Powerballs, powerballs what are powerballs? Basically they are powerfull gyroscopes that you can control to have fun and excercise your muscles at the same time.
You start the powerball either using the provided string or with a quick flick of your thumb, you can roll it over a carpet too if you want, once started you can accelerate the rotor moving your wrist in circles, the faster the rotor goes the less your wrist will move and your muscles and tendons will be doing the real work.
To keep it accelerating find the moment you have to flick your wrist to go against the rotor resistance, if you fail to do it the rotor will slow down and stop and you will have to start again.
Depending on the direction of your movements and the position of your arm you can train different muscles, deltoids, bicepts, triceps, etc.
Some of the models have a counter at the top that can perform several functions, like keeping track of your RPM record, or counting revolutions in the endurance mode where the total number of revolutions in 30, 60 or 90 seconds is what counts. The record mode keeps track of the fastest you were able to spin the powerball, if you are very good with it you can try for the world record and enter the leaderboard at the official site.
The Neon Pro version in the picture has leds that turn on as you spin the powerball, blue, green and orange versions are available. The counter is powered by a coin cell, the leds are powered by the rotor motion, no need for batteries.
The powerball is really strong, you can really feel a burning sensation in your muscles after using it and if you keep a regular training program you will gain muscles (in a geeky way). The powerballs also help you reduce stress, and are great for starting conversations.
The only problem with powerballs is that they are addictive as hell, if you have read this up to this point there is probably no way back, I'm sorry (insert evil laugh here).
The neon pro model costs $48 and you can order and read a lot more about powerballs from the official website. You will find records, videos, user forums and many other nice features in the Powerballs website.