
Show HN: Effort Lab – Same running pace, different heart rate zonesHi HN,If you are into fitness, I hope you’ll find this interesting.I’ve been building a fitness app around a question that ordinary activity summaries and fitness apps don’t answer particularly well:“How hard did this session ask my body to work?”Imagine two friends running a 5K together at 5:30/km. Same route, same distance and the same 27:30 finish time.In the synthetic example linked here, they even have the same average heart rate. Most fitness apps would treat those runs as virtually identical. However, relative to their individual profiles, Alex is working at 69% of his current maximum heart rate—Zone 2—while Sam is at 82%, which places him in Zone 4.I built a quick interactive page based on that thought experiment. Move the pace control between 3:00 and 7:00/km and watch the same external output place each runner in different personal heart-rate zones.I’m not suggesting that training raises maximum heart rate, (that is a far more nuanced debate). What is clear is that each perso
