There is more than one theory about the best time of day to exercise. The first school of thought is "Mornings are best."  This is obvious to proponents of this theory because exercising before eating breakfast causes the body to burn calories that have been stored as body fat. Fewer distractions and schedule interruptions occur during the early morning hours, temperatures are cooler, and morning exercise causes people to begin their day with a feeling of increased energy, improved mental acuity, and a metabolism that has been kicked into high gear in preparation for the day's challenges.

A second school of thought says, "Examine the facts." Research studies have shown that when body temperature is low, workouts are less productive and when body temperature is high, workouts are more productive. Because body temperature is at its lowest about 1 to 3 hours before waking up in the morning and body temperature reaches its peak during the late afternoon, research indicates that exercising later in the day produces better performance and more power.

A third school of thought says, "Just do it." Proponents of this theory are alarmed about a recent report from the Centers for Disease Control and Prevention showing that 60% of Americans don't exercise enough and over 25% are physically inactive. According to an official spokesperson for the American Council on Exercise, the most important factor in an exercise regimen is consistency, so whatever time works best for your schedule is the best time for you to exercise.