Biopsychosocial influence on shoulder pain: results from a randomized preclinical trial of exercise-induced muscle injury

The relationship between sustained hamstring pain and reorganisation of somatosensory representations: a randomised, controlled study

ABSTRACT

Recurrent hamstring injuries are highly prevalent amongst sporting populations. It has been hypothesised that pain from an initial hamstring injury may induce reorganisation of somatosensory representations that could contribute to reinjury. However, because of the cross-sectional nature of existing research, it remains unknown whether somatosensory changes are a cause or effect of pain or if they are driven by other potentially confounding factors. Here, we explored the effect of experimentally induced sustained hamstring pain on tasks that interrogate somatosensory and spatial representations. Fifty healthy participants were randomly allocated to an experimental group that performed an eccentric exercise protocol on the right hamstring to induce delayed onset muscle soreness or a control group performing a repetition-matched concentric exercise protocol. The tactile cortical representation was assessed using two-point discrimination and tactile localisation, whereas the proprioceptive representation was assessed using a left-right judgement task. Peripersonal spatial representations were assessed using an auditory localisation task. Assessments were performed at baseline and day 2. No between-group differences in tactile acuity were observed. However, improvements in left-right judgments and worsening of auditory localisation occurred in the experimental group compared with the control group. This study provides preliminary evidence showing that somatosensory changes occur in response to sustained hamstring pain. Experimentally induced, sustained hamstring pain elicited enhancements in proprioceptive processing and deficits in peripersonal spatial processing, suggesting a shift in the allocation of attentional resources from the external (peripersonal) to internal (body) environment. These findings may hold important implications for reinjury risk and rehabilitation following hamstring pain.

Nociceptive, neuropathic, or nociplastic low back pain? The low back pain phenotyping (BACPAP) consortium's international and multidisciplinary consensus recommendations

The potential to classify low back pain as being characterised by dominant nociceptive, neuropathic, or nociplastic mechanisms is a clinically relevant issue. Preliminary evidence suggests that these low back pain phenotypes might respond differently to treatments; however, more research must be done before making specific recommendations. Accordingly, the low back pain phenotyping (BACPAP) consortium was established as a group of 36 clinicians and researchers from 13 countries (five continents) and 29 institutions, to apply a modified Nominal Group Technique methodology to develop international and multidisciplinary consensus recommendations to provide guidance for identifying the dominant pain phenotype in patients with low back pain, and potentially adapt pain management strategies. The BACPAP consortium's recommendations are also intended to provide direction for future clinical research by building on the established clinical criteria for neuropathic and nociplastic pain. The BACPAP consortium's consensus recommendations are a necessary early step in the process to determine if personalised pain medicine based on pain phenotypes is feasible for low back pain management. Therefore, these recommendations are not ready to be implemented in clinical practice until additional evidence is generated that is specific to these low back pain phenotypes.

Circulating Inflammatory Biomarkers Predict Pain Change Following Exercise-Induced Shoulder Injury: Findings From the Biopsychosocial Influence on Shoulder Pain Preclinical Trial

Shoulder pain is a highly prevalent musculoskeletal condition that frequently leads to suboptimal clinical outcomes. This study tested the extent to which circulating inflammatory biomarkers are associated with reports of shoulder pain and upper-extremity disability for a high-risk genetic by psychological subgroup (catechol-O-methyltransferase [COMT] variation by pain catastrophizing [PCS]). Pain-free adults meeting high-risk COMT × PCS subgroup criteria completed an exercise-induced muscle injury protocol. Thirteen biomarkers were collected and analyzed from plasma 48 hours after muscle injury. Shoulder pain intensity and disability (Quick-DASH) were reported at 48 and 96 hours to calculate change scores. Using an extreme sampling technique, 88 participants were included in this analysis. After controlling for age, sex, and BMI, there were moderate positive associations between higher c-reactive protein (CRP; βˆ = .62; 95% confidence interval [CI] = -.03, 1.26), interleukin-6 (IL-6; βˆ = 3.13; CI = -.11, 6.38), and interleukin-10 (IL-10; βˆ = 2.51; CI = -.30, 5.32); and greater pain reduction from 48 to 96 hours post exercise muscle injury. Using an exploratory multivariable model to predict pain changes from 48 to 96 hours, we found participants with higher IL-10 were less likely to experience a high increase in pain (βˆ = -10.77; CI = -21.25, -2.69). Study findings suggest CRP, IL-6, and IL-10 are related to shoulder pain change for a preclinical high-risk COMT × PCS subgroup. Future studies will translate to clinical shoulder pain and decipher the complex and seemingly pleiotropic interplay between inflammatory biomarkers and shoulder pain change. PERSPECTIVE: In a preclinical high-risk COMT × PCS subgroup, 3 circulating inflammatory biomarkers (CRP, IL-6, and IL-10) were moderately associated with pain improvement following exercise-induced muscle injury.