heart rate data

Earlier in August, Cardiogram, the startup whose new DeepHeart algorithm has revealed its ability to pinpoint dangerous heart conditions, announced that its apps would officially integrate with Garmin products that measure heart rate. The integration has been long awaited, but it’s far from perfect, depending on who you ask. iPhone and Android users would tell you two slightly different stories.

There are lots of apps designed to record heart rate information, but apps like Cardiogram help users visualize that data — which, to the average user trying to make sense of their body, is key to understanding physiological patterns and the conditions that cause them. But an app for data visualization is only as good as the data that feeds into it, which, as Johnson Hsieh, an co-founder at Cardiogram, explains to Inverse, is largely dependent on how that data is written and stored.

“When Garmin writes into the Health app on the iPhone, it only writes data every two minutes or so,” Hsieh says. “But when we get data through Garmin’s server, like we do on Android, it’s actually much higher resolution. I think it’s every 15 seconds or 30 seconds.”

When you’re measuring heart beats, the gap between two minutes and 15 seconds is huge, which makes competing smart watches wildly different in how they present “real-time” health info.

heart rate data cardiogram
Cardiogram's labelling feature, which organizes HR based on activity 

Cardiogram is hoping to eventually become “device agnostic” so it will be able to process heart rate data no matter what device it comes from. But the company is constrained by the fact that, for now, all heart rate-tracking devices store its data on servers. To use that data, apps like Cardiogram must find the right software tools to pull that data from the wearable into an app to analyze it. This is where the differences between iOS and Android phones emerge.

The differences may seem small and likely won’t affect the typical smartwatch user. But members of the r/garmin thread on Reddit, who were among the first to test out Cardiogram, actually noticed that the app’s dependence on Apple Health caused some syncing problems.

“The kind of information [Cardiogram] claims to offer is the kind of thing I’d be interesting in seeing on my iPhone,” one Redditor, Bob_Om, tells Inverse. “Sadly it’s not reliable at all. The app relies on Apple’s health kit rather than taking the information directly from the Garmin product that I use. This means sometimes it just doesn’t sync data.”

Most of the early critiques of Cardiogram are similar, coming from iPhone users whose data from fitness trackers must first aggregate within Apple’s Health app. On iOS, says Hsieh, Garmin products sync their information into Apple Health, and then Cardiogram can read that data from there. It is this intermediary step that has frustrated some early users. On Android, Cardiogram reads the data directly from Garmin’s own server without needing an intermediary. In this way, it’s able to maintain “higher resolution data.”

So for iOS users who might be experiencing some syncing issues between Garmin devices and Cardiogram, this technological quirk may be the source of your woes. With the responses of the early Reddit users in mind, Hsieh says that Cardiogram hopes to move away from its dependence on Apple Health’s processing of data from Garmin watches. Trials like this one are part of the reason they do these early tests, especially on Reddit, where he notes the users are particularly engaged.

“Potentially we may change that structure so that it bypasses health kit all together and so it works the same way as Android,” he says. “In which case the Garmin server will push the data to our server.”