Baoding balls

Baoding balls were named after the city of Baoding in the province of Hebei, China, during the Ming dynasty. Construction methods varied. Formerly, they were usually called "iron balls", as they were originally made of iron. As metalworking advanced, "iron balls" became more popular. Baoding balls continue to be produced there.

• Illustration — Baoding balls in use The basic exercise consists of holding a pair of Baoding balls in the palm of one hand, rotating them (switching the relative position of the two balls) while maintaining constant contact between them. Once this technique has been mastered, the rotation speed can be gradually increased until the balls separate in the hand. Eventually one hand can learn to rotate them completely without the balls making contact with each other. Exercises have been developed involving more balls, where the main technique is to avoid contact with the other balls. This requires using a finger, usually the index finger, as a divider. An average user should be able to start with a 45 mm (1.8 in) ball and move up to 60 mm (2.4 in) as their muscles get accustomed to the exercise. Larger Baoding balls between 70 and 100 mm (2.8 and 3.9 in) can be used. Keeping larger balls separate while rotating them is an advanced skill. The area of the hand exercised can be varied, altering the part of the hand they rotate over, or changing the orbit of the balls so that more force is exerted on a particular finger or finger joints.

Baoding balls are often used in physical therapy and occupational therapy to exercise the soft tissues of the hand, wrist, and arm, such as after surgery to the hand. They are sometimes recommended for treating traumatic stress in children and adolescents. Well-known strongmen such as John Brookfield used shot put balls as Baoding balls, rotating them to develop forearm muscles and improve their grip.

Proponents of alternative medicine claim that baoding balls can improve brain function and reduce stress by stimulating the acupuncture points on the hand.