While researching a book on endurance a few years ago, I interviewed a German scientist named Wolfgang Freund who had recently completed a study on the pain tolerance of ultra-endurance runners. Subjects in the study had to hold their hands in ice water for as long as possible. The non-athlete control group lasted an average of 96 seconds before giving up; every single one of the runners, in contrast, made it to the three-minute safety cut-off, at which point they rated the pain as a mere 6 out of 10 on average.
The results were consistent with previous research showing that athletes can tolerate more pain than non-athletes. But not all sports impose the same demands, Freund pointed out: “Maradona, at least, had the illusion that a brilliant soccer player didn’t need to suffer.” As a runner myself, I liked the implication that endurance athletes are uniquely tough, so I happily included that quote in my book. But is it really true?
As it happens, researchers at Norway’s University of Tromsø tackled exactly that question, along with several other interesting ones, in a recent study in Frontiers in Psychology. They compared 17 national-level soccer players with 15 elite endurance athletes (cross-country skiers and runners, also “competing at the highest national level in Norway”) and 39 non-athlete controls in three pain tests. They also administered a series of psychological questionnaires to explore what traits are associated with greater pain tolerance.
The first pain test was the same one used in Freund’s study: dunking the hand in barely-above-freezing water for as long as possible (again with a three-minute cut-off, though the subjects weren’t told about it in advance). On average, the endurance athletes lasted 179.67 seconds (meaning virtually all of them made it to three minutes, with the exception of one person who stopped five seconds early). The control group averaged 116.78 seconds, and the brilliant soccer players just 113.90 seconds.
This was exactly what the researchers expected. After all, embracing open-ended discomfort is exactly what endurance athletes do every day in training, so it makes sense that they have a high pain tolerance. But pain threshold—the point at which a sensation goes from unpleasant to painful—might be different. Soccer players, like other team sport athletes, experience briefer spikes of pain associated with “short bouts of supramaximal intensity and receiving blows from opponents or the ball,” the researchers point out. As a result, they hypothesized that the experience of this more intense pain would give soccer players a higher pain threshold than endurance athletes.
To test pain threshold, they applied a heated aluminum thermode to the inner forearm of the subjects, starting at 90 degrees Fahrenheit and slowly increasing to a maximum of 126 degrees. The subjects had to press a button when the sensation changed from warmth to pain, and this process was repeated five times. This time, contrary to their hypothesis, the soccer players and endurance athletes were essentially the same, at 117.7 and 118.2 degrees, and both were significantly higher than the non-athletes at 115.8 degrees. (Those numbers are from the first test; when the test was repeated a second time, the numbers were slightly higher but the pattern was the same.)
The third test looked at yet another aspect of pain response, pain sensitivity. While pain is fundamentally a subjective experience, pain sensitivity tries to quantify how intensely you feel a given stimulus. It’s obviously related to both threshold and tolerance, but it’s not identical: one person might feel pain very intensely but nonetheless be willing to tolerate it for longer than someone else who feels it less intensely. To measure sensitivity, the temperature of the heated thermode was ramped up to 117.5 degrees for 30 seconds, and participants had to rate their pain on a scale of 0 to 100. The researchers expected no difference between the soccer players and the endurance athletes. Instead, the average pain scores for the first test were 45.5 out of 100 for the endurance athletes, 51.9 for the soccer players, and 59.4 for the non-athletes. In the second test, the scores were 37.9, 45.4, and 53.7. The differences aren’t statistically significant, but there’s a pretty suggestive trend.
There are two big questions here. One is why the three groups have different perceptions of pain; the other is whether the athletes were born with these differences, or whether they acquired them as a result of their training. The most widely held view is that the big differences are psychological, as opposed to some sort of physiological dulling of pain sensors. In this study, the researchers assessed the subjects’ “Big Five” psychological traits (openness, conscientiousness, extraversion, agreeableness, and neuroticism), and gave separate questionnaires to assess grit and fear of pain.
The results are a little convoluted, given that there are seven psychological traits, three groups, and three pain perception outcomes. Both grit and conscientiousness had a bit of predictive power on some outcomes, which isn’t surprising since some critics argue that grit is basically just a fancy repackaging of the older concept of conscientiousness. The one psychological characteristic that predicted all three outcomes was fear of pain, which makes sense. But there were no statistically significant differences between the three groups in their average fear of pain scores, though the endurance group seemed to have slightly better (i.e. less fearful) scores. That means it can’t be the main reason the three groups scored differently on the pain tests.
As for the second question on nature versus nurture, this study can’t answer it. There have been some hints in previous studies that pain tolerance is a trainable trait, and that endurance training is one way of enhancing it. On the other hand, I’d be surprised if there isn’t some element of athletes being “chosen by their sport” in part based on pre-existing psychological attributes like willingness to suffer. The new study adds fear of pain to the list of relevant psychological attributes, alongside others from previous research like tendency to catastrophize (bad) and ability to ignore negative feelings (good).
It seems to me that we’re unlikely to find one neat mental trick that distinguishes pain gluttons from pain avoiders. Instead, successful athletes likely have an array of different mental tactics for dealing with different types of discomfort in different contexts. Teasing out the best strategies is a great topic for future research. But to be honest, it’s all a digression from the main point I wanted to emphasize from this paper—which is that Wolfgang Freund was right.
For more Sweat Science, join me on Twitter and Facebook, sign up for the email newsletter, and check out my book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance.
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