Heart rate monitor - in my 40s...what should I be pushing?

[Jjcrackers]

Sat next to a girl today on the spin bike who was a good 15 years younger than me and she was (easily) pushing 170. If I kill myself I can do 166/167.

So what should I hit if I am early 40s and really want to push myself?

No totally reliable way to say.

You can google "heart rate zones" and see what figures come up depending on your theoretical maximum heart rate. Most sources would say work mostly in Zones 2 & 4 & you have to google what those are (depends on the exercise guru). You can refine that by figuring out your lactate threshold or getting individual estimate for your maxHR.

I'm 48yo, fairly fit, & 150-155 is pushing hard for me, but also what I can sustain once I warmed up, too. Someone else might be +20 or -25 from that & still pushing hard for them at same age.