I didn't have any problems getting my HR over 150 on the windtrainer on Saturday and I was barely even trying!
So at a guess I'd say my 20 years extra means my 150 is like your 170 - which you only just got over. And I didn't do any one-legged work.
I didn't do single leg on Saturday either or even much of an effort, just horribly out of form. That kind of session would normally be well under 150 for me, just like today's shouldn't have gone over 170 but did it easily.