NPR Health: Exercising To Ease Pain: Taking Brisk Walks Can Help. “For people who live with chronic pain, getting up, out and moving can seem daunting. Some fear that physical activity will make their pain worse. But in fact, researchers find the opposite is true: The right kind of exercise can help reduce pain.”

“”Movement is essential for nutrition of the cartilage,” says Dr. Virginia Byers Kraus, a professor at Duke University’s Molecular Physiology Institute who serves on the research and medical committees of the Arthritis Foundation.

“Cartilage doesn’t have a blood supply but does have living cells,” she explains. “So the way it gets nutrition is by dynamic motion — putting weight off and on as you walk and move. The fluid inside the joint flows into and out of the cartilage like a sponge, so all the nutrients in the joint fluid get into the cartilage” and help slow any degradation there.

Neuroscientist Benedict Kolber with Duquesne University in Pittsburgh says exercise may also cause changes in the brain that can make a big difference in damping down pain.

“Exercise engages the endogenous opioid system,” he says, “so our bodies make opioids and use these opioids to decrease pain.”

In addition to other mechanisms still being worked out, natural opioids are thought to bind to the same receptors in the brain as opioid painkillers, Kolber says, but without the complications or potential for addiction. “There are some circumstances,” he says, “in which your body can produce so much of these natural opioids that you actually get some sense of euphoria” — hence the term runner’s high, a phenomenon athletes have long described.

Kolber says exercise also seems to activate parts of the brain that are involved in decreasing pain. “We get pain signals that are coming from our hands to our spinal cord and up to our brain,” he says, “and then we get these control systems — parts of our brain that seem to be activated in exercise — and that then turns down the pain system.”

And finally, Kolber says, exercise also seems to decrease stress. And stress can make people more sensitive to pain.”