Attentional focus effects on joint covariation in a reaching task

Area of Science:

• Motor control and learning
• Biomechanics
• Cognitive psychology

Background:

• External focus (EF) generally enhances motor skill performance compared to internal focus (IF).
• Previous research focused on performance outcomes (e.g., accuracy), with limited investigation into movement coordination.
• Human movements exhibit kinematic and kinetic abundance, suggesting attentional focus may alter the central nervous system's (CNS) use of motor abundance.

Purpose of the Study:

• To investigate how focus of attention (FOA) instructions influence the utilization of motor abundance during a reaching task.
• To analyze the effects of EF versus IF on joint coordination using uncontrolled manifold (UCM) analysis.

Main Methods:

• Thirty-eight healthy young adults performed planar reaching movements under EF and IF conditions without online visual feedback.
• Joint kinematics (clavicle-scapula, shoulder, elbow, wrist) were recorded.
• Uncontrolled manifold (UCM) analysis was used to quantify joint covariation and its effect on endpoint control.

Main Results:

• Internal focus (IF) resulted in significantly higher mean radial error compared to external focus (EF).
• UCM analysis revealed that IF increased goal-relevant variance (V_ORT) from the early to late stages of the reach.
• Goal-irrelevant variance (V_UCM) and the index of stability (ΔV) did not differ between EF and IF conditions.

Conclusions:

• Internal focus (IF) disrupts goal-relevant joint coordination during reaching movements, consistent with the constrained action hypothesis.
• These disruptions in coordination occur early in the movement and impact performance accuracy.
• External focus (EF) appears to facilitate more optimal use of motor abundance for skilled performance.