Source
r/running•
BeguilingOrbit

Slower During Nighttime Run?

Question

I ran after work yesterday, as I usually do on Tuesdays. It was the first time I had run after work since Daylight Saving Time ended and I was running in the dark toward the beginning of my run, as opposed to last Tuesday when it didn’t turn dark until the end of the run.

It felt so much more difficult than last Tuesday's run! I was running 30-45 seconds per mile slower than I had the week before. Nothing seemed out of the ordinary as far as energy, hydration, lack of sleep, stress, etc. It seemed to be just a regular Tuesday run after work. I began wondering how I had lost two months of fitness overnight.

There might have been several contributing factors to last night's slowdown: One, not only was it dark, but it had been raining all day and the path was littered with water puddles that I was trying to dodge. It was foggy, too. Also, I was carrying a flashlight strapped to my wrist, which affected my arm swing.

The temperature was 10° F higher than it had been in a week and the humidity was much higher than lately, too. Even so, this is right after a summer of running during heat and humidity so my body has long since adapted thoroughly to those conditions.

I wondered if there was anything else that I might be missing, so I did the old Google search today and discovered the concept of "fast optic flow":

Optic flow is your visual sensation of moving through an environment. When you run in the dark, you see only objects that are close to you. This sensation is analogous to "fast" optic flow, in which scenery seems to be speeding by you more quickly than normal.

This sounds like a purely psychological phenomenon and I'm shocked to think that it could have such a profound physiological effect on my running.

What do you all think? Is "fast optic flow" something to consider when running at night, or was last night's difficulty a combination of all those factors or even something else?

Posted Nov 6, 2019, 9:00 PM UTC

812
nermal543•

Totally anecdotal, but last night was my first dark nighttime run... possibly ever since I've only been running for about 6 months. I went out for a 5 mile run and could have sworn I was running closer to a 10'30" min/mi pace but it was more like 11'00" pace. It wasn't because it was a hard effort, just felt like I was moving faster. Both are a good training pace for me, so it's no big deal, but still, it was weird. So I'd believe it, just think it's funny you posted this because of what I was thinking last night.

7
BeguilingOrbitOP•

Glad to know I wasn't the only one who noticed a difference.

2
AppropriateTooth•

This happens to me and I actually love the feeling of flying through the night when I’m really doing my usual easy pace. I seem to either have good night vision or a high tolerance for tripping over things as I don’t slow down much, but I could imagine that others might be subconsciously holding back.

5
BeguilingOrbitOP•

Huh. Interesting perspective.

1
Runnnerb•

I have the same issue and avoid night time runs as much as possible because of it, easy runs don’t bother me as much but any kind of speed workout is a no no after dark. I put it down to my already poor eyesight making me overly cautious even if it is a subconscious thought process.

4
BeguilingOrbitOP•

I couldn't imagine having to do any real speed work while navigating those puddles last night. Good thing I'm in a base-building phase. I won't have to worry about that for a few weeks. Then it's off to a track, I guess. Thanks for giving me that to consider. I'll have some time to plan.

3
getrealpeople•

Training in S. FLA so yah lots of night runs. And I too average a minimum of a 30 second slowing of pace. Mainly due to having to concentrate on the path, puddles, frogs, etc. I bought a nice rechargeable chest light from the running store and that was extremely helpful. Consistent light path in front vs bobbing and weaving with the hand swing. The feeling of moving well is consistent with practice, and your speed will increase but for me never as fast as daylight.

I notice here when the temps drop 10 degrees I speed up nicely. So temps will definitely affect pace, hotter is harder!

3
BeguilingOrbitOP•

Yep! I just bought a rechargeable chest flashlight this afternoon! Great minds think alike. ;)

2
Fire53•

which one chest light did you get?

1
BeguilingOrbitOP•

Lixada LED Chest Running Light

1
WhatEvery1sThinking•

Seems normal to me. I typically run slower at night simply because I have to be more careful of my surroundings (cars, dogs, people, footing, etc.)

2
Freeasabird01•

I run at night a lot. Even on a familiar path, less light will slow you down as you just can’t see each step as well, meaning your muscles will hesitate a bit before committing to each step. All the other things you mentioned like temperature, humidity, and obstacles also definitely play a major role.

2