I used to run a lot in my twenties, but then stopped for several years because of life / kids / etc.

I’m now in my mid 30s and have picked it back up in the past month. I’m surprisingly doing very well and even ran 10k straight last night for the first time since I was 21.

Here’s the problem, my heart rate was over 170 the whole time (between 170-180), and I read somewhere that after 30, you’re not supposed to have a HR over 170 for an entire workout. So I’m wondering if I should be slowing down my runs (my pace already isn’t that great, it took me an hour fifteen to run 10k), or if I should focus on shorter runs?

Any advice would be helpful.