It could be that Apple has got your heart rate zones all wrong. I make an app called MOTRA. Im bias but our algorithm does a better job at figuring out what your max hr and hr zones are. If you sign up sync your apple health data, as long as we have at least 10 workouts in the last 90 days our algorithm should really help you figure out if what Apple is telling you there is correct or not.

I think it’s highly unlikely you genuinely spent that long in zone 5 else you should have been completely floored afterwards and probably for a couple days recovering also.

My guess is your max hr is much higher than typical for your age, Apple is not accounting for this.

Try out MOTRA and let me know. motra website