The natural ebbs and flows of our biology can inform us how to maximize energy, mood, and performance each day. Trying to tightly manage energy or pushing too hard through fatigue can backfire – leading to de-conditioning, more fatigue, and more pain, on the one hand, or overwork, illness, and burnout, on the other. Think of energy as something to allow or make way for, with support for our biological cycles in place.
Understanding daytime (diurnal) rhythms
When we wake, body temperature begins to increase several degrees from early morning temperature lows. The brain starts to warm up and synchronizes its daytime versus nighttime patterns 
using zeitgebers -- cues from our environment, such as sunlight, that the body uses to engage in a physio-logical process, such as waking up or changes in body temperature. The typical pattern is twenty-four hours, more or less, following the rising and setting of the sun. But this is hardly the only system cycling in a twenty-four hour rhythm. Upon waking, blood pressure rises and platelet coagulation increases. The hormone cortisol releases from the adrenal glands to help increase alertness. Typically, humans feel more awake within thirty minutes of waking (unlike cats who wake quickly from a “cat nap”). Many of us then reach for a cup of coffee -- the world’s most utilized performance enhancer. The digestive system, including the liver and pancreas, are also on the clock preparing us to break the fast of slumber. Even adipose tissue, or body fat, keeps time using leptin and ghrelin -- the hormones that help regulate food intake and satiability. Ghrelin triggers a preparation of gastric acids that prepare the stomach for food. Meanwhile, muscle cells oscillate along with every other organ and almost every single cell. Russel Foster and Leon Kreitzman who study circadian neuroscience at Oxford University describe these rhythmic biological processes in the following way:
For cells to function properly they need the right materials in the right place at the right time. Thousands of genes need to be switched on and off in order and in harmony. Proteins, enzymes, fats, carbohydrates, hormones, nucleic acids and other compounds have to be absorbed, broken down, metabolized, and produced in a precise time window. Energy has to be obtained and then partitioned across the cellular economy and allocated to growth, reproduction, metabolism, locomotion, and cellular repair. All of these processes, and many others, take energy and all have to be timed to best effect by the millisecond, second, minute, day and time of year. Without this internal temporal compartmentalization and its synchronization to the external environment our biology would be in chaos.3
Indeed at times it feels just like that – chaos – or at least out of synch with nature. Daytime fatigue can feel unpredictable and unmanageable.
When our biological rhythms have become synchronized to work together, the general daily pattern of energy, mood and productivity is fairly predictable. It increases throughout the morning hours peaking around lunchtime. This peak is followed by a downhill turn, the infamous dip of mood, focus, and vigilance in the afternoon (possibly leading to another cup of coffee). The afternoon slump is followed by a recovery in the evening hours with increased mood and productivity returning to slightly lower levels than the mid-day peak. This is a normal ebb and flow of our circadian cycle during the day.
Energy, mood, and productivity are affected by many zeitgebers and fluctuate according to temporal landmarks: the timing and amount of light our eyes receive; the amount, type and timing of food; and when and how much we move our bodies. These behaviors and many others directly and immediately affect hormones, proteins, the brain and every other organ. These systems have memory and help our systems anticipate what will happen at the same time tomorrow. Disruption of these habits can lead to an un-pairing of the sleep-wake cycle from other cycles (e.g., digestion) and strains the boundaries of human capacity to keep it all synchronized and functioning at their best. Circadian clock disruption can affect many aspects of wellness including blood sugar, weight gain, blood pressure, liver function, mental health, and the chance of engaging in high-risk behaviors such as smoking. Circadian rhythm disruption has been shown to increase tumor growth rate and has recently been classified by the World Health Organization as potentially carcinogenic.3, 4, 5
Dr. Till Roenneberg6 at Ludwig-Maximilians University in Munich, Germany, has studied hundreds of thousands of people (fruit flies and mice too) and their circadian rhythms across countries, time zones, stages of life, genders, and jobs. Performance has been measured in a variety of settings and people including school-aged students, investors, and healthcare providers respectively measuring grades, risk taking, and medical procedures. The human diurnal pattern is fairly predictable with executive brain function improving in the morning whether it be elementary math skills or large investment decisions. Outcomes of colonoscopies and surgeries are significantly better in the morning hours compared to the afternoon.7 A health care worker is 38% more likely to wash her or his hands in the morning in between tasks that would require sanitation than during the afternoon slump.8
But all is not lost in the afternoon. While reasoning and judgment are better in the morning, creativity and openness to new ideas flourish in the afternoon.6, 9 Research participants are more likely to solve problems that require out-of-the-box thinking in the afternoon. Some physical tasks are better performed in the evening as well -- or at least some aspects of them. Badminton serves are more accurate in the afternoon, yet tennis serves are more accurate in the morning (although slower), while soccer dribbling speeds are faster in the evening. Stanford Sleep Disorders Clinic found west coast NFL teams beat their east coast opponents 64 % of the time during Monday night games when played at home. They suggest that home field advantage may have something to do with time zone changes as west coast players are active closer to their peak performing time than east coast players at a west coast game.10 Similar results have been found for race horses, honey production by bees, and many other types of physical performance.3
How do these cycles become desynchronized?
