High-intensity exercise represents a challenge for the cardiovascular system, especially under conditions of insufficient sleep. For example, following one night of partial sleep restriction, healthy young men exhibited increased heart rate, minute ventilation, and plasma lactate concentration during submaximal and maximal exercise compared to one night of normal sleep . In addition to sleep duration, day-to-day variability in sleep duration has emerged as a possible risk factor for cardiovascular outcomes (e.g. poorer microvascular function ). However, whether sleep duration regularity predicts exercise-induced changes in heart rate, blood pressure, and perceived exertion is unclear. Thus, in the present study, we monitored sleep duration over 1 month before a standardized exercise test. Specifically, we included 18 healthy young adults without reports of sleep problems or cardiovascular complications at the time of investigation (age and body mass index [BMI] [mean ± SD]: 24.6 ± 3.1 years and 23.4 ± 3.2 kg/m2; eight females). The present study complied with the Declaration of Helsinki and was approved by the locally appointed ethics committee (DNR2016/398). Informed consent was obtained from the subjects.