In this World Cup year, when football (soccer) passions are running high, supporters might be forgiven for objecting to every decision to award a foul against their team, made by referees. But they might also have a point. Researchers at Rotterdam School of Management, Erasmus University have researched all recorded fouls in three major football competitions over seven years. They discovered an ambiguous foul is more likely to be attributed to the taller of two players.
Dr. Niels van Quaquebeke and Dr. Steffen Giessner, scientists at Rotterdam School of Management, Erasmus University began their research by transferring their insights from decision making in business into the arena of sports. Specifically, they wanted to investigate whether people consider the available information in such ambiguous foul situations in an unbiased, i.e. subconsciously unprejudiced, way. Based on evolutionary and linguistic research which has revealed that people associate the size of others with concepts such as aggression and dominance, Van Quaquebeke and Giessner speculated that ambiguous fouls are more likely to be attributed to the taller of two involved players. Results indicate that respectively taller people are more likely to be perceived by referees (and fans!) as foul perpetrators and their respectively smaller opponents as foul victims.
To put their assumption to a test, the scientists analysed all fouls recorded by Impire AG in seven seasons of UEFA Champions League (32,142 fouls) and German Bundesliga (85,262 fouls), the last three FIFA World Cups (6,440 fouls) as well as data from two additional perceptual experiments with football fans. For all seasons, leagues, and data collection methods, their analyses revealed the same picture confirming their initial assumption: taller people are indeed more often held accountable for fouls than shorter ones -- even when no actual foul was committed.
A scientific article based on their research will be published in the Journal of Sport & Exercise Psychology in February 2010. This article can also be found on hdl.handle.net/1765/17827.
Van Quaquebeke said: "We chose football as the context of our studies because the sport often yields ambiguous foul situations in which it is difficult to determine the perpetrator. In such situations, people must rely on their 'instincts' to make a call, which should increase the use and thus the detectability of a player's height as an additional decision cue. Furthermore, the use of referee assistance technology and adequate referee training is frequently debated in association football. Thus, by providing scientific insights on potential biases in refereeing, our work might help officials weigh the options."
Both researchers say, however, that it is not their call how to derive conclusions for football practice.
Thursday, January 28, 2010
Monday, January 25, 2010
Soccer Injuries: Cleat-Natural Grass Combination May Be Less Likely to Result in Anterior Cruciate Ligament Injury
SAthletes put less strain on their anterior cruciate ligament (ACL) while making a cut on a natural grass surface while wearing a cleat.
This is the conclusion from a study by investigators at Hospital for Special Surgery (HSS) that tested the strain placed on the ACL of four different shoe-surface interactions: Astroturf/turf shoe, modern playing turf/turf shoe, modern turf/cleat, and natural grass/cleat. The study appears in the January 2010 issue of the Journal of Biomechanical Engineering.
"It appears that a similar cut made on four different surfaces, the best strain profile is in grass/cleat combinations," said Mark Drakos, M.D., formerly an orthopedic fellow in the Sports Medicine and Shoulder Service at HSS. "So, there is less force occurring at your ligament for the same cut on that particular surface using this model."
He added that the study investigated noncontact injuries. "These are injuries where an athlete plants his or her foot while making a cut and blows out his or her knee," Dr. Drakos said. "The reason that I think this is so interesting is because there are still environmental factors, which have yet to be optimized. We don't know all the science behind why ACL injuries may be more common on turf than on grass. This study starts developing some of the science behind that, so that it can be looked at more closely because, at the end of the day, I think we need to optimize some of those environmental factors."
Previous studies have suggested that increased traction at the shoe-surface interface may increase the risk of sustaining an ACL injury. While the majority of studies reveal that ACL injuries are more likely to occur on artificial turf, there are some studies that have shown that injuries occur more frequently on grass fields. So, investigators have concluded that confounding factors, such as weather and footwear, must play a role in injuries. Some investigators have constructed models to test how the shoe-surface interface impacts loading conditions at the level of the foot, but no studies have investigated how the interface directly impacts the knee.
