Abstract
Introduction
Where attention is focused influences the performance of motor skills. According to the constrained action hypothesis, internal focus of attention (IFA) on the body disrupts movement control by prompting conscious, effortful regulation of processes that are otherwise handled automatically, whereas external focus of attention (EFA) preserves automaticity by directing attention to environment. There is also evidence to suggest that far EFA from the person is better than near EFA (McNevin, Shea & Wulf, 2003). Walking is an important motor skill for everyday living, but performance deteriorates with age and neurological diseases and may alter the role of attentional focus. This study examined how IFA and EFA affect walking performance and movement control in healthy young adults to provide a basis for future research in clinical populations.
Methods
Forty participants walked under six conditions: preferred speed walking without instruction (Pref), EFA on a distant target (EFA-Fr), EFA on the ground (EFA-Nr), internal focus on the head (IFA-He), lower back (IFA-Ba), and foot (IFA-Fo). Walking performance was measured using an instrumented walkway, while tri-axial accelerometers recorded head, lower back, and foot acceleration across anteroposterior (AP), mediolateral (ML), and vertical (VT) axes. Speed, stride length, and stride time were analyzed using one-way repeated measures ANOVA. Movement control was quantified by acceleration amplitude (RMS), log-normalized dimensionless jerk (LDJ) indicated smoothness, and sample entropy (SampEn) indicated predictability. Each analyzed using linear mixed models with walking speed included as a covariate to isolate the effect from speed changes. Bonferroni-correction was used as post hoc comparison.
Results
All IFA conditions and EFA-Nr resulted in disrupted walking performance compared to EFA-Fr or Pref, which were not significantly different from each other. Focus of attention (FoA) instructions also impacted motion of the head and foot, but not the lower back. After accounting for changes in speed, FoA conditions reduced head AP and ML accelerations (RMS) compared with Pref. This was generally associated with higher LDJ (less smooth) and higher SampEn (less predictable) head AP movement. EFA-Nr resulted in lower LDJ (smoother) or lower SampEn (more predictable) AP head motion than EFA-Fr, IFA-He, and IFA-Ba. Focusing on the foot reduced foot acceleration (RMS) and increased SampEn (less predictable).
Discussion and
Conclusion
These findings partially support the constrained action hypothesis: IFA broadly disrupted movement control and walking performance. IFA on the foot reduced accelerations and predictability of foot motion and slowed walking speed. While EFA-Fr preserved walking speed but led to more constrained and regulated head motion. EFA-Nr slowed walking down, but head motion was less regulated than EFA-Fr or IFA on head or back. These findings indicate that the EFA distance effects on walking speed and movement control are not a function of constrained action, and it provides a rational for examining attentional focus effects on movement control in future gait rehabilitation research.