Does anybody else find exercise / walking / jogging harder on the treadmill then it is in real life?

In real life I can walk 7 kilometres and not feel tired but on the treadmill if I walk at the same speed I am exhausted after 10 minutes. I think it's because I'm not used to the artificial tension of the treadmill.
Does anybody else find exercise / walking / jogging harder on the treadmill then it is in real life?
Post Opinion