INTER-LIMB COORDINATION DYNAMICS: EFFECTS OF VISUAL CONSTRAINTS AND AGE

Abstract

This study aimed to verify the effect of visual afference (eyes open – EO vs. eyes closed – EC) on inphase (IP) and anti-phase (AP) homolateral inter-limb coordination performance in relation to age. Forty individuals (12 youths, age=12±1 years; 16 young adults, age=24±3 years; 12 older adults, age=59±11 years) performed IP and AP synchronized (80, 120, and 180 bpm) hand and foot flexions and extensions. Variability of IP and AP movements was obtained by calculating the within-subject standard deviation of each condition. Significant interactions between coordination mode × age and coordination mode × age × visual afference showed joint effects on IP and AP variability, while no main effects emerged. In the IP-EO condition, posthoc analysis showed higher (p=.0003) variability in older adults (24.8±6.6 s) with respect to young adults (10.5±10.9 s), whereas in the IP-EC condition, older adults showed higher (p=.03) variability (23.4±10.7 s) with respect to both youths (13.7±8.6 s) and young adults (24.1±12.2 s). In both AP conditions, older adults showed lower (p<.002) variability values (EO=9.5±12.1 s; EC=4.6±7.5 s) with respect to the other age groups, with only the youth group showing differences between EO (16.6±12.1 s) and EC (23.6±8.4 s) conditions. Findings show that the age-related worsening of inter-limb coordination is independent of the use of visual afferences. In contrast, at developmental age, visual perception seems to play a differential role depending on the coordinative task complexity (IP/AP). It becomes crucial only in the AP condition, with a lower variability in the EO than in the EC condition indicating youths’ tendency to rely more on visual information for stabilizing complex inter-limb coordination performance.

Key words: vision, hand-foot coordination, motor control