Heart Rate Monitor

amyzen

My doctor told me that I need to workout at 75% rate of effort.  I like to wear a heart rate monitor to just ensure that I am within that zone.  I have a Garmin 305, which I wear for running.  However, it's too big to wear around the gym.  I want to get something smaller.  I've been looking at the Polar FT4.  Does anyone have this model? If so, please let me know your thoughts.  I am also trying to figure out the chest strap size.  I am measuring at 29" around the area where the chest strap would be.  Size small is 20" - 30" and medium is 30" - 45".  I don't want it sliding down on me right now, but I figure that I am just going to be getting bigger from here.  Also, if there are any other heart rate monitors you could recommend, I would appreciate it.  

 Thanks for all your help and advice, as always! :-)