I’ve just returned from the first Endurance Research Conference, a gathering of experts interested in the science of endurance sport hosted by the University of Kent’s Endurance Research Group. The great thing about a small, focused conference like this is that everyone is interested in similar things, so you get plenty of chances to discuss and debate ideas with one another, both during the conference sessions and over meals and breaks. I think the next one is tentatively scheduled for two years from now - if you have the opportunity to attend, I highly recommend it.
Anyway, in addition to the big keynote talks (Samuele Marcora, Stephen Seiler, Andy Jones, Yannis Pitsiladis, Dominic Micklewright, Guillaume Millet and many others), there were also plenty of shorter talks discussing new and in-progress results. Conference results always have to be taken with a grain of salt, since they haven’t yet been peer-reviewed, but they offer a preview of what we can expect to see in journals in the next year or two. Over the coming week, I’ll share a few of the topics that caught my attention during the conference, starting with a few results about the role of pain in endurance exercise.
Pain or effort? When you race, you go as hard as you can until the pain becomes too much to bear, and then you slow down... or do you? Over the last few years, Samuele Marcora has been arguing that effort (“the conscious sensation of how hard, heavy, or strenuous a physical task is”) is the relevant parameter, not pain. He and his collaborators Walter Staiano and John Parkinson presented some data that attempts to tease apart effort and pain.
First, to establish the range of pain, the subjects did a “cold pressor” test: dip your hand in ice water and hold it there as long as you can, while periodically rating the pain on a scale of 0 to 10. Typically, the pain steadily mounts until it reaches 10, at which point you quit.
After that, the subjects did a cycling test to exhaustion at 80 per cent of peak power, which took about 12 minutes to complete. During the test, they again rated pain on the 0 to 10 scale, and also rated effort on the 6-to-20 Borg scale. When they reached exhaustion, the subjects rated their pain as 4.8 (moderate) on average, and their effort as 19.6 (pretty much maximal). The implication is that effort, not pain, is what limits performance.
Or pain after all? Not so fast, according to Alexis Mauger, one of Marcora’s colleagues at the University of Kent. Mauger has been studying pain for several years; he previously showed, for example, that taking paracetemol allows cyclists to boost their performance by about two per cent. But taking paracetemol has other effects in addition to blocking pain: it may also keep core temperature from rising too much and affect how efficiently signals are transmitted from the brain to the muscles, so it’s not a slam-dunk proof that pain matters.
To get around that, Mauger has been looking for other ways to modulate pain. Earlier this summer, he and his colleagues published a paper using transcranial direct-current stimulation (tDCS, which basically involves running a weak electric current through certain regions of your brain). By targeting brain regions associated with pain processing, he was able to reduce the pain experienced during a cold pressor test (the ice-water challenge mentioned above). But the same technique didn’t produce any changes in pain during a cycling test to exhaustion, suggesting that the pain associated with exercise may be somehow processed differently from other types of pain.
At the conference, Mauger’s student Ali Astokorki presented results using two other pain-modulating techniques: transcutaneous electrical nerve stimulation (TENS) and interferential current (IC). I don’t know much about either of these techniques, but the idea seems to be that you apply some sort of electrical stimulus directly to your muscle, and it blocks or interferes with the transmission of pain signals from your muscle to your brain.
To everyone (including Mauger)’s surprise, this actually worked. In a time-to-exhaustion cycling test, the volunteers reported lower exercise-associated pain, no change in effort, and - crucially - an increase in endurance time in the cycling test.
So in this experiment, it seems to be pain rather than effort that controls performance. What’s the resolution of this apparent contradiction? I don’t know, but it suggests that there’s some interesting research to come. In the past, many researchers haven’t really bothered trying to distinguish between pain and effort, but it’s clear that they’re distinct sensations that may play different roles.
Training pain? One other result worth mentioning, from Thomas O’Leary and Martyn Morris of Oxford Brookes University, looked at the question of whether you can increase your pain tolerance through training. Previous studies (as I’ve blogged about before) have found that endurance training does indeed increase pain tolerance; but does the intensity of the training matter?
To find out, the researchers had volunteers complete six weeks of either high-intensity interval training or lower-intensity continuous training (at 90 per cent of lactate threshold). The training programs were matched so that both groups completed similar amounts of overall work, and the physiological results in the two groups were pretty much the same: ~10 per cent increase in VO2 max and ~25 per cent increase in lactate threshold.
But there were two key differences. Pain tolerance (as measured by a test that involved clenching your hand repeatedly with a tourniquet around your arm) increased by 45 per cent in the high-intensity group, but just three per cent in the medium-intensity group. And, crucially, cycling performance in a time-to-exhaustion test also increased far more in the high-intensity group than in the medium-intensity group, and the individual improvements correlated to how much their pain tolerance had increased.
So this is another piece of evidence that one of the benefits of hard training is that you learn to tolerate more pain, and that in turn translates into better endurance performance independent of whatever physical benefits you get from the training. Which raises an interesting question: can you improve endurance performance simply by improving your pain tolerance? I wouldn’t be surprised - though for well-trained athletes, the grind of hard interval workouts may be the only pain training you need (or can stand!).