Does caffeine improve team-based morning performances more than habituation?

Abstract

Repeated sprint performance (≤6 s) has a 3-10% diurnal variation of an evening compared to a morning (17:00-19:00 vs. 06:00-10:00 h; Pullinger et al., 2019). Research distinguishing the effect of habit in comparison to other stimuli on morning performance is unestablished. Therefore, the present study investigates whether caffeine can improve team-based morning performance of 20 m repeated sprints, more than habituation. Eight team-based participants (age: 21 ± 1 years, body mass: 83 ± 9 kg, stature: 181 ± 5 cm) participated in this study. The participants retired at 22:30 h and raised at 06:30 h to be in the laboratory for 07:00 h throughout the study period. The participants completed with two familiarisations and were randomly allocated to two experimental conditions either 1) having taken caffeine on waking (300 mg at 06:30 h), then enter the laboratory at 07:00 h or, 2) The participant rose and retire as above but enter the laboratory at 07:00 h to sit on a cycle ergometer (60 mins) prior to the day of testing. They return the following day at 07:00 h. On entering the laboratory participants were seated, completed sleep questionnaires and mood was assessed using Perceived Onset Mood State (POMS) questionnaire. After 30-min Intra-aural temperature and fingertip blood glucose and lactate measured (as well as post warm-up and immediately after the RSP test). Thereafter, right- and left-hand grip strength (the best of 3 were recorded) and maximal repeated sprint performance measures were taken (RSP, 10 x 20m, 30s recovery period). Heart rate (HR), thermal comfort (TC), and rating of perceived exertion (RPE) were all recorded after each sprint. Data were analysed using a general-linear model.