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Watch out if you are a Major League Baseball (MLB) pitcher prior to the All-Star break. Pitchers are 34 percent more likely to be injured than fielders, according to a study presented today at the American Orthopaedic Society for Sports Medicine’s (AOSSM) Annual Meeting. The study looked into the epidemiology of MLB players’ injuries from 2002 – 2008. It also found that 77 percent of all injuries to pitchers happen before the All-Star Game.
“Even though baseball is a passion of many people and our national pastime, there is very little information about the epidemiology, characteristics or distribution of injuries in Major League Baseball,” said Maj., Matthew Posner, MD, orthopaedic surgeon at the William Beaumont Army Medical Center in El Paso, Texas. “This study attempts to evaluate Major League injuries over the period of six years.”
The study authors analyzed Major League Baseball disabled list data from a single internet website for the years 2002 – 2008. Then they calculated the frequency and proportional distribution of injuries by anatomic region, league, time of season and position. The study found that upper extremity injuries accounted for 51.4 percent of all injuries. Lower extremity injuries accounted for 30.6 percent, while back injuries accounted for 7.4 percent and core muscle injuries accounted for 4.3 percent.
Pitchers had a 34 percent higher injury rate than fielders prior to the All-Star Game, according to the study. Not surprisingly, pitchers experienced 67 percent of the injuries to the upper extremity compared to fielders while fielders also had a greater proportion of the lower extremity injuries and injuries to other anatomic regions, according to the study.
The study also noted that pitchers also spent a greater proportion of days on the disability list (62.4 percent) when compared to fielders (37.6 percent). But both pitchers and fielders spent significantly more days on the disabled list for upper extremity injuries than for lower extremity injuries.
National League or American League? The study found that the distribution of injuries by anatomic region was nearly identical between players in the National League and the American League when all players (pitchers and fielders) were considered. National League players injured their upper extremities 51.7 percent of the time, lower extremities 30.7 percent and other anatomic regions 17.7 percent.
American League players injured their upper extremities 51.1 percent of the time, lower extremities 30.5 percent and other anatomic regions 18.4 percent, according to the study.
As for the timing of the injuries, 74.4 percent of all MLB players’ injuries occurred before the All-Star break. Pitchers sustained 76.5 percent and fielders sustained 71.7 percent of their total respective injuries prior to the All-Star game. Seventy-nine percent of all shoulder and elbow injuries happened to pitchers before the All-Star game and 74.8 percent of all hamstring, quadriceps, groin and core injuries to fielders happened before the All-Star game.
Monday, July 19, 2010
Wednesday, July 7, 2010
Fouls go left: Soccer referees may be biased based on play's direction of motion
Penn study finds left-to-right readers more likely to call foul for right-to-left attacks
Soccer referees may have an unconscious bias towards calling fouls based on a play's direction of motion, according to a new study from the of University of Pennsylvania School of Medicine. Researchers found that soccer experts made more foul calls when action moved right-to-left, or leftward, compared to left-to-right or rightward action, suggesting that two referees watching the same play from different vantage points may be inclined to make a different call. The study appears in the July 7 online edition of PLoS ONE.
It's been documented that individuals who read languages which flow left-to-right are more likely to have a negative bias for events moving in the opposite direction, from right-to-left. In the Penn study of twelve members of the University of Pennsylvania's varsity soccer teams (all native English speaking), researchers found that participants viewing the soccer plays were more likely to call a foul when seeing a right-to-left attack
"The effects are impressive considering that left-moving and right-moving images were identical, with the only difference being that they were flipped along the x-axis to create right-to-left and left-to-right versions," said lead researcher Alexander Kranjec, PhD, a post-doctoral fellow in the Neurology Department at the University of Pennsylvania School of Medicine. "If the spatial biases we observed in this population of soccer players have similar effects on referees in real matches, they may influence particular officials differently: referees on the field will more frequently be in positions that lower their threshold for calling fouls during an attack, compared to assistant referees working the lines."
In real matches, referees and linesmen tend to be exposed to different quantities of right-to-left or left-to-right attacking plays, as referees employ a system to help them cover the field efficiently. Referees are encouraged to use a diagonal patrolling technique, choosing to run either a left or a right diagonal, while the assistant referees are tasked with running the sidelines.
Based on this study, the left diagonal system would favor the offense (viewing more attacks from right-to-left), and the right diagonal system would favor the defense (viewing more attacks from left-to-right). Given the relational opposition, the authors suggest that referees should avoid switching diagonals at halftime.