Working swing or night shifts
Time change (daylight saving)
Traveling to different time zones (traveling West is easier than traveling East)
Depression, anxiety
Grief
Chronic daily stress
Illness or injury
24/7 access to light, food, work, travel and socializing
Sitting (the new smoking)
Traveling to and from different time zones, working swing shift and night work schedules can disrupt these rhythms. Depression, loss, and stress can disrupt one or more system and impact sleep, mood, and mental focus. Following trauma or chronic stress, cortisol can lose its healthy diurnal pattern of being higher in the morning and tapering before bedtime. Chronic stress, trauma, and depression can lead to higher than optimal levels of cortisol at rest, yet having a substandard response to stressors when more cortisol is required. This overactive yet underperforming hormonal pattern can increase daytime fatigue, leave you feeling exhausted after activity or stress, but still unable to sleep well at night.11, 12 This is especially true for stress that is considered a “social threat,” a situation where we are subject to negative evaluation by others.13
We also have to consider our modern 24/7 life. Time as we know it with the precision of 60 seconds in a minute and 60 minutes in an hour is a relatively modern invention with the first electricclockmade in the 1800s. Television, computer, and personal phones are even newer to our daily and nightly lives. Another challenge of modern life is 24-hour access to an energy source (food) that can contribute to disrupting our digestive patterns when we eat late at night or skip breakfast. This was discovered studying nocturnal mice that were given access to high fat foods all day (their night). This profoundly disrupted their sleep.6 Nearly all living things are subject to the light and dark cycle of the sun, yet we follow a natural pattern with sunrise and sunset less so than in the past with 24/7 access to light, food, activity, socializing, and substances.
Should we all be on identical schedules?
In a word, no. Although the 24-hour day is what we need to live by on this planet, not everyone fits perfectly into this rhythm. Some people are born with slightly longer or shorter clocks even though the majority of people are in the middle. According to Roenneberg and other researchers, this trait is genetic. The term used for this is chronotype with each human falling on the bell curve with two thirds of us landing in the middle. Like height or personality traits, we all fall somewhere on the continuum. Those of us on a faster clock tend to need to go to bed earlier and wake more easily in the morning (larks) compared to our night owl counterparts. Night owls feel more awake at night and have a difficult time waking up early. Knowing what chronotype you are may be helpful to understanding your natural cycle better. If your schedule requires you to be out of synch with your natural chronotype, the following are things you can do to entrain, or adopt, the desired 24-hour pattern.
10 ways to entrain your biological rhythms
Take breaks
Time important tasks for earlier in the day
Increase natural light exposure
Reduce screen time
Move more
Eat regular meals and time your caffeine
Wake at the same time every day and get out of bed
Practice low and slow breathing
Have fun and find meaning in your work
Express emotions in a healthy way
How to entrain your biological rhythms.
Strengthening zeitgebers (cues from our environment) during the day can improve nighttime sleep and also daytime energy, mood and performance. We can curb our chronotype -- whether fast or slow – thus modifying individual genetic propensity by what we do, how we do it, and when we do it.
