When is the best time to exercise to maximize performance?
Exercise performance tends to be better in the late afternoon/early evening (1–8 p.m.) than the morning (8–10 a.m.), particularly for short-duration maximal exercise (e.g., a 30-second Wingate test or tests of jump height, repeated sprint ability, or maximal voluntary contraction). Currently, there is limited evidence to suggest that a specific time of day is best for endurance exercise performance.
The main mechanism that underlies this finding is core body temperature, which reaches a peak in the evening hours. An increase in core body temperature may improve exercise performance by enhancing metabolic reactions, increasing the extensibility of connective tissue, reducing muscle viscosity, and increasing the conduction velocity of action potentials. Moreover, using cold water immersion to decrease core body temperature before evening exercise has been shown to decrease muscular strength and repeated sprint ability.
While exercise performance may be better in the evening than the morning at baseline, consistently training in the morning can offset this natural diurnal variation in performance. Indeed, long-term resistance exercise interventions that have participants train in the morning or evening report similar increases in strength and hypertrophy. This suggests that training at a consistent time each day is more important than the time of day training takes place. Therefore, an individual interested in maximizing exercise adaptations should choose a time of day that suits their preferences and will facilitate long-term training adherence.
Besides consistently training in the morning, there are acute strategies that can diminish the natural diurnal variation in exercise performance, including exercising in a warm and humid environment, performing an extended warm-up (e.g., 12 minutes of cycling at 50% of VO2max interspersed with brief accelerations of 5 seconds), ingesting caffeine, and listening to music.