If you’ve ever felt as if the treadmill seems to be going uphill in the morning and downhill in the evening, or that you run noticeably faster after work than at lunchtime, don’t worry—you’re not alone. In 30 interviews with runners, from average club plodders to Commonwealth Games 1500m champion Michael East, every one claimed to run better at one time of day than another. Many had even put this to the test.
For example, Andrew Grace, a 2:53 marathoner from London, had to do the majority of his running early in the morning because of work. On Wednesday, however, he was able to leave work a little earlier, so he trained in the evening, which always felt easier. He put it to the test and found he was consistently at least a minute quicker over the same seven-mile course without expending any extra effort. "If anything, the evening run seemed easier, even though I was going faster," he said.
Many of the runners thought the reasons for this change were psychological. "I just feel better when I’ve got work out of the way," and, "I always feel miserable in the mornings," were common reasons. Others blamed poor sleep or even the previous night’s meal! According to a significant branch of science, however, a more likely explanation is a perfectly natural phenomenon known as circadian rhythms. These are small fluctuations in the performance of bodily functions on a 24-hour basis. "Practically every bodily function shows daily rhythmicity," said Dr. Roberto Refinetti, Chief Editor of the Journal of Circadian Rhythms. "So that means, in theory at least, you can improve your ability to do something simply by selecting the right time of day to do it." In total we have more than 100 different circadian rhythms controlled by the suprachiasmatic nucleus, a biological clock in a part of the brain called the hypothalamus. Although scientists have yet to pinpoint the exact mechanism it uses to pace your body, they know that daylight, social contact, and meal times are all factors.
The important thing, from a running perspective, is that many of the functions vital to putting in a good performance peak at the same time. For example, one of our daily fluctuations is in body temperature. Scientists have found that body temperature is at its lowest in the early hours of the morning and peaks in mid- to late-afternoon. It has also been shown that athletes perform better when body temperature is higher, which is perhaps why Grace found it so much easier to run in the evening. A new study also suggests our lungs work best at this time too. To analyze which time of day is right for you, here’s a quick survey of the specific positives and negatives of running at different times.
Early Morning
You may be unsurprised to hear that the peak time for running is definitely not first thing in the morning. Virtually all bodily functions are at their worst at this hour. Body temperature is low—meaning your muscles will feel stiff—lung function is poor, and you’re unlikely to have had any substantial food intake for about ten hours—so your energy stores will also be depleted. All this means the same level of exertion is likely to feel much harder at this time of day than later on. To top things off, exercising early will leave you more prone to injury or worse. "Research shows this is the most common time of day for heart attacks and strokes," said James Waterhouse, Professor of Biological Rhythms at John Moores University, Liverpool.
Just because nearly everything physical is against you at this time, however, doesn’t mean the early morning session has no benefit. The very fact that it feels harder means it’s good for building up mental strength. "I dread those early-morning runs," said East. "You always feel like you’re fighting your body. But there’s absolutely no doubt they’ve made me stronger—from a mental perspective especially."
Mid-Morning
Lung performance and body temperature are much improved from the early morning, plus if you’re training at this time you should have had a good protein and carb-filled breakfast, meaning your energy levels will be much higher. However, although most of your physical functions will be improved from the early morning, they are still not as good as later in the day. Furthermore, if you work normal hours, a mid-morning run is likely only to be possible on the weekend anyway. If you do put in a mid-morning run, on a Saturday for example, you might want to make it a speed or hills session in which building up your calf and quad muscles is the aim. The reason is that most scientists agree this is the best time of day to boost muscle. "There’s a strong argument for doing weight training in the morning if you’re interested in building muscle," said Dr. Stephen Bird, from the School of Human Movement Studies in Australia. "This is because testosterone, the hormone most responsible for muscle-boosting, is at its highest around this time."
Lunchtime
The lunch-time run is extremely popular with all those who work normal hours. Getting out of the office and breaking up the day with some running seems like a great idea. And indeed there are positives to training at this time, but mostly they have to do with your work performance rather than your running performance. "Many people choose to exercise at lunch because it doesn’t eat into their free time," said workplace psychologist Mike Clinton. "Plus it perks you up and is likely to make you more productive in the afternoon."
In fact, nearly all bodily functions experience a lull in the middle of the day, particularly those such as lung function and body temperature, which are crucial to running performance. Like the early morning, this doesn’t necessarily make it a bad time of day to train; just make sure you save those time trials, or sessions where you’re looking to run your absolute best, for later.
Afternoon and Evening
It has been known for some time that most physical activities are best performed in the mid- to late-afternoon, as this is when body temperature peaks, meaning the muscles are at their most supple and running at speeds that feel tough in the early morning will feel much easier. Recently this has been bolstered by a study by Dr. Boris Medarov of the Long Island Jewish Medical Center in New York, which found that lung function was more than 6 percent better in the afternoon than at other times during the day. "Everything just feels easy and relaxed, and the miles go by that much quicker," said East. So this is definitely the time of day to run if you’re going for a personal best.
Physically there are no negatives connected with this time of day, meaning the only drawbacks are likely to be psychological. Many of the runners interviewed said the hardest part about running after work was finding the motivation after a long day in the office. Although the late afternoon is our physical peak, it’s not our mental one. Mentally we’re at our best shortly after waking, and things just get worse as the day goes on, especially if work has anything to do with it. So by late afternoon, you’re unlikely to feel like running, but if you can force yourself to pull those trainers on, you might be surprised. "At my club night on a Wednesday evening, you always hear people saying they’re not up for it or they’re tired," said Grace. "Then after a couple of miles they’re the ones pushing the pace!"
