the standard for an upper tier athlete is to get 20 or more rounds when doing Cindy. Most I believe hover around that number. Assuming you can complete that it is 100 pullups, 200 pushups, and 300 squats in 20 minutes. If you were to break that down into 5 minute intervels you would have to do 25 pullups, 50 pushups, and 75 squats or 2 seconds per rep. Still doesn't come close to L8D3 which is 50 pullups, 100 pushups, and 100 squats requiring 1.2 seconds per rep. Plus that is with people breaking up the exercise. In L8D3 you have to do each exercise unbroken before moving on. I believe that requires a significantly elevated level of effort on the athletes part. Basically your talking all out effort for 5 minutes without rest. Are there any athletes anywhere that achieve 5 minutes straight balls to the wall effort? Not even VO2 max is tested at that level as its a continuous graduation up in intensity. I've heard of training programs that go 2 minutes, especially bike, but not much more than that. Of course Crossfit metcons are supposed to be balls to the wall all out effort for the duration of whatever the WOD is, however, you will rarely see an athlete not take a break (even if only for a few seconds). To do L8D3 you can't break at all as doing full range of motion takes more time.