Perception of postural limits during reaching.
The relationship between perceived and actual postural limits in reaching by healthy young and middle-aged participants was assessed. Subjects (N = 51) first estimated their expected performance and then executed maximum reaches along a tape measure mounted at shoulder height. Measures of standing and bending reaches were obtained. Subjects estimated their reach limits reasonably accurately but significantly underestimated bending reach and overestimated standing reach. That finding suggests that individuals scale perceived abilities with perceived risk in attempting a given action. The accuracy of a participant's perceived bending reach was unrelated to his or her height, weight, age, and gender, and was only weakly correlated with actual reach excursion (bending - standing reach). The accuracy was strongly correlated with the accuracy of subjects' perceived standing reach; individuals who underestimated standing reach underestimated bending reach much more. That result and the observed lack of correlation between the magnitudes of estimated bending reach and estimated standing reach suggest a serial strategy of estimating bending reach by considering and summing perceived arm's length and perceived reach excursion.
Robinovitch
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Biomechanics Laboratory Department of Orthopaedic Surgery, San Francisco General Hospital University of California.