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.

The clinical course of acute, subacute and persistent low back pain: a systematic review and meta-analysis.

BACKGROUND: Understanding the clinical course of low back pain is essential to informing treatment recommendations and patient stratification. Our aim was to update our previous systematic review and meta-analysis to gain a better understanding of the clinical course of acute, subacute and persistent low back pain. METHODS: To update our 2012 systematic review and meta-analysis, we searched the Embase, MEDLINE and CINAHL databases from 2011 until January 2023, using our previous search strategy. We included prospective inception cohort studies if they reported on participants with acute (< 6 wk), subacute (6 to less than 12 wk) or persistent (12 to less than 52 wk) nonspecific low back pain at study entry. Primary outcome measures included pain and disability (0-100 scale). We assessed risk of bias of included studies using a modified tool and assessed the level of confidence in pooled estimates using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) tool. We used a mixed model design to calculate pooled estimates (mean, 95% confidence interval [CI]) of pain and disability at 0, 6, 12, 26 and 52 weeks. We treated time in 2 ways: time since study entry (inception time uncorrected) and time since pain onset (inception time corrected). We transformed the latter by adding the mean inception time to the time of study entry. RESULTS: We included 95 studies, with 60 separate cohorts in the systematic review (n = 17 974) and 47 cohorts (n = 9224) in the meta-analysis. Risk of bias of included studies was variable, with poor study attrition and follow-up, and most studies did not select participants as consecutive cases. For the acute pain cohort, the estimated mean pain score with inception time uncorrected was 56 (95% CI 49-62) at baseline, 26 (95% CI 21-31) at 6 weeks, 22 (95% CI 18-26) at 26 weeks and 21 (95% CI 17-25) at 52 weeks (moderate-certainty evidence). For the subacute pain cohort, the mean pain score was 63 (95% CI 55-71) at baseline, 29 (95% CI 22-37) at 6 weeks, 29 (95% CI 22-36) at 26 weeks and 31 (95% 23-39) at 52 weeks (moderate-certainty evidence). For the persistent pain cohort, the mean pain score was 56 (95% CI 37-74) at baseline, 48 (95% CI 32-64) at 6 weeks, 43 (95% CI 29-57) at 26 weeks and 40 (95% CI 27-54) at 52 weeks (very low-certainty evidence). The clinical course of disability was slightly more favourable than the clinical course of pain. INTERPRETATION: Participants with acute and subacute low back pain had substantial improvements in levels of pain and disability within the first 6 weeks ( moderate-certainty evidence); however, participants with persistent low back pain had high levels of pain and disability with minimal improvements over time (very low-certainty evidence). Identifying and escalating care in individuals with subacute low back pain who are recovering slowly could be a focus of intervention to reduce the likelihood of transition into persistent low back pain. PROTOCOL REGISTRATION: PROSPERO - CRD42020207442.

The Relationship Between Pain and Interoception: A Systematic Review and Meta-Analysis.

Interoception refers to the ability to sense internal bodily sensations. Research suggests that dysfunctions in interoception may be implicated in the transition to chronic pain, however, little work has examined interoceptive ability in pain states. Therefore, this systematic review aimed to assess whether interoception is altered in individuals experiencing pain. Following a systematic search of 4 electronic databases from inception to February 2023, 28 studies were included. Outcomes of interoceptive accuracy, interoceptive sensibility, and interoceptive awareness were meta-analysed. The risk of bias was assessed, and the certainty of the evidence was evaluated. Meta-analyses indicated that those with chronic pain display reduced interoceptive accuracy and increased interoceptive sensibility. Subgroup analyses indicated that the change in interoceptive sensibility is dependent on the measure used, with those with chronic pain scoring higher on measures focusing on attention to bodily sensations, while also scoring lower on emotional reactivity. No difference in interoceptive awareness was observed between individuals with chronic pain and pain-free controls. Only one study was found that measured interoception in those experiencing acute pain, while another study recruited those experiencing recurrent pain. These findings suggest that while those with chronic pain self-report as more interoceptively aware, they are less accurate at detecting internal bodily signals. Further research investigating domains of interoception in those experiencing acute and recurrent pain is needed. Data should be interpreted with caution as the certainty of evidence was very low for all completed analyses. This review was registered on the PROSPERO International Prospective Register of Systematic Reviews (Registration ID = CRD42022318843). PERSPECTIVE: This review considered the relationship between interoception and pain and found that an individual's ability to accurately sense internal signals is decreased in those with chronic pain, despite them reporting being more aware of internal sensations. However, there remains little research examining interoception in non-chronic pain states.

