Are you a morning lark or night owl? Here's how your body clock works

Genetics can determine your body clock type, but it's also largely influenced by schedule and lifestyle.

Whether you’re a morning person or love burning the midnight oil, we’re all controlled by so-called “body clocks.” These body clocks (which regulate your circadian rhythms) are inside almost every cell in the body and 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 realised. In fact, our body clocks actually effect 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 behaviours. For example 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 individuals differences may also be seen in multiple other physiological, behavioural 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 6pm, making them feel tired by 9pm or 10pm. For night owls, melatonin can increase at 10pm/11pm or even later, meaning many aren’t tired until 2am or 3am.

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 ten 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 ten. However, even with these lifetime 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), and a physical task to measure their maximum grip strength. The tests were completed at three different times between 8am and 8pm 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 (8am in cognitive tasks and 2pm in physical tasks), and were 7% to 8% better than night owls at these times. Night owls performed best at 8pm in both cognitive and physical tasks. Grip strength was found to be significantly better during the evening for owls by 3.7% compared to larks.

Business Standard