FIG. 1 is a front and top perspective view of a sit-up exercise device, showing my new design;
FIG. 2 is a rear and bottom perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof;
FIG. 9 is a perspective view thereof, showing the sit-up exercise device in an unfolded position; and,
FIG. 10 is a perspective view thereof, showing the sit-up exercise device in a folded position.
The broken lines in the figures illustrate portions of the sit-up exercise device that form no part of the claimed design.