Just like most aspects of fitness, the best time of day to workout is not set in stone. Each time slot has its advantages and drawbacks. If you workout late at night, you may experience both negative and positive effects. Ultimately, it is a personal decision as to whether late night exercise works for you.
If you exercise late, you may have a better workout in terms of interruptions and distractions. Gyms are not as busy late at night. You do not have to wait in line for the elliptical trainer or squat machine. It is less likely at 10 p.m. as opposed to 7 a.m. that you will have to share the bench press with a fellow lifter. Telephone calls and emails are less of a distraction late at night than in the morning or afternoon.
One possible drawback of a late exercise session is that it could disrupt your sleep patterns. The National Sleep Foundation recommends exercising at least three hours before you go to bed as this gives your body time to cool down. However, research suggests that late night exercise may not affect sleep patterns. A study published in the "Medicine & Science in Sports & Exercise" journal in 1999 concluded that vigorous late night exercise did not disturb sleep in male cyclists.
The inconsistent advice regarding late night workouts may be due to individual biological rhythms. According to the American Council on Exercise, or ACE, each individual has a circadian rhythm, or cycle. These cycles regulate various physiological responses, including metabolism, body temperature and blood pressure. Due to these rhythms, your body temperature is typically at its highest in the late afternoon and this may be the optimal time to work out. However, each individual's cycle can be different and peak at different times of the day.
ACE recommends you work out when it feels best for you. It is more important to create a regular habit of working out than it is to exercise at some specific time of the day. If you enjoy exercising late and it doesn't disrupt your sleep, then don't change your schedule. However, if you have difficulty sleeping after a late workout, try shifting your workout back a half hour or an hour. Experiment with different times until you find the one that works best.