@jyne OP uses Karvonen's formula, where Z2=60-70% of heart rate reserve. In Karvonen's formula, the aerobic threshold is at 0.7*(max HR-resting HR)+resting HR. With OP's numbers, that results in 131.4-144.3 for Z2, with the caveat that this is an estimate, not an exact range.
You are using a...