Peripheral electrical stimulation (ES) is commonly used as an intervention to facilitate movement and relieve pain in a variety of conditions. It is widely accepted that ES induces rapid plastic change in the motor cortex. This leads to the exciting possibility that ES could be used to drive cortical plasticity in movement disorders, such as stroke, and conditions where pain affects motor control. This paper aimed to critically review the literature to determine which parameters induced cortical plasticity in healthy individuals using ES. A literature search located papers that assessed plasticity in the primary motor cortex of adult humans. Studies that evaluated plasticity using change in the amplitude of potentials evoked by transcranial magnetic stimulation of the motor cortex were included. Details from each study including sample size, ES parameters and reported findings were extracted and compared. Where data were available, Cohen's standardised mean differences (SMD) were calculated. Nineteen studies were located. Of the parameters evaluated, variation of the intensity of peripheral ES appeared to have the most consistent effect on modulation of excitability of corticomotor pathway to stimulated muscles. There was a trend for stimulation above motor threshold to increase excitability (SMD 0.79 mV, CI -0.10 to 1.64). Stimulation below motor threshold, but sufficient to induce sensory perception, produced conflicting results. Further studies with consistent methodology and larger subject numbers are needed before definitive conclusions can be drawn. There also appeared to be a time effect. That is, longer periods of ES induced more sustained changes in cortical excitability. There is insufficient evidence to determine the effect of other stimulation parameters such as frequency and waveform. Further research is needed to confirm whether modulation of these parameters affects plastic change.

Meta-analyses and single studies offer some support for the effectiveness of passive sensory training in relation to sensory impairment and motor function. However, empirical evidence for active sensory training is limited. Further high-quality studies with greater statistical power and meaningful clinical measures are required in order to accurately determine the effectiveness of sensory retraining following stroke.

In the last decade transcranial magnetic stimulation (TMS) has been the subject of more than 20,000 original research articles. Despite this popularity, TMS responses are known to be highly variable and this variability can impact on interpretation of research findings. There are no guidelines regarding the factors that should be reported and/or controlled in TMS studies. This study aimed to develop a checklist to be recommended to evaluate the methodology and reporting of studies that use single or paired pulse TMS to study the motor system. A two round international web-based Delphi study was conducted. Panellists rated the importance of a number of subject, methodological and analytical factors to be reported and/or controlled in studies that use single or paired pulse TMS to study the motor system. Twenty-seven items for single pulse studies and 30 items for paired pulse studies were included in the final checklist. Eight items related to subjects (e.g. age, gender), 21 to methodology (e.g. coil type, stimulus intensity) and two to analysis (e.g. size of the unconditioned motor evoked potential). The checklist is recommended for inclusion when submitting manuscripts for publication to ensure transparency of reporting and could also be used to critically appraise previously published work. It is envisaged that factors could be added and deleted from the checklist on the basis of future research. Use of the TMS methodological checklist should improve the quality of data collection and reporting in TMS studies of the motor system.

There are concerns about the safety of texting while walking. Although evidence of negative effects of mobile phone use on gait is scarce, cognitive distraction, altered mechanical demands, and the reduced visual field associated with texting are likely to have an impact. In 26 healthy individuals we examined the effect of mobile phone use on gait. Individuals walked at a comfortable pace in a straight line over a distance of ∼8.5 m while; 1) walking without the use of a phone, 2) reading text on a mobile phone, or 3) typing text on a mobile phone. Gait performance was evaluated using a three-dimensional movement analysis system. In comparison with normal waking, when participants read or wrote text messages they walked with: greater absolute lateral foot position from one stride to the next; slower speed; greater rotation range of motion (ROM) of the head with respect to global space; the head held in a flexed position; more in-phase motion of the thorax and head in all planes, less motion between thorax and head (neck ROM); and more tightly organized coordination in lateral flexion and rotation directions. While writing text, participants walked slower, deviated more from a straight line and used less neck ROM than reading text. Although the arms and head moved with the thorax to reduce relative motion of the phone and facilitate reading and texting, movement of the head in global space increased and this could negatively impact the balance system. Texting, and to a lesser extent reading, modify gait performance. Texting or reading on a mobile phone may pose an additional risk to safety for pedestrians navigating obstacles or crossing the road.

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BackgroundChronic low back pain is a worldwide burden that is not being abated with our current knowledge and treatment of the condition. The fear-avoidance model is used to explain the relationship between pain and disability in patients with chronic low back pain. However there are gaps in empirical support for pathways proposed within this model, and no evidence exists as to whether physical activity moderates these pathways.MethodsThis was a cross-sectional study of 218 people with chronic low back pain. Multiple mediation analyses were conducted to determine the role of fear, catastrophizing, depression, and anxiety in the relationship between pain and disability. Separate analyses were performed with physical activity as the moderator. Individuals were classified as performing regular structured physical activity if they described on average once per week for > 30-minutes an activity classified at least moderate intensity (≥ 4–6 METs), activity prescribed by an allied health professional for their back pain, leisure time sport or recreation, or self-directed physical activity such as resistance exercise.ResultsFear, catastrophizing, and depression significantly mediated the relationship between pain and disability (p<0.001). However the mediating effect of catastrophizing was conditional upon weekly physical activity. That is, the indirect effect for catastrophizing mediating the relationship between pain and disability was only significant for individuals reporting weekly physical activity (B = 1.31, 95% CI 0.44 to 2.23), compared to individuals reporting no weekly physical activity (B = 0.21, 95% CI -0.50 to 0.97). Catastrophizing also mediated the relationship between pain and fear (B = 0.37, 95% CI 0.15 to 0.62), with higher scores explaining 53% of the total effect of pain on fear.ConclusionsThese results support previous findings about the importance of fear and depression as factors that should be targeted in low back pain patients to reduce back pain related disability. We have also extended understanding for the mediating effect of catastrophizing on back pain related disability. Back pain patients engaged with regular physical activity may require counselling with regards to negative pain perceptions.

Primary motor cortical (M1) adaptation has not been investigated in the transition to sustained muscle pain. Daily injection of nerve growth factor (NGF) induces hyperalgesia reminiscent of musculoskeletal pain and provides a novel model to study M1 in response to progressively developing muscle soreness. Twelve healthy individuals were injected with NGF into right extensor carpi radialis brevis (ECRB) on Days 0 and 2 and with hypertonic saline on Day 4. Quantitative sensory and motor testing and assessment of M1 organization and function using transcranial magnetic stimulation were performed prior to injection on Days 0, 2, and 4 and again on Day 14. Pain and disability increased at Day 2 and increased further at Day 4. Reorganization of M1 was evident at Day 4 and was characterized by increased map excitability. These changes were accompanied by reduced intracortical inhibition and increased intracortical facilitation. Interhemispheric inhibition was reduced from the "affected" to the "unaffected" hemisphere on Day 4, and this was associated with increased pressure sensitivity in left ECRB. These data provide the first evidence of M1 adaptation in the transition to sustained muscle pain and have relevance for the development of therapies that seek to target M1 in musculoskeletal pain.

PROSPERO 2016, CRD42016032592.