’re travelling across time zones, you should be able to harness this effect just like a light visor!
If you have any interest whatsoever in the role of science in evaluating the claims made by fitness products, you’ll be thrilled about this. The makers of Power Balance bracelets, which purport to “work with your body’s natural energy field” to improve your strength, flexibility and balance, have been compelled by an Australian tribunal to admit that they have “no credible scientific evidence” whatsoever to support their misleading advertising claims, and to offer a refund to unsatisfied customers. For full details, read Ross Tucker’s Science of Sport report here. (And Ross’s follow-up post, in response to those who ask why it matters whether the bracelets are placebos as long as they work, is also worth reading.)
There’s a new preprint online at Medicine & Science in Sports & Exercise, from researchers at the University Clinic Essen in Germany, describing a study of heart disease in marathon runners. They recruited 100 runners aged 50-75, all of whom had completed at least five marathoners in the previous three years, and ran them through a battery of tests to assess the health of their arteries, both in the heart and elsewhere in the body. (They used, among other measures of risk, ultrasound imaging and “electron beam computed tomography,” which I’ve never encountered before and which sounds pretty cool!)
Anyway, the gist: they found plaques in the arteries of all but 10 of the runners. They run a bunch of analyses trying to figure out how to predict what differentiates the plaque-free runners from the plaque-y runners — but eventually they conclude that the subjects at highest risk are those who would be identified as high-risk by conventional analyses (e.g. the Framingham Risk score). In other words, being a runner doesn’t exclude you from or make you immune to these conventional risk factors.
Is this news? Well, it reminded me of an anecdote Tim Noakes told me last summer, about the conventional wisdom in the 1970s that devoted runners were essentially immune to heart disease. So what did Noakes, a lifelong paradigm-buster, do? Amby Burfoot described it a few years ago in a Runner’s World article about the very first New York Academy of Sciences meeting on the running and medicine in 1976:
So Tim Noakes, M.D., gave a presentation that documented the heart attack of a veteran marathoner, which became one of the most-talked-about sessions. Prior to this, several running physicians enjoyed notoriety for claiming that a marathon finisher could never have a heart attack.
Still, it’s always good to get a reminder — or as the German researchers conclude: “These data support an increased awareness of atherosclerosis prevalence and cardiovascular risk factor in marathon runners.”
I did a little crystal-ball gazing (some might call it navel gazing) in my column in today’s Globe, picking 10 topics in sports science that I think we’ll be hearing about in 2011:
It’s January, which means the gyms are full of exercisers resolving that 2011 will be the year they meet their fitness goals. In labs around the world, meanwhile, exercise scientists are resolving to settle some of the fitness questions that still dog us. Here are 10 confusing, contradictory, or just plain complicated areas of exercise science that will see significant progress in 2011… [READ THE WHOLE COLUMN]
Most will be familiar to regular readers of Sweat Science, since I think the best predictor of what researchers will be studying is which topics we’ve been discussing and arguing over the past few years. Needless to say, I’d love to hear suggestions of what I missed — which also doubles as a request for ideas for future columns, blog entries and so on. What sports science topics would you like to hear more about in 2011?
(One “miss” that I’ll mention: I didn’t include the debate over running shoes and the ideal stride, even though I’m sure it will remain a hot topic, because I’ll be revisiting it in a couple of columns next month.)
I wrote last month about the relationship between alcohol and muscle recovery following vigorous exercise, and the news was generally good for “moderate” drinkers. Now Gretchen Reynolds has an interesting piece in the New York Times about some research suggesting that regular exercise may make people drink more alcohol:
Half of the rats were given access to running wheels for three weeks. The others were kept in cages without wheels. After three weeks, the running wheels were removed, and half of the animals from each group were allowed unlimited access to alcohol for 21 days… the exercising animals turned to alcohol with significantly more enthusiasm than the sedentary rats…
As Reynolds points out, these findings are in line with a recent human survey study that found, among other things, that “heavy drinkers exercise about 10 more minutes per week than current moderate drinkers and about 20 more minutes per week than current abstainers.”
