o 60 seconds at approx. 95% max. heart rate,
o 75 seconds active recovery.
Should do 8 to 12 reps (plus standard 5 minute warmup and cooldown).
This fits under the general rubric of "high intensity interval training" (HIIT).
This particular protocol has some limited specific research going for it; I found the study by Gibala encouraging. I can get to 95% max. heart rate on a regular spinning bike, and I find the combination of level of discomfort and time of discomfort acceptable and perhaps preferable to sharper shorter efforts (e.g. Tabata).
With the first two weeks done I'm decreasing the number of sessions per week from three to two (with allowance for zero during recovery weeks). I expect that I'll continue with them at least through the end of June (looking for fitness gains through the end of May and then maintenance through June training disruptions).
Here's the most interesting piece that I've found so far that relates to HIIT and long-term training of endurance athletes:
[Hat Tip: a comment on a web forum]