Remember those days of staying up well past midnight in college? Weekend or weekdays, hanging with friends or no friends, we all may think in our thirties and forties, how did we do that? The answer lies in tiny molecular clocks present in every tissue of the body that synchronizes with the master clock of the brain and the environment.As we develop, the ticking of our master clock changes. During puberty, it is slower encouraging us to go to bed late and sleep in. During adulthood, it gets progressively faster and faster. The timing of these clocks is ultimately linked to and describes a chronotype.
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What Are Chronotypes?
A chronotype is a pre-determined sleep-wake schedule programmed by one’s genetic blueprint. The molecular clocks of every individual on this planet “tick” at a certain speed. One of the primary genetic drivers of speed is called PER2. Individuals that have naturally occurring genetic mutations of PER2 called single nucleotide polymorphisms (SNPs) result in people you know as “larks” or “owls”.
Although we still require 7 - 8 hours of restorative sleep every night, some have a natural preference to go to bed no earlier than midnight and wake up long after the sun has risen. Someone who is a lark prefers to be in bed well before 9 PM and will wake up well before the sun has risen. Someone who is neither like most of the general population will naturally fall asleep around 11 PM and wake up around the time the sun is rising.
Chronotypes can also predict the time of the day in which you reach peak performance. For some, they may peak physically and cognitively in the late morning and late evening. Someone who is a lark, however, would peak physically and cognitively in the very early morning, have a second wind in the late afternoon, and would be tapped out after dinner. In the world of fitness and athletics, not one chronotype is better than another.
There are genetic trade-offs. For example, my research has shown that the sport of endurance ultra-running can often pre-select larks (Brager et al. 2019) but we also recently reported in a book chapter (in press) that weightlifting may pre-select for vampires. We will discuss more of these “trade-offs” in the form of benefits in a bit.
Are Chronotypes Universal?
Chronotypes are universal. One of the founding fathers of the field of circadian biology used the term “mammalian bottleneck” to describe how chronotypes have evolved in Mother Nature. In general, a mammal regarded as prey will have the opposite chronotype of its predator.
This was first demonstrated in the 1980s when the biological clock of ground squirrels was disrupted. With a disrupted biological clock, the squirrels could no longer maintain their normal sleep-wake schedule. The squirrels would breach the surface of their underground hiding spot at night instead of during the daytime. This ultimately made the squirrels more susceptible to being eaten by predators.
Certainly, the chronotypes we as humans are born with aren’t a matter of “life or death.” But these chronotypes can certainly help determine when we should work, shouldn’t work, train, and not train, eat, and not eat, and of course, recover through sleep. Many organizations including the military are starting to embrace these inter-individual differences in chronotype understanding that not everyone can perform at their best at all hours of the day.
5 Ways to Use Your Chronotype to yOur Advantage
As I alluded to, here are five wellness and fitness-related ways to best utilize your chronotype
1. Plan Your Peak Training Sessions Around Your Chronotype. My research and the research of my colleagues have shown that certain fitness attributes peak at different times of the day. People are more likely to have peak endurance workouts in the morning and peak lifting workouts in the evening. The performance is supported by our biology, particularly for rhythms of cortisol and norepinephrine. See also sleep and exercise connections for more context.
2. Plan Your Eating Schedule Around Your Chronotype. Mistimed meals can contribute to weight gain or an inability to build lean muscle mass as well as lose weight. Therefore, once you know your chronotype, plan your meals accordingly. Although the bedtime of a lark and vampire will vary, both should not eat too close to bedtime. Doing so may spike blood glucose levels making it difficult to achieve the most restorative sleep.
3. Plan Your Sleep Schedule Around Your Chronotype. Similar to meals, your bedtime should be regimented. Develop a strong bedtime routine at least ninety minutes before bed and make sure it accounts for a minimum of seven hours of sleep penciled around your daily activities.
4. Don’t Disrupt your Chronotype on the Weekends. One reason for the case of Mondays is that people will often stay up too late past their usual bedtime on Friday and Saturday. For a vampire, this is fine except that early morning awakening on Monday is a bear. For a lark, a later bedtime on the weekend may make falling asleep Sunday night very difficult. Remember, our biological clocks crave routine so let them.
5. When Necessary, Use Blue Light. Blue Light is a powerful stimulus for wakefulness. Although blue light should be avoided at night to avoid disrupted sleep, blue light in the morning after waking can help a vampire better power through the early morning.
How to Find Your Chronotype
The biggest question is how to find your chronotype. There are a few clinically validated questionnaires free for use and download developed over the years. The gold standard is the Morning-Eveningness Questionnaire. The questionnaire takes 20 minutes to complete but it can be life changing.
I have often given this questionnaire to athletes I’ve worked with over the years. Many have found it tremendously helpful for improving their athletic performance and sleep. Regardless of your wellness goals, this questionnaire is a great tool to assess your baseline and adopt the strategies above. Check it out today!