Abstract
Background: Time of day has been shown to impact athletic performance with changes of up to 10% detected throughout the day. Physiological factors such as body temperature and hormonal responses display individual circadian rhythms and are believed to be associated with alterations in performance. These factors may also contribute to variations in the distribution of energy expenditure or power output throughout an event (i.e. pacing); however, we are aware of only one study that has investigated the influence of time of day on pacing. Therefore, the aim of this study was to investigate the influence of time of day on performance and pacing selection within a 4 km cycling time trial.