Any workout plan assumes that you have taken the time to crystallize your goal and organize the most effective steps to reach it.
A warm up sequence is the first step regardless of your plan.
After warm up, the first exercise is determined by the degree of challenge.
Exercises that involve lifting your lower body are more challenging and more productive that exercises that involve your upper body. Many of lower body exercises engage your hip flexors and should be avoided if you have tight hip flexors, lower back or knee pain.
An effective sequence in workout routines is to begin with more challenging ones when you are fresh and can keep your mental focus. If you leave challenging exercises for the end of your workout, chances are that you either skip them or give them a superficial attention.
Knee tuck in this beginner abs workout routine engages your lower body and abs and because of the seated position on the floor, you also engage your triceps and shoulder. The slow 4 second timing is designed to give you one minute of engagement with emphasis on the right spots. Watch the instructions in the video for performance and safety details.