This Could Be a Strong Weapon for Cancer Pain (or Any Pain)

Exercising for upwards of 30 minutes most days may help relieve pain in patients who've been diagnosed with cancer, according to a study of exercise and pain outcomes from more than 60,000 people, including 10,000 with a history of cancer. 

Study participants who'd been diagnosed with cancer and surpassed 150 minutes of moderate activity a week were 16% less likely to report pain than those who did not exercise or who exercised less. Exercise was particularly helpful for those with moderate to severe pain. In general, the more people exercised, the less pain they felt — and that was true for those with and without a history of cancer.

"This adds to a large evidence base regarding other benefits of exercise after cancer," said lead study author Christopher Swain, PhD, a researcher at the University of Melbourne, Australia, who studies how physical activity can protect against cancer. "It would be great for physicians to encourage physical activity" for anyone who's ever been diagnosed with cancer. 

The findings also add to mounting evidence — including observational and experimental studies — that physical activity may help ease people's pain. One large cross-sectional study of Norwegian adults found that the prevalence of chronic pain was 10%-38% lower among people who exercised. Randomized trials suggest exercise could be an effective pain management tool for a range of conditions, including neck and low-back pain, osteoarthritis, myofascial pain, and fibromyalgia. 

Still, the analgesic effects of exercise are less established for cancer-related pain, the authors wrote in the recent study — even though cancer pain remains a common and critical issue. 

Cancer-related pain is unique, stemming from multiple potential causes, said Shakil Ahmed, MB, an anesthesiologist at Weill Cornell Medicine who specializes in treating cancer pain. (Ahmed was not involved in the study.) Patients "might be having pain from the tumor itself," — such as a tumor pressing on nerves— "or as a result of treatment, including surgery, radiation, chemotherapy, or complications from long-term medications," Ahmed said. Indeed, some 40% of patients have chronic pain post cancer diagnosis, and it's often undertreated and underdiagnosed.

How Does Exercise Reduce Pain?

Researchers aren't exactly sure how exercise modulates pain, but they have some theories.

A 2021 meta-analysis found that exercise training can raise a person's pain threshold, particularly at the pain site, suggesting adaptations in central inhibition, a process in the central nervous system that suppresses the perception of pain. This echoes a 2017 review that suggests exercise may help relieve pain by activating central inhibitory pathways. 

"There's definitely evidence that there is improvement in the pain-reduction chemicals and augmentation of the pain inhibitory process in the central nervous system," said Ahmed. That is, exercise may induce chemical changes that alter how much pain the brain's sensory neurons can detect. 

Regular exercise can also reduce inflammation and improve blood flow, noted William McCarthy, PhD, a public health researcher with UCLA Health — both effects that may help to reduce pain.

Psychological factors may be another part of it. "There's a lot of psychological stress as a result of a cancer diagnosis, which can lower the pain threshold," said Ahmed. Exercise may help boost mood and reduce stress, increasing pain tolerance. 

"People who are physically active also tend to be more socially active," McCarthy added. "Engaging in social networks that provide social support can often palliate a sense of constant battling with fatigue, pain, and other negative effects of cancer." Social activity, in turn, may promote physical activity: Studies show that when sedentary people socialize with active people, they become more active themselves — often by joining in walks or sports. 

Help Patients Reap the Pain-Relieving Benefits of Exercise 

For beginners, the key to establishing a long-term exercise routine is to start low and slow, said Ahmed. That is, start with low-intensity activities like walking (walking was the most common activity reported in the study) or using light weights. Then, build slowly from there. 

Keep in mind that some pain or stiffness is normal at first, as one's muscles and joints get used to the new activity. But be sure to investigate any new pain, Ahmed said. "Especially for patients who have had cancer, you want to see if the patient has any recurrence of disease," Ahmed said. "That has to be kept in mind when you recommend any kind of exercise. " 

It's worth acknowledging that pain can be a significant barrier to exercise. If appropriate, you may consider referring out to exercise or physical therapy professionals in your network. Emphasizing the benefits of exercise — like the pain relief — may help motivate patients as well. 

For Swain, encouraging exercise is less about prescribing specific quantities and more about helping patients find activities "that give them enjoyment, that they feel comfortable doing, and that they can sustain over time."

"The field needs to consider the different ways of supporting physical activity after a cancer diagnosis and treatment," Swain said. "We have a lot of great research that shows the benefit of physical activity but not as strong an understanding of how to encourage and support it."