HR Goes Up Fast & Stays High?

krennie8

I've been debating about buying a fitbit, however I'm not sure how accurate it would be. It seems like as soon as I step on the elliptical/treadmill, my heart rate is supposedly up between 160-185. Like within the first minute. Is it just that I'm out of shape? (entirely likely). I mean, I find it incredibly difficult to keep it below 150, ever, while working out.

Stats,

27, F, 162 lbs, 5' 3.5"
Resting HR, about 75 bpm