Effects of vision and cognitive load on anticipatory and compensatory postural control.

This study assessed the effects of vision and cognitive load on anticipatory postural adjustments (APAs) and compensatory postural adjustments (CPAs) in response to an externally triggered postural perturbation. A ball-hitting test was repeated under different visual conditions (eyes open, EO; eyes closed, EC) and cognitive loads (no load, 3-subtraction task, time-limited 3-subtraction task). Data were collected separately for I) surface electromyography from the right side of the biceps brachii (BIC) and erector spinae (ES) to detect the latency and response intensity (RI); and II) displacement of the centre of pressure (ΔCOP) to detect the standard deviation (ΔCOPSD) and maximum value (ΔCOPmax) in the anterior-posterior direction. Compared with the results under the EC condition, the ES latency was shorter and the RI of the BIC was lower under the EO condition. Accordingly, the ΔCOPSD and ΔCOPmax were increased in the APAs phase and decreased in the CPAs phase. Cognitive load had no effect on APAs and CPAs or on ΔCOP in the APAs phase. However, ΔCOPmax was decreased in the CPAs phase during the EC condition. In conclusion, vision played an important role in APAs and CPAs for muscle activation and ΔCOP. Cognitive load had no effect on neuromuscular APAs or CPAs except when the postural perturbation occurred when visually unexpected.