Based on these skills, Tennis players must develop joint stability and connective tissue strength through the knee, ankle, and shoulder (to support and stabilize rapid changes of direction, and the striking motion), reactive ability, and quickness (for lateral speed and defensive ability), core strength and rotary speed (to support the lower lumbar spine during striking motion, and ability to create torque through the separation of hips and hands to generate racket speed), balance and stability (to maintain control of the body while rapidly transferring weight), grip/forearm strength (to aid in racket speed) posterior chain strength and power (to develop strength through glutes, hips, and legs).