Moderate aerobic exercise includes activities such as brisk walking, biking, swimming and mowing the lawn. Vigorous aerobic exercise includes activities such as running, heavy yardwork and aerobic dancing. Between 2 p.m. and 6 p.m., your body temperature is at its highest. This may mean you'll be exercising during the window of time your body is most ready, potentially making it the most effective time of day to workout.