Explain how all three of Newton's Laws of Motion apply to weightlifting.

Newton's first law, an object will stay at rest only if there are no external forces acting on the object or if the net external force acting on the object is zero. Since the barbell is at rest (not moving), the net external force acting on it must be zero

Newton's Second Law of Motion via the equation f = ma, or put differently, force is equal to mass multiplied by acceleration. To generate more force, we must either increase mass or acceleration (or both)

Newton's Third Law of Motion is known as the equal and opposite reaction principle