A circadian rhythm is a natural bodily process that happens roughly every 24-hours. It’s a cycle, like sleeping & waking, or eating & digesting, that completes & restarts daily. Our circadian rhythms are tied to the earth’s rotation and light/dark cycle, but they are also encoded in our genes.
We are naturally diurnal animals, meaning we’re awake during the day and asleep when dark. It’s how we evolved, like how mice are designed to be nocturnal mammals that sleep during the day and forage at night.
Another example of an internal process operating on a circadian rhythm is the human digestive system. Our digestive system cannot create and burn fat simultaneously, so our cells alternate according to a circadian rhythm. When we’re awake and actively taking in calories, our digestive system breaks down food and creates stored fat. When we sleep, our stored fat keeps our bodies fueled.
Going against your natural rhythms and not establishing routines can have systemic effects, like sleep disturbances and metabolic slowdowns. Poor sleep can affect hormone production as well as your ability to recover from injury and overcome inflammation.
Dr. Satchin Panda of the Salt Institute is the author of the book The Circadian Code, which discusses circadian biology in much greater detail. Dr. Panda writes about three “core rhythms” that our body aligns with.
Without artificial lighting and screens, we will typically sync with the planet’s day/night cycle: rising with the sun and sleeping when it’s dark. We’ve come a long way from those origins, but our bodies are still designed to work with an abundance of light during the day and restful sleep when it’s dark at night. If you sleep from 5 am to 2 pm every day, you may get enough sleep, but the quality of your sleep will likely not be as good.
Our bodies work best when we’re getting restful sleep every day. But even if you’re getting 7–8 hours, you may not be aligned with your body’s optimal sleep cycle.
According to Dr. Satchin Panda, our body has an 8 to 10-hour window for optimal food intake that begins when we take our first bite in the morning. Digestion of even a small bite of food takes hours, and efficiency slows dramatically once we’re outside that window. There’s a set window of time because our internal organs follow circadian rhythms to do their jobs, like processing food and liquids.
The stomach, liver, pancreas, and other key internal organs work best when our eating aligns with our circadian rhythm. Following a routine or schedule with your eating that allows your body to operate along the same patterns is more efficient for your digestion, nutrient absorption, and overall metabolism. Limiting your food intake to a specific window of time is also ideal.
Our bodies are programmed to shift into a night mode after the sun goes down. Heart rate and breathing slow, body temperature lower, and we usually go to sleep. When you’re exercising after dark, your body has to work hard to make and use all that energy and then start the recovery process late in the day. This can clash with your sleep cycle and the circadian rhythm of digestion & eating, making your recovery and fat burning less efficient.
It might seem obvious, but our bodies are made to be active while we’re awake. Physical activity during the day, in line with our sleep and digestion cycles, is a key part of a balanced, healthy lifestyle. Exercise has too many health benefits to list, but it’s most beneficial when you get your main activity done during the day, not late at night.
Light intake is one of the most important factors in sleep and circadian rhythm. The brain interprets light as a sign of when to be asleep and awake. Your circadian rhythm is designed around the sun, but the bright lights and screens of modern life can knock the body’s natural signals and rhythms out of whack. If you stare at a bright screen at midnight, your body may be tired, but your brain is getting the message that it’s time to be awake. Too much bright, artificial light after dark can make it much more difficult to sleep and establish a healthy wake/rise schedule.
Two hormones that regulate the sleep cycle are directly affected by light. Cortisol, a steroid hormone produced by your adrenal glands, helps wake us up and keep us going. Cortisol levels tend to be highest in the mornings and lowest when we’re in our deepest sleep, typically around 3–4 am. Bright artificial light can stimulate cortisol levels that keep you awake, as documented in clinical studies.
The hormone melatonin is a counterpart to cortisol. Produced by the pineal gland, melatonin helps you fall asleep and stay asleep. Your body usually starts producing melatonin in the early evening, when you’re starting to wind down and get closer to bedtime. Bright light, especially bright blue light from phones and computers, has disrupted melatonin production.
