Morning Lark or Night Owl? How Our Body Clocks Affect Our Mental and Physical Performance

Our most productive time can be strongly affected by our most wakeful hours
By Elise Facer-Childs, University of Birmingham
January 8, 2019 Updated: January 8, 2019

Whether you’re a morning person or love burning the midnight oil, we’re all controlled by so-called “body clocks.” These body clocks regulate your circadian rhythms and are inside almost every cell in the body. They control when we feel awake and tired during a 24-hour period.

But as it turns out, our latest study found that our body clocks have a much bigger impact on us than we previously realized. In fact, our body clocks actually affect how well a person performs on both mental and physical tasks.

Our circadian rhythms are controlled by the brain’s suprachiasmatic nucleus, which detects light. When cells in your eyes register that it’s dark outside, they send these signals to the suprachiasmatic nucleus. It then releases the hormone melatonin, which makes you feel tired.

Your chronotype is another factor that determines how your biological clocks affect your daily behaviors. For example, people with early chronotypes (“morning larks”) rise early and are most active in the morning, but feel tired late in the afternoon or early evening. Late chronotypes (“night owls”) are tired during the morning, but feel awake in the evening.

These differences may also be seen in multiple other physiological, behavioral, and genetic rhythms that happen over a near 24-hour period. For example, chronotype determines the time melatonin is released. For morning larks, melatonin can rise around 6 p.m., making them feel tired by 9 or 10 p.m. For night owls, melatonin can increase at 10 or 11 p.m. or even later, meaning many aren’t tired until 2 or 3 a.m.

Genetics can determine your body clock type, but it’s also largely influenced by schedule and lifestyle. It also changes over your lifetime. People tend to be larks during the first 10 years of their life, then shift towards night owls during adolescence and early twenties. By the time you’re 60, you’ll probably have similar sleeping patterns as when you were 10. However, even with these changes, the factors that determine your chronotype are unique to every individual.

Peak Performance and the Body Clock

Our study recruited 56 healthy individuals and asked them to perform a series of cognitive tasks to measure reaction time and their ability to plan and process information. They were also asked to perform a physical task to measure their maximum grip strength. The tests were completed at three different times between 8 a.m. and 8 p.m. to see how an individual’s performance varied throughout the day. Our results showed peak performance differed significantly between larks and owls.

Larks performed best earlier in the day (8 a.m. in cognitive tasks and 2 p.m. in physical tasks), and were 7 percent to 8 percent better than night owls at these times. Night owls performed best at 8 p.m. in both cognitive and physical tasks. Grip strength was found to be significantly better during the evening for owls by 3.7 percent compared to larks.

Peak performance was also related to the number of hours it takes for you to perform your best after waking up. Larks performed their best in cognitive tasks immediately after waking up, and seven hours after waking up in the physical task. Night owls performed best in all tasks around 12 hours after waking up.

When it comes to elite performance, athletes are striving for minute gains where a winning margin can be narrow. For example, at the 2016 Olympics, if the last placed competitor in the men’s 100-meter sprint had run 0.25 seconds faster, he would’ve beaten Usain Bolt.

Understanding your body clock might help you determine your winning chances. (Shahjehan/ Shutterstock)

Our previous research found that being a morning lark or a night owl is a key contributor in the timing of peak individual and team athletic performance.

Our new study shows that compared to larks, night owls are significantly sleepier in the morning, making their reaction time slower by 8.4 percent. They’re also 7.4 percent weaker (using a maximum grip strength test) than their morning lark counterparts.

Night owls also seem to show a larger variation in peak performance throughout the day, suggesting they may be more sensitive to time-of-day changes than larks. For example, a night owl competing against a morning lark at 8 a.m. would be more impaired than a lark competing against a night owl at 8 p.m.

However, other things, like traveling, can also affect performance. Moving across time zones de-synchronizes our body clocks, which need a chance to adjust. People that constantly change their sleeping patterns may experience “social jetlag”, which impairs performance too.

Since athletic success depends on the smallest margins, understanding precise peak performance times could mean the difference between winning a gold medal or finishing in last place. Our study found that overall, morning larks tended to perform better earlier in the day, and night owls performed better later in the evening.

Knowing just how much our body clock affects us could be useful even in our everyday life. It can help us understand more about how we can gain maximum productivity in business or the best academic performance in school.

The typical structure of our society greatly favors larks over owls. Since our typical working day doesn’t let night owls follow their preferred sleep and wake patterns, maybe it’s time we start thinking about being more flexible.

Elise Facer-Childs is a research fellow at the University of Birmingham in the UK. This article was first published on The Conversation

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