I have used my Polar FT4 Heart Rate Monitor (HRM) for my last three workouts. I am currently on Stage 1, Round 6 of the New Rules of Lifting for Abs (NROLFA). So, I used the HRM during both workouts in Round 5 and the first workout in Round 6.
What I learned is (1) weight lifting IS a cardiovascular workout—the heavier I lift, the more my heart rate increases; (2) a 45-60 second break is perfect for getting my heart rate below my target heart rate zone.
The HRM monitor is useful for (1) counting the amount of time you’re in your zone during and (2) reminding you when you’re out of it. It also calculates how many calories you’ve burned. I burned over 500 calories in my last workout and close to 400 in my earlier two workouts. My latest workout was definitely the most challenging. So, I believe the calorie count is pretty accurate.
I honestly don’t think a heart rate monitor is a must have device, but it is handy for reminding you not to be lazy (i.e., if you go below your zone, you should probably work harder or end your break). It also counts calories if that’s your thing. Finally, it gives reassurance that even though you’re not doing “cardio” while you’re lifting, your heart rate will definitely reach the maximum in the zone if you lift heavy enough.