Although smartwatches and other wearable technology can track health data, the results they provide are not always accurate. However, there are still benefits to using wearables to improve your health and fitness as long as you view them as a "directional arrow rather than a precise measuring tool," Brian Chen writes for the New York Times.

Is health data from wearable technology accurate?

Currently, smartwatches from  Apple  and  Garmin claim to allow you to measure your VO2max, or the maximum amount of oxygen your body can use during intense exercise. According to exercise experts, the higher your VO2max, the better your cardiovascular health.

Although a traditional VO2max test involves someone wearing multiple sensors while exercising in a lab, you can get an estimate of your VO2max score by just wearing a smartwatch and getting active.

According to Chen, he first became interested in his own VO2max when his Apple Watch notified him that he had a high heart rate while he was out celebrating his birthday. When he looked at his VO2max, his watch said it was 32, "well below average for a man in his late 30s," he wrote.

In an effort to improve his VO2max, Chen joined a high-intensity interval gym, which specializes in training to boost cardio fitness. After five months, Chen said he "burned fat, gained muscle and felt more energetic."

When he checked his VO2max again, his Apple Watch gave him a score of 40, just below average, while another Garmin smartwatch gave him a score of 45. Compared to his original score, he had shown improvement after months of training.

However, when Chen underwent a real VO2max test, he scored a 25, a "poor" rating of cardiovascular fitness.

Although both Apple and Garmin ran studies involving people doing a real VO2max test, as well as other exercises, to inform their algorithms, the VO2max ratings they return are still just estimates and largely inaccurate. "The watches aren't actually measuring your oxygen intake and, therefore, aren't actually measuring your VO2max," Chen writes.

"It's at best an imputed VO2max," said Ethan Weiss, a cardiologist in San Francisco who has studied wearable technology for years. "Not only do you not have an oxygen mask, you're not actually exerting yourself to exhaustion."

Wearables are a 'directional arrow' rather than a precise tool

Although Chen's real VO2max rating was lower than he wanted, the report he received from the test showed many positives, such as "a very high metabolic rate and fat-burning efficiency and healthy breathing pattern."

Altogether, Cassie Hecker, who conducted Chen's test at her gym, said she would rate his fitness level as "average," which was higher than his Apple Watch's cardio fitness rating of "below average."

According to Weiss, Chen's experiment with his VO2max shows both the pros and cons of using smartwatches to improve your health. "On the one hand, you can give it credit for kicking you in the butt to tell you to go work out," he said. "But on the other hand, now you're sort of burned with this real test and like, 'What do I do with this number?'"

In general, Steven Adams, a sports medicine doctor and a personal trainer, said the best way to approach wearables is to "view them as directional arrow rather than a precise measuring tool," Chen writes.

"It's the trend that's important, not the absolute number, because this stuff's not accurate," Adams said.

Ultimately, Chen said that even though the data from his smartwatch was flawed, he had achieved a net positive with his training. "Even if the smartwatch numbers were wrong, they were correct in broad strokes, and I was probably better off wearing one than not," he writes. "… The Apple Watch nudged me to pay closer attention to my health, and as a result I'm healthier now." (Chen, New York Times, 4/12)