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The effect of training at the same time-of-day on the diurnal variations of technical ability and swimming performance

Abstract The aim of this study was to examine the effects of training at the same time of day on diurnal variations of technical ability and swimming performance, to provide some recommendations with regard to adjusting training hours in accord with the time of day of competitive events. Eighteen participants volunteered for this study, and these were randomly assigned to either a morning training group (MTG, who trained only between 07:00 and 08:00 h, n = 6), an evening training group (ETG, who trained only between 17:00 and 18:00 h, n = 6), or a control group (CG, did not train but participated in all tests, n = 6). Swimming performance and technical ability – (i) stroke parameters: swim velocity (V), stroke rate (SR), and stroke length (SL); and (ii) motor organization: arm stroke phases and arm coordination (Idc) – were recorded 2 weeks before and 2 weeks after an 8-week regular training period. For all participants, the morning and evening tests were scheduled at the same time of day as the morning and evening training sessions. After training, the major finding of this study was that both ETG and the CG showed significantly lower P, V, SR, phase (B), phase (C), and Idc values in the morning than in the evening. However, P, V, SR, phase (B), phase (C), and Idc of the MTG measured at 07:00 and 17:00 h did not differ. Thus, training at a specific time of day increased performance in MTG at this time and modified the diurnal variation of swim performance. This study indicates that training at a specific time of day can result in marked changes in both swimming performance and technical aspects of swimming. Furthermore, training in the morning improved morning swimming performance and its components, and the amplitude of the morning–evening difference decreased. Training in the evening improved swimming performance and its components more in the evening than the morning, and the amplitude of the morning–evening difference increased.