Stairs
50 sets
25:46 (new PR by 26 seconds), 161 BPM avg heart rate.

May not get a second set in this afternoon - stuck in the control room. Depends on the good will of my shift partner...

Edit:

I have a gracious shift partner who agreed to kick back in the control room for a while, as I huffed and puffed on the stairs

In return I took care of a couple of unpleasant chores for him, so it works out.

Stairs (afternoon of 12-12-20)
28:15 avg heart rate 163 BPM