When I saw Monday night's trainer workout being "Sprints" which were 2x30 seconds, 2x20 seconds, 3x10 seconds and 3x5 seconds "as hard as you can go" with 30 second easy spins in between each, I thought, how absolutely easy is this going to be? You stand, you go like hell for about 10 seconds, then sit and go like hell for another 20 seconds and then it gets easier! Simple as pie -- I can handle this. I forgot to mention you do the above routine 5 times. The first set wasn't bad at all. The 30 seconds seemed kind of long, but I still was figuring it would be over in no time. The 2nd set was a little harder. By the time the 3rd set rolled around, my heart rate wasn't coming down during the 30 second easy spin sections. Hmmmm.... I think this might be a little harder than I first thought. "As hard as you can go" means really working the heart and after a couple minutes, it was starting to stress out. By the time the 4th and 5th sets rolled around, I was spinning for 40 seconds easy between the intervals to give my ticker a little more of a rest. Total time in the 95% zone was about 12 minutes with it coming down only to the 90% zone in between each for another 12ish minutes. But "hard as you can go" had another effect on the bod other than the ticker -- my hams. The quads endured the strain, but as soon as I got off the bike, I could feel the hams just above the backs of my knees. They were a bit overworked -- a good overworking (no injured feeling). This frickin' workout was not at all easy and I like the fact something new was feeling the workout (hammys). I now know exactly how track bike racers feel and why they are built like brick shit houses with massive quads. None of these trainer workouts are easy which is exactly what the old body needs to get more fit. Thank you Mr. Bike Trainer - you're doing a great job.