The Gyro Ball easily gets going with one quick pull of its starter cord. Subtle movements of your wrist cause the balanced rotor inside the Gyro ball to spin faster and faster. As maximum RPMs approach 13,000, it develops up to 35 lbs. of gyroscopic force. The progressive resistance strengthens the muscles of your fingers, hand, wrist and forearm to relieve tension, improve coordination and strengthen your grip. The ball was designed not only to be user friendly but to aid in sports rehabilitation and conditioning.