I do alot of walking outside the gym because I take the public transit. I don't have a car so I walk to the grocecry store etc. When I used a pedometer, I always average about 70,000 steps a week. If that makes much of a difference.
Huge huge difference. You're pretty active already and you're probably able to walk for some time without a racing heart rate and without tiring.
The heart rate monitors on the machines are notoriously inaccurate. If you want to train by heart rate, get a monitor that you wear. Polar is the big brand but there are others.