Movement-evoked pain: a new way of understanding (chronic) pain?
Physical activity is known to play an important key role in the treatment of pain conditions and is an effective strategy to relieve pain and improve level of functioning in daily activities in various chronic musculoskeletal pain disorders (Daenen, et al., 2015). However, some groups of (chronic) pain patients can experience increased levels of pain during physical activity and movement tasks (Nijs, et al., 2012; Sullivan, et al., 2009) with observed dysfunctional responses in relation to exercise. The release of endorphins and activation of nociceptive inhibitory pain mechanisms, known processes in healthy individuals, seem to be “off” in some of the chronic pain patients (Nijs, et al., 2012; Van Oosterwijck, et al., 2012).
This means that in those particular patients, physical activity leads to more pain symptoms and decreased levels of activity, making therapeutic interventions in chronic musculoskeletal pain patients even more tricky. There is clearly a paradoxical relation between physical activity and pain: physical activity to “treat” pain on one hand and movement evoking and worsening pain on the other.
Recent literature shows a growing interest in movement-evoked pain (MEP) in individuals with persistent pain conditions (Mankovsky-Arnold et al. 2017). MEP refers to pain that is experienced in response to a physical task and allows differentiation between pain experienced before, during and after movement tasks.
A proper differentiation between MEP and resting or spontaneous pain is imminent and necessary as literature suggests they are likely driven by different underlying mechanisms (Corbett, et al., 2019). Further evidence links psychological constructs, such as fear of movement and/or pain catastrophizing, with MEP in persistent musculoskeletal pain conditions, including whiplash-associated disorder, low back pain, and knee osteoarthritis (Simon, et al., 2016; Sullivan, et al., 2009; Wideman, et al., 2014).
Despite the recognized importance of distinguishing between MEP and resting or spontaneous pain, we notice a lot of researchers neglecting this issue. Most studies do not even differentiate between both measures and/or only assess spontaneous pain or pain at rest. Pain experience during physical activity is often not measured at all or not assessed by means of retrospective questionnaires.
There is increasing evidence that changes in pain as a response to physical activity might represent a dimension of pain experience that is different from spontaneous pain in terms of prognostic value (Mankovsky-Arnold, et al., 2014). It seems to be more disability-relevant as well (Wideman, et al., 2014). Therefore, the increased use of MEP measures may help us understand the relation between pain and movement, and eventually lead to a better understanding of the complex phenomenon of chronic pain.
a PhD-researcher at the Vrije Universiteit Brussel, Belgium, and is a member of RERE and the Pain in Motion research group. She worked as a physiotherapist and manual therapist in clinical practice for several years before engaging in research.
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