Exercising in your target heart rate zone gets you the most bang for the buck in your workout. But who wants to stop to take his or her pulse during a long run?

Heart rate monitor watches do the job for you. These monitors include a straplike transmitter that goes around your chest to measure your heart rate, and a watch for your wrist that wirelessly connects to the chest strap and displays your workout data.

The best heart rate monitors track other metrics while you exercise, such as your speed, distance and location as well as heart rate. Many models include options to enter your height and weight to better tailor your information. Buyers also need to look for features such as a long battery life, good memory capacity and the ability to measure a wide variety of heart ranges.

Doctors recommend exercising at 60 percent to 80 percent of your maximum heart rate, also known as your target zone. Doing this minimizes the risk of having a cardiovascular problem or musculoskeletal injury caused by pushing too hard, while still providing enough of a challenge to improve health, according to the Cleveland Clinic. A simplified formula for calculating your maximum heart rate is 220 minus your age.

But there's a caveat: Heart rate monitors probably aren't necessary for many exercisers who want to hit this zone. The reason, said Brandon Alderman, a professor of exercise science at Rutgers University in New Jersey, is that how you feel usually matches your heart rate.

"If a person feels like they are exercising at moderate intensity, if you put a heart rate monitor on them, their heart is going to say they're exercising at moderate intensities," Alderman told Live Science.

Casual exercisers may be better-served with fitness trackers that use accelerometers to measure movement, he said.

However, for athletes, people training seriously for marathons or half-marathons, or even for casual exercisers who would rather not go with their gut to stay in their target zone, heart rate monitors can be nice motivational tools, Alderman said. People strongly invested in their workouts are more likely to take the trouble to use the heart rate data to track their fitness from day to day, he said.

Video: How To Tell If You Really Need A Heart Rate Monitoring Fitness Tracker:

With so many heart rate monitors on the market, picking the best can be tough. Live Science's sister site Top Ten Reviews does in-depth research on consumer products, including heart rate monitors for exercise. Here are the site's top three picks.

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#1: Suunto Quest

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The Suunto Quest ranked first among heart rate monitors for its accuracy and extras: Unlike many other heart rate monitors, this one comes with the ability to set up an online exercise tracking account on Movescount. The watch also tracks more than just heart rate. Users also get feedback on calories burned, duration of exercise and distance. All of this information is easily uploaded into Movescount. The chest strap is included when you buy the watch, but the GPS pods for distance tracking must be purchased separately. The watch has an impressive memory, with the ability to store up to 1,000 laps.

Ease of use: Reviewers were impressed by the Suunto Quest's design, which includes a large face, backlight and four color choices (black, orange, blue and yellow). Setup with Movescount was simple, and the training summaries were easy to read. One downside to the watch is that it lacks the vibrating alarm that other devices have that can alert you to when you enter your target heart rate zone.

Help and support: Suunto's website includes useful tutorials, manuals, FAQs and lists of dealer locations, and heart rate monitors bought through the manufacturer come with a two-year warranty. A help line is available to U.S. residents around the clock.

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#2: Polar RS300X

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Polar's RS100 heart rate monitor was Top Ten Reviews' No.1 pick for heart rate monitors in 2013, and the company now has another winner with its Polar RS300X model. This monitor won praise for having alarms that alert users when they enter their target heart rate zone. The watch will also let you know when its battery is getting low — although, inconveniently, those batteries will have to be replaced at a service center. The expected battery life is two years, which is longer than that of most heart rate monitors.

Ease of use: Handy features such as a backlight and a lightweight design make this watch an appealing option for exercisers. However, the watch requires an additional accessory to transfer any data to another device, so if you don't buy the accessory, your information remains trapped on the watch. The device can, however, store the data from up to 99 laps at a time.

Help and support: Email and phone support are available from Polar Electro, the company that makes the Polar RS300X, and manuals and FAQs are available on the company's website.

#3: Garmin Forerunner 15

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The Garmin Forerunner 15 pulls ahead of other heart rate monitors by including GPS in the package — most other devices require additional accessories to track location, distance and pace. For many users, this feature may offset the fact that the Forerunner offers rather limited storage, keeping data from only seven laps. The watch comes with a USB cable for the frequent data transfers you'll need if you want to track workouts over time. This watch is also rechargeable, again through the included USB cable.

Ease of use: Reviewers liked that the GPS function can be turned off, saving battery life when not needed. The Garmin has a bold, simple display for easy reading and has useful features such as a calories-burned estimator and personalized heart rate zones.

Help and support: Garmin sells this watch with a one-year warranty and organizes its products page with links to useful resources, including FAQs, manuals and contacts for technical support.

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