I think its all core stability work. Our footy manager said he had read before a story about Rooney, they tested his core strength before the PL season and they found when he kicks a ball 60% of the power came from his core. He worked on his core throughout the year and they tested it again before the world cup and it had gone up to 80%. Meaning again 80% of the power came from his core, leaving his legs to work on carrying him around the pitch.
Those big pilates balls are good for core stability work, ever tried doing sit ups on them! It's hard.
I don't know whether thats true of our manager made it up because we were whinging about preseason fitness.