To fill this knowledge gap, investigators at HSS used a cadaveric model to test various shoe-surface interactions; they used the lower extremities (knee, foot, and ankle) from eight cadavers. One at a time, each specimen was positioned in a box-like structure, rigged to be in a standing position. The knee was positioned at a 30 degree angle, the flexion angle where the anterior cruciate ligament is most sensitive to strain. Investigators constructed an apparatus that placed weight on the leg, to simulate the weight of a body. Underneath the foot was a turf box that housed whatever turf they wanted to test and underneath the turf box, they placed a force plate that registered how much load was being placed on the shoe-surface interface. A lazy Susan was placed underneath the force plate that allowed the force plate and turf box to rotate. In this way, researchers could simulate a cut or a person pivoting in, for example, a soccer game.
"Our model looks at how forces travel up the kinetic chain, and that is something that should be looked at more closely, meaning you can't just look at the knee injuries by looking at the knee in isolation," Dr. Drakos said.
The investigators found that the natural grass/cleat combination placed a statistically lower maximum strain on the leg than any of the remaining three groups. All other combinations placed a greater amount of strain compared to the natural/grass cleat combination. The Astroturf shoe was 80.2 percent greater, modern playing turf/turf shoe was 47.5 percent greater, and the modern playing turf/cleat was 45.1 percent greater.
"As a former football player. I was always curious about why I was more sore after playing on artificial surfaces than playing on grass, and I wanted to find out the reasons behind that using a biomechanical model," Dr. Drakos said. "There are basically 200,000 ACL injuries every year in the United States alone and this [type of playing field and type of shoe] is an environmental factor which has been shown to play a role in injury, but has yet to be optimized. I think it is a scenario that deserves attention and further research."
Astroturf can be thought of as a carpet with ½ inch fibers on a 5 millimeter foam pad. The newer, modern playing turf consists of two inched fibers with a crumb rubber infill, three pounds of infill per square foot of turf. Investigators used fresh Kentucky bluegrass sod for the natural grass samples.
This is the conclusion from a study by investigators at Hospital for Special Surgery (HSS) that tested the strain placed on the ACL of four different shoe-surface interactions: Astroturf/turf shoe, modern playing turf/turf shoe, modern turf/cleat, and natural grass/cleat. The study appears in the January 2010 issue of the Journal of Biomechanical Engineering.
"It appears that a similar cut made on four different surfaces, the best strain profile is in grass/cleat combinations," said Mark Drakos, M.D., formerly an orthopedic fellow in the Sports Medicine and Shoulder Service at HSS. "So, there is less force occurring at your ligament for the same cut on that particular surface using this model."
He added that the study investigated noncontact injuries. "These are injuries where an athlete plants his or her foot while making a cut and blows out his or her knee," Dr. Drakos said. "The reason that I think this is so interesting is because there are still environmental factors, which have yet to be optimized. We don't know all the science behind why ACL injuries may be more common on turf than on grass. This study starts developing some of the science behind that, so that it can be looked at more closely because, at the end of the day, I think we need to optimize some of those environmental factors."
Previous studies have suggested that increased traction at the shoe-surface interface may increase the risk of sustaining an ACL injury. While the majority of studies reveal that ACL injuries are more likely to occur on artificial turf, there are some studies that have shown that injuries occur more frequently on grass fields. So, investigators have concluded that confounding factors, such as weather and footwear, must play a role in injuries. Some investigators have constructed models to test how the shoe-surface interface impacts loading conditions at the level of the foot, but no studies have investigated how the interface directly impacts the knee.
To fill this knowledge gap, investigators at HSS used a cadaveric model to test various shoe-surface interactions; they used the lower extremities (knee, foot, and ankle) from eight cadavers. One at a time, each specimen was positioned in a box-like structure, rigged to be in a standing position. The knee was positioned at a 30 degree angle, the flexion angle where the anterior cruciate ligament is most sensitive to strain. Investigators constructed an apparatus that placed weight on the leg, to simulate the weight of a body. Underneath the foot was a turf box that housed whatever turf they wanted to test and underneath the turf box, they placed a force plate that registered how much load was being placed on the shoe-surface interface. A lazy Susan was placed underneath the force plate that allowed the force plate and turf box to rotate. In this way, researchers could simulate a cut or a person pivoting in, for example, a soccer game.
