On September 9, Apple unveiled a new feature during its back-to-school keynote, introducing a higher frequency for heart rate monitoring on the Apple Watch Series 12 and Ultra 4. The new feature measures heart rate every five seconds in the background, a significant increase compared to the previous model, the Series 11, which measured heart rate every five minutes outside of sports sessions. Apple claims this new capability provides up to 24 times more heart rate data than before, allowing the watch to track short-term fluctuations in heart rate. This data is used to calculate a new "readiness score," which Apple says helps users understand their overall physical preparedness. In response to Apple’s announcement, Garmin, a major competitor in the wearable technology space, posted a mocking Instagram message on September 23. The post, spotted by MacGeneration, claimed that Garmin watches “do not need to breathe every five seconds,” highlighting that their optical sensors measure heart rate every second, around the clock. This comment referenced a blog post from November that praised Garmin’s continuous heart rate monitoring and criticized other devices for measuring less frequently, such as every five seconds or even every five minutes. Apple has since defended its approach by publishing a study on the accuracy of its heart rate measurement technology, conducted in July and August 2026. The study involved 1,460 adults who wore Apple’s Series 12 on one wrist and a competing device on the other, alongside a Polar H10 chest strap used as a reference. According to the study, the Apple Watch performed better than six other devices, including the Garmin Forerunner 970, Pixel Watch 4, and Galaxy Watch 8. However, the study was conducted, designed, and funded by Apple, and it remains unclear whether independent researchers have validated these findings. Despite Apple’s claims, AppleInsider reported that the Garmin Forerunner 970 measures heart rate more frequently during training sessions, capturing data every 0.25 to 0.5 seconds—much more than the Apple Watch’s five-second intervals. Apple has not yet explained why it opted for a five-second measurement interval instead of continuous monitoring. MacGeneration suggested that this may be related to power consumption, as optical sensors used for heart rate monitoring consume energy with each measurement. This could be a strategic choice to balance accuracy with battery life.