Jumped on the treadmill yesterday (first time for C25k), as the indoor track was closed for an event. I didn't get any of the cramps like I usually do, and didn't have to push myself nearly as hard as running outdoors.

I guess it's because you're running at a single set speed, and there's no inclines or declines. Even on the track where there are no inclines/declines your speed fluctuates, however, on the treadmill you lose all of that, making it easier to maintain speed and control your breathing.

I think from now on I'm going to use the treadmill on days I might have to repeat or days I don't feel 100%. Running outdoors in my mind is tougher physically, and more fulfilling mentally.

And I live in Canada, running outside subzero makes you feel like a beast, lol and you can't really slow down since it gives the chilly winds time to freeze your legs haha.