I am in the middle of the program (week 5), which I do on a treadmill. I have a treadmill at home, and there is also one at a gym near where I work. Recently I am using the one at work, but would really like to use the one at home more often. However, my home treadmill seems MUCH HARDER then my work one, and I can't understand why. at work I walk at 7.1 and run at 9 (kph) without too much trouble, at home walking at 6.3 is already unbearable. Has anyone experienced this?