Ben Greenfield is a featured contributor on the TrainingPeaks blog at http://blog.trainingpeaks.com. Here is a recent post:
Q: Should I exercise in the morning or the evening?
A: Depends on your goals! If you are exercising for sports performance and want to be able to achieve the highest possible intensities during your routine, then the optimal time to exercise is when your body temperature is at its highest. For most people, this is about 4p to 5p in the afternoon. On the other hand, your body temperature is at its lowest just before you wake, so rolling out of bed for an interval training session may not be the best idea. In addition, research has shown that your aerobic capacity, strength output, and sprint capabilities are also higher in the afternoon (but only by 4-5%).
Conversely, morning exercise does has benefits. By jump-starting your metabolism and increasing your core temperature early in the day, you increase your post-exercise oxygen deficit and calorie-burning rate throughout the remainder of the day. Therefore, if you are trying to lose weight or burn fat, a morning exercise session can be highly effective. Psychologically, you may be more likely to exercise in the morning, versus after a hard day of work, when your mind and body may be tired or you may have too many other duties to fulfill. It doesn't matter if you're able to exercise with higher intensity in the afternoon if you never actually get around to doing it!
The ultimate combination, and the system I implement for my clients who want simultaneously build fitness and burn fat, is an aerobic morning exercise session of 30-60 minutes, followed by a more intense interval, sport-specific, or resistance training session in the late afternoon or evening.
Do you have a question for Ben? E-mail [email protected]