Skateboarding is probably frowned on by the All Blacks but Sonny Bill Williams has come up with an ingenious way to use one as he battles back from major injury.

The All Black posted a short video to his Twitter account showing him with his left foot, which is in a moon boot after surgery, strapped to a skateboard to allow him to use a rowing machine.

Williams suffered a partial rupture of his Achilles in the New Zealand seven side's opening game against Japan at the Rio Olympics last month. He was expected to be out of action for up to nine months.