Fisioterapia guiada por EMT reduz a dor e induz a plasticidade no córtex motor na osteoartrose crônica do joelho / TMS-guided physiotherapy reduces pain and induces plasticity in the motor cortex in chronic knee osteoarthritis

INTRODUÇÃO: A osteoartrite do joelho (OA) está associada à dor crônica, comprometimento da função e perda da qualidade de vida. A plasticidade mal-adaptativa do cérebro pode estar envolvida, impedindo efeitos benéficos de exercícios e outras intervenções. A neuromodulação com estimulação elétrica periférica guiada pelo mapeamento da TMS pode influenciar especificamente as modificações mal-adaptativas. OBJETIVO: Comparar a organização cortical e excitabilidade de três músculos (reto femuris, vasto lateral e vasto medial) em um sujeito com OA joelho. MÉTODOS: Este estudo de caso único envolveu uma mulher de 66 anos com OA de joelho que estava considerando se submeter a uma artroplastia. Ela foi avaliada para dor (VAS), função (WOMAC e ICOAP) e força do quadríceps uma vez por semana, durante 10 semanas - ABA (A - avaliação de quatro semanas; B - avaliação de duas semanas e intervenção; A - avaliação de quatro semanas). O mapeamento de TMS foi realizado no início do estudo, após o período de intervenção de duas semanas e no final do estudo. Esse exame inicialmente revelou uma diminuição proeminente no volume da porção do músculo quadríceps do vasto medial sobre o córtex motor primário (M1), que determinou um protocolo de estimulação elétrica periférica projetado especificamente para aumentar a excitabilidade desse músculo. Durante o período de intervenção, o participante também realizou exercícios específicos diariamente. RESULTADOS: Os escores do WOMAC e a força do quadríceps não foram alterados durante o período do estudo. Melhoras foram observadas nas três subescalas do ICOAP após a intervenção. Esta alteração clínica foi associada a um aumento do vasto medial e também do vasto lateral, e uma diminuição nos volumes do mapa da TMS do músculo reto femoral, que foram mantidos até a última avaliação. CONCLUSÃO: O mapeamento do TMS pode guiar intervenções específicas para contrabalançar a plasticidade mal-adaptativa do córtex motor e influenciar positivamente a dor e a função na OA do joelho. [AU]

BACKGROUND: Knee osteoarthritis (OA) is associated with chronic pain, impaired function and loss of quality of life. Brain maladaptive plasticity may be involved and prevent beneficial effects of exercises and other interventions. Neuromodulation with peripheral electrical stimulation guided by TMS mapping may specifically influence those maladaptive modifications. OBJECTIVE: To compare the cortical organization and excitability of three muscles (straight femuris, vastus lateralis and vastus medialis) in a subject with OA knee. METHODS: This single case ABA study involved a 66 yo woman with knee OA that was considering an arthroplasty. She was assessed for pain (VAS), function (WOMAC, ICOAP), and quadriceps strength one time a week, for 10 weeks (A ­ four weeks assessment; B ­ two weeks assessment and intervention; A ­ four weeks assessment). TMS mapping was performed at baseline, after the two-week intervention period and at the end of the study. This examination initially revealed a prominent decrease in the volume of vastus medialis portion of the quadriceps muscle over the primary motor cortex (M1), which determined a peripheral electrical stimulation protocol specifically designed to increase this muscle's excitability. During the intervention period the participant also carried over specific exercises daily. RESULTS: WOMAC scores, and quadriceps strength were not changed during the study period. Improvements were seen in the three subscales of the ICOAP following the intervention. This clinical change was associated with an increase in vastus medialis and also Vastus lateralis, and a decrease in rectus femuris TMS map volumes, which were maintained until the last evaluation. CONCLUSION: TMS mapping may guide specific interventions to counteract motor cortex maladaptive plasticity and positively influence pain and function in knee OA. [AU]