Pain does not always need a pill, sometimes a barbell might be part of the necessary prescription. This idea may seem counterintuitive; when experiencing pain, the thought of exercising may sound daunting. However, exercise is a powerful stimulus, a fact routinely highlighted in health and fitness literature. There are countless studies and articles that cover the benefits of exercise, from increased strength, hypertrophy, and aerobic capacity. Yet, another potential use is not discussed as often: exercise-induced hypoalgesia (EIH), using exercise to help manage pain.
In the 1960s and 1970s, there were substantial shifts in the understanding of pain, its physiology, and a growing interest in endogenous pain regulation. After observing analgesia following therapeutic interventions and periods of high stress, researchers began applying these concepts to exercise. In the 45 years since those early studies related to EIH, several consistent themes have emerged.
One theme is that exercise affects the whole body, not just the muscles being used. When it comes to pain, exercise can elicit local and systemic reductions in pain sensitivity, which is often assessed through mechanical pressure or thermal stimuli. The largest reductions in pain sensitivity are typically observed within the muscle that was exercised, but systemic responses have also been observed in muscles unrelated to the exercise bout (i.e., reduced upper body pain sensitivity following lower body exercise), albeit to a lesser degree.
A second theme is that exercise intensity and duration matter. To achieve EIH, the exercise bout must be a combination of high intensity and/or long duration. Reductions in pain sensitivity have been observed following resistance training (a single bout to fatigue and prolonged training sessions), sustained fatiguing and maximal isometric exercise, maximal anaerobic exercise, and prolonged moderate- to high-intensity aerobic exercise. Although the mode of exercise can vary, achieving EIH typically requires prolonged (>30-minutes) moderate intensity exercise, maximal intensity exercise, or exercise that is completed to fatigue.
When something sounds too good to be true, there is usually a catch, which is a third theme: these reductions in pain sensitivity are transient. Specifically, EIH responses after traditional exercise typically last for about 15 minutes, sometimes up to 30 minutes, before returning to pre-exercise levels. The prospect of using exercise as a pain management intervention is enticing. But the high levels of effort or time required to achieve such a short reduction in pain limit the utility of traditional exercise as a pain management modality.
This is where low-load resistance training with blood flow restriction (LL+BFR) comes in. By applying a pneumatic cuff to the proximal portion of a limb (at 40-80% of total arterial occlusion pressure), we can reduce arterial blood flow into the limb and fully occlude venous flow out. This is typically paired with low loads (30% of maximal strength) or low intensities (<40% of VO2max). Recent research has shown that a single session of LL+BFR can elicit the same initial local and systemic EIH responses as traditional high-load exercise. However, unlike traditional resistance exercise, where pain sensitivity returns to baseline within 30 minutes, we have found measurable reductions in pain sensitivity up to an hour after LL+BFR. One study has also found a limited level of pain reduction lasting up to 24 hours. These results suggest that LL+BFR may be a clinically relevant pain management modality.
A typical LL+BFR session, which can achieve EIH, is relatively short (just four sets of exercise, with the whole exercise intervention lasting about six minutes) and uses a lower load (30% of maximal strength). There is also an abundance of research showing that LL+BFR can elicit similar hypertrophy responses and close to similar increases in strength compared to traditional high-load resistance exercise. While more research is needed, there is clear potential. For clinicians, a modality that can help reduce pain for a prolonged period of time and elicit positive muscular adaptations, potentially treating an underlying problem, is an attractive option.
It is important to note that this reduction in pain is not like the numbing effect of a narcotic; rather, it is like turning down the volume. By dulling pain, exercise may reduce the need for additional, more potent pain management interventions, open the door to meaningful movement, and help people re-engage with the activities that make life enjoyable.
Christopher Proppe, PhD, ATC, CSCS, is an assistant professor in the Department of Human Performance Studies at Wichita State University. He started his career as an athletic trainer working in college athletics before transitioning to academia. His work blends clinical experience with research, focusing on neuromuscular adaptations to exercise, using exercise to manage pain, and blood flow restricted exercise. The overall goal of his research is to improve patient outcomes through evidence-based interventions.
