Peripheral Constraint Versus On-line Programming in Rapid Aimed Sequestial Movements

The purpose of this investigation was to examine how the programming and control of a rapid aiming sequence shifts with increased complexity. One objective was to determine if a preprogramming/peripheral constraint explanation is adequate to characterize control of an increasingly complex rapid aiming sequence, and if not, at what point on-line programming better accounts for the data. A second objective was to examine when on-line programming occurs. Three experiments were conducted in which complexity was manipulated by increasing the number of targets from 1 to 11. Initiation- and execution-timing patterns, probe reaction time, and movement kinematics were measured. Results supported the peripheral constraint/pre-programming explanation for sequences up to 7 targets if they were executed in a blocked fashion. For sequences executed in a random fashion (one length followed by a different length), preprogramming did not increase with complexity, and on-line programming occurred without time cost. Across all sequences there was evidence that the later targets created a peripheral constraint on movements to previous targets. We suggest that programming is influenced by two factors: the overall spatial trajectory, which is consistent with Sidaway’s subtended angle hypothesis (1991), and average velocity, with the latter established based on the number of targets in the sequence. As the number of targets increases, average velocity decreases, which controls variability of error in the extent of each movement segment. Overall the data support a continuous model of processing, one in which programming and execution co-occur, and can do so without time cost

Development and Feasibility of a Smartphone, ECG and GPS Based System for Remotely Monitoring Exercise in Cardiac Rehabilitation

Background Despite its efficacy and cost-effectiveness, exercise-based cardiac rehabilitation is undertaken by less than one-third of clinically eligible cardiac patients in every country for which data is available. Reasons for non-participation include the unavailability of hospital-based rehabilitation programs, or excessive travel time and distance. For this reason, there have been calls for the development of more flexible alternatives. Methodology and Principal Findings We developed a system to enable walking-based cardiac rehabilitation in which the patient's single-lead ECG, heart rate, GPS-based speed and location are transmitted by a programmed smartphone to a secure server for real-time monitoring by a qualified exercise scientist. The feasibility of this approach was evaluated in 134 remotely-monitored exercise assessment and exercise sessions in cardiac patients unable to undertake hospital-based rehabilitation. Completion rates, rates of technical problems, detection of ECG changes, pre- and post-intervention six minute walk test (6 MWT), cardiac depression and Quality of Life (QOL) were key measures. The system was rated as easy and quick to use. It allowed participants to complete six weeks of exercise-based rehabilitation near their homes, worksites, or when travelling. The majority of sessions were completed without any technical problems, although periodic signal loss in areas of poor coverage was an occasional limitation. Several exercise and post-exercise ECG changes were detected. Participants showed improvements comparable to those reported for hospital-based programs, walking significantly further on the post-intervention 6 MWT, 637 m (95% CI: 565–726), than on the pre-test, 524 m (95% CI: 420–655), and reporting significantly reduced levels of cardiac depression and significantly improved physical health-related QOL. Conclusions and Significance The system provided a feasible and very flexible alternative form of supervised cardiac rehabilitation for those unable to access hospital-based programs, with the potential to address a well-recognised deficiency in health care provision in many countries. Future research should assess its longer-term efficacy, cost-effectiveness and safety in larger samples representing the spectrum of cardiac morbidity and severity

The kinaesthetic fusion effect: Fast-forward 30 years

This study investigated the Kinaesthetic Fusion Effect (KFE) first described by Craske and Kenny in 1981. The current study did not replicate these findings following a change in the reporting method used by participants. Participants did not perceive any reduction in the sagittal separation of a button pressed by the index finger of one arm and a probe touching the other, following repeated exposure to the tactile stimuli present on both unseen arms. This study’s failure to replicate the widely-cited KFE as described by Craske et al. (1984) suggests that it may be contingent on several aspects of visual information, especially the availability of a specific visual reference, the role of instructions regarding gaze direction, and the potential use of a line of sight strategy when referring felt positions to an interposed surface. In addition, a foreshortening effect was found; this may result from a line-of-sight judgment and represent a feature of the reporting method used. Finally, this research will benefit future studies that require participants to report the perceived locations of the unseen limbs