Take Breaks
Breaks can restore focus and thus productivity to normal levels despite natural ebbs and flows. A break could be beneficial before or at the time of an expected dip, such as mid-afternoon, in order to restore mental focus. Regular short breaks can be scheduled every hour just as many secondary education classes have a 10-minute break every 50 minutes of lecture.
What you do during the break does matter. Going from your computer to phone will do little for restoring brain function. Completely and quite literally unplugging from work is ideal and maximize the break time by including these three elements: change of scenery to include nature, movement, and socializing.9, 14 If you cannot have all of them, go for one or two. Look for green spaces with plants and trees or at least where you can see the sky. If you cannot get away for a quick walk, stop and say hello to a colleague. Don’t feel like chatting? Walk up and down the stairwell listening to your favorite music.
Time important tasks
Timing tasks that match our peak and dip performance can enhance the outcome of that task. Since critical thinking and focus are rising throughout the morning and peaking right around lunchtime, prioritize tasks in a similar manner. Do the tasks that need the most serious executive skills in the morning leaving more mundane, creative thinking, or physical tasks for the afternoon.
If you cannot change the timing of your work tasks, improve your focus-muscles any time of day by doing one task at a time rather than attempting to multi-task. Make each task as pleasant as possible: drive mindfully listening to relaxing music, gently guide your focus to listening during a meeting, tasting each bite you are chewing, or feel the warm water of the dishes. Observe how you hold your body and the pattern of your breathing during mundane tasks and make small adjustments as needed.
Increase natural light exposure
Working indoors is a relatively new phenomenon for humans and it limits our exposure to natural sunlight. Natural light has the full spectrum of colors to affect our rhythms in a way that artificial light cannot. Its power to impact the genetic code is more influential than social cues and cultural norms. Increasing daytime light will enhance the zeitgebers that assist sleep, mood, and attention as it helps the brain and body distinguish daytime from nighttime. It is beneficial even on a cloudy day as it still more than 10,000 Lux -- about ten times the amount of natural light of a well-lit room. There are full spectrum lights for light therapy on the market that may be around 10,000 Lux and especially helpful during darker months.
Start by increasing natural light by ten minutes per day and move towards two hours of daylight every day. (This latter amount is approximately the amount of natural light needed to advance chronotype by one hour). Sit by a window, take micro-breaks by looking outside or take a brisk 2-minute walk outside several times per day.6
Limit screen time
The fact that our society has moved indoors for most of the day has not only reduced natural light exposure, but has increased the use of the internet, video games and cell phones. The compelling nature of these technologies has given rise to their related behavioral addictions. Depression, anxiety and substance abuse frequently accompany such behaviors and less time is spent exercising, relaxing, and socializing face-to-face. Although the exact statistics about how many times people check their phones are difficult to pin down, people report lower stress levels when limiting the checking of emails to three times per day. Adrenaline and dopamine both play role in repetitive phenomenon feeding fear and also our drive for novel stimulation.15
Consider the amount of time you sit, plugged in to a device and evaluate it fairly. If you must use a computer for work, try to reduce leisure time on screens. If you insist on using screens for leisure, be sure to take breaks as described above. Address the quality of what you listen to, what you watch, what you ‘like,’ and what you share. Seek professional help if you are unable to cut back on your own.
Move more
Daytime is when you want to feel awake -- so daytime is the best time to be physically active. Specific types of training at specific times of day apply to professional athletes, but for the rest of us, exercise is best at any time of the day that we can fit it in. Any exercise beats nothing. Muscle movements are fueled by adenosine triphosphate (ATP), a nucleotide that holds energy; however, ATP is not stored in the cells for more than a moment or two. The real production of ATP begins within about 2 minutes of exercise, which leads to more energy.
Gradually increase physical activity during the time of day you would like to have more energy. Moving the body increases energy and also helps you sleep more deeply as mental fatigue is often not enough. Walk somewhere you would normally drive; plant something that needs attention regularly; or go for a brisk walk during the afternoon slump. (That is unless you work outside, in which case a power nap may be better). Walking, jogging, jumping rope, swimming, hitting a ball, yoga and tai chi offer rhythmic movements that the body enjoys. They can help to build endurance over-time, strengthen the immune system, all the while combating de-conditioning.
