Garmin Body Battery slammed indirectly by Altini: "Made Up Scores" In his regular newsletter, world sports-HRV expert, Marco Altini, had a no-holds-barred tear into many of the 'Made Up Metrics' used by today's crop of wearable tech. This includes Garmin Body Battery, an industry favourite similar to those from many other brands. Altini's article follows my critique of Siepe et al.'s study, which found that "Garmin Vivosmart can't measure stress," and how that study was reported in mainstream media outlets like The Guardian and Wareable. https://the5krunner.com/2025/08/12/garmin-vivosmart-cant-measure-stress-study-shows-little-correlation-to-self-reported-levels/ Here's what Altini has to say, and I have to agree with what he says almost word for word. My only criticism was that he used "Made Up Scores" whereas I prefer "Made Up Metrics" :-). Here's what the Marco Altini newsletter article adds in case you don't subscribe: Explicit Condemnation of Continuous Stress Monitoring: Altini stated that the Siepe study "put the application of HRV-based continuous stress monitoring as proposed by wearables to the test, and found that the correlation between wearable data and self-reported stress scores was 'basically zero'". He emphatically declares that "there is no such thing as continuous stress monitoring using HRV" and calls these applications "a wild extrapolation merely serving user engagement". I'm perhaps sometimes sensationalist on this site, but Altini's view is a stronger, more categorical denouncement of continuous stress monitoring than mine. Personal Stance and Prior Work: Altini additionally states, "Continuous stress monitoring was the nail in the coffin for me when it comes to wearables, as the misuse of HRV data for this application was something I couldn’t get behind". He also explicitly refers to his more detailed discussions on this topic, which I summarise, edit and link to in an article he wrote on this site. https://the5krunner.com/2025/05/20/hrv-everything-you-need-to-know-garmin-whoop-oura-hrv-hrv4training-training-readiness/ Broader Critique of "Made-Up Scores": Beyond just stress, Altini extends his criticism to other "made-up scores" in wearables, such as "readiness, recovery, etc.". He asserts that "none of these parameters are good at tracking what they claim to be tracking". Again, this site and one or two others have quietly said this for some time. Distinction with Appropriately Measured HRV: Altini highlights a recent study that found a negative correlation between self-reported stress measures and HRV when measured during the night and a positive correlation with resting heart rate. He states that "night data provides a good assessment of an individual’s resting physiology and stress response", emphasising that HRV can be a sensitive marker of stress when measured correctly. This contrasts with the flawed continuous monitoring approach discussed in the Siepe study. Direct Advice to Users: I concur with Altini's advice to readers - "Keep that in mind before you invest your mental energies and trigger additional worries and concerns for you or your athletes because of made-up data with no physiological meaning". Take Out I could have one of those 'I told you so' moments, but I will refrain as it's Monday :-) And I know many regular readers are aware of this in any case. There you have it. These all-day stress metrics, like Body Battery, are nonsense! Albeit good fun. The story gets worse. I am in some private discussion groups with various people in the industry. I/we can assure you that all major wearables companies have excellent in-house HRV science advisors. The companies all know precisely what they're doing and the flaws of their various approaches. The information on this site and from Altini is nothing new to any of them. I believe commercial pressures are being applied to deliberately misstate the usefulness of many of the current crop of wellness metrics...aka Made Up Metrics.
