Winter Arc: the light protocol for the darkest months of the year

What is Winter Arc, and why is it about light?

Winter Arc is the idea of using the last months of the year to build habits instead of waiting for January. Training, food, focus, sleep. It sounds like discipline, and it is. But in Scandinavia there is a factor people rarely mention: how little daylight there is and how long the evenings stay lit.

In Gothenburg the shortest day this year is just over six and a half hours long, and in mid-December the sun sets just before half past three. That means an ordinary weekday has six or seven hours of evening light from lamps and screens before it is time to sleep. Every hour of it tells the body it is still daytime.

That matters because evening light suppresses melatonin, the hormone that marks the start of the night. A 2019 study in PNAS showed that under 30 lux, roughly a floor lamp, was enough to halve melatonin in an average participant.

Morning: get the light

The protocol does not start in the evening. How sensitive you are to light at night depends partly on how much light you got during the day. Go outside within the first hour or two, even when it is overcast. A grey December morning outdoors still gives far more light than most offices. If it is pitch dark when you leave home, take the walk at lunch instead.

Day: work in light

Sit near a window if you can. The researchers' recommendation of at least 250 lux of melanopic light during the day is higher than many workplaces provide. Daylight is not something to filter out. If you want glasses at the screen during the day, the yellow lens or LOWLIGHT ONE are made for that and let more light through.

Evening: lower the light in two steps

This is where the big difference lies for anyone who wants to lock in their sleep. Think of the evening in two steps instead of one switch.

• Step one, from sunset or after dinner: use lower, warmer lamps, dim your screens and put on the orange lens. It filters 98% of light between 400 and 500 nm.
• Step two, the last two hours: switch to the red lens, which filters 99% between 400–550 nm. Keep them on until the light goes out, bathroom included.

The glasses remove the wavelengths that drive the light signal, between 446 and 477 nm, from every light source at once. That is the difference from your phone's night mode, which only changes one screen. Nobody can promise what it means for your sleep in particular, but it is the part of the evening you can actually control.

Night: properly dark

The recommendation for the bedroom is no more than 1 lux, as dark as possible. Blackout curtains, no charging light at eye level, your phone face down or in another room. They are boring details, but this is where the evening's work either holds or drains away.

What if I train late?

Gyms are bright, and a session at seven puts a couple of hours of strong light in the middle of your evening. Train in that light, that is not a problem in itself. The difference is made afterwards: lower the light at home, take a shower and put the red lens on for the rest of the evening.

Sleep is where I grow.

Emil Roos, bodybuilder and BLUR-IT athlete

For the evening as a printable checklist, see The Evening Routine. The mechanism behind it is in Blue light and melatonin.