An exercise device includes a flat base having a first end and an opposing second end. The base is configured to engage a flat exercise surface. The exercise device further includes a pair of opposing sidewalls extending away from the base and an arcuate upper surface extending between the first end and the second end between the pair of opposing sidewalls. A first angle is defined between the base and the upper surface proximate the first end and a second angle is defined between the base and the upper surface proximate the second end. The exercise device also includes a coccyx cutout in the upper surface proximate at least one of the first end and the second end.