"There could be an unfair advantage if one team goes into halftime with a lead and the referees switch to a right diagonal system in the second half, favoring both defenses," said Dr. Kranjec. "However, because referees viewing leftward action may be more likely to see a foul when no foul was actually committed, as seemed to be the case when the referee disallowed what should have been the US team's third goal against Slovenia, the bias could work against the offense sometimes."
Study participants called approximately three more fouls when images of soccer plays where viewed from right-to-left (66.5 fouls) compared to mirror images moving left-to-right (63.3 fouls). Participants were statistically more likely to call a foul when seeing a right-to-left attack.
Previous studies suggest that similar directional effects are reversed in populations that read right-to-left languages, but other populations (e.g. Arabic or Hebrew readers) would need to be tested directly to see if the effects reported in this study correlate with reading habits.
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The study will be available online at http://dx.plos.org/10.1371/journal.pone.0011667.
Friday, July 2, 2010
New World Cup Soccer Ball Will Unsettle Goalkeepers, Predicts Scientist
The new football that is being used for the first time in the World Cup is likely to bamboozle goalkeepers at some stage of the tournament, a leading scientist has warned.
The Adidas ‘Teamgeist’ football has just 14 panels - with fewer seams - making its surface ‘smoother’ than conventional footballs which have a 26 or 32 panel hexagon-based pattern.
This makes it aerodynamically closer to a baseball and, when hit with a slow spin, will make the ball less stable, giving it a more unpredictable trajectory in flight.
“With a very low spin rate, which occasionally happens in football, the panel pattern can have a big influence on the trajectory of the ball and make it more unpredictable for a goalkeeper,” said Dr Ken Bray, a sports scientist at the University of Bath and author of the new popular science book How to score – science and the beautiful game.
“Because the Teamgeist ball has just 14 panels it is aerodynamically more similar to the baseball which only has two panels.
“In baseball, pitchers often throw a ’curve ball’ which is similar to a swerving free kick and the rotating seam disrupts the air flow around the ball in much the same way as a football does.
“Occasionally though, pitchers will throw a ’knuckleball’ which bobs about randomly in flight and is very disconcerting for batters.
“It happens because pitchers throw the ball with very little spin and as the ball rotates lazily in the air, the seam disrupts the air flow around the ball at certain points on the surface, causing an unpredictable deflection.
“With the world’s best players in Germany this summer, there are bound to be plenty of spectacular scoring free kicks.
“But watch the slow motion replays to spot the rare occasions where the ball produces little or no rotation and where goalkeepers will frantically attempt to keep up with the ball’s chaotic flight path.”
The ball, which has been used by teams competing in the World Cup in practice sessions, has already been criticised by England goalkeeper Paul Robinson and Germany goalkeeper Jens Lehmann for its light-weight and unpredictable behaviour.
The Adidas ‘Teamgeist’ football has just 14 panels - with fewer seams - making its surface ‘smoother’ than conventional footballs which have a 26 or 32 panel hexagon-based pattern.
This makes it aerodynamically closer to a baseball and, when hit with a slow spin, will make the ball less stable, giving it a more unpredictable trajectory in flight.
“With a very low spin rate, which occasionally happens in football, the panel pattern can have a big influence on the trajectory of the ball and make it more unpredictable for a goalkeeper,” said Dr Ken Bray, a sports scientist at the University of Bath and author of the new popular science book How to score – science and the beautiful game.
“Because the Teamgeist ball has just 14 panels it is aerodynamically more similar to the baseball which only has two panels.
“In baseball, pitchers often throw a ’curve ball’ which is similar to a swerving free kick and the rotating seam disrupts the air flow around the ball in much the same way as a football does.
“Occasionally though, pitchers will throw a ’knuckleball’ which bobs about randomly in flight and is very disconcerting for batters.
“It happens because pitchers throw the ball with very little spin and as the ball rotates lazily in the air, the seam disrupts the air flow around the ball at certain points on the surface, causing an unpredictable deflection.
“With the world’s best players in Germany this summer, there are bound to be plenty of spectacular scoring free kicks.
“But watch the slow motion replays to spot the rare occasions where the ball produces little or no rotation and where goalkeepers will frantically attempt to keep up with the ball’s chaotic flight path.”
