Timing your workout

Before dawn. Before bed. When should you work out? Does it make a difference? Aware of natural daily rhythms in body functions, called circadian rhythms, many people wonder whether there is an ideal time for exercise. The answer is that exercise itself is ideal at any time - and getting exercise is more important than getting it at a certain time of day. But research does show that your body's intrinsic cadences can affect quality of your athletic performance.

Not everyone's circadian rhythms are identical, but most people experience similarities. In addition, cues in the environment keep these "pulses" on track. Natural light and darkness, meal times, and household routines all influence highs and lows. Variations and disruptions can occur when you travel, when you are under stress, or when you vary your sleeping habits.

A closer look For example, when you wake up, your body temperature is low. By late afternoon, it may be as much as one or two degrees higher - its peak for the day. Likewise, muscles may be cold and inflexible first thing in the morning. Although we are not aware of it, many body processes, such as blood pressure and hormone production, go through daily cycles, too.

Afternoon advantages
If achieving high performance is critical, late afternoon is likely to be your pick. Flexibility, strength, endurance, and ability to handle pain are highest at this time. This is the time you are most likely to break your own record, achieve your best time on a run or a swim, or cycle further than you've ever cycled before.

Another advantage of an afternoon workout: Studies show exercise can improve your sleep patterns - particularly when the exercise occurs in late afternoon. A half-hour workout tends to help you go to sleep faster, and sleep more soundly. However, exercise right before bed can make you too alert, keep you awake, and start a damaging cycle of exhaustion. If you like the late-day approach to exercise, try to plan at least two hours between end-of-workout and bedtime.

According to researchers, people who exercise in the morning are more likely to stick with their routines. One consideration is schedule-juggling: If you do it first, it can't be put off. Late-day workouts, on the other hand, can be postponed or missed when demands of the day become too hectic, or when the day's events drain your energy.

Morning has its perks, too Morning exercise can have an energizing effect, setting the stage for a successful day. Like coffee, morning exercise can pick up your heartbeat, heighten your alertness, and help you feel ready to tackle your day. If you like outdoor exercise, another pro for mornings is that air pollution levels are typically at their daily low. If you do opt for AM, take extra time to warm up muscles and stretch to prevent injury.

People who exercise in the early hours tend to be very productive at whatever they do throughout the morning. However, the afternoon sleepiness that hits most of us for an hour or so every day can be intense, and afternoon may become a low-energy period. This time of day is ideal for a relaxing break, a nap - or another brief exercise, such as a 10-minute walk.

Any time is terrific!
Being aware of your body's circadian changes may give you reason to experiment for yourself, and decide when exercise is most comfortable for you. More importantly, take a hard look at your own schedule, and decide when it will fit most realistically and reliably. In other words, the best time to exercise is the time that you can stick with. Routine itself helps you maintain your healthy habits - and helps keep your circadian rhythms on an even keel.