What is Strain? Understanding your daily load
Learn how daily and workout Strain differ, why the 0–21 scale is nonlinear, and how to read your personal range, TRIMP and training load. Includes 14 app screenshots.
Apple Watch
How Often Does Apple Watch Measure HRV?
Series 12 and Ultra 4 can measure HRV as often as every five minutes. See how earlier watches differ, what happens during sleep, and how to check your actual recording times.
Can Apple Watch Measure Cortisol?
What HRV and stress scores can tell you, how cortisol is tested, and how to follow your readings with Wellhero.