Proper sleep is crucial for health and balance, and light therapy can play a big role in your sleep cycle and your circadian rhythms. If you want to get the best of your sleep time, here are 5 tips:
Caffeine is a powerful stimulant that you should avoid beyond the early afternoon. Most people need hours to process caffeine and overcome the jolt it gives you. Try to avoid caffeinated drinks afternoon if you can, but definitely lay off the coffee and soda at night. Drinking alcohol at night can make it seem easier to fall asleep, but in reality, it’s closer to sedation. Try to have your last drink of the evening with dinner, so your body has a few hours to process it before hitting the proverbial sack.
Our body’s activity level has its own circadian rhythm. When we’re awake, we’re designed to move. Exercise, especially in the morning or early afternoon, can help you sleep better at night. Regular exercise raises your body temperature, and the cooldown period has a relaxing effect that promotes better sleep. By contrast, exercising later in the evening can make it more difficult to sleep because your body hasn’t fully recovered from activity mode.
The research is detailed: high amounts of stress throughout the day make it more difficult for our brains to relax and sleep at night. If you have a stressful day, be mindful about claiming some relaxation in the evening with meditation, reading, walking, or whatever works for you. Bottom line: prioritize your peace of mind before getting into bed.
The human body decreases in temperature while we sleep. Our heart rate and breathing slow down to help regulate this temperature drop. You can give your body a better sleep environment if your bedroom is in the 18–24 degrees range. Hot rooms make it harder to get to sleep and stay asleep. Avoid waking up in sweat by keeping your bedroom cooler. It’s better for your sleeping rhythm if you don’t wake up several times in the night because you’re hot. These small disruptions can build up and lead to larger sleep problems.
Don’t overlook the importance of light for your sleep quality. Your body and brain respond to the light you’re exposed to during the day, and some kinds of light are better than others when it comes to your sleep quality. You should absolutely try to get outside every day and take in natural sunlight. However, blue light from screens is extremely bright and can trick your brain and disrupt your sleep hormones, especially at night.
Blue light has been a big advancement for screen technology that’s made our phones and computers so powerful. But this bright, artificial light can have major negative effects on our sleep quality. Blue light is so bright that it can trick our brains and bodies into thinking it’s time to be alert and awake. Blue light from a screen has a very high color temperature. It’s even brighter than standing outside on a sunny day. If you look at your phone in bed, your brain is getting the message that it needs to be alert.
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Lack of sleep is a villain in America and Europe. Light intake is a big part of the problem. Over 65% of adults say they don’t get enough good sleep every week. Most people also don’t get nearly enough natural light for optimal health: the average American spends over 90% of their time indoors.
In addition to not getting enough natural light, people today are surrounded by artificial blue light from screens and overhead lighting. An overload of artificial blue light can cause headaches and make it harder to get to sleep and stay asleep. When we take in all that bright blue light from laptops, TVs, and phones, especially before we go to bed, our bodies get the signal that it's time to be awake, even if we're tired.
Melatonin is the naturally-occurring hormone that regulates sleep and wakefulness. Emerging research is showing that red light therapy treatments can help people produce more of their own, natural melatonin than exposure to other light sources like blue light. Red light therapy is natural light. It’s much less bright than blue light, with a lower color temperature than daytime sun, as the image above shows. Research has shown that red light doesn’t upset your sleep cycle like bright blue light. Red light therapy is showing great clinical results for people with insomnia and sleep disorders.
The light therapy is a simple, non-invasive treatment that delivers concentrated natural light to your skin and cells. Clinical research is showing that red light therapy can improve sleep quality and duration, and help people produce more of their own melatonin.
Light plays a major role in your sleep cycle. The body’s circadian clock interprets light as a sign of when to sleep and when to be awake. Artificial blue light from phones, computers, and other screens is extremely bright and can knock your circadian rhythm out of whack. Red light has the opposite effect: it’s ideal for evenings because it has a low color temperature—far lower than blue light and much closer to the natural sunset.
