Can an increase in noradrenaline induced by brief exercise counteract sleep inertia?

Emergency responders often credit ‘adrenaline’ (i.e. sympathetic activity) as the reason they respond quickly upon waking, unimpaired by sleep inertia. Movement upon waking may promote sympathetic activity in this population. This pilot study (n = 4 healthy males) tested the effects of a 30 s exercise bout (maximal sprint) upon waking during the night (02:00 h) on sympathetic activity and sleep inertia. When compared to sedentary conditions, exercise reduced subjective sleepiness levels and elicited a temporary increase in sympathetic activity, measured by plasma noradrenaline levels. These findings provide preliminary support for exercise as a potential sleep inertia countermeasure.