The ornamental design for an exercise apparatus, as shown and described.
FIG. 1 is a perspective view of an exercise apparatus showing our new design;
FIG. 2 is a front elevational view thereof, taken in the direction of arrow 2 in FIG. 8;
FIG. 3 is a top plan view of view thereof, taken in the direction of arrow 3 in FIG. 8;
FIG. 4 is a bottom plan view of view thereof, taken in the direction of arrow 4 in FIG. 8;
FIG. 5 is a rear elevational view thereof, taken in the direction of arrow 5 in FIG. 8;
FIG. 6 is a left side elevational view thereof, taken in the direction of arrow 6 in FIG. 8;
FIG. 7 is a right side elevational view thereof, taken in the direction of arrow 7 in FIG. 8; and,
FIG. 8 is a view identical to FIG. 1 with directional arrows included, in accordance with good engineering practices, so as to best indicate in what directions previous views are taken so that nothing regarding the design sought to be patented is ambiguous or left to conjecture.