I've got the NSD Powerball 250 Hz about a year ago and it's been one of the best toys I've ever had! You can buy them online or in any bigger sports or toyshop, they come in several variants, there are two major competitors - Powerball The Original and NSD Powerball, my review is about the latter.
-Construction- Powerball is a ballanced wheel (a gyroscope) consisting of 2 main parts - inner ball that rotates around its axis which is set in a hollow globe that misses its bottom part. The globe's made of two parts that click into eachother and the join line is hidden under a tight-fit rubber band with NSD Powerbal logo on it. The inner ball has a groove into which a cord's inserted, wrapped around the ball and by pulling it loose quickly you get the ball moving.
It's possible and also recommended to open your powerball, to check how it's made and also to clean it once in a while. I had hard time opening it because that needs really strong arms as you're supposed to press on its sides until they fall apart, or you can use a vice (that worked fine).
-Types of NSD Powerballs- You can have it with or without a mini counter to see how fast you spun it, you can save your best achievements and select from several spin modes - time limited speed attack or just concentrate on the highest speed you reach. I guess if you already buy a powerball, you'd get it with the counter (it can also be bought separately later, however), because sooner or later you'll wanna not only fool around it, but also know how good you are and how did you improve.
Other option is to have a flash or scream model and I'm glad mine is just simple without extra noise or flashing lights, because the powerball itself produces quite a noise. So even if you might like messing with these features, it might bother people around you.
There also are superspecial powerballs made of steel, which are way more difficult to master as they're heavy and tricky to handle and they work on higher frequencies (500 Hz), those have their own league.
You can also train legs and feet, there's a special powerball device for that, but I have no experience with that one.
-Fun- Speaking about a league, this is another powerball's lure. After you will have trained a bit, you can join powerball forums and compete in all cathegories with other members, posting pictures or videos of your best results online. Challenge your friends who own powerballs and get those who don't have it yet interested! I believe soon there will be international powerball leagues and who knows, maybe one day we'll have a world championship ;)
Powerball is also recommended as a rehabilitative toy for people after arm surgeries, stroke and whatever condition that needs muscles to be re-trained as well as for those who spend a lot of time working on a computer. You don't always need to go for records, mild practise is also possible and if regularly performed, it does give results. You need to know your capabilities and not overdo, as otherwise you're likely to suffer muscle pains. Easy to say but more difficult to do, powerball is highly addictive and especially after you've just bought it you won't wanna put it down. I know something about it...wasn't able to lift a kid at work after almost a whole afternoon of training...
-Technique- It's quite important to master the technique from the beginning, because if spun incorrectly, the powerball quickly develops little faults in its inner construction, which is made to operate precisely and rough handling will only result into powerball slowing down and being unable to reach really high speed levels. You should particularly avoid stopping the spinning by shaking the powerball or dropping it - it won't crack, but the insides will get shaken and the powerball will rattle and give weird "kicks" instead of rolling around smoothly.
The technique isn't difficult, even having no such or similar experience I got into it pretty quickly, but it's nt such a good idea to let all your friends to try and learn, else you end up with a destroyed powerball soon. You need to start the ball using either the cord, some people can do it with thumb or rolling it on forearm, and then keep it moving and speed up gradually by arm moves. If you concentrate on the moves, you will feel a difference when changing the position of your arm and using different muscles, this is great to train muscles as much as you want. As it rolls faster, the powerball "pushes" against your muscles and you need to keep the muscle tight to win over the ball. The grip is very important as well, the powerball should fit into your palm, when you reach higher speed, the powerball will wanna slide out of your hand, so you need to hold it really tight - make sure your fingertip won't get under the globe's hole else that would get you a very nice burn if you go fast at the moment.
-Conclusion- Powerball is just great! It looks cool, works cool and it helps you to get your muscles into shape so can be used as a part of training no matter what sport you do. Or you can jsut play with it for fun and compete on powerball boards. It's catchy and addictive, simply enjoyable! However, you need to treat your powerball well to make it last, it looks robust and almost indestructible, but its inside is quite a sensitive machine.
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