Gyroscopes aren’t actually magical, but watching one in action definitely gives the impression of sorcery being afoot. This cool-looking exercise gadget makes use of the same principle to provide your wrists and forearms with a low-impact yet surprisingly thorough workout.

One consequence of this gyroscopic design is that you determine the amount of force acting on your hands by how fast you rotate them, making it difficult to overstrain your joints.

Another is that it needs no batteries to operate, yet produces an impressive 25 pounds-inches of torque (the same amount of rotational power as two pounds of pressure on the other side of a wrench a foot long). It this isn’t enough for you, you can also opt for the more expensive model constructed from metal and capable of generating 50 lbs-in.

Quite Easy to Use

To use it, simply wind up the interior ball using your thumbs – cheaper competitors require you to start it with a string, which doesn’t work nearly as well – then hold it in one hand while twirling your wrist.

The ball’s internal inertia will automatically push back against your movement, giving you a pretty noticeable workout without weights or resistance bands.

When done correctly, your wrist’s motion actually causes the gyroscope to speed up, increasing the tension level and allowing you to keep exercising for longer. If you choose a model with a digital RPM counter, you can even keep track of your performance over time.

Remember that your hands don’t contain any real muscles; instead, you’re strengthening those in your forearms while also conditioning the tendons and bones in your wrist and fingers. The latter don’t adapt quickly, though, so it is possible to overdo things with this device. That having been said, devices like these are used by athletes as well as people recovering from surgery or carpal tunnel syndrome.

Both flexibility and grip strength are improved with regular use, while playing with it is undeniably a huge amount of fun.