Time: You must complete this workout within 20 minutes. Therefore, ALL rest periods must be minimal.
Intra-set rep count: In every 100 rep set, you will be doing what are called "cluster-sets". Every cluster-set you do, you will have a certain number of repetitions which will count toward your total rep number (100).
Each cluster-set must NOT go beyond 20 repetitions. You must stay within the 2 - 20 repetition range for every cluster-set you do. This means you must choose a weight where you cannot go past 20 repetitions.
Load: The load can be divided up any way you see fit. You can go heavier at the beginning, or choose to go heavier on the last 10 repetitions. Just be conscious of the time limit you have. I recommend you stay in the 10 - 20 range until you hit the end, and then you can go heavier where you are performing 2 - 5 reps per cluster. However, you can manipulate this how you want.
Rest (intra / inter): Intra-rest periods (within the 100 rep set) need to be brief. I recommend you take 5 - 10 seconds between cluster sets. For inter-rest periods (between each movement) I recommend you take 1 - 2 minutes rest, then move on to the next movement.
Muscle group split: This method is for the purpose of hitting one muscle group only. Choose one muscle group, choose your 3 movements, tackle it. So your frequency will be just once a week.
Muscular failure: You will only reach muscular failure on the very last repetition of the movement. So at the end of every 100 rep set, I recommend choosing a load where you are working VERY hard (less reps). This way you can reach momentary muscular failure at the end of each 100 rep set. All other sets (clusters), leave 1 - 2 reps in the tank ONLY. So for every cluster set you do, you are STILL working hard, you just aren't pushing to muscular failure each time. Reserve that for the very end.