I'm new to distance running. I'm training to run a half marathon running about 35 miles per week and lifting 3 times a week. A couple of my friends who have gotten me into distance running and I were talking about our hrvs. They can run under 3 hour marathons and have, run close to 70 miles a week and yet my HRV usually sits around 130-140 on well rested nights while there's sit at about 80 on well rested night. We use the same Harmon device and whoop. What would cause this? Assuming they are significantly more advanced in their cardio training.