Cardio Question

[ChrisTheo]

Do you get a better workout from running on or off a treadmill? It seems like when I run outside, I get tired a lot sooner. Which do you prefer?

 

[overthepond]

What sort of surface are you running on? I have noticed that running on something hard, like pavement, really takes it out of me sooner than something good, like sand or treadmill.