That being said, the rat experiment seems to be testing something else: it’s not whether exercise makes you drink more, but whether being deprived of your accustomed exercise makes you drink more. And that makes sense, given that both exercise and drinking probably trigger similar reward pathways. So maybe this helps explain why you’re more likely to hit the sauce when you’re injured — though that never seemed like a particularly big mystery to me.
More research from Andrew Jones’s group at the University of Exeter on the endurance-boosting effects of beet juice, which they previously reported can extend time-to-exhaustion by about 15% (equivalent to about a 1% improvement in a race over a specific distance), in a forthcoming paper in the Journal of Applied Physiology (press release here).
The most interesting new twist: they’ve developed a way of filtering the nitrates out of beet juice using an “ion-exchange resin,” allowing them to create a placebo form of beet juice that is identical to the real thing in every way except for the absence of nitrates. They’ve hypothesized that it’s the nitrate in beet juice that reduces the “oxygen cost” of running and other endurance exercise — i.e. you burn less energy to produce the muscular force needed to propel yourself forward, allowing you to last longer. But beet juice has a whole bunch of potentially beneficial ingredients, including big names like quercetin and resveratrol, so they needed some way to check which ingredient was actually making the difference. The new double-blinded study does that nicely: the nitrate-free beet juice had no effect on subjects, while the regular beet juice lowered blood pressure and improved performance in various endurance running tests.
One other new result is that they tested low-intensity exercise as well as high-intensity. Sure enough, they found that the oxygen cost of walking was significantly decreased after just four days of drinking 500 ml of beet juice per day.
For senescent populations or individuals with pulmonary, cardiovascular or metabolic disorders, [they write,] a reduction in the O2 cost of daily activities might significantly improve functional capacity.
Maybe, maybe not — I’m not convinced seniors will really care about shaving 1% from their evening walk time. But for competitive athletes, the body of evidence for beet juice is getting solid enough to make me reconsider my initial skepticism. I’d like to see similar results from other labs, though.
One of my greatest regrets about writing this blog is that the more I dig into the evidence behind most of the supposed “performance-boosting” supplements out there, the less I believe most of them have any legitimate effect. If I never looked at the actual research, I could be popping all sorts of pills in blissful ignorance — and because I’d believe in them, they’d give me a nice robust placebo effect. In fact, I’ve toyed (mostly in jest) with the idea of suggesting that elite athletes should avoid finding out too much about the science of ergogenics, so that they can maintain the fantasy that these things work and thus get an edge from them.
But a recent study from Harvard suggests that one of my key assumptions may be false. The study (which is freely available here and described by a press release here) set out to determine whether you have to believe in a placebo in order for it to work. To that end, they recruited 80 patients with irritable bowel syndrome (IBS). Half of them received no treatment, while the other half received placebo pills to take twice daily — but they knew that the pills were nothing but sugar:
“Not only did we make it absolutely clear that these pills had no active ingredient and were made from inert substances, but we actually had ‘placebo’ printed on the bottle,” says Kaptchuk. “We told the patients that they didn’t have to even believe in the placebo effect. Just take the pills.”
To everyone’s surprise, nearly twice as many placebo patients reported relief from their symptoms (59% vs. 35%), and “patients taking the placebo doubled their rates of improvement to a degree roughly equivalent to the effects of the most powerful IBS medications.”
So what on earth is going on here? The researchers speculate that “there may be significant benefit to the very performance of medical ritual.” This isn’t a new idea — I read a very interesting book on the placebo effect a few years ago that argued, in effect, that the doctor-patient relationship is the most powerful placebo mechanism available to us. Of course, “feeling better” is not the same kind of outcome as “running faster” or “growing bigger muscles.” I’d love to see a study that investigated whether undisguised sugar pills could enhance athletic performance. What would WADA do if the results came back positive? 🙂