Arnold Schwarzenegger has thanked fans for showing support after his son's boogie boarding accident.

Christopher Schwarzenegger - the youngest son of the former Governor of California and his estranged spouse Maria Shriver - is expected to be back "at full speed" after the 13 year old suffered a collapsed lung, various broken bones and broken ribs during the incident in Malibu, California, earlier this month that left him in intensive care.

Arnold wrote on his twitter account: "Thanks for all your support for Christopher. It means a lot to me & to him. He's doing much better & we'll have him back at full speed soon."

The 62-year-old actor - who recently split from Maria following revelations he fathered a child with their former housekeeper Mildred Patricia Baena - tweeted on the same day his lawyer filed an updated version of his Response to Maria's divorce petition, which reversed his original decisions asking for the court not to award Maria spousal support or attorney fees. 

Last week, Arnold and Maria released a joint statement last week revealing Christopher is expected to make a "full recovery" and thanking medical staff and emergency personnel for their help during the episode.

They said: "A few days ago our son Christopher suffered an accident at the beach. While it has been a very scary week, Christopher is surrounded by his family and friends. He is a brave boy and is expected to make a full recovery.

"On behalf of our entire family, we want to sincerely thank the paramedics and lifeguards who responded so swiftly as well as the doctors, nurses, emergency room and hospital staff who have cared for our son.

"They have been extraordinary to him and to us. We thank everyone for their thoughts and prayers and ask for respect and privacy for Christopher and our family."