Over the last few years, wearable fitness trackers have become popular items for people wishing to keep tabs on their physical activity. Fitbit, one of the most prominent manufacturers of such technology, has sold millions of these devices. Earlier this year within a month of their release, their Blaze and Alta devices sold more than one million units each. The company was worth $8 billion when it went public in June 2015, but the honeymoon may be coming to an end.
An amended class action lawsuit was filed on Thursday, May 19, 2016, against Fitbit on behalf of several customers who purchased devices programmed with the heart rate monitoring feature. This feature uses technology which Fitbit calls “PurePulse”. The PurePulse heart rate monitoring feature is included in FitBit’s more expensive models, such as the Surge, Blaze, and Charge HR. PurePulse, according to Fitbit, promises to allow the wearer to “check real-time heart rate to ensure [they’re] giving the right amount of intensity during workouts.” Fitbit describes this technology as utilizing “always-on optical heart rate sensors” which use “finely tuned algorithms that provide insight through interactive charts and graphs.”
Several people argue that the technology used in the heart rate monitoring system does not work as advertised.
However, several people argue that the technology used in the heart rate monitoring system does not work as advertised. The lawsuit was filed on behalf of people who bought these devices specifically for the ability to track their heart rates, either for health or physical fitness purposes. The suit alleges that the monitoring feature poses a risk to those who rely on it to provide accurate heart rate readings for medical purposes. Jonathan Selbin, an attorney for the Plaintiffs, said, “We are not arguing that it is a medical device. … This is about the way [Fitbit] market[s] and that they charge a premium for the heart rate monitor, but it’s not giving a meaningful measurement.”
The Plaintiffs argue there is no reasonable way for them to know or to have known that these devices and the PurePulse technology are or could be inaccurate. They also assert that their reliance on Fitbit’s promise to perform as advertised was part of their reasoning in making the purchase. They are not making any claims about Fitbit’s other advertised features.
In support of their amended argument, the Plaintiffs have included a newly released study conducted by Dr. Edward Jo and Dr. Brett Dolezal at California State Polytechnic University in Pomona, CA. This study, performed on 43 healthy adults, found that the PurePulse technology was off by an average of 20 beats per minute during moderate to high-intensity exercise. The doctors concluded that PurePulse technology was “not a valid method for heart rate measurement, and cannot be used to provide a meaningful estimate of a user’s heart rate.” It must be noted, however, that this study was funded by the legal team bringing the lawsuit.
Consumer Reports found Fitbit’s heart rate readings to be “quite accurate.”
Fitbit has responded to the lawsuit with a statement rejecting the study for not only being biased but also “lacking scientific rigor” and being conducted using “flawed methodology.” Fitbit argues the study was performed with consumer-grade evaluation tools, not medical-grade, and that there was no evidence showing the devices used in the study were properly calibrated or tested for accuracy.
Fitbit counters the Plaintiffs’ argument with independent studies by Consumer Reports. In a study prior to the class action suit, Consumer Reports found Fitbit’s heart rate readings to be “quite accurate.” In light of the recent lawsuit, Consumer Reports retested the Fitbit models with heart rate monitoring technology to determine if they (Consumer Reports) should continue to recommend them to consumers. The results were consistent and in conflict with the Plaintiffs’ claims.
During Consumer Reports’ retest, subjects were evaluated while using the Fitbit Charge HR and the Surge, as well as a properly calibrated chest-strap monitor for comparison. Each Fitbit device was tested independently of the other. Heart beats-per-minute (BPM) were tested while the subjects were at rest, at a walking pace (110 bpm), at a jogging pace (130 bpm), and at a running pace (150 bpm). Each test, regardless of pace, was independently conducted twice with each device.
The Consumer Reports study concluded that both the Charge HR and the Surge were “very accurate” when compared to the chest monitor. There was one accuracy issue based on device placement on one particular subject’s wrist. This error was corrected when the subject wore the device on her forearm.
The challenge with these devices is in how they measure the wearer’s heart rate.
The challenge with these devices is in how they measure the wearer’s heart rate. Medical-grade devices such as chest strap heart rate monitors measure electrical impulses. Comparatively, wrist-worn devices, such as Fitbit’s, use light to track the user’s heart rate. Specifically, the devices illuminate the capillaries in the wearer’s wrist with an LED light and a sensor next to the light then measures the rate at which the wearer’s blood pumps past it. This is then calculated into a BPM reading.
In order to get an accurate reading, the wearer must be absolutely still. Making matters even more complicated is the blood itself. By the time it has reached the capillaries in the wrist, it has slowed down enough that it does not necessarily reflect the wearer’s true heart rate, especially at BPM’s over 100.
Additional factors such as the wearer’s skin pigmentation can affect these readings. Bharat Vasan, COO and co-founder of Basis fitness trackers, explained, the device’s light must penetrate through several layers. The higher the wearer is on the Fitzpatrick scale (which measures skin tone), the more difficult it is for light to bounce back to the device. “For someone who is very pale in a very brightly-lit setting, the light could get washed out. … The darker the skin, the brighter the light shines, the lighter [the skin] the less it shines,” said Mr. Vasan.
“You shouldn’t think you are buying a medical-grade device, and the company never says that.”
Plaintiffs’ attorney Jonathan Selbin argues it is about truth in advertising. “If they had just been honest and said it can give you a ballpark figure most of the time, or if the marketing emphasized that you can use these when you are aspiring to be healthier, that would have been OK, but that’s not how they market it and they charge a premium for it.”
If Fitbit’s heart rate monitor technology is flawed, and its readings are as significantly off as the Plaintiffs claim, then, as Dr. Allan Stewart, director of aortic surgery at The Mt. Sinai Hospital said, “Athletes may be at a minimum improperly training and, at worst, potentially elevating their heart rates to an unsafe level where a massive heart attack is entirely possible.”
But as Alex Montoy, an assistant professor of clinical exercise physiology at Ball State University points out, Fitbit does not claim to be 100% accurate. In fact, they use words such as “track” rather than “measure” to keep a record of steps taken. Regardless, as Professor Montoy said, “You shouldn’t think you are buying a medical-grade device, and the company never says that.”