SUNRISE
HEARTBEAT CHRONICLES

Have you ever pushed through the last minute of a hard run, glanced at your smartwatch, and wondered whether that number is safe? Or noticed that a workout you used to finish strong now leaves your heart rate climbing higher than it used to? Maximum heart rate is one of those numbers many of us have seen on our watches without really understanding what it means. It is often estimated with a simple formula and treated as fixed. In reality, your maximum heart rate can carry mor