Had one for years I call it a wobbly board Reebock brought them out about 3 years ago but got it wrong, [not enough angle].Its best to try these with your eyes shut, the response is better, also bare footed. the roller and balls, you are working on touch and feel, while the muscles are stableizing form and response over 3 inch. ankle metatarsus toe and achilles where move ment is generated from in a vertical posture. Plus its stretching the hhamstrings by up to 3 inch at speed without to much impact while the whole body has a job to do as far as cordination and speed response, thats a bit of what it does. Try it you will shocked at the improvement in speed.