Red light therapy treatments are quick and simple: you just sit or stand in natural light for 5 to 15 minutes, ideally every day. This stimulates your mitochondria and gives your cells the natural light they need to make energy.
Natural light is a key ingredient for a healthy circadian rhythm and restful sleep. If you struggle to sleep, your light intake could be a big factor. Red light therapy delivers natural light like you’d get from the sun, but without UV rays, excess heat, or the need for sunny weather.
Red light therapy treatments supercharge your cells with the natural light they need to make more core ATP (adenosine triphosphate) energy. This helps your body run more efficiently, heal faster, and has shown great results for producing more natural melatonin and improving sleep disorders like insomnia.
Red light therapy treatments have shown great sleep results in a range of peer-reviewed clinical studies. One study on the sleep of pro basketball players showed that a 2-week course of red light therapy in the evening improved players’ sleep quality in the short term. Based on the results, the researchers suggested red light therapy would be a good non-invasive, drug-free solution to sleep struggles.
Kaiyan's light therapy products are registered with the FDA as class II medical devices for the treatment of pain, strain, and inflammation. While the existing clinical research has been very positive for red light therapy and sleep, keep in mind that Kaiyan's devices are not cleared with the FDA for the treatment of various sleep disorders or melatonin.
Recent research on sleep disorders among people with migraine headaches has shown that red light therapy both decreased headache frequency, and was the only treatment that improved patients’ sleep disorders.
A 2014 study on cognitive function and traumatic brain injury (TBI) recorded that participants had significantly decreased episodes of post-traumatic stress disorder (PTSD), and improved sleep.
Analyzing patients’ electrical brain activity, a 2013 sleep study concluded that red light therapy was especially effective at helping people with sleep disorders fall asleep.
When I’m indoors training under the buzz of artificial lights, my body doesn’t get the natural light it needs. Add computers, cell phones, televisions, etc. and it’s easy to overload yourself with blue light. I used to have trouble sleeping after long training days, but since adding more natural light to my routine with red light therapy, I’ve been falling asleep as soon as I lie down, and I’ve been staying asleep all night.*
Sanne Wevers
Gold-Medal Winning Dutch Gymnast
Research is showing how closely mood and sleep disorders are interconnected. Parts of the brain that regulate sleep have also been found to closely affect mood. A 2013 review concluded that “nearly all people suffering from mood disorders have significant disruptions in circadian rhythms and the sleep/wake cycle.”
This Greatist post on natural light and serotonin gives good background on the connections between natural light intake, mental health, and sleep. It also mentions using Kaiyan's red light therapy devices to get more natural light, even when you can’t get more sunlight.
Trouble sleeping is one of the most common symptoms of seasonal affective disorder, a type of depression most common in the darker winter months. Some physicians treating patients with mental health disorders have said red light therapy both improves mood, and helps people with depression get better sleep.
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Good sleep is a prerequisite for optimal performance. Given that people spend about one-third of their lives asleep, sleep has substantial development, daily functioning, and health. Perhaps no daytime behavior has been associated more closely with improved sleep than exercise. Researchers have shown that exercise serves as a positive function for sleep. Regular exercise consistently has been associated with better sleep. Moreover, the American Academy of Sleep Medicine considers physical exercise a modality of nonpharmacologic treatment for sleep disorders. When studying the influence of exercise on sleep, most investigators have compared acute and sedentary control treatments. In the study of regular moderate-intensity endurance exercise, researchers also provided compelling evidence that exercise promotes sleep.
However, exercise can negatively affect sleep quality. Exercising immediately before going to sleep is detrimental to sleep quality. Athletes train very hard to improve their on-field performances, but excessive training may decrease performance, known as overtraining syndrome. Researchers have shown that symptoms of overtraining indicate poor-quality sleep. Good sleep is an important recovery method for the prevention and treatment of overtraining in sports practice.
