![The massage device consists of two wooden balls held in place by a metal rod that is attached to a frame.](https://imagenes.elpais.com/resizer/v2/ATA3ZCP6VK2BLXZTPHZUH25R6Y.jpg?auth=1a39a83a706d999498fb6f8d324a6617d9caea0a5d01b3fe30580f1f19595a6b&width=414&height=233&smart=true)
A rod for your own back? Spaniard invents new massage tool
Simple device consisting of a bar and two wooden balls wins prize but effectiveness is questioned by specialists
Simple device consisting of a bar and two wooden balls wins prize but effectiveness is questioned by specialists