Proprioception and Stimulus-response Compatibility

Sixteen subjects pressed a left or right key in response to lateralised visual stimuli, in uncrossed (left index finger on left key, right finger on right key) and crossed conditions (left finger on right key and vice versa), with varying finger separations. Visual, tactile, or "efference copy" cues about relative finger positions were unavailable. Subjects had to press the key on the same side as (compatible group) or opposite side to the stimulus (incompatible group). Separate proprioceptive judgements of the relative finger positions were obtained. Findings of an overall reaction time (RT) advantage for compatible instructions and for uncrossed hands were replicated. With decreasing finger the RT advantage for compatible instructions decreased and the probability of responding with either hand increased. The compatibility effect disappeared completely at the six cm crossed position, not at the position that was hardest to judge proprioceptively. This suggests that two forms of neural activation are summed: automatic activation of the anatomically same-side limb, and an integrated, rule-based activation. The results further demonstrate that independent proprioceptive cues from each limb, unassociated with skin contact between the limbs, can mediate the determination of relative position for response selection in stimulus-response compatibility tasks

Fitness for work in mining: Not a "one size fits all" approach

Health promotion programs can help prevent work-related illness or injury. However, in many industries only a very small number of organizations effectively plan, implement, monitor and review risk management processes, and the emphasis has been on injury management rather than prevention. In coal mining, this is exemplified by the lack of accepted strategies to maintain and enhance the fitness levels of miners. A recent survey of a cross-section of OH&S officers working in Queensland and New South Wales mines, nevertheless, indicated that lack of fitness, stamina and skill rank highest, along with work environment factors, as contributors to injury. There is relatively little evidence on the efficacy and cost effectiveness of existing injury prevention programs. An opportunity exists to develop a more holistic approach to the fitness of miners as a component of the health surveillance program. This begins with the selection of miners following a medical examination supplemented by relevant fitness or work related tests, enabling more targeted strength, aerobic and flexibility programs designed to match the physical demands of mining and maintain or enhance fitness at levels required for injury minimisation. This presentation uses the workplace health literature and surveys of the mining industry to suggest strategies to implement realistic and more holistic fitness interventions for miners in line with continuing health surveillance and preservation of longer term health

Directional stimulus-response compatibility: a test of three alternative principles

The basis of directional stimulus-response compatibility was studied using a task in which 128 participants moved a cursor into targets with a joystick, resembling the operation of certain industrial and construction equipment. Compatible and incompatible versions of three alternative compatibility principles were compared in all combinations. Visual Field (VF) compatibility was present if cursor and controlling limb movement were in the same direction in the visual field, Control Display (CD) compatibility meant that the control motion was in the same direction as, and parallel to, cursor motion, and Muscle Synergy (MS) compatibility was defined as use of the muscle synergy normally associated with the required direction as seen in the visual field. VF-compatible conditions had significantly shorter reaction, movement and homing times, and fewer reversal errors, for males and females, in two testing sites. These advantages were maintained over practice. VF compatibility was confirmed as a robust spatial compatibility principle that is affected by neither the orientation of the operator's limb or head, nor the muscle synergy used in executing the task. It offers not only more rapid performance, but also a markedly reduced rate of potentially dangerous directional errors. The relationship between this finding and theoretical aspects of stimulus-response compatibility is discussed

Motor Learning Processes In A Movement-Scaling Task In Olivopontocerebellar Atrophy And Parkinson's Disease

Nine Parkinson's disease (PD), seven olivopontocerebellar atrophy (OPCA) patients and two age-matched control groups learned a linear arm movement-scaling task over 2 days, requiring movements proportional in length to visually presented target-bars. Scaling was acquired through knowledge of results (KR concerning the direction and magnitude of errors) following every second acquisition trial. Initial acquisition of both groups was significantly worse than their respective controls (poorer movement scaling), but rapidly improved to nearly identical levels. Retention for the PD group's movement scaling was as good as controls initially, but markedly poorer after 24 h. The OPCA group did not show this deficit. Both patient groups extrapolated accurately to longer, previously unpracticed target distances (no KR provided), suggesting an unimpaired capacity to generate and use an internal representation of the movement scaling. They also rapidly learned a new scaling relationship when the gain was changed. Overall, the learning of this movement-scaling task was not adversely affected in OPCA, and the impairment was restricted primarily to longer-term retention in PD. The study suggests that: (1) the ability to acquire movement scaling in a task that requires conscious use of error feedback and no new coordination may depend little on the cerebellum, and (2) the basal ganglia may participate in longer-term storage of scaling information

