What is motor imagery?

Motor imagery is also known as mental practice. The only distinction is that mental practice is related to enhancing performance (which  is hopefully the aim of motor imagery anyway). Motor imagery is the imagining of an action or movement without physically doing it. Similar areas of the brain are activated whether you imagine a movement or physically perform it. Motor imagery particularly activates areas of the brain responsible for motor planning such as the pre-motor cortex, and for this reason, it has been used to assist with motor learning and skill acquisition.

It sounds a bit like action observation therapy. Can you clarify the distinction?

Motor imagery and action observation are both motor simulation techniques, they are both used to simulate a physical task. Motor imagery requires a patient to imagine themselves performing a task, ideally, from a first-person perspective. While imagining a movement, patients are encouraged to imagine what they can see and what they can feel. For example, they might imagine seeing their knee straightening and feeling their quadriceps tensing to straighten the knee. Action observation is more externally guided, and it involves an individual watching movements or activities performed by someone else. Typically, someone will watch a video of someone else successfully completing an activity. Recently, it has been found that the use of motor imagery and action observation in combination appears to be more effective than either technique alone. So, someone would watch a video of someone performing an activity then imagine performing that activity themselves.

Has motor imagery been shown to have effects in healthy people or patient groups?

From a physiotherapy research perspective, motor imagery has been most widely used in neurological patient groups such as Parkinson’s disease and stroke. For example, motor imagery is effective at improving upper limb function and gait in stroke patients when used in combination with physical practice. In healthy adults, motor imagery can assist with strength gains, it is considered as a substitute or additional training tool to preserve muscle function. Motor imagery is also routinely used in sporting and music settings to augment physical practice.

What sort of research did you and your co-authors do to investigate motor imagery?

We did a systematic review and meta-analysis of randomised trials of motor imagery versus control in older adults (≥60 years) without neurological conditions. We identified 12 eligible studies that used motor imagery training in older adults, 10 of these studies were included in the meta-analysis.

The stipulation ‘without neurological conditions’ seems to encompass a wide range of possibilities. Did that mean you ended up with evidence from wildly differing patient populations?

Not really, the evidence fell into two main groups: apparently healthy older adults, and adults that had undergone knee or hip replacements. We wanted to stipulate ‘without neurological conditions’ because most clinical motor imagery studies to date have been conducted on neurological patient groups, but until this review we weren’t too sure if motor imagery was effective in the gerontology/ortho-gerontology setting.

Were the review’s outcome measures appropriate for those groups?

Yes. We were interested in balance, mobility and falls, which are all important measures for older adults.

What effects did you find?

Motor imagery training significantly improved balance (1.03 SMD, 95% CI 0.25 to 1.82). Motor imagery training also significantly improved gait speed (MD 0.13m/s, 95% CI 0.04 to 0.22) and the Timed-up and Go (TUG) test (MD 1.64 seconds, 95% CI 0.79 to 2.49). None of the included studies collected falls data.

What’s your opinion about the clinical value of those effects?

It’s tricky to say whether motor imagery had a clinically worthwhile effect for balance because even though there was a large effect size, there were different balance assessments used across studies and large 95 per cent confidence intervals. The improvements identified for gait speed and the TUG test may be large enough to be clinically worthwhile as the mean difference exceeded levels previously identified as clinically important. The results for mobility measures (gait speed and TUG) were quite consistent across studies. However, the confidence interval around each of these estimates does extend below the nominated threshold; therefore, it must be acknowledged that the effects may or may not be clinically worthwhile. Motor imagery is a safe technique that can be done independently so we think even small effects can be achieved with minimal effort. Not surprisingly, we still need more high-quality data to get a better picture of the clinical value of motor imagery in older adults, but at least we know it has beneficial effects.

So it looks promising but more data are required. Does your research group plan to generate evidence in this field?

Yes, we’ve recently started a randomised controlled trial assessing the effect of motor imagery (combined with action observation) on lower limb strength in older adults with restricted weight bearing (typically following a lower limb fracture). Most of these patients are unable to do standard rehabilitation for several weeks because of their weight bearing status, leading to rapid reductions in strength and function. So, we’re trying to work out whether doing motor imagery helps to slow down these strength losses, which might mean quicker functional gains once they can commence standard rehabilitation.

Click here to read the systematic review and meta-analysis, published in the Journal of Physiotherapy.

Dr Vaughan Nicholson is a lecturer of physiotherapy and early-career researcher at Australian Catholic University, Brisbane. His research focuses on interventions to improve strength, balance and function in older adults. His current research program is assessing the influence of motor imagery training in older adults.