Circadian Rhythms and Exercise

WHAT ARE CIRCADIAN RHYTHMS?

At its core, a circadian rhythm is an internal biological clock that regulates numerous physiological and behavioural processes on a 24-hour cycle. This clock is primarily controlled by the suprachiasmatic nucleus (SCN) in the brain, which receives signals from the eyes and other sensory organs to synchronise with light and darkness cues in the environment.

In simpler terms, our bodies have an internal clock that tells us when to sleep, eat, and wake up. This clock is influenced by the natural light and darkness cycles of the world around us, and helps us to maintain a healthy and regular schedule.

THE BIOLOGICAL CLOCK AND ITS IMPACT ON HEALTH

Many vital processes in the body, including hormone release, sleep-wake cycles, and digestion, are influenced by the body’s circadian rhythm. When this rhythm is disrupted, it can have serious consequences for our health. For example, people who work night shifts or irregular hours may be more likely to experience sleep disturbances, which can lead to fatigue and irritability.

Studies have also linked disruptions to the circadian clock with a range of health problems, including obesity, diabetes, cardiovascular disease, and even some types of cancer^[1]. This is because the body’s natural rhythms help to regulate important processes like metabolism and hormone production, and when these rhythms are disrupted, it can have a negative impact on our overall health and wellbeing.

HOW EXERCISE INFLUENCES CIRCADIAN RHYTHMS

Regular exercise can have a positive impact on our circadian rhythms and overall health. When we exercise, our body temperature and energy levels increase, signalling to the brain that it’s time to be awake and alert. Exercise also helps regulate our sleep-wake cycle, especially when paired with a consistent sleep schedule.

Studies have shown that regular exercise can improve the timing and strength of our circadian rhythms^[2], leading to better sleep quality, more consistent energy levels throughout the day, and even improved cognitive function. Exercise has also been linked to lower rates of depression and anxiety, which are often associated with disruptions to circadian rhythms.

In addition to these benefits, exercise can also improve our overall physical health. Regular exercise has been shown to reduce the risk of chronic diseases such as heart disease, diabetes, and obesity. It can also improve our immune system function, making it easier for our bodies to fight off infections and illnesses.

THE ROLE OF EXERCISE IN SLEEP REGULATION

One of the most important ways that exercise can support our circadian rhythms is by improving our sleep quality and duration. Regular aerobic exercise has been shown to reduce the time it takes to fall asleep, increase deep sleep, and decrease the frequency of wakeful periods during the night^[3]. This is particularly true when exercise is done earlier in the day, allowing the body to gradually wind down and prepare for sleep in the evening.

In addition to aerobic exercise, other forms of physical activity such as yoga and stretching can also have a positive impact on our sleep quality. These activities can help reduce stress and promote relaxation, making it easier for us to fall asleep and stay asleep throughout the night.

It is important to note that while exercise can have many benefits for our circadian rhythms and overall health, it is also important to listen to our bodies and not overdo it. Over-exercising can lead to fatigue, injuries, and disruptions to our sleep-wake cycle.

OPTIMAL EXERCISE TIMING FOR CIRCADIAN RHYTHMS

MORNING EXERCISE

For many people, exercising in the morning can be an effective way to align their circadian rhythms with their daily routine. Morning exercise has been linked to improved sleep quality, more consistent energy levels throughout the day, and even better appetite regulation^[4]. Additionally, morning exercise can help establish a consistent exercise routine, which is essential for maintaining long-term health.

AFTERNOON AND EVENING EXERCISE

While morning exercise is often recommended for its potential circadian health benefits, afternoon and evening exercise can also be effective for different reasons. For example, exercising after work can help release stress and tension from the day, making it easier to relax and fall asleep. However, for some people, late-night exercise can interfere with sleep quality and make it harder to wind down before bed.

INDIVIDUAL DIFFERENCES IN EXERCISE TIMING PREFERENCES

Ultimately, the optimal exercise timing for your circadian rhythms may depend on personal factors such as your chronotype (whether you’re a morning or evening person), work schedule, and lifestyle habits. Experimenting with different timing strategies and paying attention to how your body responds can help you identify the optimal exercise routine for your needs.

THE IMPACT OF CIRCADIAN RHYTHMS ON ATHLETIC PERFORMANCE

When it comes to athletic performance, circadian rhythms play an important role in determining when our body is primed for peak physical activity. Studies have found that overall performance tends to be highest in the late afternoon and early evening, when body temperature, reaction time, and strength have all reached optimum levels^[5].

However, it is important to note that this peak performance window may vary depending on the individual. Some people may find that they perform better in the morning, while others may find that they peak in the late evening. This is due to a variation in each person’s circadian rhythm, which is influenced by factors such as genetics, age, and lifestyle.

Despite these variations, studies have consistently shown that athletes who train and compete at the same time of day tend to perform better than those who do not. This is because the body becomes accustomed to the demands of physical activity at a particular time, allowing it to prepare more efficiently for peak performance.

STRATEGIES FOR OPTIMISING PERFORMANCE BASED ON CIRCADIAN RHYTHMS

While individual variations in circadian rhythms and performance preferences may impact these recommendations, athletes can use certain strategies to align their bodies with their optimal performance window.

One such strategy is to adjust training schedules to match the time of day when peak performance is typically achieved. For example, an athlete who performs best in the late afternoon may choose to schedule their most intense training sessions during this time.

Another strategy is to modify pre-competition meals and sleep routines in order to optimise performance. Research has shown that eating a meal high in carbohydrates a few hours before competition can help improve endurance and delay the onset of fatigue.

Additionally, getting adequate sleep is crucial for maintaining peak physical performance, and athletes may need to adjust their sleep schedules in order to align with their optimal performance window.

Finally, using light exposure to regulate internal clocks can also help athletes optimise their performance. Exposure to bright light in the morning can help reset the body’s circadian rhythm, making it easier to fall asleep at night and wake up feeling refreshed in the morning. Similarly, avoiding bright light in the evening can help prepare the body for restful sleep.

As our understanding of the importance of circadian rhythms continues to grow, it’s becoming clearer that exercise plays a vital role in supporting these internal clocks and promoting overall health and wellbeing. By understanding how exercise timing and strategies can affect our circadian rhythms, we can develop more effective and sustainable exercise routines that maximise both physical and mental performance.