Quite the reverse. In daylight I focus on the horizon - or equivalent - and set myself the target to getting to a certain point in a set time. In darkness the distance seems stretched out precisely because I can only see as far as my head toch allows. I also go slower because I am less certain of my footing and also - if I am on a trail rather than road - I am worried I might miss my turning, even on a familiar route.
I struggled for years until I was prescribed Symbicort which I started on at x2 puffs twice a day. It took a few weeks to really become effective but I am now virtually asthma free having previously having attacks of such severity I required emergency hospital treatment.
The other possibility is a stress fracture of the pubic ramus where the pain which is initially felt in the groin area can radiate to the knee, in which case a knee x ray would reveal nothing. More common in women, but a possibility in men.