Running in the dark is a tough reality for many during the winter months. The amount of daylight you will receive in winter depends on your latitude. At the Winter Solstice, when the northern hemisphere is at its maximum tilt away from the sun, days can be depressingly short. New York City, for example, receives nine hours and 20 minutes of daylight and London (at a similar latitude to Berlin) gets just seven hours 49 minutes. Find yourself any farther north than Alaska and you’ll be living in nothing brighter than twilight for 179 days.
Experience the Dark – the effects of twilight hours on runners
Lack of daylight in winter months can have a detrimental effect on our mental state and make us feel lethargic due to increased Melatonin (the chemical that controls sleep). It is no wonder that our motivation for running after dark wanes during the winter. As well as energy levels and motivation, sight and balance are affected too.
The eye is one of the most complex parts of the body. It contains more than two million working parts, can detect 10 million colors and distinguish between 500 shades of grey – a useful skill when running in low-light conditions.
Some of the strongest muscles in the body are the ones that move our eyes. In fact, they are 100-times more powerful than necessary.
In the dark the pupil dilates to let in as much light as possible to help us see but this immediately reduces our field of vision by 10 percent.
The eye takes a little time to adapt to the dark. When you first go into the dark the rods do not react at first, so your vision is very poor. During the next half an hour, the rods respond and you are dark adapted and see better so it’s ideal to warm up for a run outside in the dark to prepare your eyes.
Our bodies know how to adapt to terrain through sight, so if running from a paved road to grass, we will have adapted to the grass after seeing it – even before our foot hits it – in terms of changing gait and force. In the dark, you don’t know what terrain you are going to hit before you hit it which can put your balance way off.
Reaction times in the dark
One of the biggest challenges for running in the dark is ensuring others can see you, especially drivers.
Ninety percent of a driver’s reaction depends on vision, and in low-light conditions a driver’s vision is compromised by reduced depth perception, color recognition and peripheral vision
A driver who during the day has 20/20 vision can experience a reduction of visual acuity to 20/40 at night
Reflective materials and lights boost recognition distance of a driver to as much as 200m
During daytime driving, the Perception Reaction Time (PRT) of a normally alert driver can be around 1.5 to 1.75 seconds. In dark conditions, this perception time can be increased up to 2.5 seconds or more, depending on the conditions and at 62mph (100kph), this 1.0 second difference – from 1.5 to 2.5 seconds – equates to almost 90 feet (28 meters)
Continue reading more about how Nike Running gear helps protect runners from the dark. Download the full feature via the link on the left.