Eat regular meals and time your caffeine
Regular meals help prompt your digestive rhythms that are chemical and also mechanical --contracting and relaxing to move food through. Eat something for breakfast even if you are not hungry, and have a decent lunch and a small dinner. Avoid eating several hours before bed unless you would like to be awake to use that energy. Have set times to eat and give your digestive system a break in between (i.e., avoid snacking all day). Sugars and many sugar substitutes, even if they are “calorie free”, are fatigue-inducing -- as is overeating at any meal.16
Keep coffee use to the morning hours (with one exception noted below) and wait thirty minutes after you wake before having morning coffee to allow your natural cortisol to kick in. While writing When: The Scientific Secrets of Perfect Timing, Daniel Pink says against his common sense he was converted to the practice of a “nappacino,” a coffee-then-20-minute-nap to increase productivity as the caffeine kicks in while you are power napping.9 Power naps are in fashion, if they can be taken on a regular basis, not too close to bedtime and not for more than 20 minutes.
Sleep on it and wake up the same time every day
Since our executive brain functions better in the morning, hold off on major decisions or even important emails late at night or even in the afternoon. “Sleep on it” is still good advice. Respond once your mind is refreshed.
Wake up the same time every day. Avoid sleeping-in past your regular waking time and don’t try to catch up on any missed sleep. This is one key anchor in the 24-hour cycle and is more in our personal control than falling asleep. If you find that you wake up earlier than you want to, try going to bed later the following night. Do not hit the snooze button in the morning as dozing increases shallow sleep and increases fatigue. You might think the few extra minutes are helping to prep you for the day, but the shallow, dozing sleep makes you feel foggier and desynchronizes circadian rhythms the following night.
Practice low and slow breathing
Breathing is a rhythm, expanding and contracting every few seconds, and alters itself based on our emotional, mental and physical states. It can be observed and changed at any given moment. Observe your breathing for patterns of either holding, shallow chest breathing, or over-breathing. Inefficient breathing rhythms can result from anxiety, depression, health problems, bad habits, time pressure, and many other reasons. Such breathing rhythms can also making these problems worse. The rate of approximately 6 breaths per minute is ideal for someone at rest as this synchronizes with cardiac rhythms and enhances heart rate variability and blood flow, relaxes muscles, and reduces sweating -- all measures of how balanced the nervous system is. Observe yawns and sighs as they can be signs that you have been holding or shallow breathing that can be signs you are tired or stressed. Take a break to breathe and increase oxygen flow to your brain and muscles. Avoid forcing the breath. Return to low, slow abdominal breathing, allowing a soft, relaxed exhale and gentle, natural inhale.17
Have fun and find meaning
Pink9 recommends finding your “syncher’s high” by involving yourself in other rhythmic activities such as singing in a choir or playing a musical instrument, running, rowing, dancing, cooking, yoga, or even joining a flash mob. Improvisational comedy groups are popping up more than ever before, setting the stage for on-the-spot fun and necessary timing with others. Dance if you can, chair dance, or, at the very least, tap your finger along to your favorite tune. Enjoyable activities are required.
Finding meaning in your work may be more of a challenge, but finding meaning in any given task or portion of a task may be more realistic. Notice with each task how you are engaged and participating in life and likely working to support those you love in some way -- even if that person is yourself.
Express your emotions
Unexpressed emotions often reveal themselves physically with increased pain and fatigue. One example is demonstrated in people with inflammatory bowel disease who tend to have more severe relapses if they are introverted or have difficulty finding ways to express what they are feeling.18 It can be difficult to get in touch with deep feelings of sadness or fear and even more challenging to communicate them to others. Few people have exactly the right words at the right moment, but don’t be afraid to circle back to clarify or express what you really meant to say after you have had time to think about it. Public or private apologies are important and meaningful when they are appropriate and sincere.19 According to Dr. Luskin’s work in the Stanford Forgiveness Project, forgiveness is a skill that can be learned. After fully acknowledging and accepting the emotional pain of any given hurtful situation, forgiveness can reduce our anger and stress, and improve our health.20
References
1. While feeling tired every day, all day, is common with chronic pain, it may also be a symptom of other health problems, including depression. It is important to seek professional help to determine the nature of your fatigue. This article focuses solely on fatigue that is common with benign, chronic pain conditions.
