Citation

Souissi Y, Souissi M, Chtourou H. Pharmacol. Biochem. Behav. 2019; 177: 69-74.

Affiliation

Institut Supérieur du Sport et de L'éducation Physique de Sfax, Université de Sfax, Tunisie; Activité Physique: Sport et Santé, UR18JS01, Observatoire National du Sport, Tunis, Tunisie.

Copyright

(Copyright © 2019, Elsevier Publishing)

DOI

10.1016/j.pbb.2019.01.001

PMID

30611752

Abstract

The purpose of this study was to evaluate the effects of caffeine ingestion on the daily variation of cognitive (i.e., reaction time (RT), attention) and repeated high-intensity exercise performances. Fifteen active males (age: 20 ± 1 years, height: 174.3 ± 4.3 cm, body-mass: 70.8 ± 3.5 kg) performed cognitive and physical tasks under two different circumstances [after a placebo or caffeine ingestion (6 mg/kg of body-mass)] at six different time-of-day (07 h00, 09 h00, 11 h00, 13 h00, 15 h00 and 17 h00) in a randomized double-blind balanced crossover design. During each session, RT, attention and 5-m multiple shuttles run test' performances were recorded. During both the placebo and the caffeine conditions, a significant diurnal variation was found with improvement of cognitive performances recorded at 11 h00 (e.g., RT: 0.37 ± 0.02-s and 0.36 ± 0.02-s for placebo and caffeine respectively) and 17 h00 (e.g., RT: 0.37 ± 0.02-s and 0.35 ± 0.03-s for placebo and caffeine respectively) compared to (i.e., worst performances) 07 h00 (e.g., RT: 0.41 ± 0.02-s and 0.38 ± 0.02-s for placebo and caffeine respectively) and 13 h00 (e.g., RT: 0.41 ± 0.02-s and 0.38 ± 0.02-s for placebo and caffeine respectively) (p < 0.05). For physical performance, improved values were recorded at 17 h00 (e.g., total distance: 730.00 ± 43.92-m and 733.93 ± 43.08-m for placebo and caffeine respectively) compared to 07 h00 (e.g., total distance: 698.14 ± 45.39-m and 709.21 ± 43.78-m for placebo and caffeine respectively) (p < 0.05). Compared to placebo, cognitive (e.g., RT: by 6.4% at 07 h00, 4.1% at 09 h00, 3.4% at 11 h00, 6.0% at 13 h00, 3.8% at 15 h00 and 3.8% at 17 h00) and physical (e.g., total distance: 1.6% at 07 h00, 0.9% at 09 h00, 0.1% at 11 h00 (p > 0.05), 0.5% at 13 h00, 1.0% at 15 h00 and 0.5% at 17 h00) performances increased at all time-of-day (p < 0.05). In conclusion, cognitive and physical performances are time-of-day dependent and caffeine is an effective ergogenic aid to improves both cognitive and physical performances especially at the moment of their lowest values.

Copyright © 2019. Published by Elsevier Inc.

Language: en

Keywords

Attention; Caffeine; Cognitive function; Diurnal variation; Exercise; Reaction time; Sport