Why physical activity works
Although exercise and physical activity are widely recommended for people in pain, researchers are still examining how and why it works, and what dose is best for pain relief.
The traditional view of how exercise helps relieve pain has focused on how exercise impacts the structures surrounding the spine – for example, by increasing the strength of the muscles in the spine and abdomen. While these ideas are supported in part by research, they don’t explain fully why exercise can relieve back pain.
There’s growing evidence suggesting that exercise leads to beneficial changes to certain functions in the nervous system, including in the brain. Essentially, exercise directly influences how we experience pain by decreasing our sensitivity to potentially damaging stimuli. This phenomenon is known as exercise-induced hypoalgesia.
In research on pain-free adults, a single bout of high-intensity aerobic exercise (such as cycling or running for 15 minutes) is able to trigger these pain relief effects for approximately 30 minutes afterwards.
These pain-relieving effects are underpinned by several interacting mechanisms – most notably the release of the body’s naturally-produced pain relief agents, such as endocannabinoids, adrenaline, noradrenaline, endorphins and serotonin – within the nervous system and via the circulatory system. These chemicals signals not only help to reduce pain directly, but have the added benefit of improving mood. This is an important benefit as the experience of pain is known to be influenced directly by one’s thoughts and feelings and by our perceived control over pain.
Another key mechanism thought to be involved in exercise-induced hypoalgesia involves the formation of new and helpful connections within the nervous system, a process called neuroplasticity. These structural changes in the nervous system operate over slower time scales than the chemical alterations that happen as a result of exercise-induced hypoalgeisa, but are thought to lead to a decrease in pain associated with movement over time.
While the search to establish the exact mechanisms that underpin exercise-induced hypoalgesia continue, the good news is that exercising even despite pain helps to activate these pain-relieving effects.