2. Snekkevik, H., Eriksen, H., Tangen, T., Chalder, T., & Reme, S. (2014). Fatigue and depression in sick-listed chronic low back pain patients. Pain Medicine, 15(7):1163-1170. doi: 10.1111/pme.12435.
3. Foster, R. & Kreitzman, L. (2017). Circadian rhythms: A very short introduction. New York: Oxford University Press. Extended quote used by permission of Oxford University Press.
4. Arendt. J. (2010). Shift work: Coping with the biological clock. Occupational Medicine, 60, 10-20.
5. Bhatti, P. Mirick, D. K., & Davis, S. (2012). Invited commentary: Shift work and cancer. American Journal of Epidemiology, 176, 760-763.
6. Roenneberg, T. (2012). Internal time: Chronotypes, social jet lag, and why you’re so tired. New York: Harvard University Press.
7. Sanaka, M., Mullen, K., Ferguson, D., Thomas, C., & McCullough, A. (2006). Afternoon colonoscopies have higher failure rates than morning colonoscopies. American Journal of Gastroenterology, 101(12):2726-2730.
8. Dai, H., Milkman, K., Hofmann, D., & Staats, B. (2015). The impact of time at work and time off from work on rule compliance: The case of hand hygiene in health care. Journal of Applied Psychology, 100(3): 846-862.
9. Pink, D. (2018). When: The scientific secrets of perfect timing. New York: Riverhead Books.
10. Smith, R., Guilleminault, C., & Efron, B. (1997). Sports, sleep, and circadian rhythms: Circadian rhythms and enhanced athletic performance in the National Football League. Sleep, 20(5), 362-365.
11. Burke, H., Davis, M, Otte, C., & Mohr, D. (2005). Depression and cortisol responses to psychological stress: A meta-analysis. Psychoneuroendocrinology, 30(9):846-856.
12. Kemeny, M. (2003). The psychobiology of stress. Current Directions in Psychological Science, 12(4): 124-129.
13. Dickerson, S. & Kemeny, M. (2004). Acute stressors and cortisol responses: A theoretical integration and synthesis of laboratory research. Psychological Bulletin, 130(3): 355-391.
14. Kuo, M., Browning, M., & Penner, M. (2018). Do lessons in nature boost subsequent classroom engagement? Refueling students in flight. Frontiers in Psychology, 8, 2253 doi.org/10.3389/fpsyg.2017.02253
15. Moretta, T. & Buodo, G. (2018). Autonomic stress reactivity and craving in individuals with problematic internet use. PLoS One, 13(1). doi: 10.1371/journal.pone.0190951.
16. Swithers, S. (2013). Artificial sweeteners produce the counterintuitive effect of inducing metabolic derangements. Trends in Endocrinology and Metabolism, 24(9): 431-441.
17. Khazan, I.(2018). Breathing, overbreathing, and mindfulness. Biofeedback, 46(1): 2-8. doi.org/10.5298/1081-5937.46.1.02
18. Sajadinejad, M., Asgari, K., Molavi, H., Kalantari, M. & Adibi, P. (2012). Psychological issues in inflammatory bowel disease: An overview. Gastroenterology Research and Practice, 2012, 106502. doi: [10.1155/2012/106502]
19. Rosalsky, G. (Producer). (2018, October 10). How to optimize your apology (Audio Podcast). Retrieved from How to Optimize you Apology.
20. Harris, A., Luskin, F., Benisovich, S., Standard, S., Bruning, J., Evans, S. & Thoresen, C. (2006). Effects of a group forgiveness intervention on forgiveness, perceived stress and trait anger: A randomized trial. Journal of Clinical Psychology, 62(6): 715-733.
