Postural control: learning to balance and responses to mechanical and sensory perturbations

The purpose of the current research was to examine how a novel balance task is learnt by individuals with a mature neurological system, and to investigate the responses of experienced hand balancers to mechanical and sensory perturbations. Balance in each posture was assessed by various techniques, including: traditional measures of centre of pressure, nonlinear time series analysis of centre of pressure, estimates of feedback time delay from cross correlations and delayed regression models, and calculation of small, medium, and large movement corrections. Data from this study suggests that the best balance metric for distinguishing between each of the balance conditions was the traditional balance measure of sway velocity. However, sway velocity cannot provide any further information on the underlying process of balance. Nonlinear measures of balance offer insight into the underlying deterministic processes that control balance, offering measures of system determinism, complexity, and predictability. Assessments of feedback time delay and movement corrections provide both an insight into the control of posture and help distinguish one condition from another. Both feedback time delay and movement corrections and magnitudes may be used simultaneously to delve further into the control of posture. Delayed regression models seem to be an appropriate and useful tool for estimating feedback time delays during balance. Findings support the use of the third term in the adapted regression model as a means of estimating the effect of passive stiffness on feedback time delay. Generally, with increased duration in handstand subjects displayed reduced sway as measured by traditional measures of balance. A more marked change in nonlinear measures of balance can be seen, with quicker reductions in variance for some nonlinear measures of balance than in the traditional measures. It may be that more pronounced changes in nonlinear measures represent changes in the subjects underlying process of postural control, whereas less pronounced changes in traditional measures relate more to their general ability or performance in the balance task

WEIGHT TRANSFER CHANGES DURING GOLF SHOTS FROM DIFFERENT LIES

The aim of the present study was to examine changes in weight transfer during golf shots from flat, uphill, and downhill lies. Twelve male amateur golfers with a mean handicap of 1.6 ± 2.4 hit a total of 30 golf shots from flat, downhill, and uphill lies. A computer assisted rehabilitation environment (CAREN) was used to collect 3D kinematics and kinetics and a Foresight GC2 launch monitor was used to measure performance outcomes (ball speed, launch angle, azimuth, side spin, and offline displacement). The mean position of the centre of pressure moved approximately 9.4% closer to the front foot for downhill lies and approximately 8.9% closer to the back foot for uphill lies. The speed of the ball was not significantly affected by the lie, but the distance the ball travelled was. An uphill lie encourages spin of the ball to the left, and may increase the risk of playing a hook shot

A COMPARISON OF SPRINT TECHNIQUE BETWEEN PROFESSIONAL FOOTBALL PLAYERS AND ELITE SPRINTERS

This study compared sprint technique between professional footballer players and elite sprinters. Professional football players sprint technique was assessed using 2D video analysis and compared to publicly available data of elite sprinters from the IAAF biomechanical reports. Results showed sprinters had higher step frequencies and contacted the ground further back, with lower touchdown and higher toe-off distances

Earlier detection facilitates skilled responses to deceptive actions

High-skilled and recreational rugby players were placed in a semi-immersive CAREN Lab environment to examine susceptibility to, and detection of, deception. To achieve this, a broad window of seven occlusion times was used in which participants responded to life-size video clips of an opposing player ‘cutting’ left or right, with or without a deceptive sidestep. Participants made full-body responses to ‘intercept’ the player and gave a verbal judgement of the opponent's final running direction. Response kinematic and kinetic data were recorded using three-dimensional motion capture cameras and force plates, respectively. Based on response accuracy, the results were separated into deception susceptibility and deception detection windows then signal detection analysis was used to calculate indices of discriminability between genuine and deceptive actions (d’) and judgement bias (c). Analysis revealed that high-skilled and low-skilled players were similarly susceptible to deception; however, high-skilled players detected deception earlier in the action sequence, which enabled them to make more effective behavioural responses to deceptive actions

Statistical Results from Balance control strategies during perturbed and unperturbed balance in standing and handstand

ANOVA and repeated t-test values for all comparison

The effect of ball impact location on racket and forearm joint angle changes for one-handed tennis backhand groundstrokes

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Sports Sciences on 27 July 2016, available online: http://www.tandfonline.com/10.1080/02640414.2016.1211308.Recreational tennis players tend to have higher incidence of tennis elbow, and this has been hypothesised to be related to one-handed backhand technique and off-centre ball impacts on the racket face. This study aimed to investigate for a range of participants the effect of off-longitudinal axis and off-lateral axis ball-racket impact locations on racket and forearm joint angle changes immediately following impact in one-handed tennis backhand groundstrokes. Three-dimensional racket and wrist angular kinematic data were recorded for fourteen university tennis players each performing thirty ‘flat’ one-handed backhand groundstrokes. Off-longitudinal axis ball-racket impact locations explained over 70% of the variation in racket rotation about the longitudinal axis and wrist flexion / extension angles during the 30 ms immediately following impact. Off-lateral axis ball-racket impact locations had a less clear cut influence on racket and forearm rotations. Specifically off-longitudinal impacts below the longitudinal axis forced the wrist into flexion for all participants with there being between 11º and 32º of forced wrist flexion for an off-longitudinal axis impact that was one ball diameter away from the mid-line. This study has confirmed that off-longitudinal impacts below the longitudinal axis contribute to forced wrist flexion and eccentric stretch of the wrist extensors and there can be large differences in the amount of forced wrist flexion from individual to individual and between strokes with different impact locations

The Developmental Stage of Adult Human Stem Cell-Derived Retinal Pigment Epithelium Cells Influences Transplant Efficacy for Vision Rescue

Age-related macular degeneration (AMD) is a common cause of central visual loss in the elderly. Retinal pigment epithelial (RPE) cell loss occurs early in the course of AMD and RPE cell transplantation holds promise to slow disease progression. We report that subretinal transplantation of RPE stem cell (RPESC)-derived RPE cells (RPESC-RPE) preserved vision in a rat model of RPE cell dysfunction. Importantly, the stage of differentiation that RPESC-RPE acquired prior to transplantation influenced the efficacy of vision rescue. Whereas cells at all stages of differentiation tested rescued photoreceptor layer morphology, an intermediate stage of RPESC-RPE differentiation obtained after 4 weeks of culture was more consistent at vision rescue than progeny that were differentiated for 2 weeks or 8 weeks of culture. Our results indicate that the developmental stage of RPESC-RPE significantly influences the efficacy of RPE cell replacement, which affects the therapeutic application of these cells for AMD