Eye Position Shifts Body Sway Under Foot Dominance Bias in the Absence of Visual Feedback

Postural stability assessment in expert versus amateur basketball players during optic flow stimulation

We evaluated the role of visual stimulation on postural muscles and the changes in the center of pressure (CoP) during standing posture in expert and amateur basketball players. Participants were instructed to look at a fixation point presented on a screen during foveal, peripheral, and full field optic flow stimuli. Postural mechanisms and motor strategies were assessed by simultaneous recordings of stabilometric, oculomotor, and electromyographic data during visual stimulation. We found significant differences between experts and amateurs in the orientation of visual attention. Experts oriented attention to the right of their visual field, while amateurs to the bottom-right. The displacement in the CoP mediolateral direction showed that experts had a greater postural sway of the right leg, while amateurs on the left leg. The entropy-based data analysis of the CoP mediolateral direction exhibited a greater value in amateurs than in experts. The root-mean-square and the coactivation index analysis showed that experts activated mainly the right leg while amateurs the left leg. In conclusion, playing sports for years seems to have induced some strong differences in the standing posture between the right and left sides. Even during non-ecological visual stimulation, athletes maintain postural adaptations to counteract the body oscillation.

Effect of a visual dual task on postural stability-A comparative study using linear and nonlinear methods

Background and Aims

The dual-task experimental paradigm is used to study the attentional demands of postural control. Postural control is impaired in poststroke patients, and dual-task balance studies address the visual needs of postural control in stroke patients. A nonlinear approach can help us understand the overall behavior of the dynamic system.

Methods

A total of 20 chronic stroke patients and 20 healthy subjects with similar age, height, and weight participated in this study. The stability and complexity of postural control were assessed using linear and nonlinear methods. All data and parameters (center of pressure [COP] velocity, anteroposterior and mediolateral directions displacement, length of COP path, and phase plane) were analyzed using the Kolmogorov-Smirnov test.

Results

When postural control was examined based on linear analysis, the results showed that the main effect of the group was not significant, but the main impact of position was significant for all parameters of the COP variation (p < 0.05). Examination of postural control based on nonlinear analysis also showed that the main effect of the group was not significant, and the main effect of status was significant only for the parameters of approximate entropy in both directions and short-term Lyapunov view in the anterior-posterior direction (p < 0.05).

Conclusion

According to the results of this study, the assessment of postural control and gait performance in poststroke patients, as well as the dual tasks they have to perform in daily life, is crucial for their independence in activities of daily living.