"Our model looks at how forces travel up the kinetic chain, and that is something that should be looked at more closely, meaning you can't just look at the knee injuries by looking at the knee in isolation," Dr. Drakos said.
The investigators found that the natural grass/cleat combination placed a statistically lower maximum strain on the leg than any of the remaining three groups. All other combinations placed a greater amount of strain compared to the natural/grass cleat combination. The Astroturf shoe was 80.2 percent greater, modern playing turf/turf shoe was 47.5 percent greater, and the modern playing turf/cleat was 45.1 percent greater.
"As a former football player. I was always curious about why I was more sore after playing on artificial surfaces than playing on grass, and I wanted to find out the reasons behind that using a biomechanical model," Dr. Drakos said. "There are basically 200,000 ACL injuries every year in the United States alone and this [type of playing field and type of shoe] is an environmental factor which has been shown to play a role in injury, but has yet to be optimized. I think it is a scenario that deserves attention and further research."
Astroturf can be thought of as a carpet with ½ inch fibers on a 5 millimeter foam pad. The newer, modern playing turf consists of two inched fibers with a crumb rubber infill, three pounds of infill per square foot of turf. Investigators used fresh Kentucky bluegrass sod for the natural grass samples.
Saturday, January 23, 2010
Study: Perceived Ball Size Correlates With Batting Average
Athletes often say that when they are playing well – shooting hoops, hitting baseballs, catching passes – the ball appears bigger. Likewise, they say that when they are in a slump the ball appears smaller. When Mickey Mantle hit a 565-foot home run he said, "I just saw the ball as big as a grapefruit." But Joe "Ducky" Medwick of the St. Louis Cardinals said during a slump that he was "swinging at aspirins."
Appearances may be reality, in a sense.
A new study by University of Virginia psychologists has found a correlation between batting averages of softball players and how big, or small, they perceived the ball to be. The study documents that when the players were hitting well they clearly perceived the ball to be bigger. And when they were hitting less well, they perceived the ball to be smaller.
The interactions between mind and body – perception and action – may be as interlinked as athletes believe them to be, according to Jessica K. Witt, a cognitive psychology doctoral candidate at the University of Virginia. Witt and U.Va. psychology professor Dennis R. Proffitt describe the batting average and apparent ball size correlation in a paper that appears in the December 2005 issue of the journal Psychological Science.
The full article can be accessed online at: http://www.blackwell-synergy.com/doi/full/10.1111/j.1467-9280.2005.01640.x
"It's interesting that all the optical information is the same – the ball is only one size – but that it looks differently depending on the individual performance of the athlete," Witt said. She is interested in understanding if there is a feedback loop between perception and performance. "It's clear that the way we see the world affects the way we perform in it," she said. "I'm trying to get a glimpse into the role perception plays in streaks and slumps."
Witt and her colleagues conducted their experiment at several softball fields in Charlottesville, Va., and asked players who had finished playing for the day to look at eight different-sized circles on a board and pick the one that best represented the size of the softball they had been trying to hit. They also checked the hitting percentage of the players for that day. They found that the players who were hitting well were picking the larger circles, and the players who were batting .500 or above – those hitting safely at least half the time – were picking the largest-size circle.
The finding did not surprise Witt, a world-class athlete who competed last July for the gold medal-winning U.S. Ultimate Frisbee team at the 2005 World Games in Duisburg, Germany.
"As an athlete I've always been intrigued by how an athlete's physical performance can affect her state of mind," Witt said. "This study was designed to test what ball players have long been saying about how their performance is correlated with the way they are perceiving the ball."
Witt has experienced this herself as an athlete. She notes how she feels much more confident when she's throwing a Frisbee with the wind as opposed to against it. "The player I'm throwing to seems so far away when I'm throwing against the wind, but when I'm throwing with the wind it seems to be a short toss even if it's far," she said.
