Hey guys. During the winter months I walked almost exclusively on an indoors treadmill at the Y. From a pure step count perspective, indoor and outdoor walking look identical. But from a broader physiological perspective, they are vastly different.
Outdoor walking in natural daylight, even if it's cloudy and rainy, provides light exposure that regulates the body's circadian rhythm -- the internal 24-hour biological clock that governs sleep timing, hormone release, and immune function. The reason this is important is because light is detected by specialized cells in the retina, the light sensitive layer at the back of the eye. These cells send signals directly to the parts of the brain that control your circadian clock. Research has demonstrated that circadian disruption -- a misaligned body clock -- increases the risk of metabolic, cardiovascular disease, and impaired immune function. Natural light also stimulates dopamine release in the retina, which has documented benefits for your mood and also your eye health as well. Artificial light, however bright, produces light exposure of around 200-500 lux at best, whereas outdoor daylight, even on a heavily overcast day in the middle of winter, typically exceeds 5,000 lux. That difference isn't trivial!
Moving your walking outdoors costs nothing and adds benefits that indoor walking simply cannot replicate. So if you can, do what I do -- try and get your walks outside even if it's for just a couple of minutes.
Today's walk:
Today's steps:
