The evaluation of motor coordination is important for diagnosing children and adolescents with motor impairments. However, motor coordination may be affected by time-of-day effects, and thus, the intra-day variation could subsequently influence the assessment accuracy of the standardized test used in the diagnostic process. To the best of our knowledge, no study has been conducted to examine this possibility. Therefore, the purpose of this study was to investigate the time-of-day effect on motor coordination. A convenience sample of 25 youth (17-21 years) were recruited from local high schools and a local university. The Bruininks-Oseretsky Test of Motor Proficiency - Second Edition (Short Form) was administered at three different times (morning, noon, and afternoon) over three days to explore the potential time-of-day effect on motor coordination. The starting time of the test on the first day was counterbalanced. Other factors that could potentially impact motor performance were also measured, including physical activity, chronotype, and time-since-awakening. A statistically significant main effect of time-of-day was found on overall motor coordination (p< .01) and the domain of Manual Coordination (p< .01). The time-of-day effect on the domain of Strength & Agility (p = .055) was just above the threshold of statistical significance. Further analysis showed that overall motor coordination was better at noon (p< .01) and in the afternoon (p= .052) than in the morning, whereas manual coordination was the worst in the morning (p's < .01). Strength and agility were also significantly better at noon than in the morning (p< .01). In addition, poor motor coordination in the morning was also related to longer time-since-awakening. Overall, this study identifies the time-of-day effect on motor coordination that could lead to the inconsistent classification of motor performance. Therefore, in order to avoid the potential misclassification of motor coordination, health professionals should take into account the time-of-day effect on motor coordination and the possible impact of time-since-awakening while administering the assessment in the morning.
Keywords: Circadian rhythm; intra-day variation; measurement; motor coordination.