Abstract: A motorized dumbbell attached to a power source for use in exercising a muscle group of a user. The motorized dumbbell includes a handle and a weight section connected thereto. The weight section includes a base connected to the handle and a skirt extending from the base to form a cup shaped recess. A cover is positioned on a side of the skirt opposite the base to close the cup shaped recess. A motor is positioned within the cup shaped recess and connected to receive power from the power source and a disk is rotatably connected to the motor wherein the disk is caused to rotate by the motor when power is applied to thereto by the power source. Movement of the motorized dumbbell when the disk is rotating produces an inertia and gyroscopic forces which act to increase the resistance applied to the muscles group being exercised by a user.