LONDON - When Michael Phelps gets ready to race, he walks to the block, takes off his headphones, swings his arms three times, steps on to the block and he is off. His routine never changes.
Tennis player Serena Williams, five-times Wimbledon champion, who, like Phelps, begins competition on Saturday, always takes her shower sandals to the court, ties her shoelaces in a specific way and bounces the ball five times.
Tiger Woods wears a red shirt in the final rounds of golf tournaments which he has said is because his mother told him red was his power colour.
Despite all the science and massive budgets involved in sport, many sportsmen and women at all levels of sport swear by superstitions or elaborate event rituals to enhance their game with many examples of these on display at the London Olympics.
British diver Tom Daley has a lucky orange monkey and British BMX rider Shanaze Reade always carries a picture of her family.
Psychologists say people often become superstitious when faced with unknown and stressful situations, which explains why so many athletes are superstitious and frequently bound to rigid preparation routines.
"When the stakes are high and there is a great deal of uncertainty - as in top-level sport - then people will try anything to get the outcome they want," Richard Stephens, a senior lecturer in psychology at Keele University, told Reuters.
"When there is a low cost of carrying out an action but there is possibly a high gain then you may as well."
But does it make a difference?
A study by psychologists at the University of Cologne in Germany found in two experiments that superstition triumphed in both cases.
In one experiment, participants were given either a lucky golf ball or an ordinary one before being asked to sink a putt. Those with a so-called lucky ball were more successful.
Participants were also asked to bring along a lucky charm but these were confiscated from half of the participants before making them take a memory test. Those who kept their lucky charm performed better, the scientists reported in 2010 in Psychological Science.
Some sports psychologists warn, however, that superstitions can be harmful to an athlete's performance if they are taken too far and become a distraction, particularly if they have no link to their actual performance.
Australian swimmer Stephanie Rice says she is a firm believer in superstition and karma, and will do eight arm swings, four goggle presses, four cap touches before a face.
But it is shoulder problems have led Rice to play down her chances in London of repeating her Beijing success when she won three gold medals, two individual and one relay.
Andrew Lane, professor of sport psychology at Britain's Wolverhampton University, said routines were important for athletes as the hour before an event could be very stressful and go slowly.
British women footballers have spoken about their set routines with Kelly Smith putting her boots on last and leaving the dressing room last while Kim Little always puts her socks and shin pads on her left side before her right.
"It is the reliance on these routines that can be critical to keeping them level-headed," Lane said.
"But if it becomes an fixation on something that is not relevant to performance, you might need to change that."
London-based sorts psychologist Victor Thompson said athletes needed enough flexibility to cope with something going wrong with their routine such as losing their lucky shirt or an iPod malfunction so they cannot listen to their pre-game music.
"This can create anger, stress, anxiety, and physical tension," Thompson told Reuters. "It becomes a distraction and causes a drop in confidence... all of which leads to a higher chance of performing poorly. They can't rely on false self-confidence or reassurances."
Keele University's Stephens agreed.
"If you start to spend too much time focusing on these irrational things to improve your performance rather than the important things, such as your swing or being relaxed, then these superstitious techniques can take away from the outcome," he said.
Some athletes are wary of relying too much on superstitions for their performance.
"I'm superstitious about having any superstitions. I do my best to quash any of that start creeping up on me," Australian diver Matthew Mitcham, who won gold in Beijing, is quoted as saying on his official Olympic profile.