Mr.

I am a 47 yr old man. Very active physically - work out at least 4 times/week.
Resting heart rate is 45. However my heart rate accelerates up to min. of 150 after just a 1/4 mile. Should I be worried about this?
Max heart rate is 185, and I regularly do all work outs in the 160 to 180 range.

Thanks for the help!

Pete

[Cleveland Clinic]

That's all normal for you.  Athletes have very low resting HR around 40 or so, like yourself.  When we exercise, the heart rate has to go up to increase the cardiac output to accommodate for the heavy demands posed by the muscles.  It is not so much how high your heart rate gets when you exercise, but how quickly it goes back to normal that determines your fitness level.  Typically, a few minutes after stopping your exercise your heart rate should be on its way down.  Look up an article by Michael Lauer on pubmed or google (type HR recovery and Lauer) which will explain this more thoroughly and give you some examples.  

[runnertom]

Depends on how hard you are exerting in that 1/4 mile. Don't you think a track runner is at max heart rate at the end of a 400 meter race?