Gyroscopic exercise tool - POWER BALL

A gyroscopic exercise tool is a device used to exercise the wrist as part of physical therapy or in order to build palm, forearm and finger strength. It can also be used as a unique demonstration of some aspects of rotational dynamics. The device consists of a tennis ball-sized plastic or metal shell around a free-spinning mass, which can be started with a short rip string or by a snap of the thumb. Once the gyroscope inside is going fast enough, a person holding the device can accelerate the spinning mass to high revolution rates by moving the wrist in a circular motion.
The Powerball brand is trademarked in the US by DynaFlex ^[2], and is manufactured by DFX Sports & Fitness in the US.

Gyroscopic wrist exercisers are used for therapeutic and endurance purposes and are highly favored by sports & fitness enthusiasts around the world, particularly those engaging in racket sports (tennis, badminton etc.), golf, rock climbing, motocross, cycling, baseball, hockey, martial arts etc.

In addition, the non impact nature of the products combined with the soothing resistance emitted by the spinning rotor have made them ideal rehabilitation devices for persons suffering from carpal tunnel syndrome, arthritis, RSI, bone breakage etc.^{[citation needed]}

The light-emitting diodes are powered by a small generator embedded in the gyroscope. Even the original Powerball includes the magnet needed to make the revolution counters work.^[3] Other Powerball models on the market today include: the "Powerball 350Hz Metal" and "NSD SuperPowerBall" (these powerballs are made primarily of metal, have twice the weight of "regular" Powerball models and are more challenging to operate since up to 25 Nm of torque is produced); the "Powerball Signature" (featuring white LEDs) ; the "Powerball Screamer" (based on the Powerball 250 Hz model, but with 8 holes drilled in the rotor to generate a very loud sound) and the latest 'Autostart' Powerball model featuring an inbuilt rotor mechanism to allow easy starting of the device (no starting cord required for this model). Nanosecond's Powerball was the first to feature electronic revolution counters and a generator for light-emitting diodes and made its market debut in or around 1997.