Heart Rate Monitor

I would suggest that everyone invest in some type of heart rate monitor before starting any type of physical exercise. I personal use a New Balance N5 and Karen uses one by Garmin. Now, I like the type that comes with a chest transmitter, but Karen's uses the one that transmit by pressing your figure against the senor when you are done exercising. No matter which one you prefer just make the investment. This way you will have some type of record of your workout, and you will be able to keep track of when you are in the zone!