Warm up 5 minutes.
30 minute row with rate pyramid.
Rate changes every 3 min:
18, 20, 22, 24, 26, 28, 28, 26, 24, 22.
Start out at 5K+16 and build to 5K+8/10 by the top of the pyramid — then keep that pace even as the rate declines.
Cool down 5 minutes