Although it looks like a mediaeval torture device, the Finis Posture Trainer is designed to promote correct head and spine alignment, which is key to an efficient swim stroke. You put it on in the same way as you would a pair of goggles, but the plastic ‘spike’ lies against the back of the head and neck.
If your head is in the correct neutral position then the Posture Trainer should be undetectable, but if you exceed the recommended posture range then the spike (don’t worry, it isn’t sharp!) digs into your neck to remind you to realign your head. With your head in the proper position the rest of your body should also come into alignment, raising the hips, and making you more streamlined.
We found this a useful little gadget, especially if you know you need to work on head position and need a little reminder every now and then. It can be used for all four strokes.