We all learned that pain is a quite bad indicator for tissue damage. Despite this, we often hear/read that therapists tend to recommend painfree exercises for patients with chronic musculoskeletal disorders. Ben Smith and colleagues performed a systematic review with meta-analysis and compared painfree vs painful exercises in those patients. They found several papers including patients with achillodynia, shoulder pain, plantar fascitis and low back pain. Below is a critical appraised paper on that systematic review.
Have fun reading 😉
Thanks to Jan Herman van Minnen and Nils Runge for critial re-reading!
Background Chronic musculoskeletal disorders are a prevalent and costly global health issue. It has been proposed that modern treatment therapies for chronic musculoskeletal pain and disorders should be designed around loading and resistance training targeting movements and activities that can temporarily reproduce and aggravate patients pain and symptoms. Up to now there has been no systematic review about the benefits of allowing pain during these exercise programs or if it should be avoided.
Question Should exercises be painful in the management of chronic musculoskeletal pain
Design A systematic review and meta-analysis
Methods Two authors independently selected studies and appraised risk of bias. Methodological quality was evaluated using the Cochrane risk of bias tool, and the Grading of Recommendations Assessment system was used to evaluate the quality of evidence.
Results The literature search identified 9081 potentially eligible studies. Nine papers (from seven trials) with 385 participants met the inclusion criteria. There was short-term significant difference in pain, with moderate quality evidence for a small effect size of −0.27 (−0.54 to −0.05) in favour of painful exercises. For pain in the medium and long term, and function and disability in the short, medium and long term, there was no significant difference.
Conclusions Protocols using painful exercises offer a small but significant benefit over pain-free exercises in the short term, with moderate quality of evidence. In the medium and long term, there is no clear superiority of one treatment over another. Pain during therapeutic exercise for chronic musculoskeletal pain need not be a barrier to successful outcomes. Further research is warranted to fully evaluate the effectiveness of loading and resistance programmes into pain for chronic musculoskeletal disorders.
Limitations Only one reviewer screened the titles and abstracts during the literature search. This could be indicative for selection bias on the included studies for the systematic review. Additionally, there was a preselection by including only studies in English language. Patients with widespread pain disorders like fibromyalgia, headache or migraine were not included in this paper. Therefore, the results of this systematic review cannot be applied to this group of patients.
Commentary Musculoskeletal disorders are one of the most prevalent and costly disorders globally [2,3]. Low back pain for example is considered to be the leading cause of years lived with disability worldwide, ahead of other non-musculoskeletal disorders like depression, diabetes, cancer and cardiovascular diseases [4,5] and the prevalence of chronification of low back pain is rising . Active exercise interventions have been shown to be effective in the management in chronic musculoskeletal disorders [7,8] but the exact underlying mechanisms are still unclear  and it seems like it is not related to changes in physical capacities. 
Some patients suffering from chronic musculoskeletal pain belief that certain activities are harmful for their bodies [11-13]. One potential mechanism how exercise therapy works could be a change of this belief system, by confronting them with graded exposure to mechanical stimuli. A qualitative study with patient interviews by Boutevillain et al.  gives us examples, how people getting fearful about doing exercises:
“It can be harmful, I give you an example: I have a colleague with low back problems, similar to mine, and she loves to take step classes, but each time she exercises too much, she is in pain but continues. I think she should stop, it is quite dangerous for her”
“Sometimes I try to exercise and then I’m in pain, looking back had I known it would hurt I would probably not have done it”
Patients often belief that pain relates to damage [14-16] and therefore feeling pain during an exercise could raise the idea that this exercise will hurt their body. Controversially, the systematic review by Smith et al.  and also a recent study  are highlighting that feeling pain during exercises doesn’t seem to be harmful for patients. The systematic review even shows benefits for pain in the short-term compared to pain-free exercises. A reason to choose painful exercises could be the circumstance, that a patient is fearful that exercises or activities that hurt will harm their bodies in the long-term. So, the exercise therapy could act as graded exposure to loading the body and pointing up that pain will not necessarily correlate with tissue damage or associated long-term damages.
Additionally, it is important to note that the systematic review by Smith et al  should should be a guidance for therapists working with patients with chronical musculoskeletal pain. It should encourage them not to abort an active intervention if it’s painful for the client but maybe to continue it and collect new information. That seems a quite reasonable idea because the beliefs and attitudes of the therapist affect the beliefs, attitudes and outcomes of patients . A healthcare practioner being fearful of pain occurring during the patients’ active intervention could therefore slow down the process of rehabilitation.
On the other hand, painful exercises doesn’t seem to be more beneficial in the medium and in the long-term compared with pain-free exercises. This information in turn leaves us with two different therapy approaches leading to a quite similar outcome. Therefore, we can see pain itself as an optional variable during exercises.
When we include pain as a variable during exercises, an occurring question could be: how much pain is acceptable during the intervention?
A pain-monitoring system dividing a numeric analogue scale into 3 subdivisions was already introduced by Roland Thomeé in 1998 . Up-to-date several variations of this pain-monitoring system exist [20,21] but all of them use a pre-set division of pain-levels that should be accepted and pain-levels that should be avoided. For scientific reasons, a pre-set cut-off between acceptable and non-acceptable pain intensity seems useful. For clinical practice, an individually modifiable tool that gives the patient the ability to self-determine their acceptable pain-level could be beneficial as it integrates the patient into the rehabilitation process. It also gives her/him the opportunity to learn that pain doesn’t have to be harmful, in a self-selected speed of progression during the treatment sessions. This in turn could raise the perceived self-efficacy and locus of control, which are associated with better rehabilitation outcomes [22-25].
It is also conceivable to change the variable being measured with the monitoring system. Asking for pain can raise the attention to it and that has been shown to increase the pain experience itself [26-28]. Using a comfort-scale instead of a pain-scale has been shown to shift the thoughts of pain as tissue damage to pain as part of healing and recovery . But that have just been studied in women after Caesarean section where a specific tissue damage is identifiable and can therefore yet not be transferred to patients with chronic musculoskeletal disorders. Another disadvantage using a comfort scale could be the missing practical educational link that pain is not necessarily harmful.
A way to start an active intervention with patients with chronic musculoskeletal pain disorders could be to educate them that pain is not a sign of a poor outcome during exercises and that it doesn’t imply tissue damage. Another important aspect to talk about is that they do not have to wait to begin with training until the pain settled down by time or with a passive treatment. Active therapies have a hypo-algetic effect that even could be increased when people get this explained . With this knowledge and the patients’ ability to steer the intensity of his exercise plan on his own, the patients’ self-efficacy could be increased. Enhancing self-efficacy in patients with chronical musculoskeletal pain is an important predictor for less pain and less disability in the future [24,31] and should therefore be recommended.
Further research could clarify if a pre-set or an individual pain monitoring system lead to different outcomes and if the usage of a comfort-scale has advantages over a pain-scale when exercising with patients with chronical musculoskeletal pain disorders.
Thanks to Jan Herman van Minnen and Nils Runge for critial re-reading
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