For a stress test, they want you to hit your MHR.
Since there’s no way to really enforce that for the average patient (many people will quit long before they are physically incapable of continuing), the technicians use the “rule-of-thumb” MHR calculation, and want you to meet that for the test to be considered valid.
In my case, my MHR was calculated as 168, and they stopped the test at 172. I could have gone even higher, but they were satisfied as it was. Note that for stress tests, it’s not just the MHR that is of interest, but how long it takes you to get there.
5’ 10"