The ornamental design for a weightlifting supportshirt, as shown and described.
FIG. 1 is a front left side perspective view of a weightlifting support shirt showing my new design in a fastened state;
FIG. 2 is a rear right side perspective view thereof;
FIG. 3 is a front view thereof in an unfastened state;
FIG. 4 is a rear view thereof in an unfastened state;
FIG. 5 is a front view thereof in a fastened state;
FIG. 6 is a rear view thereof;
FIG. 7 is a left side view thereof, the right side view being a mirror image of the left side view;
FIG. 8 is a top view thereof; and,
FIG. 9 is a bottom view thereof.
In FIGS. 1-9, the dash-dot broken lines on the surface of the weightlifting support shirt represent stitching that forms a part of the claimed design. The entirety of the fastening straps shown in evenly broken lines represent portions of the weightlifting support shirt that do not form part of the claimed design.