Athletes have a very complicated relationship with pain. For endurance athletes in particular, pain is an absolutely non-negotiable part of their competitive experience. You fear it, but you also hug it. And then you try to understand
But pain isn’t like heart rate or lactate levels – things that you can measure and meaningfully compare from one session to the next. Every painful experience is different, and the factors that contribute to these differences seem endless. A study by researchers from Iraq, Australia, and the UK recently published in the Journal of Sports Sciences adds a new one to the list: Viewing pictures of athletes in pain immediately before a bike test resulted in higher pain ratings and poorer performance than viewing pictures of Athletes enjoying themselves.
This finding is reminiscent of a finding I wrote about last year where subjects who were told that exercise increased pain perception had more pain, while those who said movement decreased pain perception had less pain. In this case, the researchers looked at the perception of pain after exercising, rather than during exercise, to understand a phenomenon called exercise-induced hypoalgesia (which simply means you will experience less pain after exercising).
This phenomenon has been studied for more than 40 years: one of the first attempts to unravel it was published in 1979 under the title “The Painlessness of the Long Distance Runner,” in which an Australian researcher named Garry Egger performed a series of 15 runs over six months after injecting an opioid blocker called naloxone or a placebo. While running raised his pain threshold, naloxone didn’t seem to make a difference, suggesting that endorphins – the body’s own opioids – weren’t responsible for its effects. (Subsequent research has been ample but not very conclusive, and it is currently believed that both opioid and other mechanisms are responsible for this.)
But the nature of pain – the fact that seeing a picture of pain or being told that something is going to be painful can change the pain you feel – makes it extremely difficult to study. If you subject someone to a painful experiment twice, their experience the first time will inevitably discolor their perception the second time. Because of this, according to the authors of another new study, the only results you can really trust are from randomized trials comparing the effects of exercise on pain with the results of the same test sequence with no exercise – a standard that includes one Much of the existing research from.
The new study, published in the Journal of Pain by Michael Wewege and Matthew Jones of the University of New South Wales, is a meta-analysis designed to investigate whether, and if so, what type of exercise-induced hypoalgesia does exercise induce, and when whom. There were already several meta-analyzes on this topic, but these were limited to randomized controlled studies, so that only 13 studies from the initial pool of 350 were included.
The good news is that aerobic exercise actually appeared to cause a sharp rise in the pain threshold in healthy subjects. Here is a forest chart where dots to the left of the line indicate that a single study showed increased pain tolerance after aerobic exercise, while dots to the right indicate deterioration in pain tolerance.
(Figure: Diary of Pain)
The large diamond below is the total combination of the data from these studies. It’s interesting to look at some of the individual studies. The first point at the top, for example, saw essentially no change from a six-minute walk. The second and third items with the most positive results were 30 minutes of cycling and 40 minutes of running on the treadmill, respectively. Dosage likely plays a role, but there isn’t enough data to draw definitive conclusions.
Then it gets a little trickier. Dynamic resistance exercises (mostly normal strength exercises) seem to have a small positive effect, but that’s based on only two studies. Isometric exercises (i.e., pushing or pulling without moving or holding a static position) based on three studies have no clear effect.
There are also three studies looking at patients with chronic pain. This is where researchers really hope for effects because it is very difficult to find ways to treat persistent pain, especially now that the disadvantages of long-term opioid use are better understood. In this case, the subjects suffered from knee osteoarthritis, plantar fasciitis, or tennis elbow, and neither dynamic nor isometric exercises seemed to help. There were no studies – or at least none that met the criteria for this analysis – that tried aerobic exercise for patients with chronic pain.
The most important realization for me is how little we really know for sure about the connection between movement and pain perception. It is likely that the feeling of dulled pain following a good run is real (and so you shouldn’t conclude that your little injury is really healed just because it feels okay after it ends). Exactly why this happens, what it takes to trigger it, and who can benefit from it remains unclear. But if you have a race or a big workout ahead of you, based on the pain picture study, I would suggest not thinking too much about it.
Hat tip to Chris Yates for further research. For more sweat science, visit me on Twitter and Facebook, subscribe to the email newsletter, and read my book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance.
Main photo: Boris Jovanovic / Stocksy