The first video is what I call "trunk stabilization". It can be performed on a cable machine or with a thera-band. Remain braced and stiff throughout the abdominal wall. Pretend someone is about to punch you in the stomach and keep that feeling throughout the exercise. You are getting rotation in the throacic spine area (mid-spine) but that is the only movement. You do not need heavy weight with this exercise. Start off with a weight that you can control.
Along with a clean diet you need the right workout program. Check out my article called "The Best Training Program". This will give you a breakdown of how you can design your own program when going to the gym. With the right mix of science and intensity you will see the results from doing the correct things in the gym.
BE CONSISTENT, WORK HARD, EAT CLEAN, LIFT SMART and you will GET RESULTS!