Heart Rate/LT Conusion?Low Numbers?

Ok, so I have an HR monitor (a good working one now-my old one sucked) and have read all about max heart rate and LT testing in the BT articles. Even did a couple of field tests. I did the test indoors because its soooo hot and humid and I know that affects your heart rate. I'm 23, in decent shape, yet the numbers seem low to me. Average HR on the Bike LT test 134, Average HR on the Run LT test 151. It always seems like I have trouble getting my HR up unless I'm out in 90 degree temps+humidity. I do a cardio workout DVD with a friend (whose about 10 years older) and she has no trouble getting her HR in the zone; on a good day, when I'm going all out I get in the 130's. I do take a beta blocker, Propranolol, for migraines. I know that it affects blood pressure, not sure about HR, never was good in biology. But I do seem to have an even more difficult time getting my HR up in the AM after I've taken my morning dose. Resting HR 42bpm, fyi.

So are these numbers too low for my age? Does the medication I take have something to do with it?  

Here's an interesting factoid that's tangentially related to your post. Back when I was more into playing golf, which was some years back, I read in one of the golf magazines that some golfers took beta blockers as performance enhancing drugs. The idea was that it slowed their HR and made them less nervous. I don't know if this is still an issue or not.

So, the answer to your question is to take up golf! Just kidding.