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Which fitness tracker is the most accurate?

Photo: Apple

The debate over fitness trackers started almost the second these hack-your-body helpers hit the scene a few years ago. Do they actually work, or do they hinder your performance? Are they reliable or totally off-base? And, most importantly, which one is the most accurate?

Well, according to a new study, there’s an official winner right now: the Apple Watch.

Researchers at the renowned Cleveland Clinic tested four fitness trackers—the Apple Watch, Fitbit Charge HR, Mio Alpha, and Basis Peak—on how well they measured heart rate, since that is the key measurement when measuring calorie-burning and exercise levels, Time magazine reports.

Fifty healthy adults were each hooked up to an electrocardiogram (EKG), which is by far the most accurate way to measure heart rate (but it’s not exactly portable, with all those sensors and wires). Researchers measured the participants’ EKGs at rest, then while walking and jogging on treadmills. From there, the EKG results were compared with the data captured by the fitness trackers.

Among the wrist wearables, the Apple Watch was tops, matching the EKG with 90 percent accuracy. The other three “dropped off into the low 80s for their accuracy,” explains Gordon Blackburn, PhD, one of the authors of the study and director of cardiac rehabilitation at the clinic.

While that drop may not seem hugely significant—especially while weighing the varying prices—the study also showed that the gap grew even larger as the intensity was increased because contact with the wrist is key to capturing good data. (So when you’re getting your interval hill sprints on, your tracker is getting bounced around, and the accuracy suffers.)

Blackburn explains that with more convenience comes more risk of less-than-perfect data—which is undoubtedly annoying for anyone who uses their tracker as their accountability BFF, but it shouldn’t be a deal-breaker.

“What we really noticed was all of the devices did not do a bad job at rest for being accurate for their heart rate, but as the activity intensity went up, we saw more and more variability,” he says.

So if the $300-plus price tag is holding you back from investing in an Apple Watch, you’re in luck—the the next best option isn’t really much worse.

Really want to get a full-body assessment? Try out the new biomarker data boom, where trainers track your oxygen, fat, metabolic rate, and more. And whether you have a tracker or not, you can always push yourself to go harder at your next workout—try these five treadmill hacks for crushing your indoor run