Morning or night? Is there a 'right' time to exercise?

Is there a best time of day to exercise? This is a question that I often get asked.

Most of the time I avoid answering it because there’s no rule of thumb that applies to everyone. It also depends on the “type” of exercise you’re referring to (i.e. Strength training versus cardiovascular training).

Aside from the obvious that most of us aren’t fulltime athletes and need to fit our exercise in around other commitments, there is also the effect of our “circadian rhythms” or body clocks which influence a host of factors such as body temperature, digestion, hormone release, etc. – all of which directly impact our ability to exercise.

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Most of us know instinctively whether we’re “morning” people (or not). This (to a large extent) is genetically pre-determined and regulated by the hormone melatonin which is affected by day and night. In fact melatonin is often used in supplementary form to regulate circadian rhythms after long haul flights where people are trying to limit the impact of jetlag – but that’s a completely different topic!

Your body clock can be manipulated to some extent by changing your sleep pattern. In other words, you can “teach” yourself to get up early and go to the gym or for a run and still get a good workout.

The advantages of working out in the morning include:

• There are fewer distractions and schedule interruptions so you’re more likely to do it.

• You can “make time” for exercise by getting up a bit earlier.

• Exercise increases your heart and metabolic rates after an overnight fast which means you’ll metabolise fat more effectively first thing of a morning – before you eat.

• Exercise will energize you for hours to come making you more productive.

• It is generally cooler in summer.

• Air pollution is lowest in the morning if you’re outdoors exercising.

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There are, of course, a few downsides to morning exercise:

• Your body temperature is at its lowest upon awakening. Cold, stiff muscles may be more prone to injury so you’ll need to be vigilant in warming up well before doing a high intensity workout.

• If you do not enjoy morning exercise it is harder to make it habitual.

• Sports science suggest that exercise performance is closely related to body temperature, which peaks for most people in the early evening.

Hormonal Interplay - Cortisol and Testosterone

Weight training may be more effective in the early evening due the to the interplay of the hormones cortisol and testosterone.

Among other functions cortisol helps to regulate blood sugar by breaking down muscle tissue when necessary – this is known as “catabolism”, while testosterone does the opposite: it helps to build muscle (i.e. “anabolism”).

Cortisol levels generally peak in the early morning and diminish throughout the day. Whilst testosterone levels are also high in the morning the ratio of testosterone to cortisol peaks in the evening meaning that the rate of muscle building peaks later in the day if an exercise stimulus (training) is applied.

From a practical perspective what does this mean?

I’d suggest you hedge your bets like I do.

The morning time is probably the best for some form of cardiovascular exercise whilst your strength training is probably best done in the evening, but I say this with the caveat that everyone is different and you need to experiment with what works best for you.

Guy Leech is passionate about health issues like obesity and heart disease and has established a multimedia platform from which he educates and motivates Australians about the importance of fitness and health. For more information, including the 12 Week Food and Exercise program, go to guyleechfitness.com