A schoolboy, who has been unable to play sports, has found the perfect entertainment--snowboarding. Thomas Pettigrew is enjoying himself by performing difficult actions at freestyle events. The youngster can't join in PE lessons at school, because he suffers from a rare condition, which means his body dangerously overheats. This makes it difficult for his body to cool down naturally. But the ice-cool temperatures on the mountains mean Thomas can slide down the slopes freely. His father Richard came up with the idea of taking Thomas snowboarding in March, 2010. Now while other children look forward to playing outside in the sunshine, Thomas is applying his new activity at the Snow Zone in Castleford, in temperatures of about -5degC. Mr. Pettigrew said, "When Thomas tries most sports, he has to stop when he gets too hot but that never happens with snowboarding. I was surprised at how good he was when he started. He now goes every week for three or four hours. He's been so enthusiastic about his snowboarding that he's even persuaded me to have a go, so we can enjoy it together." Thomas's parents have spent the past 10 years watching the schoolboy for any signs of overheating, only taking him on holiday in the cooler months. "He has no energy and no interest in doing anything if he overheats and we do whatever it takes to cool his temperature, such as putting him in the car with the air conditioner working or running cold baths." Aiden Harington, head of the ski school at Snow Zone, said, "Snow sports are a great way for anyone to keep fit, but seem to be particularly beneficial to Thomas as he is able to make sure he stays cool. Thomas does very well in snowboarding, and he can now perform plenty of freestyle actions. I'm sure that he will continue to progress in the coming months, and hopefully take part in some of our freestyle events." Thomas Pettigrew thinks snowboarding is   _  .
dangerous pleasant healthful difficult