When it comes to working out, most people want to make sure they’re pushing their bodies hard enough to make it worthwhile, but not too much that it can cause problems physiologically. For that reason, a heart rate monitor can be a fantastic tool not only to monitor your health, but also to measure the effectiveness of a workout.

Although heart-rate monitors can be expensive, there are several reasons why you should monitor your heart when you’re exercising.

1. You Can Measure the Condition of Your Body

If you go in for your annual physical (which you should), then every once in a while, your doctor will want to measure how hard your body is working by making you walk on a treadmill. This is called a “stress test,” and can provide valuable information to your doctor as to the overall condition of your body. Measuring your heart rate during a workout can provide similar data that you can then relay to your doctor, giving you a constant source of information as to your health.

2. It Will Tell You How Fast You Recover

Health is not only tested by your ability to workout, but also how fast your body can recover from working out also. Wearing a heart rate monitor allows you to see how fast your heart is beating minutes or even hours after your workout, which can tell you how efficient your cardiovascular system is at returning to normal. If it takes a while to come back down, it might mean a trip to the doctor for a checkup.

3. It Can Tell You When to Push, or When to Back Down

Though we might like to think we know what’s best when it comes to the intensity of our own workouts, usually we’re awful at judging how hard we can push our bodies. Since your mind will usually tell you to quit long before your body tells you to, monitoring your heart rate can allow you to find that ideal zone to workout in, creating optimal conditions for you to get your ideal workout.

4. It Can Tell You How Hard You Have to Work In Regular Conditions

Do you know how much energy you’re expending during a 45-minute walk through the grocery store? How does that number change if you’ve ingested a fair amount of caffeine, or are working out late at night or early in the morning? Monitoring your heart rate gives you a crystal-clear number that tells you how hard you’re working in everyday life. If you find that your heart is laboring excessively during even mundane tasks, it might be an underlying cause for a much bigger issue.