I have been getting back into to it for the past couple months. I run outside. Started at about 1.5 miles per run, and doing about 3 miles per run now, but it really sucks after I hit the 2 mile mark. It's weird. Like I am perfectly fine at 2 miles and then it hits me hard. Though, I have only been doing 3 miles a run for a little over a week. I try and do it 3-6 times per week, but we'll see what happens when it gets hot outside, I may puss out.