I found Yasso’s to work and predict pretty much to a tee. I like Woody’s comment, 2:47’s with 2:00 min recoveries. Well, that made his workout much tougher than it should have been. That Al’s run taper didn’t help either. Don’t try to beat the system all the time. Marathon training is cumulative, not any one given day. Throw in Yasso’s with my other slow running and lot’s of it and it will work. Erhardt swears by the 800’s to and he’s run low 2:30s. I had a 19 plus 5k 3-4 weeks before the marathon. that week did Yassos in 2:58-3:00. Then hit 2:57. I’ll give them their due, alnog with the whole package. Alot of people can do the Yasso’s but it becomes like a race series instead of a workout. Then thye are left short if they expect it to work on marathon day. If you want to run longer, run slower. PSKI