Anticipatory postural adjustments are unaffected by age and are not absent in patients with the freezing of gait phenomenon.

In bipedal gait, the initiation of the first step is preceded by a complex sequence of movements which shift the centre of mass of the body towards the stance foot to allow for a step of the swing foot. These anticipatory postural adjustments (APAs) have been investigated in order to elucidate movement strategies in healthy and diseased persons. We studied the influence of several external parameters (age, type of step initiation) on APAs and investigated whether Parkinsonian patients may have different APAs. As a result, we found that externally elicited steps were preceded by faster and larger APAs than self-timed steps. Parkinsonian patients without the freezing of gait (FOG) phenomenon showed overall slightly reduced APAs but did not clearly differ from patients with FOG. Multiple APAs were seen in up to 25 % of the steps of the patients and in a much lower percentage of the steps of control subjects. The results indicate that APAs are significantly influenced by the timing of a step, i.e. are larger in externally elicited steps. The patients showed an overall preserved APA pattern but slowed movements and amplitude, indicating that increased bradykinesia due to progressive illness is a plausible explanation for these findings. The freezing phenomenon is not explained by a general absence or massive reduction in APA measures.

Normative data for arm swing asymmetry: how (a)symmetrical are we?

Arm swing asymmetry during gait may be a sensitive sign for early Parkinson's disease. There is only very limited information about how much asymmetry can be considered to be physiological. To assess the normal range of arm swing asymmetry, we investigated 60 healthy subjects. The influence of age, gender, and additional mental tasks (dual-tasking) on arm swing asymmetry was assessed. Limb kinematics of 60 healthy persons in three age groups (between 40 and 75 years) were measured with an ultrasound motion capture system while subjects walked on a treadmill. Treadmill velocity was varied (3 steps) and mental loads (2 different tasks) were applied in different trials. Additionally, a group of 7 patients with early Parkinson's disease was investigated. Arm swing amplitude as well as arm swing asymmetry varied considerably in the healthy subjects. Elderly subjects swung their arms more than younger participants. Only the more demanding mental load caused a significant asymmetry, i.e., arm swing was reduced on the right side. In the patient group, asymmetry was considerably higher and even more enhanced by mental loads. Our data indicate that an asymmetry index above 50 (i.e., one side has twice the amplitude of the other) may be considered abnormal. Evaluation of arm swing asymmetry may be used as part of a test battery for early Parkinson's disease. Such testing may become even more important when disease-modifying drugs become available for Parkinson's disease.

WITHDRAWN: Treatment outcome of visual feedback training in an adult patient with habitual toe walking.

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