Is there a causal relationship between acute stage sensorimotor cortex activity and the development of chronic low back pain? : a protocol and statistical analysis plan

Introduction: Why some people develop chronic pain following an acute episode of low back pain is unknown. Recent cross-sectional studies have suggested a relationship between aberrant sensorimotor cortex activity and pain persistence. The UPWaRD (Understanding persistent Pain Where it ResiDes) cohort study is the first prospective, longitudinal investigation of sensorimotor cortex activity in low back pain. This paper describes the development of a causal model and statistical analysis plan for investigating the causal effect of sensorimotor cortex activity on the development of chronic low back pain. Methods and analysis: Sensorimotor cortex activity was assessed within 6 weeks of low back pain onset using somatosensory evoked potentials and transcranial magnetic stimulation mapping techniques. Chronic low back pain is defined as ongoing pain (Numerical Rating score ≥1) or disability (Roland Morris Disability Questionnaire score ≥3) at 6 months follow-up. Variables that could confound the relationship between sensorimotor cortex activity and chronic low back pain were identified using a directed acyclic graph and content expertise was used to specify known causal paths. The statistical model was developed ‘a priori’ to control for confounding variables identified in the directed acyclic graph, allowing an unbiased estimate of the causal effect of sensorimotor activity in acute low back pain on the development of chronic pain. The statistical analysis plan was finalised prior to follow-up of all participants and initiation of analysis. Ethics and dissemination: Ethical approval has been obtained from Western Sydney University Human Research Ethics Committee (H10465) and from Neuroscience Research Australia (SSA: 16/002). Dissemination will occur through presentations at national and international conferences and publications in international peer-reviewed journals. Trial registration number: ACTRN12619000002189 (retrospectively registered)

Does surface slope affect dual task performance and gait? : an exploratory study in younger and older adults

An increased risk of falling is associated with changes in gait while dual-tasking. The degree to which gait stability is altered during walking is infuenced by an individual’s cognitive and postural capacity, and the difculty of the presented tasks. However, it is unknown how greater walking task difculty afects gait stability in younger and older adults when dual-tasking. The purpose of the current study was to determine the efect of walking task difculty on gait stability in younger and older adults while performing a difcult audiospatial task. Ten younger [mean (SD) age 30.8 (6.6) years; 5 women] and 10 older [66.8 (5.7) years; 6 women] healthy adults walked on a treadmill at their preferred walking speed [younger 4.8 (0.4) ms−1, older 4.5 (0.5) ms−1) on either a level, or downhill slope both with and without responding to an audiospatial task. Step width, step width SD and mediolateral centre of mass displacement were calculated to determine changes in gait, and response time and accuracy were calculated to determine secondary task performance. Results indicated that older adults displayed a consistently greater step width (p≤0.015) and maintained their mediolateral centre of mass displacement (p>0.05) while walking downhill and responding to the audiospatial task, compared to downhill walking only. In contrast, younger adults maintained a regular step width during both level and downhill dual-tasking compared to level and downhill walking only (p>0.05), however displayed a lower mediolateral centre of mass displacement during level dual-task walking compared to level walking only (p=0.013). When the difculty of the walking task was greater, older adults increased their step width, which increased their stability

Does attention switching between multiple tasks affect gait stability and task performance differently between younger and older adults?

Gait stability and secondary task performance are affected by the need to share attention when dual-tasking. Further decrements may result from the need to switch attention between multiple secondary tasks. The aim of the current study was to determine the effects of attention switching upon gait stability and task performance in healthy younger and older adults. Ten healthy younger and ten healthy older adults walked on a treadmill at their preferred speed during three trials including: (1) baseline walking; (2) non-switching task walking, requiring response to an auditory-spatial or visual-spatial cue presented in an expected order; and (3) switching task walking, which required response to an auditory-spatial or visual-spatial cue presented in an unexpected order. Response time and accuracy, the margin of stability in the frontal (MoSML) and sagittal planes (MoSA: anterior, MoSP: posterior), step width and step length were calculated for non-switching and switching tasks. The MoSML, MoSA, MoSP, step width and step length during non-switching and switching tasks were normalized to baseline walking. Older adults took significantly longer to respond to cues and made more errors during the switching task compared to younger adults. Younger adults took narrower steps (p < 0.01) and displayed a reduction in MoSML (p < 0.01) during the switching task compared with the non-switching task. Conversely, older adults displayed no differences in MoSML between tasks. These findings suggest that attention switching results in different task prioritization strategies in younger and older adults during walking

