The ornamental design for a abdominalmuscletraining apparatus, as shown and described.
FIG. 1 is a perspective view of an abdominal muscle training apparatus, showing my new design in a bent state;
FIG. 2 is a front elevation view thereof, in a flattened state;
FIG. 3 is a rear elevation view thereof, in a flattened state;
FIG. 4 is a left side elevation view thereof, in a flattened state; and,
FIG. 5 is a right side elevation view thereof, in a flattened state.
The indicia or broken lines shown on the figures are for illustrative purposes only and are hereby disclaimed as forming no part of Applicant's claimed invention.