Smartwatches have evolved from simple timekeeping devices into compact health-monitoring systems that generate data on sleep patterns, energy expenditure, and other physiological metrics. Among their most sought-after features is heart-rate monitoring. While wearable sensors can provide a useful estimate of heart rate after physical activity, can they reliably assess cardiovascular health? How accurately do they reflect an individual’s cardiac status? Understanding your Heart Rate Heart rate is the number of times the heart beats within a certain time period, usually a minute. For a healthy adult who is at rest, the heart rate is normally between 60 and 100 beats per minute (bpm). Tachycardia Our heart rate adjusts to the body’s changing metabolic demands throughout the day, whether climbing stairs or engaging in strenuous exercise. Such activity-related fluctuations are physiological and generally normal. During these episodes, you may temporarily experience tachycardia...