40 y.0. male non-smoker, weight 190 . work out on average twice a
week. get on the treadmill with my heart-strap monitor for a 30 min.
run. I've been doing soccer/road races for 15+ years (on and off).

On the treadmill, My heart starts around 80 and I can easily reach 155
bpm without pushing myself. (Obviously I don;t go the pace I do when I
play soccer or run in race, I just measure myself against the
"standard" of these heart rate catagories for my age which say I'm in
a areobic zone.) However, I don't feel myself breathing hard in these
zones. I stay like this the whole 30 min. Why does my heart rate go up
but I'm not feeling any "workout"

Because the fact you have been exercising regularly, when you exercise
your heart rate will still increase, but  because of your
conditioning, your not having to breathe hard

Thats what I was thinking, too. But I was thinking it was dangerous to
have a high heart beat and "not feeling it." (ie: not feeling any kind
of pain or discomfort while working out). They call it a workout,
after all ! :)

I have similar problem. I am 40 y.o and started to jog for two years.
My heart rate go up to 160 easily when I jog on trackmail at 9km per
hr. I don't feel breathless but don't want to push too hard to further
increase my HR. Obviuosly I am not happy jogging at 9km per hour.