Please, don't buy this: Zip Curveball Trainer

The inventors of an unusual device that uses a wrist-strap, a tension strap, and some elastic loops, claim the device trains its users "in developing the proper rotation needed to throw a curveball."

Here's an excerpt from the section that tells you how to put it on:

Bend the wrist forward and place the wrist strap on the arm below the wrist, so that tension developed from the tension strap keeps the wrist forward comfortably.
Zip Curveball Trainer (Source:

Zip Curveball Trainer (Source:

The device holds the wrist in a flexed position, but the site claims that the Zip Curveball Trainer will "quickly strengthen the arm, wrist, and finger coordination for throwing a curve."

Unfortunately, that's not how muscles get stronger. Muscles strengthen in response to resistance.

The Zip Curveball Trainer creates resistance for the extensor muscles of the forearm. For their device to do what they claim it can do, it would need to provide resistance to the flexor-pronator mass of the forearm.

Yes, the device positions the hand to the throw a traditional curveball, but it does not strengthen the muscles that are responsible for making a curveball curve.

How *not* to throw a curveball (Source:

How *not* to throw a curveball (Source:

The web site also makes an attempt to teach its readers how to throw a curveball using the diagram to the left and a brief explanation.

The diagram clearly shows an impossible release point, and this is just the beginning of the problems with their recommended delivery.

They actually recommend trying to get the ball to roll over the index finger at release, as well as throwing across the body.  These two recommendations, in particular, can be devastating to elbow health as well as shoulder health.

By trying to get the ball to roll off the index finger, a pitcher prevents himself from powerfully pronating through his release.  Combined with the mild supination of the grip, the lack of pronation causes the olecranon of the ulna to slam into the olecranon fossa of the humerus.

This irritates elbow cartilage and causes a bony tissue response that lengthens the ulna and can limit elbow extension. In young pitchers, it can cause growth plate deformation and avulsion fractures.

Throwing across the body places undue stress on the rotator cuff muscles during the deceleration phase of the delivery.

To have a look at this horrible product for yourself, click here, but please, don't buy this.

Do you know of another stupid pitching product out there? Tell me about it.