The ball, which has been used by teams competing in the World Cup in practice sessions, has already been criticised by England goalkeeper Paul Robinson and Germany goalkeeper Jens Lehmann for its light-weight and unpredictable behaviour.
Psychologists Link Hitting Skills to Vision
Why do some players hit it out of the park, when others can barely get it past the pitcher? Could it be that athletes playing well in a baseball game see the ball as a different size than it really is?
When heavy-hitter Paul Rugani steps up to plate, he's ready to knock a softball out of the park. "It's fun to hit. It's fun to get on base," Rugani says. "I like being up in situations where I can knock runners in."
Good players like Rugani can bring in home runs easily, and many athletes claim when they hit well in a game, the ball appears much bigger than it really is. Now, cognitive psychology student Jessica Witt sets out to find out if the theory is true.
"I watched players play, and after the games were over, I asked them to look at an array of different sized circles and pick which circle they thought best matched the size of the softball," Witt, of the University of Virginia in Charlottesville, tells DBIS.
Witt found players picking the larger circles performed better, proving that a player's perception of the ball's size is somehow linked to his performance. "It's hard to know which direction the effect goes," she says. "Do you see it as bigger and therefore hit better, or are you hitting better and therefore see it as bigger?"
She also found athletes who hit poorly see the ball as being much smaller than it really is. She says, "If we're a poor hitter, we see the world full of really, tiny, tiny, tiny balls that are really difficult to hit."
So to do well in a game, think big to hit big.
Witt recently conducted another study to find out if golfers who do well in a game see the cup as being bigger. Preliminary results suggest golfers do, indeed, see the cup bigger when playing well.
BACKGROUND: Perception and action -- the interactions between mind and body -- could be interlinked. Athletes often say that when they are playing well -- shooting hoops, hitting baseballs, catching football passes -- the ball appears bigger. When they are in a slump, the ball appears smaller. A new study by University of Virginia psychologists has found a connection between batting averages of softball players and how big or small they thought the ball seemed.
ABOUT THE STUDY: The scientists conducted their experiment at several softball fields in Charlottesville and asked players who had finished playing for the day to look at eight different-sized circles on a board, and to pick the one that best represented the size of the softball they had been trying to hit. They compared that data to the hitting percentage of the players for that day. The study found that when 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 scientists plan to continue their study on perceived ball size and batting averages under more controlled conditions.
HOW WE SEE "DEPTH": The human visual system is designed to allow us to detect fine detail, track a moving object, see colors, and perceive depth. All these components of a visual scene are processed and merged by the brain so that we observe them as one visual experience. How we recognize that different objects are at different distances from us depends on visual cues. For objects beyond 100 feet, the image that's projected on to the back of the eye is basically the same size to both eyes, so cues of depth perception would include knowing the relative range of sizes of objects in general. If one object partly hides another, we know that the object in front is closer. And as we move our heads and bodies, nearby objects will seem to move more quickly than distant objects, an effect called motion parallax.
For objects closer than 100 feet, we need three-dimensional vision. Because the eyes are separated by about six centimeters, each eye gets a slightly different view of the same object. So when we fixate on one object, we can tell if another object is in front of or behind it, because the object is located in two different places on the images that reach the retinas, or backs of the eyes. This is called disparity. Experiments have found that depth perception likely occurs in the primary visual cortex, where individual neurons receiving input from the retinas of the two eyes fire specifically when retinal disparity exists.
VISION PROBLEMS: If particular parts of the brain are damaged, people may lose some visual perception. They might not be able to recognize faces, for instance (prosopagnosia), or not be able to name colors (color anomia). And sometimes they can lose their stereoscopic vision (visual spatial agnosia) or lose the ability to see objects that are in motion (movement agnosia).
When heavy-hitter Paul Rugani steps up to plate, he's ready to knock a softball out of the park. "It's fun to hit. It's fun to get on base," Rugani says. "I like being up in situations where I can knock runners in."
Good players like Rugani can bring in home runs easily, and many athletes claim when they hit well in a game, the ball appears much bigger than it really is. Now, cognitive psychology student Jessica Witt sets out to find out if the theory is true.
"I watched players play, and after the games were over, I asked them to look at an array of different sized circles and pick which circle they thought best matched the size of the softball," Witt, of the University of Virginia in Charlottesville, tells DBIS.
Witt found players picking the larger circles performed better, proving that a player's perception of the ball's size is somehow linked to his performance. "It's hard to know which direction the effect goes," she says. "Do you see it as bigger and therefore hit better, or are you hitting better and therefore see it as bigger?"
