Mimi Nakajima

Investigating the Constrained Action Hypothesis: A Movement Coordination and Coordination Variability Approach

ABSTRACT The purpose of this study was to examine the effects of focus of attention cues on movement coordination and coordination variability in the lower extremity. Twenty participants performed the standing long jump under both internal and external focus of attention conditions. A modified vector coding technique was used to evaluate the influence of attentional focus cues on lower extremity coordination patterns and coordination variability during the jumps. Participants jumped significantly further under an external focus of attention condition compared with an internal focus of attention condition (p = .035, effect size = .29). Focus of attention also influenced coordination between the ankle and knee, F(6, 19) = 2.87, p = .012, effect size = .388, with participants primarily using their knees under the internal focus of attention, and using both their ankles and knees under the external focus of attention. Attentional focus cues did not influence ankle-knee, F(1, 19) = 0.02, p = .98, effect size = .02, or hip-knee, F(1, 19) = 5.00, p = .49, effect size = .16, coordination variability. Results suggest that while attentional focus may not directly influence movement coordination condition, there is still a change in movement strategy resulting in greater jump distances following an external focus of attention.

Movement screens: Are we measuring movement dysfunction or movement skill?:

Movement screens are commonly used for assessing athletic readiness or injury potential. However, these screens fail to distinguish between movement dysfunction and movement skill. The purpose of this study was to compare performance on a common movement screen test, the overhead squat, when using no instructions (Baseline), instruction from a commercial movement screen, and instructions which include verbal cues, demonstration, and practice (Instructions, Demonstration, and Practice [IDP]). Fourteen individuals performed the overhead squat under the three different conditions while their movements were recorded using a 12-camera motion capture system. Specific scoring criteria for the overhead squat such as joint angles, depth of squat, torso and shank orientation, and weight distribution were compared between instructional conditions. Compared to the Baseline and commercial movement screen conditions, IDP resulted in greater vertical center of mass displacement, better alignment of the torso and shank segments, and greater peak flexion at the hip and knee. These results show that incorporating verbal cues, providing demonstration, and allowing for practice during movement screening significantly improve performance in the overhead squat assessment. Based on these results, the authors recommend that coaches or clinicians using movement screens to identify movement dysfunction should provide demonstrations of the movement, allow the participant to practice, provide verbal instructions about the movement prior to assessment, and provide corrective feedback during practice. Excluding these elements limits the ability to distinguish between true dysfunctional movement patterns and a simple lack of movement skill.