Witt plans to continue her study on perceived ball size and batting averages under controlled conditions. She hopes to obtain funding or regular access to a batting cage and competitive baseball players to design experiments that would allow her to closely monitor hitting performance, perception and the mental state of players. She is also interested in documenting whether or not visualization techniques – such as repeatedly imagining hitting a ball before going up to the plate – have any effect on performance in actuality and on whether the ball will look bigger.
Witt says such studies have implication in all areas of life – job performance, relationships, abilities and disabilities. "Perspective and perception play a big role in what we do and how well we do it," she said.
Appearances may be reality, in a sense.
A new study by University of Virginia psychologists has found a correlation between batting averages of softball players and how big, or small, they perceived the ball to be. The study documents that when the players were hitting well they clearly perceived the ball to be bigger. And when they were hitting less well, they perceived the ball to be smaller.
The interactions between mind and body – perception and action – may be as interlinked as athletes believe them to be, according to Jessica K. Witt, a cognitive psychology doctoral candidate at the University of Virginia. Witt and U.Va. psychology professor Dennis R. Proffitt describe the batting average and apparent ball size correlation in a paper that appears in the December 2005 issue of the journal Psychological Science.
The full article can be accessed online at: http://www.blackwell-synergy.com/doi/full/10.1111/j.1467-9280.2005.01640.x
"It's interesting that all the optical information is the same – the ball is only one size – but that it looks differently depending on the individual performance of the athlete," Witt said. She is interested in understanding if there is a feedback loop between perception and performance. "It's clear that the way we see the world affects the way we perform in it," she said. "I'm trying to get a glimpse into the role perception plays in streaks and slumps."
Witt and her colleagues conducted their experiment at several softball fields in Charlottesville, Va., and asked players who had finished playing for the day to look at eight different-sized circles on a board and pick the one that best represented the size of the softball they had been trying to hit. They also checked the hitting percentage of the players for that day. They found that the players who were hitting well were picking the larger circles, and the players who were batting .500 or above – those hitting safely at least half the time – were picking the largest-size circle.
The finding did not surprise Witt, a world-class athlete who competed last July for the gold medal-winning U.S. Ultimate Frisbee team at the 2005 World Games in Duisburg, Germany.
"As an athlete I've always been intrigued by how an athlete's physical performance can affect her state of mind," Witt said. "This study was designed to test what ball players have long been saying about how their performance is correlated with the way they are perceiving the ball."
Witt has experienced this herself as an athlete. She notes how she feels much more confident when she's throwing a Frisbee with the wind as opposed to against it. "The player I'm throwing to seems so far away when I'm throwing against the wind, but when I'm throwing with the wind it seems to be a short toss even if it's far," she said.
Witt plans to continue her study on perceived ball size and batting averages under controlled conditions. She hopes to obtain funding or regular access to a batting cage and competitive baseball players to design experiments that would allow her to closely monitor hitting performance, perception and the mental state of players. She is also interested in documenting whether or not visualization techniques – such as repeatedly imagining hitting a ball before going up to the plate – have any effect on performance in actuality and on whether the ball will look bigger.
Witt says such studies have implication in all areas of life – job performance, relationships, abilities and disabilities. "Perspective and perception play a big role in what we do and how well we do it," she said.
Thursday, January 21, 2010
How does an outfielder know where to run for a fly ball?
While baseball fans still rank "The Catch" by Willie Mays in the 1954 World Series as one of the greatest baseball moments of all times, scientists see the feat as more of a puzzle: How does an outfielder get to the right place at the right time to catch a fly ball?
Thousands of fans (and hundreds of thousands of YouTube viewers) saw Mays turn his back on a fly ball, race to the center field fence and catch the ball over his shoulder, seemingly a precise prediction of a fly ball's path that led his team to victory. According to a recent article in the Journal of Vision ("Catching Flyballs in Virtual Reality: A Critical Test of the Outfielder Problem"), the "outfielder problem" represents the definitive question of visual-motor control. How does the brain use visual information to guide action?
