Geez I push up to 200 HR BPM sometimes on average like 185 BPMThe improvement you can make is indeed crazy once you start. Awesome stuff man - I try to go on regular 10 and 15k runs if I can keeping the HR under 155. was able to make my "forever" pace at 8:40 at one point.
That heart rate is suspiciously low if accurate though - guessing the wrist sensor was off or something?