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. 2016 Jan;234(1):229-40.
doi: 10.1007/s00221-015-4454-y. Epub 2015 Oct 5.

Testing the Concurrent Validity of a Naturalistic Upper Extremity Reaching Task

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Free PMC article

Testing the Concurrent Validity of a Naturalistic Upper Extremity Reaching Task

S Y Schaefer et al. Exp Brain Res. .
Free PMC article

Abstract

Point-to-point reaching has been widely used to study upper extremity motor control. We have been developing a naturalistic reaching task that adds tool manipulation and object transport to this established paradigm. The purpose of this study was to determine the concurrent validity of a naturalistic reaching task in a sample of healthy adults. This task was compared to the criterion measure of standard point-to-point reaching. Twenty-eight adults performed unconstrained out-and-back movements in three different directions relative to constant start location along midline using their nondominant arm. In the naturalistic task, participants manipulated a tool to transport objects sequentially between physical targets anchored to the planar workspace. In the standard task, participants moved a digital cursor sequentially between virtual targets, veridical to the planar workspace. In both tasks, the primary measure of performance was trial time, which indicated the time to complete 15 reaches (five cycles of three reaches/target). Two other comparator tasks were also designed to test concurrent validity when components of the naturalistic task were added to the standard task. Spearman's rank correlation coefficients indicated minimal relationship between the naturalistic and standard tasks due to differences in progressive task difficulty. Accounting for this yielded a moderate linear relationship, indicating concurrent validity. The comparator tasks were also related to both the standard and naturalistic task. Thus, the principles of motor control and learning that have been established by the wealth of point-to-point reaching studies can still be applied to the naturalistic task to a certain extent.

Keywords: Concurrent validity; Naturalistic; Reaching; Upper extremity.

Figures

Fig. 1
Fig. 1
Top view of setup for each task, all shown with the corresponding effector (e.g. hand, spoon) moving to the left (135°) target. A more detailed graphical description about the naturalistic task can be found in Schaefer, 2015.
Fig. 2
Fig. 2
Representative data for each task. a) Overhead view of the hand trajectory over the course of the trial. b) A close-up view of the hand trajectory around the start location. The shaded circle represents a 5-cm radius around the start location. c) Resultant hand velocity profiles for the corresponding trials.
Fig. 3
Fig. 3
Mean ± SE trial time (top), cumulative hand distance (middle), and peak hand velocity (bottom) across participants for each task (Steel-Dwass **p<.001; ***p<.0001; ns = not significant relative to the naturalistic task).
Fig. 4
Fig. 4
Mean ± SE individual reach interval (IRI) per cycle across participants for each task (Steel **p<.01; ***p<.0001).
Fig. 5
Fig. 5
Polar plot of mean initial movement direction for reaches to the three different targets in cycles 1 (black) and 5 (gray). The direction of the vector indicates the direction of the hand’s movement, and the length of the vector indicates the magnitude of peak velocity (see scale to right).

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