An article by Coach Hughes / RoadBikeRider.com convinced me that HIIT should be a permanent part of my riding fitness routine. I've no power meter, never raced, and am worried that the (COVID) 2-year absence of century rides might have caused me to slip below the fitness level I'll need when they resume this fall. I'm 82, so just staying fit enough to ride the metrics takes deliberate effort. I do monitor (and record) my FITBIT data which gives me confidence that I'm maintaining the same level of effort. On a typical 30 mile ride (coffee and sweet roll at the turnaround) I'll do at least 5 or 6 intervals; 30 - 60 seconds at an unsustainable 200%, spaced out at least 10 minutes apart. I'm fairly religious about this, and can't wait to ride with a big group again to see if I can still keep up. If I can, I'll give Coach Hughes and HIIT the credit.