2x20 Sweet Spot

Warm up for 15 min. Then do 2 x 20 min sweetspot intervals with 2 min rest interval between.
These should be done at 88 to 93% of threshold power or 92-95% of threshold HR.
Warm down after.
Heart rate users should remember that it will take several minutes for your HR to raise to the prescribed level.
Go by perceived effort at the beginning, dont force it!