She also found athletes who hit poorly see the ball as being much smaller than it really is. She says, "If we're a poor hitter, we see the world full of really, tiny, tiny, tiny balls that are really difficult to hit."
So to do well in a game, think big to hit big.
Witt recently conducted another study to find out if golfers who do well in a game see the cup as being bigger. Preliminary results suggest golfers do, indeed, see the cup bigger when playing well.
BACKGROUND: Perception and action -- the interactions between mind and body -- could be interlinked. Athletes often say that when they are playing well -- shooting hoops, hitting baseballs, catching football passes -- the ball appears bigger. When they are in a slump, the ball appears smaller. A new study by University of Virginia psychologists has found a connection between batting averages of softball players and how big or small they thought the ball seemed.
ABOUT THE STUDY: The scientists conducted their experiment at several softball fields in Charlottesville and asked players who had finished playing for the day to look at eight different-sized circles on a board, and to pick the one that best represented the size of the softball they had been trying to hit. They compared that data to the hitting percentage of the players for that day. The study found that when 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 scientists plan to continue their study on perceived ball size and batting averages under more controlled conditions.
HOW WE SEE "DEPTH": The human visual system is designed to allow us to detect fine detail, track a moving object, see colors, and perceive depth. All these components of a visual scene are processed and merged by the brain so that we observe them as one visual experience. How we recognize that different objects are at different distances from us depends on visual cues. For objects beyond 100 feet, the image that's projected on to the back of the eye is basically the same size to both eyes, so cues of depth perception would include knowing the relative range of sizes of objects in general. If one object partly hides another, we know that the object in front is closer. And as we move our heads and bodies, nearby objects will seem to move more quickly than distant objects, an effect called motion parallax.
For objects closer than 100 feet, we need three-dimensional vision. Because the eyes are separated by about six centimeters, each eye gets a slightly different view of the same object. So when we fixate on one object, we can tell if another object is in front of or behind it, because the object is located in two different places on the images that reach the retinas, or backs of the eyes. This is called disparity. Experiments have found that depth perception likely occurs in the primary visual cortex, where individual neurons receiving input from the retinas of the two eyes fire specifically when retinal disparity exists.
VISION PROBLEMS: If particular parts of the brain are damaged, people may lose some visual perception. They might not be able to recognize faces, for instance (prosopagnosia), or not be able to name colors (color anomia). And sometimes they can lose their stereoscopic vision (visual spatial agnosia) or lose the ability to see objects that are in motion (movement agnosia).
Science of Soccer: Ball Aerodynamics Focus of Research
With the attention of sports fans worldwide focused on South Africa and the 2010 FIFA World Cup, U.S. scientist John Eric Goff has made the aerodynamics of the soccer ball a focus of his research.
In an article appearing in the magazine Physics Today this month, Goff examines the science of soccer and explains how the world's greatest players are able to make a soccer ball do things that would seem to defy the forces of nature.
Goff's article looks at the ball's changing design and how its surface roughness and asymmetric air forces contribute to its path once it leaves a player's foot. His analysis leads to an understanding of how reduced air density in games played at higher altitudes -- like those in South Africa -- can contribute to some of the jaw-dropping ball trajectories already seen in some of this year's matches.
"The ball is moving a little faster than what some of the players are used to," says Goff, who is a professor of physics at Lynchburg College in Virginia and an expert in sports science.
For Goff, soccer is a sport that offers more than non-stop action -- it is a living laboratory where physics equations are continuously expressed. On the fields of worldwide competition, the balls maneuver according to complicated formulae, he says, but these can be explained in terms the average viewer can easily understand. And the outcomes of miraculous plays can be explained simply in terms of the underlying physics.
Goff also is the author of the recently published book, "Gold Medal Physics: The Science of Sports," which uncovers the mechanisms behind some of the greatest moments in sports history, including:
* How did Cal beat Stanford in the last seconds with five lateral passes as the Stanford marching band was coming on to the field?
* How did Doug Flutie complete his "Hail Mary" touchdown pass that enabled Boston College to beat Miami?
* How did Lance Armstrong cycle to a world-beating seven Tour de France victories?
* How did Olympic greats Bob Beamon (long jump), Greg Louganis (diving) and Katarina Witt (figure skating) achieve their record-setting Olympic gold?
