Celestial cycles, health and yoga (wow!)

Today is the new year, although personally I think of the winter solstice as the real start of the year. From that point until the summer solstice, the days get longer and the nights shorter (at least for those of us in the northern hemisphere).

That’s probably only the most trivial way in which we are disconnected from the planetary rhythms that governed our evolution. Like all biological organisms, we evolved to respond to fluctuations in daylight and temperature. Those rhythms affect our food supply and influence energy expenditure, hormonal secretions and many other aspects of our lives.

Of course, today we spend most of our time in artificial environments that insulate us from those celestial cycles – at a cost.

I’ve been thinking about this after returning home from teaching anatomy for a teacher training in Bali. Anyone who’s traveled halfway around the world knows how disruptive it is to find yourself awake at midnight because your body thinks the sun should be shining.

Going from the heat of the tropics to winter in New York added an extra level of disorientation. Nevertheless, when I stepped outside to catch the train at the airport, the cold somehow felt right. Not that I hadn’t enjoyed two weeks of sunshine in Bali. But my body expects short days and cold temperatures now.

Yoga has a tradition of honoring those celestial rhythms. Yogis practice at the transitional times of sandhya – dawn and dusk — and avoid practicing during the new or full moon. Sun salutations are a moving meditation on the annual journey of the earth around the sun; the twelve poses in the standard sequence represent the twelve months of the year and the twelve signs of the zodiac.

I used to think of those traditions as superstition. But the more I learn about the health consequences of overriding our biological clocks, the more respect I have for them. They remind us that celestial rhythms profoundly influence our lives.

People who work night shifts or who are chronically jet-lagged suffer a multitude of health problems, including gastrointestinal distress, obesity, diabetes and cardiovascular disease. And, while there is less research about what happens when we disrupt seasonal rhythms, I suspect that has health consequences too.

Animals vary their activity level and energy expenditure throughout the year, the most extreme examples being those that hibernate. We don’t hibernate, but our hunter-gatherer ancestors also would have faced seasonal variations in food supply. It makes sense that our bodies would adjust energy expenditure to adapt to those variations. And, in fact, research consistently shows that people are less active and sleep more during the winter than during the summer. Since we’re less active and need fewer calories now, it’s small wonder that Americans gain so much weight during the holiday season.

In the west, we largely insulate ourselves from seasonal extremes. We spend our time indoors, maintaining an artificial room temperature throughout the year and extending short winter days with artificial light. My gut feeling is that this seasonal sameness isn’t so good for those of us who live in temperate climates. It disconnects us from our natural environment.

What can you do?

For one thing, it’s probably wise to get outdoors when you can. Vary the temperature in your house too: colder at night and warmer in the day. If possible, adjust your sleep cycle to the season. Go to bed earlier in the winter (not that I’m so good at following my own advice on this one!).

Adapt your light environment to the season. Get outdoors first thing in the morning. I take a five minute walk around the courtyard behind my building as soon as I get up. Early morning sunlight helps reset your biological clock, aligning your body’s internal time with the external environment.

Adjusting your indoor lighting to more closely match ancestral conditions  can help too. Bluer light during the day is closer to natural sunlight, while warmer tones in the evening recall light from camp fires. I recently downloaded f.lux — software for the Mac that changes  the light from my laptop screen to match the current daylight cycle. When the sun goes down, the screen shifts from blue light to a warmer, pinker tone. It sounds a little silly, but I found it very easy to adapt to, and it makes evening computer work feel less jarring to my system.

I also think it’s wise to adapt your yoga practice to the season. If piling up the blankets and opting for a restorative practice rather than a vigorous vinyasa class feels right, honor the urge to hibernate. Give yourself permission to be less active in the cold weather.

It’s also smart to modify your practice according to the time of day. People have different “chronotypes.” Some are morning people, others are evening people. Don’t feel that you need to follow rigid rules about the right time to practice. Roll out the mat when it feels best for your body. However, if you practice in the morning, recognize that you’ll be colder and stiffer than you would be in the evening — especially in the winter. Spend more time warming up, and focus on an active practice to start your day.

Your body temperature increases throughout the day, reaching a peak in the early evening. However, even if you practice in the evening, you’ll need more time for your warm up in the winter than you would in the summer. In addition, avoid highly stimulating poses, such as deep backbends, late in the evening, as they may keep you up past your  bedtime.

Oh, and happy new year!

Image: NASA


Atkinson G, Davenne D. Relationships between sleep, physical activity and human health. Physiol Behav. 2007;90(0):229–235. 

Manenschijn L et al. Shift work at young age is associated with elevated long-term cortisol levels and body mass index. J Clin Endocrinol Metab. 2011;96(11):E1862-5. 

Küller R. The influence of light on circarhythms in humans. J Physiol Anthropol Appl Human Sci. 2002;21(2):87-91. 

Reilly T, Peiser B. Seasonal variations in health-related human physical activity. Sports Med. 2006;36(6):473-85.


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