Time of Day - Effects on Motor Coordination and Reactive Strength in Elite Athletes and Untrained Adolescents

Objectives: the issue of time-of-day effects on performance is crucial when considering the goal of reaching peak results in sport disciplines. The present study was designed to examine time-of-day effects in adolescents on motor coordination, assessed with Hirtz's battery and neuromuscular components of strength, evaluated with reactive strength tests. Methods: forty-two elite female gymnasts, aged 13.3 +/- 0.5 years (Mean +/- SD), were recruited for the study. Fifty healthy female students (aged 12.8 +/- 1.7 years) served as the control group. All participants underwent the testing sessions over two days at two different times of day in a randomized order. Results: Oral temperature was measured at the two times of the day and a significant diurnal variation (p < 0.01) in both groups was found. MANOVA revealed significant group differences in the overall tests (p < 0.01). The gymnast group showed no significant differences in the coordination tests with respect to the time of day, but significant differences were observed for reactive strength as assessed with the vertical jump tests (p < 0.01). Gymnasts attained better results in the evening in the reactive strength tests [flight time (F-1.90 = 17.322 p < 0.01) and ground contact time (F-1.90 = 8.372; p < 0.01) of the hopping test]. Conclusion: the temperature effect was more evident in the reactive strength tests and orientation test, especially in the gymnast group in which this effect added to their usual training time effect. The time-since-awakening influenced coordination performances in complex tasks more than reaction strength tests in simple tasks. The main outcome of the study was that we did not observe time-of-day effects on coordination skills in elite gymnasts and in untrained adolescents. The time of day in which athletes usually trained these skills could influence these results.