FIG. 1 is a perspective view of a waist-twisting exercise device showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view of the waist-twisting exercise device, wherein the broken line showing of the person is for illustrative purposes only and forms no part of the claimed design.