A 50 pound-mass dumbbell is pulled downward by the Earth's gravitational field at an acceleration of 32.174 feet-pound-mass per second squared, so the force to lift it is 1,608.7 pounds-force. Newton's second law of motion states that force is equal to mass multiplied by acceleration, gravitational or otherwise.
A pound-mass needs to be distinguished from pound-force because they are not equivalent units. A pound-mass refers to how much mass an object possesses; in the case of the dumbbell, it is a 50-pound-mass object. A pound-force is the unit of force that an object is acted upon. In the example given, lifting a 50-pound-mass weight requires 1,608.7 pounds-force away from the surface of the Earth.