Publications by authors named "Peter C Poortvliet"

Purpose: Parkinson's disease (PD) is a neurodegenerative disorder associated with progressive disability. While the precise aetiology is unknown, there is evidence of significant genetic and environmental influences on individual risk. The Australian Parkinson's Genetics Study seeks to study genetic and patient-reported data from a large cohort of individuals with PD in Australia to understand the sociodemographic, genetic and environmental basis of PD susceptibility, symptoms and progression.

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Objective: The consensus is that life expectancy for individuals with Parkinson's disease (PD) is reduced, but estimations vary. We aimed to provide an overview of 20 years of mortality and risk factor data from the Queensland Parkinson's Project.

Methods: The analysis included 1,334 PD and 1,127 control participants.

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We are gradually becoming aware that there is more to Parkinson's disease (PD) than meets the eye. Accumulating evidence has unveiled a disease complexity that has not (yet) been incorporated into ongoing efforts aimed at slowing, halting or reversing the course of PD, likely underlying their lack of success. There is a substantial latency between the actual onset of PD pathology and our ability to confirm diagnosis, during which accumulating structural and functional damage might be too advanced for effective modification or protection.

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Differences in neural drive could explain variation in adaptation to acute pain between postural and voluntary motor actions. We investigated whether cortical contributions, quantified by corticomuscular coherence, are affected differently by acute experimental pain in more posturally focused position-control tasks and voluntary focused force-control tasks. Seventeen participants performed position- and force-control contractions with matched loads (10% maximum voluntary contraction) before and during pain (injection of hypertonic saline into the infrapatellar fat pad of the knee).

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Neural control differs between position- and force-control tasks as evident from divergent effects of fatigue and pain. Unlike force-control tasks, position-control tasks focus on a postural goal to maintain a joint angle. Cortical involvement is suggested to be less during postural control, but whether this differs between position- and force-control paradigms remains unclear.

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Objective: When matching target force during pain, single motor unit (SMU) discharge is modified in a manner thought to redistribute load in painful tissue. This adaptation might not be appropriate when maintaining joint posture against an external load. We compared changes in SMU discharge rate of knee extensor muscles in a force-control and a position-control task during pain.

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Objective: Maintenance of a limb position against external load (position-control) fails earlier (time to task failure: TTF) than maintenance of identical force against rigid restraint (force-control). Although possibly explained by physiological differences between contractions, we investigated whether less constraint of movements in other planes and proximal segments (commonly less in position-control tasks) shortens TTF.

Methods: Seventeen adults (32±7 years) contracted knee extensor muscles to task failure in a position-control task, with and without constraint of motion in other planes and proximal segments, and a force-control task with constraints.

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Many food components can influence satiety or energy intake. Combined together, these food components could represent an interesting dietary strategy in the prevention and treatment of obesity. The aims of this study were: 1) to determine the effect of a functional food in the form of a healthy meal course on subsequent energy intake and satiety; 2) to verify if it is possible to maintain palatability while preserving the satiating effects of the test meal.

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