To test three theories that might explain an outfielder's ability to catch a fly ball, researcher Philip Fink, PhD, from Massey University in New Zealand and Patrick Foo, PhD, from the University of North Carolina at Ashville programmed Brown University's virtual reality lab, the VENLab, to produce realistic balls and simulate catches. The team then lobbed virtual fly balls to a dozen experienced ball players.
"The three existing theories all predict the same thing: successful catches with very similar behavior," said Brown researcher William Warren, PhD. "We realized that we could pull them apart by using virtual reality to create physically impossible fly ball trajectories."
Warren said their results support the idea that the ball players do not necessarily predict a ball's landing point based on the first part of its flight, a theory described as trajectory prediction. "Rather than predicting the landing point, the fielder might continuously track the visual motion of the ball, letting it lead him to the right place at the right time," Warren said.
Because the researchers were able to use the virtual reality lab to perturb the balls' vertical motion in ways that would not happen in reality, they were able to isolate different characteristics of each theory. The subjects tended to adjust their forward-backward movements depending on the perceived elevation angle of the incoming ball, and separately move from side to side to keep the ball at a constant bearing, consistent with the theory of optical acceleration cancellation (OAC). The third theory, linear optical trajectory (LOT), predicted that the outfielder will run in a direction that makes the visual image of the ball appear to travel in a straight line, adjusting both forward-backward and side-to-side movements together.
Fink said these results focus on the visual information a ball player receives, and that future studies could bring in other variables, such as the effect of the batter's movements or sound.
"As a first step we chose to concentrate on what seemed likely to be the most important factor," Fink said. "Fielders might also use information such as the batter's swing or the sound of the bat hitting the ball to help guide their movements."
Thousands of fans (and hundreds of thousands of YouTube viewers) saw Mays turn his back on a fly ball, race to the center field fence and catch the ball over his shoulder, seemingly a precise prediction of a fly ball's path that led his team to victory. According to a recent article in the Journal of Vision ("Catching Flyballs in Virtual Reality: A Critical Test of the Outfielder Problem"), the "outfielder problem" represents the definitive question of visual-motor control. How does the brain use visual information to guide action?
To test three theories that might explain an outfielder's ability to catch a fly ball, researcher Philip Fink, PhD, from Massey University in New Zealand and Patrick Foo, PhD, from the University of North Carolina at Ashville programmed Brown University's virtual reality lab, the VENLab, to produce realistic balls and simulate catches. The team then lobbed virtual fly balls to a dozen experienced ball players.
"The three existing theories all predict the same thing: successful catches with very similar behavior," said Brown researcher William Warren, PhD. "We realized that we could pull them apart by using virtual reality to create physically impossible fly ball trajectories."
Warren said their results support the idea that the ball players do not necessarily predict a ball's landing point based on the first part of its flight, a theory described as trajectory prediction. "Rather than predicting the landing point, the fielder might continuously track the visual motion of the ball, letting it lead him to the right place at the right time," Warren said.
Because the researchers were able to use the virtual reality lab to perturb the balls' vertical motion in ways that would not happen in reality, they were able to isolate different characteristics of each theory. The subjects tended to adjust their forward-backward movements depending on the perceived elevation angle of the incoming ball, and separately move from side to side to keep the ball at a constant bearing, consistent with the theory of optical acceleration cancellation (OAC). The third theory, linear optical trajectory (LOT), predicted that the outfielder will run in a direction that makes the visual image of the ball appear to travel in a straight line, adjusting both forward-backward and side-to-side movements together.
Fink said these results focus on the visual information a ball player receives, and that future studies could bring in other variables, such as the effect of the batter's movements or sound.
"As a first step we chose to concentrate on what seemed likely to be the most important factor," Fink said. "Fielders might also use information such as the batter's swing or the sound of the bat hitting the ball to help guide their movements."