In a recent study in which red-light therapy (wavelength = 670 nm, light dose = 4 J/cm2) was used, researchers indicated that red light could restore glutathione redox balance upon toxicologic insult enhance both cytochrome c oxidase and energy production, all of which may be affected by melatonin. Melatonin is a neurohormone that is produced by the pineal gland and regulates sleep and circadian functions. No one knows whether sleep is regulated by melatonin after red-light irradiation in athletes. Researchers have demonstrated that phototherapy improves muscle regeneration after exercise. A red light could protect human erythrocytes in preserved diluted whole blood from the damage caused by experimental artificial heart-lung machines.
Twenty female athletes of the Chinese People’s Liberation Army team (age = 18.60 ± 3.60 years) participated in the study. All participants were healthy and were not using medications regularly or temporarily during the measurements. Athletes were excluded if they had participated in less than 80% of the scheduled team physical training and basketball sessions for the last 3 months or used any nutritional supplements or pharmacologic agents. All participants provided written informed consent, and the Ethical Committee approved the China Institute of Sport Science study.
Participants were assigned randomly to either a red-light therapy intervention group (n = 10) or non–red-light therapy intervention group (placebo group, n = 10). Measurements were collected at preintervention (baseline) and postintervention (14 days). The exercise training schedule of the 2 groups was unchanged during the 14 days; the red-light treatment group used a red-light therapy instrument every night for total body irradiation for 30 minutes. The training routine of the athletes during the 14 intervention days included 12 exercise sessions with the following specifications: 2 hours of morning training, 2 hours of afternoon training, and no training on Sunday.
The red-light treatment participants lay in the supine position. Continuous illumination was performed using noncoherent red light from a whole-body red-light treatment machine-like Kaiyan’s red light therapy bed, with an average wavelength of 658 nm and a light dose of 30 J/cm2. The whole body received the phototherapy treatment. The placebo participants also lay in the supine position under the red-light device but did not receive any light illumination. All participants wore swimsuits to enhance irradiation from the device and were blind to the treatment.
The Chinese version of the PSQI measured sleep quality. The 19-item measure assesses sleep quality and disturbances over a half-month time interval. The total PSQI score ranges from 0 to 21, and higher scores reflect poorer-quality sleep. The 7 items of this instrument measure several aspects of insomnia: difficulties with onset and maintenance of sleep, satisfaction with the current sleep pattern, interference with daily functioning, noticeable impairment attributed to sleep problems, degree of distress, and concern caused by any sleeping problems.
Participants were instructed to complete as many laps as possible on a 400-m outdoor track during the 12-minute test period. Emphasis was placed on pacing oneself throughout the test. The test administrators counted the laps completed during the 12-minute test period while calling out the time elapsed at 3, 6, and 9 minutes and orally encouraging the participants. At the end of the 12-minute period, the test administrator instructed the participants to stop and used a measuring wheel to determine the fraction of the last lap completed by each participant. This distance was added to the distance determined by the number of laps completed to give the total distance covered during the test.
In humans, the serum level of melatonin, derived mainly from the pineal gland, demonstrates a clear increase at night and a decrease during the day. Given that the masking effects of activities (e.g., exercise, sleep, and food intake) have little effect on the circulating melatonin level's daily pattern, melatonin secretion appears to directly reflect the function of the biological clock as a specific marker of the circadian rhythm.
The study has demonstrated that red-light illumination positively affected sleep quality and endurance performance variables in Chinese female basketball players. Based on previous studies, we can infer that red-light treatment contributes to increased melatonin secretion in the pineal gland and muscle regeneration. Although more studies involving phototherapy, sleep, and exercise performance need to be performed, red-light treatment is a possible nonpharmacologic and noninvasive therapy to prevent sleep disorders after training.
This research project was supported by the National Key Technologies R&D Program Fund of China (2006BAK37B06).
