Study Explains How More Exercise May Reduce Chronic Pain

WASHINGTON — Chronic pain, or pain that lasts over three months that you experience most or every day, affects more than 20% of adults in the United States; about 50 million people. While the source of pain is not always known, one potentially effective, non-pharmaceutical intervention is getting regular exercise.  

A recent study of 6,834 people with chronic pain found those who exercised more had lower levels of chronic pain over time. Here, we’ll explore the study, how the researchers think it may work and explain other potential mechanisms for how exercise can reduce chronic pain.

Recent Study Associates More Exercise With Less Chronic Pain

A recent study published in the Journal of the International Association for the Study of Pain found that people who reported higher levels of physical activity had a lower chance of experiencing chronic pain seven or eight years later. 

Being more active lowered their risk; for example, going from light to moderate exercise reduced their chance of chronic pain by 5%. For people with severe chronic pain, increasing physical activity reduced pain by 16%. 

A Study Within a Study

This new research is based on the findings of the Tromsø Study by the Norweigan Institute of Public Health, published in 2023. The Tromsø Study is a long-term health study on adults in Norway that began in 1974; the 2023 study reports data on exercise and chronic pain from 2007-2016. 

Researchers suggest that exercise increases pain tolerance which may reduce chronic pain. 

Self-Reported Activity Levels

Participants reported their activity levels over the previous 12 months and chose one of four categories:

• Sedentary: mainly reading and watching TV.
• Light Intensity: four hours a week of walking, cycling, or other light cardio.
• Moderate Intensity: four hours a week of recreational sports or heavy gardening.
• Vigorous Intensity: several times a week of heavy training or competitive sports.

Cold Pressor Test

Researchers measured pain tolerance by how long participants could keep their hands in cold water (three degrees Celsius or 37 degrees Fahrenheit). 

Results

People in the light, moderate, and vigorous intensity groups all held their hands eight to 12 seconds longer than the sedentary group. Each category of more intense exercise had a higher pain tolerance than the one below it compared to the sedentary group. The light, moderate, and vigorous groups had a 7%, 14%, and 16% higher pain tolerance than the sedentary group. 

Seven and Eight Year Follow-Up

Seven to eight years later, the same participants reported their physical activity levels and repeated the cold pressor test. The same associations were found (more activity, higher pain tolerance). Plus, those who increased their activity over the gap years had a higher pain tolerance than they had when taking the test for the first time. 

The study concludes that there are two important factors to consider: the amount of your physical activity can affect your pain tolerance (and chronic pain), and the direction of change over time can continue its influence. Continuing to be more active over time may keep your pain risk lower.

How It May Work: Exercise-Induced Hypoalgesia

The new study was interested in the mechanisms behind how exercise improves pain tolerance and mentioned exercise-induced hypoalgesia. EIH is a “decrease in pain sensitivity” that occurs during exercise and for at least 30 minutes afterward. 

EIH in People Without Pain:

In healthy people, EIH may happen after aerobic or resistance exercise triggers an interaction between the opioid and endocannabinoid systems and between the opioid and serotonergic systems. These systems can inhibit the sensation of pain.

EIH in People With Chronic Pain:

Some, but not all, people with chronic pain do not experience EIH. They may feel no change in their pain levels after exercise or more pain (hyperalgesia).

Impaired EIH may be due to genetics, autonomic or immune system differences, or exercise-induced inflammation. There may also be a psychological component, where people may fear pain, catastrophize their pain, or believe exercise will increase pain, all of which can intensify the pain.

However, some studies show that EIH can function differently in different body parts. For example, people with knee osteoarthritis had impaired EIH after lower-body resistance training but had functional EIH after upper-body resistance exercise. This finding suggests that exercising non-painful parts of your body may still be able to reduce overall pain. 

Other Potential Mechanisms

Apart from EIH, here are a few other potential mechanisms by which regular exercise can reduce chronic pain symptoms. 

• Brain Chemicals: Exercise produces natural opioids, blocking the pain signals in your brain. 
• Increases Strength: Resistance training builds strength and muscle, which can help support cartilage and joints.
• Improves Bone Health: Strength training and weight-bearing cardio strengthen bones, which can further support your body, taking stress off painful joints.
• Improves Cardiovascular Health: Chronic pain often occurs with other health conditions. Getting regular exercise improves cardiovascular health and can help prevent CV diseases.
• Reduces Stiffness: Exercise and regular movement can reduce stiffness that causes pain. It may also improve flexibility, which can prevent further injury.
• Improves Balance: Improving balance can help prevent falls.
• Personal Involvement: Regular exercise can improve self-efficacy and self-image. Chronic pain may also coexist with depression and anxiety, and exercise could reduce those symptoms, too.

Move More for Less Pain

Many studies find that getting more movement can reduce chronic pain, even if it doesn’t completely solve the condition. A new study associates more exercise with a higher pain tolerance. Exercise also increases strength and muscle, improves heart, bone and mental health, and can help people improve their quality of life.

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