Image credit: Nold et al. (CC BY 4.0)
Many people turn to exercise as a way to relieve pain, hoping it will help them feel better. One reason this might work is because exercise can release natural chemicals in the body, called endogenous opioids, which help reduce pain. However, scientists still do not fully understand how this process works.
Nold et al. explored how different levels of aerobic exercise – such as low vs. high intensity – affect how people feel pain. They used brain imaging and a medication called naloxone, which blocks the body’s opioid system, to better understand what is happening in the brain during exercise. The study included 39 healthy adults and looked at how factors like fitness level and sex might influence the effects of exercise on pain and how participants perceived pain.
To determine whether high-intensity exercise provides more pain relief than low-intensity exercise, Nold et al. studied 18 males and 21 females during both high- and low-intensity exercises. Following the workout, magnetic resonance imaging was used to study brain activity as the participants received nine painful heat and pressure stimuli. Throughout the entire experiment, participants received a constant dose of either naloxone or a saline solution as a control.
The study found that high-intensity exercise did not reduce pain any more than low-intensity exercise in the overall group. There were no major changes in how pain was processed in the brain and blocking the body’s opioids with naloxone made pain feel worse, regardless of how hard the participants exercised. However, more detailed analyses revealed that males with higher fitness levels experienced more pain relief after intense exercise than females. However, this effect disappeared when naloxone was given. Brain scans showed this was linked to activity in a part of the brain called the medial frontal cortex.
These findings suggest that exercise may help reduce pain for some people more than others – especially depending on their sex and fitness level. In the future, personalized exercise programs could be developed to help manage pain more effectively. But before that can happen, more research is needed to understand exactly how the body’s natural pain-relief systems work during exercise, and how they differ between individuals.
