Exercise and chronic pain

One of the most consistent recommendations in cognitive behavioural therapy approaches for chronic pain is for people to exercise. Exercise is thought to help reduce pain, improve physical fitness and support participating in social, professional and domestic activities. By being fit people can manage their daily activities at a lower percentage of their maximum aerobic capacity and, hopefully, minimise the risk of flare-up.

While the overall premise of exercise is clear, the details of how often, what kind and the best approach for recovery after exercising are rather less. The problem for people with chronic pain is that moving HURTS.  Some people have even argued that chronic pain is, in essence, an activity intolerance disorder.

Daenen, Varkey, Kellmann & Nijs (2014) have attempted to clarify the state of play in exercise for chronic pain, and propose some interesting guidelines for clinicians. You see, one type of chronic pain is not the same as another – and neither is one form of exercise exactly like another.

How does exercise “work”?

Exercise is “planned, structured and repetitive bodily movements that are performed to improve or maintain one or more components of physical fitness” (Howley, 2001).  Aerobic exercise at approximately 70% or more of maximum aerobic capacity sparks production of endorphins and descending inhibitory mechanisms (serotonergic, opioidergic, adenosinergic systems); it also reduces weight, strengthens muscles and increases bone density. People without chronic pain experience pain inhibition for up to 30 minutes after aerobic exercise, but this period is much shorter for those involved in resistance training (just a couple of minutes). Researchers think that endogenous opioids and growth factors are released, supraspinal nociceptive inhibition occurs, releasing beta-endorphins from the pituatary and hypothalamus and these enable analgesia by activating mu-opioid receptors in both the periphery and central nervous systems.

…And if you have fibromyalgia?

People with sensitised nervous systems, and in particular those people with dysfunctional descending inhibitory mechanisms, such as those with fibromyalgia, do not experience this endogenous analgesia. Instead, they can have increased pain possibly through a reduced pain threshold after exercise – myofibre (muscle fibre) damage is a normal part of exercise, but is associated with lactates and oxidative stress, and these can be potent contributions to nociception. In an individual with poor descending inhibition, this nociceptive input can trigger a flare-up of symptoms.

Stress responses

Daenen, Varkey, Kellman & Nijs (2014) also point out that people with chronic pain can have abnormal stress responses, with increased activity of the sympathetic nervous system, and problems associated with the HPA axis. What this means is that people with some forms of chronic pain are chronically “stressed”, that is, they’re exposed to stressors simply from having chronic pain, and this changes the homeostatic response of the HPA axis and sympathetic nervous system. This can lead to excessive fatigue and difficulty recovering from exercise, because exercise is also a stressor in which growth hormone, testosterone, cortisol, epinephrine, and norepinephrine are released. Normally this enables the body to gradually adjust to a stressor and maintain homestasis – by exercising in small but regular amounts, and allowing enough time to recover in between, the body becomes more able to respond to stressors.

In people who are chronically stress, failing to provide adequate recovery periods can lead to ongoing sensitisation of nociceptors and increased experience of pain. Daenen, Varkey, Kellman & Nijs (2014) consider that dysfunctional reactivity of the HPA axis contributes to exercise intolerance in people with fibromyalgia.

What does this mean for exercise for people with chronic pain?

I think this means we need to be careful about how we go about prescribing exercise. The purpose of exercising is generally to ensure people can manage their everyday activities with a little room to spare in terms of activity tolerance. My study suggests that people who cope well with pain use exercise more for their mental health than to improve fitness or muscle strength. And this group of people used low-level cardiovascular exercise such as walking, cycling, dancing and tai chi as their preferred form. Some people used their daily activities as their form of exercise – things like gardening, vacuuming the floor, washing windows, hanging out washing, cleaning the car.

I think we need to ensure we are very clear as to the goals of exercise. Why this particular set of exercises?

We also need to be clear that one size does not fit all. If a person doesn’t enjoy going to a gym, this shouldn’t be the ONLY form of exercise they’re exposed to. If the person doesn’t have an activity intolerance, maybe they need to develop recovery strategies rather than changing their exercise form.

We need to be aware that increases in pain intensity are likely for some people who have pain such as fibromyalgia. People with this type of pain problem may benefit from developing both an exercise form they enjoy and therefore can do consistently (I like to bellydance and garden!), AND to develop effective recovery strategies. Perhaps helping people use strategies such as mindfulness and diaphragmatic breathing as part of a cool-down could be a good option.

Finally, I think it’s important to avoid implying that people who have dysfunctional endogenous analgesic systems are simply “noncompliant”, need “psychological” input, or just need more encouragement. Maybe it’s time to reconsider the kind of exercise and recovery we’re prescribing, and titrate it according to the individual’s response to exercise.

 

Daenen, L., Varkey, E., Kellmann, M., & Nijs, J. (2014). Exercise, not to Exercise or how to Exercise in Patients with Chronic Pain? Applying Science to Practice The Clinical Journal of Pain DOI: 10.1097/AJP.0000000000000099

Howley ET. Type of activity: resistance, aerobic and leisure versus occupational physical activity. Med Sci Sports Exerc 2001;33:S364-9; discussion S419-20.