In the fitness world, improvements are made in small (.01) changes, not big (.10) leaps. Slow and steady is the only way to win the race, and anyone who tells you differently is either naive, or using steroids. With that in mind, it’s of the highest importance to maximize these tiny ratios in favor of improvement. Science suggests – the time you exercise is another way to do that.
Bottom line up front: Exercise at some point after the AM
In a 1998 study (http://www.ncbi.nlm.nih.gov/pubmed/9459533), several French researchers sought out to define the performance discrepancies between AM and PM workouts. The maximum performance of 23 men was measured in two exercises – jumping, an anaerobic activity, and cycling, an aerobic activity. Averages were created for both AM and PM groups, and the findings were deemed significant. The differences between the morning and the afternoon reached 3% (P < 0.05) for cycling and 5%-7% for jumping (P < 0.01).
Viewing 1% as important, and 7% as critical, it seems anyone wishing to make steady progress in their fitness goals should work out some point after the morning. The lack of energy and motivation most people people feel in the AM isn’t just in their head; it’s scientifically documented.
The study pertains to both aerobic activities (running, cycling, swimming), and an anaerobic activities (lifting / sprinting). So maybe, that 4 a.m. pre-work jog isn’t the best idea after all. However, as everyone has different demands on their time, we can’t expect everyone to cut out the morning session. For those who can’t, caffeine is one proven way to bring performance levels up to afternoon levels.