Heart rate variability (HRV) is a measure of the variation in the time interval between heat beats and a higher value indicates you are healthier, happier, and less stressed. It is often used as the key metric in recovery calculations. To view the HRV values measured by your Apple Watch, open the Apple Health app, tap the Browse tab, select Heart, and then select Heart Rate Variability. You can view the HRV data by day, week, month, six months, and one year. Whoop provides you with recommendations and insights about HRV, but Apple does not yet provide any further useful information. There are third party apps, such as Training Today, that pick up where Apple left off and provide recovery and other recommendation to help you avoid injury and maintain peak performance.