The article "Power and spin in the beautiful game" appears in the July, 2010 issue of Physics Today and is available at http://www.physicstoday.org/beautiful_game.html
In an article appearing in the magazine Physics Today this month, Goff examines the science of soccer and explains how the world's greatest players are able to make a soccer ball do things that would seem to defy the forces of nature.
Goff's article looks at the ball's changing design and how its surface roughness and asymmetric air forces contribute to its path once it leaves a player's foot. His analysis leads to an understanding of how reduced air density in games played at higher altitudes -- like those in South Africa -- can contribute to some of the jaw-dropping ball trajectories already seen in some of this year's matches.
"The ball is moving a little faster than what some of the players are used to," says Goff, who is a professor of physics at Lynchburg College in Virginia and an expert in sports science.
For Goff, soccer is a sport that offers more than non-stop action -- it is a living laboratory where physics equations are continuously expressed. On the fields of worldwide competition, the balls maneuver according to complicated formulae, he says, but these can be explained in terms the average viewer can easily understand. And the outcomes of miraculous plays can be explained simply in terms of the underlying physics.
Goff also is the author of the recently published book, "Gold Medal Physics: The Science of Sports," which uncovers the mechanisms behind some of the greatest moments in sports history, including:
* How did Cal beat Stanford in the last seconds with five lateral passes as the Stanford marching band was coming on to the field?
* How did Doug Flutie complete his "Hail Mary" touchdown pass that enabled Boston College to beat Miami?
* How did Lance Armstrong cycle to a world-beating seven Tour de France victories?
* How did Olympic greats Bob Beamon (long jump), Greg Louganis (diving) and Katarina Witt (figure skating) achieve their record-setting Olympic gold?
The article "Power and spin in the beautiful game" appears in the July, 2010 issue of Physics Today and is available at http://www.physicstoday.org/beautiful_game.html
Thursday, June 24, 2010
Left or Right? Early Detection of Soccer Penalty Kicks
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In the split second before foot meets ball, a soccer player’s body betrays whether a penalty kick will go left or right, according to recent research in cognitive science at Rensselaer Polytechnic Institute. Photo Credit: Rensselaer: Daria Robbins
In the split second before foot meets ball, a soccer player’s body betrays whether a penalty kick will go left or right, according to recent research in cognitive science at Rensselaer Polytechnic Institute. The findings could explain how some top goalkeepers are able to head off a penalty kick, diving in the correct direction in advance of the kick. It could also point the way to changes in how players kick, and goalies react.
The research, performed by Rensselaer doctoral student Gabriel J. Diaz, employed motion capture technology and computer analysis to identify five early indicators of the direction a ball would ultimately be kicked. Diaz said his research stemmed from an observation of real-world penalty kicks, in which players aim for the left or right side of the goal while hiding their choice from the goalkeeper.
“When a goalkeeper is in a penalty situation, they can’t wait until the ball is in the air before choosing whether to jump left or right — a well-placed penalty kick will get past them,” Diaz said. “As a consequence, you see goalkeepers jumping before the foot hits the ball. My question is: Are they making a choice better than chance (50/50), and if so, what kind of information might they be using to make their choice?”
Diaz tested 27 potential indicators of kick direction — 12 drawn from sports literature and 15 derived from a computer analysis of the kicks — and identified five as reliable indicators of the direction the ball will go.
In the second part of his work, Diaz also showed that four of the five early indicators he identified are used by people who are able to predict the direction of the kick before the foot strikes the ball.
Diaz used motion capture technology — cameras, sensors, and software — in Rensselaer Associate Professor Brett Fajen’s Perception and Action (PandA) motion capture lab to record the movements of three college-level penalty kickers. The technology is similar to that used to create realistic movement in computer-generated graphics.
More than 40 sensors placed on 19 major joints of the body (and the ball) recorded the movements of the kickers as they stood behind the ball, took two steps, and kicked either to the left or of the right side of a goal. Diaz recorded 126 kicks, half to the left and half to the right.
Then he tested the data he collected against the suite of 27 potential indicators.
Twelve of the indicators — such as the angles of the kicking foot, kicking upper-leg, and kicking shank — were movements of a specific, or “local,” area of the body highlighted by coaches and sports psychologists. Among them he found that two — the angle at which the non-kicking foot is planted on the ground, and the angle of the hips as the kicking foot swings forward —are reliable indicators of kick direction.
