I believe that a HRM is a great marathon training and racing aid. Here are some tips for incorporating one: 1) know your HR training zones - a good calculator for this is at http://www.stevenscreek.com/goodies/hr.shtml 2) use the monitor to assure that you don't over do it on your aerobic recovery runs or rest runs - check out my article at http://www.barn.to/staying_healthy%202.htm 3) use your HRM for special faster training sesions, like the one that you posted - here's one that I like on a 400 meter track: set your alarms respectively for 80% and 85% of your Max HR (using the heart reserve or Karvonen formula). This is usually your lactate threshold zone. Run repeats of 1000m staying in the zone and 200m jog rest continously. Build the distance to a max of 8x1000m - the total distance, including the 200s would be approx. 6 miles. 4) Use the monitor in your prep races to calculate what zone fits you best for you.