Do we really know how exercise works for pain?

A question I often ponder is - "Do we really know the mechanisms behind how exercise might help with pain?" And the honest answer is I don't think we really do!

There is a whole bunch of stuff to consider and pontificate over but actual definitive answers appear to be scarce. We have tons of modern research and commentary on the psychology and neurobiology of pain but our ideas of how this applies to exercise seems to have remained fairly static.

Article at a glance.

• We are mostly unsure of exactly HOW exercise can help for pain
• Part or all of this may not be specific to physical factors
• WHY people get better is not always clear when thinking critically
• We can under consider the non specific effects of exercise
• These include altering perceptions, locus of control, self efficacy and predicted expectations of outcome
• Non specific effects CAN affect more specific physical effects
• Your bias does NOT predict potential non specific effects
• There are very REAL neurobiological effects from non specific aspects on pain
• Collaboration, education and interaction may ALL help elicit non specific effects.

This paper HERE looks at whether exercise ACTUALLY helps, and it can, but HOW is a completely different question that is still mostly unclear.

Exercise in a therapeutic setting is still prescribed in very similar ways to how it is implemented in a non-therapeutic settings, in terms of sets & rep ranges, even though the therapeutic parameters or mechanisms of action maybe quite different and currently remain under explored. I have previously discussed the subject of dosing HERE.

I am increasingly drawn to the concept that a fair proportion of the effects of exercise may NOT be specifically physical in nature. We may not be able to attribute them solely to increasing range of movement, stability, strength, posture or whatever else we choose to measure and then attempt to effect. This article HERE explores some non specific effects.

What makes me think this? Well can we reliably, hand on heart, say that any of these things NEED to change for people to get better? Now before anybody gets their panties in a wad, like all things this probably lies on a spectrum. Some people may need and get a purely physical response, for others the benefit maybe entirely non physical. It is worth reminding ourselves that if we are truly thinking critically, reflecting on ones self being tough to do of course, that any measures that are taken post treatment do not automatically validate the potential deficit we targeted as being the sole cause of changes in how someone feels. ROM, strength or motor control all may be restored once pain subsides rather than being the actual CAUSE of the pain subsiding.

HERE we see a systematic review regarding lower back pain, with changes in strength, flexibility etc appearing to have little correlation with a successful outcome.

We see the same for many of the things that we can assess and measure.

Kinematics - HERE

Muscle firing - HERE

Range of movement - HERE

So why is this? Could it be that there are things that we don’t generally measure? Certainly we cannot really measure in day-to-day practice changes in local physiology or what happens up top cortically and these could almost certainly play a part in pain and its subsidence. We should also consider, however, how someone actually feels about what we are doing TO them or WITH them and how this affects the outcome.

Learning lessons from Manual therapy

The current understanding of the mechanisms behind manual therapy have not really aligned with what they were once thought to be since they have been explored in a research setting, even though they DO appear to have an affect on pain. We can take a leaf out of the book of critical thinkers on this subject, such as Zusman HERE and Bialosky HERE, who critiqued the traditional biomechanical explanations and offered some alternative perspectives for WHY these techniques may have a positive effect. Many of these factors will of course be present across lots of interventions, INCLUDING exercise.

So what are these non-specific effects?

It would be good to point out here that non specific means that they are not specific to the ACTUAL intervention itself, not that they are in NO WAY specific! They could be specific to someone’s perception of where they are, who they are with or what is being done with them and would include the relevance of the intervention and how that relates to their belief structure. It could be someone’s predicted expectation of the outcome that is the driving factor in their recovery. This paper HERE explores more of the contextual effects in the therapeutic encounter.

The predicted outcome does seem to be a HUGE factor in the success of a treatment, in part because it may affect the process of that treatment and this would be no different for ANY intervention, exercise included. If someone has had a previous failed experience with exercise, and this could be unrelated to pain, this might affect their perception of your chosen intervention REGARDLESS of the effectiveness shown by all those research papers you have diligently read! This was seen in a recent paper on a comparison rotator cuff exercises HERE, with the closed chain exercise group suffering with dropouts because people felt these exercises were not specific enough. Both of these papers look at predicted expectations.HERE & HERE.

We should also not take a binary view of non specific OR specific effects but realise that these non-specific effects could have a large impact on the specific effects. Lets say I don’t believe that the exercises that I have been given will make me better. I might be less likely to actually do them and therefore would not derive the physical benefit. Even away from the therapeutic use of exercise, psychological factors appear important. HERE we see that exercise works better if you believe it will. and HERE we see reframing physical activity positively had an effect on health.

It could be that someone simply has a better perception of themselves and their capabilities. This means that they view what they are doing more positively and hence they may do more of it. These perceptual factors might influence how incoming sensory information is viewed, so what was previously viewed as threatening is now viewed in a less threatening light and decreasing the need for protective mechanisms such as pain.

We might find that someone’s locus of control changes, moving from being externally focused, a sense of having little control over their current situation including pain levels, to being more internally focused and able to influence what is happening to them. This could also lead to increased self-efficacy meaning that completing tasks and reaching goals is now perceived as being within someone’s reach. All of these factors could increase analgesia acutely through activation of descending inhibitory mechanisms, eloquently described as the drug cabinet in the brain by David Butler, and longer term through changes in perception or prediction of threat or harm.

Bias

An important point to keep in mind is that just because a certain type of exercise, or any intervention for that matter, fits your biases and it seems likely it COULD give a large slug of the psychological good stuff does not mean it WILL. The recipient holds the expectations here not the giver, meaning that the person actually doing it could regard the favourite exercise you use as the exact OPPOSITE to you do. Non specific effects are not automatic, however much you believe in them or hope that they will happen. So could strength training increase someone’s perception of their robustness and sense of strength? Absolutely. But this is certainly not automatic and guaranteed; it would depend on the belief structure and perceived relevance of the person doing it! We must also consider the potential for negative non specific effects too.

How might we get some of these non specific effects from exercise?

Firstly how we explain the relevance to people and the effect it could have may go a long way to improving outcome. Coupling this with someone’s current perception, belief structure and previous experience may also have positive benefits by addressing negative elements that could alter the acute perceptual response, such as pain increasing, if someone believed exercise was actually going to make them WORSE which can be a very REAL fear.

If something has not previously worked, why would it work this time? Even if it is the most evidence based option. Using something different or exploring why it could work or perhaps did not work in more detail may have an effect on expectations and compliance. Education should not just be seen as something to use with pain in my opinion. This may extend to WHY exercise could be more more relevant than a passive or surgical intervention that is currently perceived as the gold standard or preferred course of action by the recipient. This process may or may NOT be required in exactly the same way that education about pain is not always necessary but to not CONSIDER it EVER is quite another matter entirely.

Preference may also play a huge part. We could say swimming was the BEST way to get fit and the most evidenced course of action, but if someone does not like swimming or has limited access to a pool, the BEST could become the WORST if we have not appreciated the person doing it!

Thinking about the person doing the exercise not just the component body part such as a muscle or tendon could be one of the best ways to integrate some of the lessons we have learned from subjects such as pain science when thinking about therapeutic exercise.

Take homes

• We are mostly unsure of exactly HOW exercise can help for pain
• Part or all of this may not be specific to physical factors
• WHY people get better is not always clear when thinking critically
• We can under consider the non specific effects of exercise
• These include altering perceptions, locus of control, self efficacy and predicted expectations of outcome
• Non specific effects can affect more specific physical effects
• Your bias does NOT predict potential non specific effects
• There are very real neurobiological effects from non specific aspects on pain
• Collaboration, education and interaction may all help elicit non specific effects.