Like most people, within my clinical/research practice, I draw upon my own personal every-day experiences. So, when I think about exercise prescription for people with musculoskeletal pain I am always drawn back to a story from my halcyon days of youth playing five-a-side in-door staff football on Friday afternoons at 4pm.
On one particular occasion I had been suffering from neck pain all week, it was very sore and my neck movement was stiff and Schwarzenegger-like. I was keen to play but concerned I would not be able to. Right up to the last minute I was unsure whether I should play BUT in the end I couldn’t really back out because that would leave the teams unbalanced – it was a real social faux pas to pull out of the game at the last minute without giving the lads the opportunity to find a replacement. Anyway, I digress! The game started. It was high-intensity and I do not think I had any pain during the entire game or indeed afterwards – My recovery was Lourdes-Like! Ever since, I have always had a feeling that high-intensity exercise may be a useful treatment option for people with pain.
Within the literature however, there really has been scant attention paid to details of exercise prescription for musculoskeletal pain. In terms of the FITT principals (Frequency, Intensity, Time and Type) there are quite a few studies looking at type, comparing one type of exercise to another, but very little investigating the other components. We could find only one study, which had expressly considered intensity, which used self-report, and this study suggested a U shaped curve where those doing very low amounts of low intensity activity and very high amounts of high intensity activity were at greatest risk of back pain. I was surprised at the lack of guidance in the literature on intensity, especially considering exercise is a regular feature of pain management.
My colleagues and I at Teesside University, along with the awesome Suzanne McDonough at the University of Ulster, decided to explore the issue further by undertaking a secondary analysis of the 2008 Health Survey for England dataset (Ryan et al. 2017). We chose this dataset as it contained information for over 4000 individuals who had their physical activity measured objectively using an accelerometer. We applied a relatively new statistical approach to the data called isotemporal substitution. This approach came from the field of dietetics where it has been used to investigate the health effects of replacing one type of food with another. Scientists in the field of physical activity have started using this approach to explore what is the effect of replacing one type of behaviour with another (e.g. replacing 30 minutes of sitting with 30 minutes of skipping).
In our study, we modelled what would be the effect of replacing 10 minutes of sedentary behaviour with 10 minutes of either light or moderate-to-high intensity physical . The models derived the risk ratio for each scenario using cox-regression. A 10% relative risk reduction was set as the minimally clinically important threshold. This threshold implies that for every 10 cases with chronic musculoskeletal pain, one is prevented due to the exposure in question (e.g. replacing sedentary behaviour with a specific intensity of activity). Replacing 10 minutes of sedentary behaviour with 10 minutes of light intensity exercise was not associated with a reduction in musculoskeletal pain prevalence. In contrast, replacing with 10 minutes of moderate-to-high intensity activity was associated with an 11% relative reduction in musculoskeletal pain prevalence. When the replacement increased to 30 minutes, there was a 29% relative reduction in musculoskeletal pain prevalence. Our data suggest that encouraging people to undertake light intensity may have little benefit for musculoskeletal pain. However, undertaking relatively small amounts (10 minutes) of moderate-to-high intensity activity, or dare I say it, achieving the minimal physical activity recommendations for adults set by the American College of Sports Medicine (ACSM) (i.e. 30 minutes of moderate-to-vigorous activity daily) could have positive effects on musculoskeletal pain.
There are number of limitations to keep in mind when interpreting a study like this. Probably the main one is that the work is cross-sectional. Thus, we cannot claim cause and nor can we make definitive claims about the direction of the relationship. It is possible that people who do less moderate-to-high intensity activity are more likely to develop musculoskeletal pain, contrastingly, it could be that people who have musculoskeletal pain are less likely to do moderate-to-high intensity activity. However, despite its limitations the findings raise an interesting and clinically relevant question – what should we recommend to our patients regarding physical activity intensity. I am sure many of us encourage exercise, but is that specific enough? I am sure many of us encourage gentle exercise, but is that suggestive of low intensity exercise and potentially of little benefit? I think our work reinforces that, at the very least, we should be encouraging our patients with musculoskeletal pain to achieve the recommended 30 minutes of moderate-to-vigorous physical activity per day – for direct benefits to their condition and all the other potential benefits of exercise. Additionally, I think our work highlights the need for better research into the field of exercise intensity to guide clinical exercise prescription recommendations for people with musculoskeletal pain.
About Cormac Ryan
Cormac is a Reader in Physiotherapy at Teesside University. He graduated from the University of Limerick in 2002 with a BSc in Sports and Exercise Science, and completed an MSc in Physiotherapy (pre-registration) at Queen Margaret University College, Edinburgh. He was awarded his PhD from Glasgow Caledonian University, in 2008, for investigating the relationship between physical activity and chronic low back pain. Cormac’s research interests are primarily in the area of chronic pain, its impact on patients, and interventions to manage the condition. He also has three kids under the age of eight and, as a result, is not getting much sleep, so please excuse any errors/typos!
Ryan CG, Wellburn S, McDonough S, Martin DJ, Batterham AM. (2017) The association between displacement of sedentary time and chronic musculoskeletal pain: an isotemporal substitution analysis. Physiotherapy. Vol. 103; 471-477.