when you curl up, the center of weight is moved from

below the belly button to somewhere in the chest so it will keep the upper body close to the floor, while the curled legs swing up. You need some weight on the feets to keep them on the floor.

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The supporting point make a difference too lol -喝高了- 给 喝高了 发送悄悄话 喝高了 的博客首页 (201 bytes) () 05/20/2022 postreply 12:04:57

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