Spontaneous pacing during overground hill running

Purpose: To investigate speed regulation during overground running on undulating terrain. Methods: Following an initial laboratory session to calculate physiological thresholds, eight experienced runners completed a spontaneously paced time trial over 3 laps of an outdoor course involving uphill, downhill and level sections. A portable gas analyser, GPS receiver and activity monitor were used to collect physiological, speed and stride frequency data. Results: Participants ran 23% slower on uphills and 13.8% faster on downhills compared with level sections. Speeds on level sections were significantly different for 78.4 ± 7.0 seconds following an uphill and 23.6 ± 2.2 seconds following a downhill. Speed changes were primarily regulated by stride length which was 20.5% shorter uphill and 16.2% longer downhill, while stride frequency was relatively stable. Oxygen consumption averaged 100.4% of runner’s individual ventilatory thresholds on uphills, 78.9% on downhills and 89.3% on level sections. 89% of group level speed was predicted using a modified gradient factor. Individuals adopted distinct pacing strategies, both across laps and as a function of gradient. Conclusions: Speed was best predicted using a weighted factor to account for prior and current gradients. Oxygen consumption (VO2) limited runner’s speeds only on uphill sections, and was maintained in line with individual ventilatory thresholds. Running speed showed larger individual variation on downhill sections, while speed on the level was systematically influenced by the preceding gradient. Runners who varied their pace more as a function of gradient showed a more consistent level of oxygen consumption. These results suggest that optimising time on the level sections after hills offers the greatest potential to minimise overall time when running over undulating terrain

Predictors of Driving Assessment Outcome in Parkinson’s Disease

Introduction: Clinical decisions about driving can be particularly difficult in Parkinson’s Disease (PD), since patients have a range of fluctuating cognitive, motor, and sensory symptoms that, alone or in combination, potentially impair driving. This study evaluated selected clinical and functional tests as predictors of driving safety outcomes in PD patients. Methods: Twenty five PD patients and 21 age-matched controls, all regular drivers, underwent neurological evaluation and assessment of cognitive, visual and motor function and a standardised, on-road driving assessment. The capacity of the tests to predict pass/fail driving outcomes was determined by selecting a sub-set with the highest predictive value from each domain and then subjecting these to discriminant function analysis. Accuracy, sensitivity, specificity and positive and negative predictive values were determined. Results: Three relatively simple tests from the larger battery predicted pass/fail driving outcomes with relatively high specificity (PD: 64.3%, controls: 93.8%, both combined: 85.2%); and moderate sensitivity (PD: 72.7%, controls: 60.0%, both combined: 63.2%). The tests assessed motor performance (Purdue Pegboard test), contrast sensitivity (Pelli-Robson test) and cognitive function (oral version of Symbol Digit Modalities test). Adding time since diagnosis increased specificity to 71.4 % and sensitivity to 90.9% for the PD group. Conclusion: These simple tests confer more objectivity and predictive power to clinical recommendations for driving; they reflect distinct functions that are necessary for safe driving and may be especially useful when on-road assessments are not available

Variability Effects on the Internal Structure of Rapid Aiming Movements

Two experiments are reported in which the effects of different levels of spatial variability in the initial phase of aiming movements were explored. It was found that longer, faster, and more spatially variable initial submovements were associated with an almost proportional increase in the distance between the average location at which the first submovement ended and the target. the first experiment involved a multisegmental arm motion that required a direction reversal, in which spatial variability could be estimated in all three dimensions. The second was a unidirectional, one-degree-of-freedom wrist supination task. The variability-amplitude relationship for the initial submovement was present in both. It is argued that the variability, or unpredictability, of the initial submovement is a determinant of its average amplitude, such that initial submovements approach the target as closely as is permitted by the level of variability. Such a mechanism allows task constraints such as accuracy requirements and allowable error rates to be met most efficiently, in a manner similar to the recently described optimisation of submovement durations. If this mechanism is a general, ubiquitous phenomenon in rapid aiming, certain features of its internal kinematic structure are predictable. A set of five such predictions is outlined