A max HR test can be done on a treadmill in a gym too. Unless you're used to reaching your max HR during exercise - something I don't suggest - it will be pain

A max HR test can be done on a treadmill in a gym too. Unless you're used to reaching your max HR during exercise - something I don't suggest - it will be painful, but you're not supposed to hold your heart rate at this level for long either, just long enough for the heart rate sensor to register that level.