Despite the overwhelming odds of getting a penalty kick past a goalkeeper, many soccer kickers fail during big games. For fans of England, penalties evoke a sense of dread. The team has lost six of seven matches in major tournaments during penalty shoot-outs, including three in the World Cup. In contrast, the Germans have won four Cup matches in shoot-outs since 1990, and are five for six in big games.
So what's going on here? Not enough practice? Bad karma? A one-way trip to choke city?
Actually sports scientists say it's a combination of physics and psychology that some players have mastered, and others seem to fail to understand time and time again.
"Most of these (soccer) players can pass a ball to a teammate 30 to 50 yards with pinpoint accuracy," said Greg Wood, a lecturer in sport psychology at Liverpool (U.K.) Hope University who has studied the psychological factors of taking penalty kicks. "But when it comes to hitting a ball 12 yards in top corner, they can't do it. It's because of the emotions they feel. Regulating this is key aspect to penalty taking. They've already got the skills."
Wood and other researchers have found out some interesting things about penalty kicks:
First, don't look at the goalkeeper. Studies show that either focusing on or purposely avoiding the goalkeeper indicates stress. In fact, that's why goalkeepers yell, wave their arms and sometimes do other things to make the kicker choke.
"When players are anxious, instead of looking where they are going to shoot, players focus on the goalkeeper," Wood said. "There's a tight link between where we look and where we shoot. Anxiety makes you focus on things that are threatening."
Wood developed a method of "quiet-eye" training for soccer players that gave them ways to regulate their anxiety by focusing on aiming location in the seconds before striking the ball. After a seven-week training, the players had 50 percent fewer shots save by the goalie. Of course, none of the elite soccer teams in England adopted Woods' training. "It takes a while," he said.
Don't turn your back either. It seems that players who purposely avoid the goalkeeper by turning their back before spotting the ball fare worse than those who face the goal.
Celebrating is contagious. Studies in recent years have shown that players who score a goal and then celebrate by raising their arms actually pass on their enthusiasm to the next guy to take a shot. Same thing when a player misses and slumps back over to the sideline.
Take your time. Players who kick the ball within a second of placing it usually miss. Those who take longer to set and aim do better.
Physics also plays a role in both penalty kicks, and free kicks from the corners or other parts of the field. This year at the World Cup in Brazil, a newly-designed soccer ball may even the playing field for bigger, stronger players and those who are smaller.
John Eric Goff, professor of physics at Lynchburg College and author of "Gold Medal Physics: The Science of Sports," teamed up with two Japanese scientists to study the motion of Adidas' new soccer ball, known as the Brazuca (Brazilian for national pride, or a native of Brazil).
Wind tunnel tests were used to study the new ball and the one Adidas used in South Africa in 2010 known as the Jabalani. It turns out that the new ball is likely to be more predictable, and flies through the air with less drag at lower speeds. That could help some of the underdog teams who kick the ball at 40 to 45 miles per hour, compared to the 60 to 70 mile per hour shots by the top players, Goff explained.
This year's ball is also less erratic. That's because the ball has more roughness on the surface, which causes a slight amount of turbulence on the surface and reduces drag. A similar principal is at work in a dimpled golf ball, Goff said.
Good penalty kickers, in addition to getting their heads straight, also have mastered the art of spinning a soccer ball while kicking it forward. This counter-clockwise spin (for right footed players) gives the ball a slight arc on its way to the goal -- often confusing the goalkeeper.
"It requires skill," Goff said. "You have to spin the ball just right."
Using spin, the best players can curve the ball right around a wall of players and into the goal. That's because they've harnessed the Magnus force, a principal of physics initially discovered by a 19th century scientist who noticed it while studying the trajectory of Civil War bullets.
When the World Cup opens Thursday afternoon with Brazil taking on Croatia, Goff said he'll be watching.
"These are golden opportunities for scorers," he said about the combination of physical forces in play on the field. "I'm going to be looking at these trajectories quite closely to see what kind of spin and speed they can develop."