Abstract

Near-continuous measures of inter-joint coordination and the smoothness and variability of individual joint motions were studied to explore principles underlying the coordination of squat-lifting. Measures of relative phasing between joint movements changed continuously as the lifted load was increased, despite subjects attempts to maintain the same pattern of coordination for all lifts. Differences were found between the lifting and lowering phases of the task. The stability of coordination among lower extremity joints was found to decrease continuously with changes in the relative phase of these joints when lifting heavier loads. However, knee-lumbar spine and knee-shoulder coordination showed minimal or no change in stability with load changes. Inter-trial variability and jerkiness of individual joint excursions were greater than similar measures of the hand/crate trajectory. The results support movement planning in terms of the end-effector spatial trajectory rather than individual joint trajectories. Verf.-Referat