Biomechanical differences between able-bodied and spinal cord injured individuals walking in an overground robotic exoskeleton.

BACKGROUND: Robotic assisted gait training (RAGT) uses a powered exoskeleton to support an individual's body and move their limbs, with the aim of activating latent, pre-existing movement patterns stored in the lower spinal cord called central pattern generators (CPGs) to facilitate stepping. The parameters that directly stimulate the stepping CPGs (hip extension and ipsilateral foot unloading) should be targeted to maximise the rehabilitation benefits of these devices. AIM: To compare the biomechanical profiles of individuals with a spinal cord injury (SCI) and able-bodied individuals inside the ReWalkTM powered exoskeleton and to contrast the users' profiles with the exoskeleton. METHODS: Eight able-bodied and four SCI individuals donned a ReWalkTM and walked along a 12-meter walkway, using elbow crutches. Whole-body kinematics of the users and the ReWalkTM were captured, along with GRF and temporal-spatial characteristics. Discreet kinematic values were analysed using a Kruskall-Wallis H and Dunn's post-hoc analysis. Upper-body differences, GRF and temporal-spatial characteristics were analysed using a Mann-Whitney U test (P<0.05). RESULTS: Walking speed ranged from 0.32-0.39m/s. Hip abduction, peak knee flexion and ankle dorsiflexion for both the SCI and able-bodied groups presented with significant differences to the ReWalkTM. The able-bodied group presented significant differences to the ReWalkTM for all kinematic variables except frontal plane hip ROM (P = 0.093,δ = -0.56). Sagittal plane pelvic and trunk ROM were significantly greater in the SCI vs. able-bodied (P = 0.004,δ = -1; P = 0.008,δ = -0.94, respectively). Posterior braking force was significantly greater in the SCI group (P = 0.004, δ = -1). DISCUSSION: The different trunk movements used by the SCI group and the capacity for the users' joint angles to exceed those of the device suggest that biomechanical profiles varied according to the user group. However, upright stepping with the ReWalkTM device delivered the appropriate afferent stimulus to activate CPGs as there were no differences in key biomechanical parameters between the two user groups.

A biomechanical comparison of powered robotic exoskeleton gait with normal and slow walking: An investigation with able-bodied individuals.

BACKGROUND: Overground lower-limb robotic exoskeletons are assistive devices used to facilitate ambulation and gait rehabilitation. Our understanding of how closely they resemble comfortable and slow walking is limited. This information is important to maximise the effects of gait rehabilitation. The aim was to compare the 3D gait parameters of able-bodied individuals walking with and without an exoskeleton at two speeds (self-selected comfortable vs. slow, speed-matched to the exoskeleton) to understand how the user's body moved within the device. METHODS: Eight healthy, able-bodied individuals walked along a 12-m walkway with and without the exoskeleton. Three-dimensional whole-body kinematics inside the device were captured. Temporal-spatial parameters and sagittal joint kinematics were determined for normal and exoskeleton walking. One-way repeated measures ANOVAs and statistical parametric mapping were used to compare the three walking conditions (P < .05). FINDINGS: The walking speeds of the slow (0.44[0.03] m/s) and exoskeleton (0.41[0.03] m/s) conditions were significantly slower than the comfortable walking speed (1.54[0.07] m/s). However, time in swing was significantly greater (P < .001, d = -3.64) and double support was correspondingly lower (P < .001, d = 3.72) during exoskeleton gait than slow walking, more closely resembling comfortable speed walking. Ankle and knee angles were significantly reduced in the slow and exoskeleton conditions. Angles were also significantly different for the upper body. INTERPRETATION: Although the slow condition was speed-matched to exoskeleton gait, the stance:swing ratio of exoskeleton stepping more closely resembled comfortable gait than slow gait. The altered upper body kinematics suggested that overground exoskeletons may provide a training environment that would also benefit balance training.

Where's the wine? Heavy social drinkers show attentional bias towards alcohol in a visual conjunction search task.

