Effects of Waking Time and Breakfast Intake Prior to Evaluation of Psychomotor Performance in the Early Morning
Résumé
Many studies conducted in the field of chronobiology report diurnal fluctuation in
cognitive and physical performance that occurs in phase with the body temperature
circadian rhythm. Waking time and whether or not breakfast is consumed are
currently considered to influence the diurnal fluctuation in data collected in the
morning at 06:00 h and evening at 18:00 h. Nineteen male subjects participated in
four test sessions to examine if wake-up time (04:00 h or 05:00 h) and eating or not eating breakfast influence psychomotor performance capacity at 06:00 h. All four sessions were separated by 36 h and were completed in a counterbalanced order. Each test session comprised sign cancellation, Epworth Sleepiness Scale, simple reaction time, and manual dexterity tests. Most of the results indicate that psychomotor performance when evaluated at 06:00 h under each of the four different study situations (two waking times and two breakfast conditions) is not statistically significantly different. Consequently, previous results that documented diurnal fluctuations in morning and evening performance capacities, with test sessions at 06:00 h, are confirmed. Being less efficient in the early morning than in the afternoon potentially exposes people to elevated risk of accident and injury at this time of the day. Prior waking time and/or consumption of a light meal, plus other countermeasures mentioned in the literature, are insufficient to prevent this risk.