The Physiological Profile Assessment : clinical validity of the postural sway measure and comparison of impairments by age

Background: The Physiological Profile Assessment (PPA) assesses falls risk in older adults by measuring impairments most associated with multiple falls. To date, no study has investigated the change in PPA impairment profile with age. Objective: To describe impairment profiles, by age and ability to complete the postural sway measure, of older adults fallers. Participants: We note that 885 older adults referred to multidisciplinary falls clinics located within two inner London boroughs (UK). Methods: Anonymised data was extracted from the PPA falls risk database. For comparisons, data was grouped by gender, age, and ability to complete the postural Sway test. Results: There were significant differences between all age groups in PPA falls risk, edge contrast sensitivity, quadriceps strength (Quad), postural sway and reported falls within the previous year (P < 0.01). The oldest age group (90+) had the highest PPA falls risk (P < 0.01), yet reported significantly less falls than the youngest age group (60 to 69; P < 0.05). There was significant variability in test results, with younger age groups displaying greater variability across PPA measures, and older age groups displaying more consistency (P < 0.05); 15.1% (n = 134) of patients that were able to perform the postural sway measure received a higher risk score for this test than those unable to complete the task. Conclusions: Greater variability in younger age groups indicates that specific impairments may provide the cause of falls, whereas widespread global reduction in function and frailty may provide the cause for falls in the older age groups. The postural sway scoring does not reflect ability to perform the test

Legislative History: An Act Making Unified Appropriations and Allocations for the Expenditures of State Government, General Fund and Other Funds, and Changing Certain Provisions of the Law Necessary to the Proper Operations of State Government for the Fiscal Years Ending June 30, 1998 and June 30, 1999 (HP832)(LD 1137)

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Safety and feasibility of transcranial direct current stimulation (tDCS) combined with sensorimotor retraining in chronic low back pain : a protocol for a pilot randomised controlled trial

Introduction Chronic low back pain (LBP) is a common and costly health problem yet current treatments demonstrate at best, small effects. The concurrent application of treatments with synergistic clinical and mechanistic effects may improve outcomes in chronic LBP. This pilot trial aims to (1) determine the feasibility, safety and perceived patient response to a combined transcranial direct current stimulation (tDCS) and sensorimotor retraining intervention in chronic LBP and (2) provide data to support a sample size calculation for a fully powered trial should trends of effectiveness be present. Methods and analysis A pilot randomised, assessor and participant-blind, sham-controlled trial will be conducted. Eighty participants with chronic LBP will be randomly allocated to receive either (1) active tDCS + sensorimotor retraining or (2) sham tDCS + sensorimotor retraining. tDCS (active or sham) will be applied to the primary motor cortex for 20 min immediately prior to 60 min of supervised sensorimotor retraining twice per week for 10 weeks. Participants in both groups will complete home exercises three times per week. Feasibility, safety, pain, disability and pain system function will be assessed immediately before and after the 10-week intervention. Analysis of feasibility and safety will be performed using descriptive statistics. Statistical analyses will be conducted based on intention-to-treat and per protocol and will be used to determine trends for effectiveness. Ethics and dissemination Ethical approval has been gained from the institutional human research ethics committee (H10184). Written informed consent will be provided by all participants. Results from this pilot study will be submitted for publication in peer-reviewed journals. Trial registration number ACTRN1261600062448