BACKGROUND AND AIMS: Research indicates that high consumers of alcohol exhibit attentional bias (AB) towards alcohol-related cues, suggestive of a cognitive mechanism that might drive substance seeking. Many tasks that measure AB (e.g. visual probe, addiction Stroop), however, are limited by their reliance on non-appetitive control cues, the serial presentation of stimuli and their poor internal reliability. The current study employed a visual conjunction search (VCS) task capable of presenting multiple alcoholic and non-alcoholic appetitive cues simultaneously to assess whether social drinkers attend selectively to alcoholic stimuli. To assess the construct validity of this task, we examined whether alcohol consumption and related problems, subjective craving and drinking motives predict alcohol-specific AB. DESIGN AND SETTING: A VCS task was performed in a laboratory setting, which required participants to detect the presence of appetitive alcoholic (wine, beer) and non-alcoholic (cola, lemonade) targets within arrays of matching and non-matching distractors. PARTICIPANTS: Data from 99 participants were assessed [meanage  = 20.77, standard deviation (SD) = 2.98; 64 (65%) females], with 81.8% meeting the threshold for harmful alcohol consumption (meanAUDIT  = 12.89, SD = 5.79). MEASUREMENTS: Self-reports of alcohol consumption and related problems [Alcohol Use Disorders Identification Test (AUDIT)], subjective craving (Alcohol Craving Questionnaire Short Form) and drinking motives (Drinking Motives Questionnaire Short Form) were obtained, and the VCS task measured response times for the correct detection of alcoholic and non-alcoholic targets. FINDINGS: Participants were significantly quicker to detect alcoholic relative to non-alcoholic appetitive targets (P < 0.001, dz  = 0.41), which was predicted positively by AUDIT scores (P = 0.013, R2  = 0.06%). The VCS task achieved excellent reliability (α > 0.79), superior to other paradigms. CONCLUSIONS: The visual conjunction search task appears to be a highly reliable method for assessing alcohol-related attentional bias, and shows that heavy social drinkers prioritize alcoholic cues in their immediate environment.

The effects of robot assisted gait training on temporal-spatial characteristics of people with spinal cord injuries: A systematic review.

CONTEXT: Robotic assisted gait training (RAGT) technology can be used as a rehabilitation tool or as an assistive device for spinal cord injured (SCI) individuals. Its impact on upright stepping characteristics of SCI individuals using treadmill or overground robotic exoskeleton systems has yet to be established. OBJECTIVE: To systematically review the literature and identify if overground or treadmill based RAGT use in SCI individuals elicited differences in temporal-spatial characteristics and functional outcome measures. METHODS: A systematic search of the literature investigating overground and treadmill RAGT in SCIs was undertaken excluding case-studies and case-series. Studies were included if the primary outcomes were temporal-spatial gait parameters. Study inclusion and methodological quality were assessed and determined independently by two reviewers. Methodological quality was assessed using a validated scoring system for randomized and non-randomized trials. RESULTS: Twelve studies met all inclusion criteria. Participant numbers ranged from 5-130 with injury levels from C2 to T12, American Spinal Injuries Association A-D. Three studies used overground RAGT systems and the remaining nine focused on treadmill based RAGT systems. Primary outcome measures were walking speed and walking distance. The use of treadmill or overground based RAGT did not result in an increase in walking speed beyond that of conventional gait training and no studies reviewed enabled a large enough improvement to facilitate community ambulation. CONCLUSION: The use of RAGT in SCI individuals has the potential to benefit upright locomotion of SCI individuals. Its use should not replace other therapies but be incorporated into a multi-modality rehabilitation approach.

Effects of microclimate on behavioural and life history traits of terrestrial isopods: implications for responses to climate change.

The sensitivity of terrestrial isopods to changes in both temperature and moisture make them suitable models for examining possible responses of arthropod macro-decomposers to predicted climate change. Effects of changes in both temperature and relative humidity on aggregation, growth and survivorship of species of isopods contrasting in their morphological and physiological adaptations to moisture stress have been investigated in laboratory microcosms. All three traits were more sensitive to a reduction in relative humidity of 20-25% than they were to an increase in temperature of 5-6 °C. These results suggest that predicted changes in climate in south east England may reduce the extent to which soil animals stimulate microbial activity and hence carbon dioxide (CO2) emissions from soils in the future. This may help to mitigate the potential for a positive feedback between increased CO2 emissions from soils, and increased greenhouse effects causing an increase in soil temperatures.