The 15 indicators identified in a computer analysis of the kicks were so-called “distributed movements” — patterns of coordinated movement throughout the body. Three of the “distributed” movements proved to be reliable early indicators, none of which appears to have drawn previous attention in sports literature.
Emerging evidence in the study of motor control has pointed to a significant role for distributed movements, Diaz said. He described distributed movement as a combination of movements developed over many repeated attempts to perform a task, in this case kicking in a particular direction.
“When, for example, you shift the angle of your planted foot, perhaps in an attempt to hide the direction of the kick, you’re changing your base of support. In order to maintain stability, maybe you have to do something else like move your arm. And it just happens naturally,” Diaz said. “If this happens over and over again, over time your motor system may learn to move the arm at the same time as the foot. In this way the movement becomes one single distributed movement, rather than several sequential movements. A synergy is developed.”
A distributed movement is complex, but, as Diaz’s second experiment indicates, some people may be using it — however unconsciously — to inform their judgment as to which direction the ball will go.
In his second experiment, Diaz played an animation of the motion capture data to a group of 31 subjects, and asked the subjects to pick which direction they thought the ball would go. In the animation, each body joint is represented by a dot, and movement of the body is easily recognizable as such. The animation runs from the standing-start until the foot reaches the ball, at which point the screen goes black and subjects pressed a button to the left or right of the screen, indicating which direction they thought the ball had gone.
Among his 31 subjects, all of whom were novices to the activity, 15 were not able to score above chance (50/50), even when given one-half second after the scene to ponder the outcome. Sixteen, however, did perform better than chance.
Diaz then looked for relationships between successful judgments on ball direction and each of the “local” and “distributed” movements he had tracked. His analysis revealed strong correlations between the two “local” and two of the three “distributed movements” that were reliable indicators of kick direction.
“The question is, knowing these potential sources of reliable information, what do people actually use?” Diaz said. “I found four reliable sources that were well correlated with subjects’ judgments.”
Another finding, he said, is that the 16 successful subjects waited longer than the 15 unsuccessful subjects to make their choices (if the half-second elapsed without a response from the subject, no result was entered).
“There is a clear relationship between response timing and performance,” Diaz said.
Diaz said his findings have set the stage for further exploration. He would like to create a training regime to guide subjects’ attention toward more reliable indicators of kick direction. He also wants to know if professional goalkeepers would perform better than novices on the task.
Similar studies using video data of penalty kicks among professional Dutch goalkeepers showed that not all professional players are better than novice subjects, he said.
“Only a subset are better than average. I want to know — what is it that these successful experts are doing better than novices?”
In the split second before foot meets ball, a soccer player’s body betrays whether a penalty kick will go left or right, according to recent research in cognitive science at Rensselaer Polytechnic Institute. Photo Credit: Rensselaer: Daria Robbins
In the split second before foot meets ball, a soccer player’s body betrays whether a penalty kick will go left or right, according to recent research in cognitive science at Rensselaer Polytechnic Institute. The findings could explain how some top goalkeepers are able to head off a penalty kick, diving in the correct direction in advance of the kick. It could also point the way to changes in how players kick, and goalies react.
The research, performed by Rensselaer doctoral student Gabriel J. Diaz, employed motion capture technology and computer analysis to identify five early indicators of the direction a ball would ultimately be kicked. Diaz said his research stemmed from an observation of real-world penalty kicks, in which players aim for the left or right side of the goal while hiding their choice from the goalkeeper.
“When a goalkeeper is in a penalty situation, they can’t wait until the ball is in the air before choosing whether to jump left or right — a well-placed penalty kick will get past them,” Diaz said. “As a consequence, you see goalkeepers jumping before the foot hits the ball. My question is: Are they making a choice better than chance (50/50), and if so, what kind of information might they be using to make their choice?”
Diaz tested 27 potential indicators of kick direction — 12 drawn from sports literature and 15 derived from a computer analysis of the kicks — and identified five as reliable indicators of the direction the ball will go.
In the second part of his work, Diaz also showed that four of the five early indicators he identified are used by people who are able to predict the direction of the kick before the foot strikes the ball.
Diaz used motion capture technology — cameras, sensors, and software — in Rensselaer Associate Professor Brett Fajen’s Perception and Action (PandA) motion capture lab to record the movements of three college-level penalty kickers. The technology is similar to that used to create realistic movement in computer-generated graphics.
