Simply "Fib" Board
Quote from Simply Fit Board info commercial "It's so fun I don't feel like I'm working out." That's because you're not. In order to challenge the muscles that rotate your spine (or what the fitness world would call your core) there must be a counter force resisting rotation in the opposite direction. Simply twisting on a swivel board does not provide any value. Sure you may break a sweat or increase your heart rate, but those alone do not correlate with any improvement in strength or health. It's not the movement that matters, it's the direction of resistance that determines which muscles are working. Smiling faces and zooming in on the midsection while it twists doesn't change that fact, but it sure makes for a another great perception to sell product.