When is the best time of day to exercise: 6am, 1pm, 9pm?

Getting up before dawn to meditate, then taking a 16km walk before doing some weight training might seem like the actions of a Shaolin monk. But that is the morning routine of Ernestine Shepherd, the 81-year-old American who was crowned "world's oldest female competitive bodybuilder" in 2010 and given a place in the Guinness Book of Records that year and the following one.

The personal trainer says she was largely sedentary until she was in her late 50s, which is surely encouraging for those looking to make a change in their routine. With so many fitness fanatics getting out early, it might seem it is the optimal time to exercise? But is it? Or are other times equally good?

Why you should exercise in the morning

The top reason is you can get in a workout before the day falls apart, other people’s emergencies suck up your time or work takes over. This means you can be consistent, which is key to building up your strength and fitness.

It works for  Shamrock Rovers under-15s coach Damian Duff, who schedules sessions for 6.30am. Because most people don’t like to get up earlier than they need to, gym, parks and swimming pools tend to be quiet. And you could save money, as many gyms offer severely reduced “off-peak” rates that can be half of the full membership fee.

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Then there are the physical aspects. Exercise boosts your endorphins, which makes you feel better, improves circulation and brain function, and can help to make you more productive for the rest of the day. This is true for young and older adults, as mentioned in a report in Psychology and Ageing in 2013. It can also help to balance your blood sugar so you suffer fewer cravings for sugary treats.

Why you should exercise at lunchtime

If you are in a demanding job, taking a short class in Pilates or yoga during your break can help to restore your energy so that you face the afternoon renewed.  Lunchtime classes are usually just 30 minutes long, so that you have time to eat too. It’s best to eat after your class, rather than before.

If you don’t have time for a class, then even a 10-minute walk after your lunch can help with digestion.  Any sunshine there might be can add to your vitamin D levels so long as you leave some skin uncovered.

Why you should exercise in the afternoon

Research published in the Journal of Strength and Conditioning shows that we tend to perform our best at exercise later in the day, with both strength and flexibility peaking later in the afternoon. The body tends to be one to two degrees warmer than it was in the morning, so your muscles work more efficiently and there is a lower risk of injury. That makes it a good time to do strength training or to think of lifting weights. It is also a great time to play football or go swimming.

Why you should exercise in the evening

This is when most people manage to get out to gyms, classes or the park, so it can be more sociable, which is good for one’s mental health too. Interestingly, a recent study by researchers at George Mason University in Virginia, US, indicates that those who exercise have better social lives. The study of 129 students found that on any given day those who exercised tended to participate in more “social and achievement activities” than on days they did not exercise.

Regardless of when you choose to get active, the key is to make the effort to do so

"Exercise on one day predicted greater positive social events on the subsequent day. Positive events did not affect exercise on the next day," according to the study published in Personality and Individual Differences.

Most people should avoid strenuous workouts in the late evening or right before bedtime if they want to get the best night’s sleep, according to the National Sleep Foundation of American. The increased temperature that comes with a kickass cardio workout can be too stimulating for some people and can interfere with their ability to fall sleep. Where that is the case, gentler activity such as yoga might be best.

Late evening workouts don’t have the same effect on everybody. So if your Zumba class is helping you to sleep, keep it up.

Why you should exercise at night

It may be 2am but kicking it up to the Macarena will do you much more good than sitting around sinking more alcohol. It’s not worth scheduling it into your week, however, given that we are really meant to be asleep at that time.

Our circadian rhythms, which affect sleep, wakefulness and hormone release, mean that we are at our lowest ebb between 2am and 4am. We also produce more melatonin when it is dark, indicating to our bodies that we should be at rest. As we get older, melatonin declines so that we tend to wake up earlier, according to a study by Paul Kelley of the Sleep and Circadian Neuroscience Institute at the University of Oxford. Even so, by the time we reach our 60s, we don’t need to get up before 6.30am. Dr Kelley believes that trying to override our natural circadian rhythms can lead to anxiety, exhaustion and weight gain. It can also make one tend to use more stimulants, he says.

The exception to the rule of not exercising at night is shift workers who may not have a choice. For them, the 24-hour gyms can prove a safe place in which to work out while everyone else sleeps. Those who must do this should try to leave about five hours between exercise and sleeping to give the body a chance to return to normal. That said, one 2013 study by America’s National Sleep Foundation found that 83 per cent of those who exercised found that it helped their sleep, no matter what time they did so.

Regardless of when you choose to get active, the key is to make the effort to do so. Getting up at 2.30am to exercise seems like a strangely self-inflicted form of torture to me, but it works for the very toned Shepherd. What her example really shows, however, is that there really is little excuse to slack off.

Sign up for one of The Irish Times' Get Running programmes (it is free!).

First, pick the programme that suits you.
- Beginner Course: This programme is an eight-week course that will take you from inactivity to being able to run 30 minutes non-stop.
- Stay On Track: The second programme is an eight-week course for those of you who can squeeze in a 30- to 40-minute run three times a week.
- 10km Course: This is an eight-week course designed for those who can comfortably run for 30 minutes and want to move up to the 10km mark.
Best of luck!