So why does a person lift weights? Why does a person take bike rides? Why do some choose to attack steep hills? It is because they seek greater physical strength and they recognize the personal benefits of strong legs and strong arms. After all, legs are the primary “vehicle” that accommodate human mobility, and strong arms and legs allow a person to lift and carry heavy loads. Humans benefit by increasing or maintaining good leg and arm strength, and this happens only when a person continues physical activity in the face of resistance.