A1 target around 65% HRmax
(maybe 70% HRmax if you are very fit)
A2 target around 70% HRmax
(maybe 75%-80% HRmax if you are very fit.)
Doing long pieces (30-60 minutes most days) in these ranges represents a significant commitment. The goal of splitting them into two ranges is primarily psychological -- on 'a' days the workout requires a little bit more than on 'b' days.
