If you struggle to get out of bed for a morning workout, you are not alone. A growing body of evidence suggests that most people are stronger, more powerful, and have better endurance later in the day. Your body's natural 24-hour clock, or circadian rhythm, regulates hormones, body temperature, and alertness, and research shows it is clearly linked to exercise performance, which tends to peak between 4 and 7pm.
Several factors contribute to this afternoon advantage. Core body temperature is at its lowest around 5am and rises throughout the day; when body temperature is higher, muscles contract more efficiently. Insulin levels are also highest in the morning, leading to lower blood sugar and less fuel available for exercise. Additionally, the nervous system may send signals to muscles more effectively later in the day, allowing you to recruit more muscle fibres.
Your chronotype—whether you are a morning person or a night owl—also plays a role. Night owls perform notably worse when exercising in the morning compared to early birds. Interestingly, sleep deprivation seems to affect afternoon performance more than morning performance, so if you are sleep-deprived, a morning workout might actually feel easier than an afternoon one.
Despite these differences, the timing of exercise does not matter for long-term fitness gains. If you consistently train at a particular time, your body can adapt over a few weeks, narrowing the performance gap between morning and afternoon. Ultimately, the best time to exercise is the one that fits your schedule and motivation.