Originally from:
Red Light and the Sleep Quality and Endurance Performance of Chinese Female Basketball Players
Jiexiu Zhao, Ye Tian, Jinlei Nie, Jincheng Xu, Dongsen Liu
J Athl Train. 2012 Nov-Dec; 47(6): 673–678. doi: 10.4085/1062-6050-47.6.08
PMCID: PMC3499892
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Sleep is big business these days — one in three people are believed to experience sleep deprivation — and everyone is keen to rely on the latest fashionable theory.
For years, sleep cycles were divided into two categories. People who enjoy mornings were known as “early birds.” And those of us who prefer staying up late were labeled “night owls.”
Well, step-aside birds. Mammals are the new name of the game. That’s right; scientists now believe there are four ways to classify sleep/wake cycles. In the science world, these classifications are known as chronotypes.
Chronotypes describe the periods when your body wants to sleep and when it wants to be awake. And to make it easier, the chronotype categories are named after animals. Our natural sleep tendencies are now categorized as bear, wolf, lion, and dolphin.
It is crucial to understand your animal chronotype. Once you do, you can start to schedule your life around your body’s natural cycles. Kaiyan Medical suggests that this may help you sleep better and feel more productive at work.
People have different circadian rhythms. That’s just a fact of life.
Science shows that:
“The human circadian system actively synchronizes to the 24-h day via environmental signals of light and darkness.”
Circadian? A 24-hour cycle. It’s your body clock. Sleep psychologists reckon they can determine our natural sleeping patterns. By understanding our own, we can have a happier, more productive life.
Now, Chronotype is a term that describes a person’s natural rhythm. And it doesn’t only relate to sleep. Chronotypes influence all primal instincts.
Author Michael Breus, Ph.D., recently suggested that there are 4 natural chronotypes. And he named these after 4 animals that follow similar sleep/wake patterns. So, say goodbye to night owls and early birds. Wolves, lions, bears, and dolphins are the new circadian rhythm mascots.
Check out the chronotypes below and let us know in the comment section which one sounds like you!
Alright, night owls, this is your group. Just like these nocturnal creatures, you are most alert at night. Wolves tend to stay up later and struggle with waking up early.
Only about 15% of the population falls into this group. Wolves are more productive in the later afternoon and evening.
Sleep experts recommend that wolves set their alarm for 7 a.m. (snooze for 30 minutes) and go to sleep by midnight.
Lions are the new early birds. Like these wild cats, you are most alert in the morning. You have no trouble waking up and getting to work. But, lions tend to feel the afternoon slump. And by the evening, they feel drained.
About 15% of the population identifies as a lion. Sleep experts recommend that lions wake up around 5:30 a.m. and go to sleep by 10:30 p.m.
No, you don’t need to hibernate. But, like these diurnal (awake during the day, asleep at night) creatures, you follow the solar cycle. Bears generally feel awake during the day and need 8-hours of solid sleep at night.
About 50% of the population falls into this category. This group is productive in the morning and struggles with the mid-afternoon slump. Sleep experts recommend that bears wake up around 7 a.m. and go to sleep by 11 p.m.
Dolphins “only sleep with half of their brain at a time?” Sound familiar? Well, this is the insomniac (often self-diagnosed) group. You might be anxious and have trouble turning your brain off at night. Dolphins usually don’t get a complete night’s sleep.
About 10% of the population falls in this category. And even though they wake-up tired, dolphins are most productive by mid-morning.
Sleep experts recommend that dolphins get up around 6 a.m. and try to sleep around midnight.
Who doesn’t want a better night’s sleep and a more productive day? Start scheduling your days based on your chronotypes! Once you know more about your chronotype, you can form sleep patterns that work with (not against!) your body’s natural rhythms.
So what are you waiting for? Here in Kaiyan, we are embracing our inner animals and start following our optimal sleep schedule.
www.ncbi.nlm.nih.gov/pmc/articles/PMC5479630/
Bellis, Rich. "How To Design Your Ideal Workday Based On Your Sleep Habits." Fast Company, 26 Nov. 2017,
Levi, Anthea. "This Is the Best Time of Day to Do Everything, According to Your Chronotype." Health.com, 31 Oct. 2016
