Watch: Effective 15-second Abs Workout

I have been trying to get a six-pack abs and so far I'm almost there.  Since I started working out in the gym, I make sure to add an ab workout in my routine.  Most often after the workout, I notice some changes on my abs structure.

Never it comes to my mind that there is a proven effective 15-second ab workout.  I tried it and here is the video of how it works for me.

When I'm so slim, my abs really shows after a total body workout.  But every time I gain weight mostly on my tummy, I have a hard time getting a six-pack abs.