DEFINING THE POWERBALL
The Powerball can be defined as a gyroscopic excercise tool. In marketing texts you can read that it is both useful for athletes and musiciands to build strength as well as for rehabilitation of lower forearm and wrist joints affected by carpal tunnel syndrome, repetitive strain injury, arthritis or other injuries. It can also be used as a toy, for simple entertainment. So, that's a somewhat official definition. A less conservative definition would be that the Powerball is slightly bigger than a tennis ball, fits right into your palm, and by turning your wrist, you can make the ball spin at unbelievable speeds, which creates tension and resistance. This hence leads to you getting a bit of a workout. As a further incentive, the more expensive models have both an LCD screen that shows you the speed at which the ball is spinning, as well as lights that will engage when a high enough speed to power them has been reached.

HOW IT WORKS
The Powerball is basically a hollow ball with a smaller ball inside of it. There is an opening so you can touch the small ball. The system between the two balls is actually a highly balanced gyroscope. The purpose is to get the small ball to spin inside of the big hollow ball. The big hollow ball will then be still in your hand while the small ball is spinning at very high speeds inside of the big ball. Some very few people can get the small ball spinning, by giving it a push with their thumb through the opening on the big ball. You can see videos of this on Youtube, but I can't see myself accomplishing this any time soon. Thankfully, you get a piece of red thread with the Powerball. There is a small indentation in the small ball where you can insert the tip of the thread, then slowly swirl the small ball around, so that the thread goes twice around the small ball inside of the big ball. Now, holding the other end of the thread in one hand, and firmly gripping the Powerball with your other hand, pull the thread with immense force, as if starting up a chainsaw. This will have the inner ball spinning around instantly. Now, all you have to do is start to move your wrist in a circular motion. It can be a bit difficult at first to "synch" up with the ball, but once you manage to do this, you can increase and decrease the speed, by changing how you move your wrist and by making the circle smaller and smaller. At the highest speeds the circular motion you make with your wrist will be so small, your hand will seem not to move in a circle at all, just shaking with the tension. Surprisingly, you can easily reach speeds of several thousand revolutions per minute. The world record at the moment is a peak speed of 16,732rpm.

MODELS OF POWERBALLS
The cheapest Powerball is just a gyroscope with nothing added, although it's possible to buy an LCD screen as an addon. All the more expensive models come with an LCD screen. The LCD screen shows you statistics, like how fast you managed to spin the ball. It's really worth getting the LCD screen, even if you think you don't care how fast you can get the ball to spin, as it will help you monitor your process and set goals. The more expensive models will usually have lights that are triggered when you are generating enugh power spinning the ball to power them. For a starter, I would recommend any model with an LCD screen and lights, which you can get for around £13 or so (250Hz Neon for instance). The 350 Hz Metal Pro reviewed here is twice as heavy as the beginner models and should only be used by experienced Powerball users. It is made of chrome and comes in a transparent display case, nice to look at, but also expensive. I'd say too expensive, costing around £50. A good thing is that all powerballs come with a 25 year guarantee.

PERSONAL EXPERIENCE
I'm a guitarist, and I wanted a Powerball out of curiosity and to strenghten my wrist and fingers. I originally read about it in a musician's forum, when it was said traditional finger grip excercisers can actually lead to carpal tunnel syndrome, which defeats the purpose of using them in the first place. So I embraced the Powerball from the perspective of being an excercise tool I could use to strenghten my hands and fingers for my guitar playing to avoid developing carpal tunnel syndrome or any other issues which are common among active guitarists. When I got my first Powerball I figured I'd be be using it casually while watching TV and such, but I found it being too noisy and too much of a consuming process, which took my attention away from the TV. So I find myself rather spinning it as fast as I can for five minutes a day, giving it all of my attention, rather than multi tasking with it.