There is really no best time to exercise. It depends largely on the individual and what do you want to achieve through exercise. I believe you should exercise whenever you can, it really doesn't matter what time you do it, as long as you do it. Unless of course you are an elite athlete who wants to achieve that extra 0.5% gain in your performance during training. Even that I don't think it really matters, as professional competition schedules are generally not based on peak performance timing but rather on broadcasting viewership and organisational convenience. There is also no concrete scientific evidence to suggest that calories are burnt more efficiently at certain times of the day. However, for those who want to exploit the subtle differences between different exercise timings in the hope of maximising benefits, please read on.
- Can improve sleep at night and hence promote weight loss (see my article about weight loss and sleep).
- Morning exercise promotes consistency. People are more likely to keep up with the exercise schedule. If you have trouble with consistency, exercise in the morning.
- Fat burning if exercising on an empty stomach.
- Can boost energy and mental alertness for the rest of the day hence creating better mood and moral compares to that of people exercise in late afternoon.
- More prone to injuries due to slow metabolism and cold muscles. Need to stretch properly before strenuous exercise.
- A lack of energy hence a reduction in performance/endurance if exercised on an empty stomach.
Noon/early afternoon exercise
- Body is warmer than in the morning, body temperature is better regulated in the afternoon.
- Better energy and endurance compares to morning.
- Increased blood flow to the brain, which could be beneficial to afternoon duties.
- Unlikely to have enough time to exercise and eat.
Late afternoon and evening exercise
- Highest body temperature (metabolism) at around 6pm.
- Less likely to have injuries compares to doing exercise in the morning.
- Highest muscular strength of the day.
- Highest anaerobic and aerobic performance levels.
- Late night exercise may affect sleep as metabolism is stimulated during a time the body is trying to slow it down.
While subtle differences have been detected between different timings of exercise in controlled scientific studies, the effects of these differences may not be measurable in the real world. The above pros and cons listed correlate with an average person's circadian rhythm. Everyone's different. Therefore, the best time for a workout should be the time that allows you to exercise regularly in accordance with your schedules and makes you feel the best.