Spinball. Grip strength of the fingers: Holding the Spin Ball with the fingertips. Wrist strength: Holding the Spin Ball in the hand with wrist rotation. Stable wrist during rotation. Bicep strength: Rotation with the ball angled upwards. Tricep strength: Slightly raised, extended arm, rotating the back of the hand forward and inward. Shoulder strength: Rotation with the arm extended sideways. The special rotational movements of the Spin Ball allow for targeting different muscle groups and tendons depending on the positioning of the arm and wrist. The small rotor inside the Spin Ball can reach speeds of up to 12,000 revolutions per minute. The greater the rotational speed, the greater the forces generated, which can correspond to a maximum weight of 15 kg. This relationship prevents overexertion and activates important deep muscles.