How important is heart rate when monitoring athlete work loads?

Heart rate is a really important marker when you want to understand the physiological internal response to the external load. There is a lot that goes into an athlete’s well-being that is not always measurable objectively - eg. family relationships, lack of sleep, stress etc. Capturing that psychological stress through a physiological response enhances your understanding of each athlete. If Catapult is the car dashboard showing speed and distance, heart rate data is showing whether the car is overheating or low on fuel.