A heart rate monitor measures electric signals from the heart and uses that information in addition to information you input -- such as age, gender, height and weight -- to calculate how many calories you burn. There are two kinds of heart rate monitors. A watch-style monitor requires you to touch your finger on special area to calculate heart rate. Many people use this kind of heart rate monitor to stay within a target heart rate to maximize fitness goals, but it doesn't offer constant heart rate information. A chest-strap-style monitor sends information to a watch for fast feedback, but it doesn't require a finger pulse. It can receive information at all times, so you can use it to keep track of your heart rate all day.
Wearing a Heart Rate Monitor All Day
You can wear a chest-strap heart rate monitor all day to track an estimated caloric expenditure based on your heart rate. Whether you're watching TV, grocery shopping or hitting the gym, it will keep track of your heart rate and let you know how many calories you are burning. While it probably isn't practical to wear a heart rate monitor all day, every day, wearing it on occasion could give you a good idea of how many calories you're burning, but this is only an estimate; different monitors have different levels of accuracy. If your goal is weight loss or weight gain, you also need to keep track of how much you eat to get a sense of your overall caloric gain or deficit.