IMHO, it's leg raises on wall bars:
By doing this core exercise only, you can develop the strength needed to perform numerous other core exercises with ease, making them unnecessary. Wall bars (a.k.a. stall bars) behind the back prevent the use of swing and momentum instead of strength, which is inevitable when performing this exercise on the horizontal bar.
By doing this core exercise only, you can develop the strength needed to perform numerous other core exercises with ease, making them unnecessary. Wall bars (a.k.a. stall bars) behind the back prevent the use of swing and momentum instead of strength, which is inevitable when performing this exercise on the horizontal bar.
