Let's end with some final thoughts on ab crunch machines and training the abs while conveniently sitting on our butts. Come on, this contradiction alone should raise the question, "What am I doing in the gym in the first place?"
Part 1 thru part 3 outlined the specifics, so let's step back and look at common sense. We know that our abdominal muscles help to stabilize our trunk, support our strong posture, and even protect our internal organs.
We further know that they play a major role in movement of our torso BUT also prevent undesired movement in our torso.
Therefore, it is complete nonsense that we should consider training this area while seated AND within a limited range of motion. (The ab crunch machines accomplish both.)
Take it one step further and consider that most of us sit throughout our working day. We also sit in our cars, we sit on the couch, and we sit during our meals.
So, why in the world would we SIT while training our bodies, especially our abdominal muscles? No can do!
Find some open floor space, hold your positions, and leave these ab machines in the dust!
Make it a great day!