Monday, January 11, 2010
Program may prevent knee injuries
A soccer-specific exercise program that includes individual instruction of athletes appears to reduce the risk of knee injuries in young female players, according to a report in the January 11 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
Soccer is a dominant cause of sports-related injuries in part because of its increasing popularity, according to background information in the article. Between 2000 and 2006, the number of female soccer players around the world increased by 19 percent, to 26 million. "The most frequent and severe type of injury among soccer players is to the legs, especially the knees. The anterior cruciate ligament (ACL) injury incidence is highest among young athletes," the authors write. "Knee injuries, and especially ACL ruptures, may have long-term consequences, including a long absence from soccer, incomplete recovery and secondary osteoarthritis of the knee."
Ashkan Kiani, M.D., of Uppsala Primary Care, Uppsala County Council, Sweden, and colleagues assessed an intervention program specifically designed to reduce the risk of soccer-related knee injuries among 1,506 13- to 19-year-old Swedish female players. The program featured strengthening exercises designed to achieve an improved motion pattern, reducing strain on the knee joint. The training sessions were integrated into the regular soccer practices and required no additional equipment. In addition, players, parents and team leaders attended a seminar to raise awareness of injury risk.
During 2007, 777 girls on 48 teams participated in the program and 729 players on 49 teams served as controls. Three knee injuries, including one non-contact injury (not involving another player), occurred among players participating in the program, compared with 13 knee injuries and 10 non-contact injuries among girls in the control group. Therefore, the program was associated with a 77 percent reduction in the incidence of knee injuries and a 90 percent reduction in the incidence of non-contact knee injuries.
"The rate of injury was not only lower among teams participating in the preventive program but the injuries that did occur were also less severe," the authors write. All three injuries in the intervention group were categorized as major, but all three players regained full activity within six months. Among the control participants, most injuries were severe, and only four of the 13 regained full activity within six months.
Coaches reported their teams' adherence to the program at two time periods, after the preseason training period and after the competitive season. Of the 48 teams participating in the intervention, 45 (94 percent) reported a high adherence of at least 75 percent. "The high compliance rate in this study suggests that the program is easy to implement and incorporate into regular soccer practice," the authors conclude.
Soccer is a dominant cause of sports-related injuries in part because of its increasing popularity, according to background information in the article. Between 2000 and 2006, the number of female soccer players around the world increased by 19 percent, to 26 million. "The most frequent and severe type of injury among soccer players is to the legs, especially the knees. The anterior cruciate ligament (ACL) injury incidence is highest among young athletes," the authors write. "Knee injuries, and especially ACL ruptures, may have long-term consequences, including a long absence from soccer, incomplete recovery and secondary osteoarthritis of the knee."
Ashkan Kiani, M.D., of Uppsala Primary Care, Uppsala County Council, Sweden, and colleagues assessed an intervention program specifically designed to reduce the risk of soccer-related knee injuries among 1,506 13- to 19-year-old Swedish female players. The program featured strengthening exercises designed to achieve an improved motion pattern, reducing strain on the knee joint. The training sessions were integrated into the regular soccer practices and required no additional equipment. In addition, players, parents and team leaders attended a seminar to raise awareness of injury risk.
During 2007, 777 girls on 48 teams participated in the program and 729 players on 49 teams served as controls. Three knee injuries, including one non-contact injury (not involving another player), occurred among players participating in the program, compared with 13 knee injuries and 10 non-contact injuries among girls in the control group. Therefore, the program was associated with a 77 percent reduction in the incidence of knee injuries and a 90 percent reduction in the incidence of non-contact knee injuries.
"The rate of injury was not only lower among teams participating in the preventive program but the injuries that did occur were also less severe," the authors write. All three injuries in the intervention group were categorized as major, but all three players regained full activity within six months. Among the control participants, most injuries were severe, and only four of the 13 regained full activity within six months.
Coaches reported their teams' adherence to the program at two time periods, after the preseason training period and after the competitive season. Of the 48 teams participating in the intervention, 45 (94 percent) reported a high adherence of at least 75 percent. "The high compliance rate in this study suggests that the program is easy to implement and incorporate into regular soccer practice," the authors conclude.
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