Finding your personal heart rate zone and training with heart rate intervals allows you to maximize your workout. Simply put, if you train at lower heart rates (BPM or Beats Per Minute) it will require you to workout longer to achieve benefits. If you work out at BPMs that are too high for a prolonged period, you will burn out too fast, before you've reached your workout goals. Scosche Rhythm+ has advanced optical sensors that will give you a precise BPM reading so you can stay in your zones and receive the maximum benefit from your workout! Train Smart, Get Fit!™.