Fitness Bands Fail on Calorie Counts 

运动手环难以计算卡路里 

Activity trackers accurately reckon heart rate-but they’re way off in estimates of energy expenditure. Christopher Intagliata reports. 

运动记录仪能够准确地测算心率，但是它们却在估计能量消耗上出现很大偏差。克里斯托弗·因塔利亚塔报道。 

撰文/播音：克里斯托弗·因塔利亚塔（Christopher Intagliata） 

翻译：郭鑫鹏 

审校：杨枭 

Fitness bands like the Apple Watch and the Fitbit aim to track your vitals, like heart rate. But early models weren’t all that accurate. “We thought of them a little bit like random number generators. They really didn’t seem to be providing anything that bore any relationship to heart rate.” Euan Ashley, a cardiologist who studied wearables at Stanford University. 

像Apple Watch和Fitbit这样的运动手环旨在记录你的生命特征，比如心率。但是早期模型并不是那么精确。“我们认为它们有点像随机数生成器。它们提供的数据看起来和心率并没有什么联系。”斯坦福大学研究穿戴设备的心脏病学家尤安·阿什利 （Euan Ashley）说。 

He and his colleagues have now tested seven newer fitness bands-from brands like Apple, Fitbit and others-and he says those heart rate stats have gotten way better. “Yeah we were pleasantly surprised actually by how good the accuracy of the heart rate monitoring was.” 

他和他的同事们测试了七款较新的运动手环，它们分别来自Apple、Fitbit和其他品牌。他表示，这些手环的心率测试更精准了。“我们感到相当地高兴和惊讶，因为它们的心率监测相当精确。” 

For most of the devices, the error rate was less than five percent-good enough for your doctor. But where all the devices failed to measure up was estimating calories burned. Even the most accurate devices were off by 27 percent, compared to lab measurements of energy expenditure. One device was off by more than 90 percent. 

对于大多数设备，它们的错误率小于5%，这已足够你的医生来了解你的身体状况。但是所有设备都未能正确估算卡路里的消耗。即使是最精准的设备，比起实验室中测量到的能量损耗都有27%的偏差。甚至有一个设备出现了90%的偏差。 

“If you think about going to the gym and working out for an hour and maybe that’s around 400 calories, in reality that could be anything from 200 to 800. And that’s a big difference if you’re thinking about somebody who’s incorporating those estimates into their lifestyle and thinking about what to eat that evening based on the workout they did that afternoon.” The results are in the Journal of Personalized Medicine. [Anna Shcherbina et al., Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort] 

“你或许认为，去健身房运动一个小时大概消耗400卡路里，但实际上它可能从200到800的范围不等。一些人相信这样的估算并将其结合到生活方式，以此来决定下午的运动和晚上的饮食，这样的估算失误对他们来说将产生巨大的差异。”研究结果发表在期刊《个体化医学》上。 

The reason for the discrepancy, Ashley says, could be that we all burn energy at different rates-and that’s hard to reckon from simple input stats like weight and height. “Some people are incredibly efficient and look incredibly elegant when they run. And others really clearly look like they’re burning a lot more calories to cover the same amount of ground.” So if you own a wearable, it’s probably safe to trust the heart data. What it can’t tell you is whether your time on the treadmill really justifies that chocolate shake. 

（阿什利）说，出现这种差异的原因是因为我们每个人消耗能量的效率不同，因此只依靠体重和身高这样简单的输入很难去估算能量消耗。“一些人在跑步的时候看起来很优雅，却有着惊人的效率。其他一些人跑了同样的路程，却看起来像是消耗了更多的卡路里。”所以，如果你有一个手环，你可以相信它的心率数据，但是它没法告诉你，你在跑步机上运动的时间能否抵消你喝下的巧克力奶昔。 

-Christopher Intagliata