Like the Badger says, numbers are less important and very person specific.
What counts is stroke/volume, the amount of blood your heart pumps each beat.
For measuring max heart rate I use the following. Bear in mind that max attainable heart rate can change slightly from day to day. If you’re tired it’ll be lower. You can’t get it up there….
Note – Road bike is best for this as the gear ratios are closer.
On a turbo, with a Heart Rate Monitor (HRM) following a thorough warm up, shift to a harder gear and pedal for three minutes. Note that your heart rate goes up, then stabilises at the new work rate. Now go up another gear, another three minutes work, then another and so on…………
There will come a point where you’re working harder than you can maintain. Instead of your heart rate going up and then stabilising at the new workload it will continue to rise. This is your aerobic threshold. Worth noting what it is.
So now you’re working really hard, your legs are filling up with lactic acid, your starting to lose form and it hurts. Now you push on until just before you throw up. Your at your max. Hopefully your HRM will have recorded it.
Thorough warm down required.
SB