When wanting to build endurance in different regions of the body, then you have to keep tension and activation going in those tissues. We see this a lot when it comes to our cardio endurance, when we spend a selective amount of time with any given activity. The same remains true in our muscle fibers as well, and in this workout we focus on the lower and upper part of the body. Hence the name, Lower-Upper workout.
In this workout, we start off by keeping the lower body muscles engaged for 3 sets of 4 exercises. This places a lot of demand on the muscles as the exercises are not timed, there is a specific rep count to reach.
The second half of the workout works more of your mid section to upper body. Same idea applies here, you have 3 sets of 4 exercises to complete. This entire workout might take some time to finish up, so listen to your body and take breaks as needed.