The ornamental design for a martialartstrainingdevice, as shown and described.
FIG. 1 is an isometric view of the martial arts training device;
FIG. 2 is a front view of the martial arts training device;
FIG. 3 is a rear view of the martial arts training device;
FIG. 4 is a right side view of the martial arts training device;
FIG. 5 is a left side view of the martial arts training device;
FIG. 6 is a top side view of the martial arts training device;
FIG. 7 is a bottom side view of the martial arts training device; and,
FIG. 8 is an isometric environmental view of the martial arts training device.
In FIG. 8, the broken lines are for the purpose of showing additional equipment that can be attached to the device that form no part of the claimed design.