In the opening matches of the Paralympic goalball competition here in London, both of Britain's teams lost to the world champions: Lithuania won the men's opening match and China won the women's match. But both British teams managed to score against their opponents - with the goals credited to Michael Sharkey and his sister Anna Sharkey.

Goalball is designed for competitors who have visual impairment, like both 27-year-old Michael and 24-year-old Anna. It's a team sport in which three competitors take to the court wearing black-out blindfolds. The audience is hushed to silence as the athletes hurl a heavy blue ball at each other; it contains a bell so they can hear it as it heads toward the goal, which runs across the entire end of the court. Competitors also make noises to let their teammates keep track of them. Amazingly, they manage to stop the vast majority of throws by diving in front of the oncoming ball.

Michael and Anna both trained as physiotherapists, and are fairly sports-mad in general, spending spare time on country walks and rock-climbing. Michael realised that goalball "was the first sport where my visual impairment wasn't a disadvantage when competing". He won his first gold medal at age 18 at the 2003 World Youth Championships, where he was named most valuable player.

Anna says it was love at first sight after her first match. She also admits that she followed her big brother into goalball. "We have been close growing up," she said. "I followed in his footsteps all the way." Anna was on the gold-winning team at the European Goallball Championships in 2009.

And both of them are active in their church, counting their faith as integral to their sport. "I want to use everything I do to glorify God as much as possible," said Michael. "Some people can sing beautifully. Some can write beautiful poetry. I can throw a goalball very hard."

Michael is especially inspired that the Paralympics are being held in his home country. "There are so many world class athletes who never get an opportunity to compete at their own Paralympics," he said. "What an honour!"