Walk/Jog for just 3 miles. Ugh -- my avg HR was 128 bpm after the first mile. That is HIGHER than 70% of Max HR, which is what I should be doing on most of my runs (not my super easy jog/walks). I'm very curious to know if staying at this low HR will eventually lead to improved aerobic fitness (and faster paces at these low HRs. It seemed to work once before, so I'm hopeful that it will work again.