I recently switched from a 30 second/1:30 ratio to the 2:4 ratio. And I like it. I think you can give max effort for the two minutes. You just cannot start out as if you were going to only give max effort for a lesser period of time. You have to know that your are going have to give max effort for the longer period of time. I had and continue to use HIIT either running or on an elliptical. I wear a heart rate monitor and track my beats per minute. Using the 2:4 ratio, I am able to get my heart rate up as high or higher than the 30/1:30 ratio and it stays at that level for a longer period of time. And it takes the full four minutes for it to come back down and sometimes does not come back down. For example, I did HIIT this morning. On my last session, my fifth session, my heart rate reached 182 beats per minute. Normally, I can get my heart rate back down beneath 100 beat per minute before I begin the next sprint. But even after the four minutes of rest, I was still at 110 beats per minute. I do not claim to be a HIIT expert, but to my common sense tells me these large and sustained swings are good. But maybe I am wrong.

My friend who is a runner, said that in studies it shows that the maximum distance a human can sprint at 100% effort is 800 m.  This is in a highly trained sprinter too.  This is slightly more than one lap on the track.No one here can sprint 100% for two minutes.  I personally recommend 30-45 second sprints.

What? An 800m race is a little less than 2 laps...

If you were to hook a device that measured your power output it would peak at about 10 seconds, maintain it until 25 seconds or a little bit longer if you are highly trained.  After this your power output will drop no matter what.  You can't maintain your peak power for 2 minutes, it's physically impossible.