A study reveals peaks of activity at 8am and 6pm correlate to a lower risk of bowel cancer. Could adapting the timing of exercise benefit us?
Do you drag yourself out of bed to exercise before work, or go to the gym on your way home? Does a lunchtime walk rev you up for the afternoon, or is it yoga you rely on in the evening to relax? We all know exercise is good for us, but increasing evidence suggests when we exercise can also have an impact our mood, fitness and health.
On Tuesday, a study published in the journal BMC Medicine that tracked the activity of 86,252 people aged 42 to 79, revealed participants who had two daily peaks of activity at 8am and 6pm were associated with an 11 per cent reduced risk of bowel cancer, compared to those who were active at other times of the day.
Lead investigator Professor Dr Michael Leitzmann, of the University of Regensburg, Germany, said the findings could “open new avenues for targeted prevention strategies.” The reason for the reduced risk isn’t clear, but begs the question: could we benefit psychologically or physically by adapting the timing of our exercise routine? And if so, how?
Aerobic exercise in the early morning
Working up a sweat first thing serves several purposes, if you can face it. Not only is it often the most practical way to get a workout out of the way before being waylaid, but neuroscientist Andrew Huberman says it will also help us feel more alert by raising our body temperature, which is lowest in the morning.
Personal trainer Kate Rowe-Ham, author of Owning Your Menopause, says lifting weights on waking four times a week, makes her “more energised and motivated for the rest of the day.” She points out that resistance training is proven to balance blood sugar and, long term, lower levels of the stress hormone cortisol. “It leaves me less stressed.”
Exercising early can also be more efficient for controlling weight – research in the journal Medicine & Science in Sports & Exercise found 45 minutes of vigorous aerobic exercise can elevate the metabolic rate for 14 hours, meaning you’re burning more calories during the hours you consume them, as opposed to overnight, while another study on 35 women in the same journal found when participants exercised in the morning they were more likely to increase their activity throughout the day.
“Research suggests there may be a slight advantage to doing aerobic exercise earlier in the day because it enhances bloodflow and oxygen to the brain which can improve your productivity,” adds Arj Thiruchelvam, sports scientist and coach at Performance Physique. In terms of boosting feelings of wellbeing, he says resistance training and aerobic exercise are likely to be equally beneficial, “because both trigger the release of endorphins, which is the most important factor in improving mood.”
Post-breakfast for longer workouts
While studies have found exercising on an empty stomach, whatever the time of day, can increase fat burning by as much as 70 per cent, this need not be prescriptive. “I have to eat a protein breakfast – usually scrambled eggs – up to half an hour before because my workouts are long and I don’t want to run out of energy,” says personal trainer Cornel Chin, who does a two-hour weights session at 11am every Saturday. “This fits into my lifestyle. During the week I speedwalk and do bursts of bodyweight exercises in between coaching clients.”
Lunchtime walk in the park
A lunchtime session, meanwhile, can help you cope with the demands of work, especially if done outdoors during our ever-dwindling daylight hours. A two week 2017 Finnish study found a 15-minute walk in the park helped participants more than indoor relaxation exercises, making them feel more relaxed and detached from their work, whereas the “relaxation group experienced only an increase in their feelings of relaxation,” said Kalevi Korpela, professor of psychology at Finland’s Tampere University.
Amanda Daley, health psychologist at Loughborough University, says “exercising at lunch time can help clear your head after a morning of work or other activities (and) boost your mood and brain power in the afternoons.”
Resistance training in the afternoon
It may also carry advantages for our physical health. Last year, a major study in the journal Nature Communications found that while moderate to vigorous physical activity at any time of day is linked to lower risk of cancer and cardiovascular disease, those who exercised between 11am and 5pm had a lower risk of premature death from all causes than those who exercised in the morning or evening.
The reports’ authors speculated that this may be because blood pressure recovers faster in the afternoon, or because of implications for meal timings – a walk after a meal, for example, has been found to control blood sugar levels – but admitted “the underlying mechanisms remain to be elucidated”.
What we do know is that our body temperature peaks in the afternoon, “and being slightly warmer makes muscle fibres react quicker, which can improve our performance,” says Thiruchelvam. “This is why athletes may want to train then because they’ll be slightly more powerful. Studies show resistance training can be more effective in the afternoon.”
HIIT in the evening for some…
Reaction times are also often quickest at this point, potentially improving performance in competitive sports and stop-start exercise such as High Intensity Interval Training. Indeed, research by the American Academy of Sleep Medicine found American football players usually played better in games starting at 8 or 9pm than they did in games starting at 1 to 4pm.
This was due to them being at the peak of their circadian rhythm – the 24-hour internal clock. Yet the time of day you’re happiest exercising will depend in part on your chronotype, or your natural propensity to fall asleep at certain times, and if you’re an early bird who wakes at 5am, for example, evening exercise is still likely to feel a challenge.
…but less is best for most in the PM
The most recent research overturns the long-held belief that evening exercise can interfere with sleep, however – and found it may even help us nod off quicker. This summer, a study of 30 participants found those who did three-minute bursts of body weight exercises such as squats and calf raises every 30 minutes over a four-hour period starting between 5pm and 5.30pm slept for an average of 27 minutes longer than the sedentary control group.
The exception appears to be doing high-intensity exercise training, which releases the stress hormone cortisol, and is thought to reduce sleep quality when done close to bedtime. Yet any impact is likely to be minimal, says Thiruchelvam, “and it’s still better for you than scrolling on your phone.” He stresses, however, that exercising when tired is more likely to result in injury: “Mental and physical fatigue is when slip-ups occur.”
Yoga or stretching before bed
If cardio sounds too strenuous, consider evening stretching – one four-month study on patients with chronic insomnia found stretching three times a week from 5pm to 6pm improved symptoms. A 2019 meta-analysis, meanwhile, found mind-body therapies including yoga and tai chi can be “effective in treating insomnia and improving sleep quality.”
Yoga has been shown to increase levels of melatonin, the hormone that regulates the sleep cycle, and is “a great addition to a bedtime routine,” says Rowe-Ham, although research isn’t clear as to whether it needs to be practised in the evening to be of benefit.
What’s “vital,” stresses Thiruchelvam, is that we exercise, full stop, and no study should “put people off exercising at their only opportunity.” Rowe-Ham concurs: “I don’t want people to think they’re at greater risk of cancer because they can’t exercise at certain times, or that there’s no point. Movement is beneficial, whatever the hour.”
