As defined in both Fitness for Life, Seventh Edition and Fitness for Life: Middle School, Second Edition, strength is the ability of the muscles to lift a heavy weight or exert a lot of force. Speed is the ability to get from one place to another in the shortest possible time. The combination of strength and speed is commonly referred to as power. Power, the ability to combine strength with speed while moving, allows you to do explosive movements such as jumping high, putting a shot, or swinging a softball or baseball bat to hit a ball a great distance. Strength is considered a health-related part of physical fitness, and speed is considered a skill-related part of physical fitness. Power is a combination of strength and speed, it is now considered a part of health-related physical fitness primarily because of its relationship with good bone health.