More than 40 sensors placed on 19 major joints of the body (and the ball) recorded the movements of the kickers as they stood behind the ball, took two steps, and kicked either to the left or of the right side of a goal. Diaz recorded 126 kicks, half to the left and half to the right.
Then he tested the data he collected against the suite of 27 potential indicators.
Twelve of the indicators — such as the angles of the kicking foot, kicking upper-leg, and kicking shank — were movements of a specific, or “local,” area of the body highlighted by coaches and sports psychologists. Among them he found that two — the angle at which the non-kicking foot is planted on the ground, and the angle of the hips as the kicking foot swings forward —are reliable indicators of kick direction.
The 15 indicators identified in a computer analysis of the kicks were so-called “distributed movements” — patterns of coordinated movement throughout the body. Three of the “distributed” movements proved to be reliable early indicators, none of which appears to have drawn previous attention in sports literature.
Emerging evidence in the study of motor control has pointed to a significant role for distributed movements, Diaz said. He described distributed movement as a combination of movements developed over many repeated attempts to perform a task, in this case kicking in a particular direction.
“When, for example, you shift the angle of your planted foot, perhaps in an attempt to hide the direction of the kick, you’re changing your base of support. In order to maintain stability, maybe you have to do something else like move your arm. And it just happens naturally,” Diaz said. “If this happens over and over again, over time your motor system may learn to move the arm at the same time as the foot. In this way the movement becomes one single distributed movement, rather than several sequential movements. A synergy is developed.”
A distributed movement is complex, but, as Diaz’s second experiment indicates, some people may be using it — however unconsciously — to inform their judgment as to which direction the ball will go.
In his second experiment, Diaz played an animation of the motion capture data to a group of 31 subjects, and asked the subjects to pick which direction they thought the ball would go. In the animation, each body joint is represented by a dot, and movement of the body is easily recognizable as such. The animation runs from the standing-start until the foot reaches the ball, at which point the screen goes black and subjects pressed a button to the left or right of the screen, indicating which direction they thought the ball had gone.
Among his 31 subjects, all of whom were novices to the activity, 15 were not able to score above chance (50/50), even when given one-half second after the scene to ponder the outcome. Sixteen, however, did perform better than chance.
Diaz then looked for relationships between successful judgments on ball direction and each of the “local” and “distributed” movements he had tracked. His analysis revealed strong correlations between the two “local” and two of the three “distributed movements” that were reliable indicators of kick direction.
“The question is, knowing these potential sources of reliable information, what do people actually use?” Diaz said. “I found four reliable sources that were well correlated with subjects’ judgments.”
Another finding, he said, is that the 16 successful subjects waited longer than the 15 unsuccessful subjects to make their choices (if the half-second elapsed without a response from the subject, no result was entered).
“There is a clear relationship between response timing and performance,” Diaz said.
Diaz said his findings have set the stage for further exploration. He would like to create a training regime to guide subjects’ attention toward more reliable indicators of kick direction. He also wants to know if professional goalkeepers would perform better than novices on the task.
Similar studies using video data of penalty kicks among professional Dutch goalkeepers showed that not all professional players are better than novice subjects, he said.
“Only a subset are better than average. I want to know — what is it that these successful experts are doing better than novices?”
Wednesday, June 9, 2010
Sleep preference can predict performance of Major League Baseball pitchers
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Pitchers who are 'morning types' appear to have an advantage over night owls
A Major League Baseball pitcher's natural sleep preference might affect how he performs in day and night games, according to a research abstract that will be presented Wednesday, June 9, 2010, in San Antonio, Texas, at SLEEP 2010, the 24th annual meeting of the Associated Professional Sleep Societies LLC.
Results indicate that pitchers who were morning types performed statistically better overall than those who were evening types. In early games that started before 7 p.m., the earned run average (ERA) of pitchers who were morning types (3.06) was lower than the average ERA of pitchers who were evening types (3.49); however, in games that started at 7 p.m. or later, pitchers who were evening types performed slightly better (4.07 ERA) than morning types (4.15 ERA).
"We were surprised to see that chronotype did affect pitching," said principal investigator and lead author W. Christopher Winter, MD, medical director of the Martha Jefferson Hospital Sleep Medicine Center in Charlottesville, Va. "We were also surprised to see that pitchers who were more 'morning type' seemed to do better overall."
Individual pitchers showed a trend toward higher ERAs in the late games. According to Winter, this supports previous research showing that the peak performance time for most athletes is between mid-afternoon and early evening.
The study involved 18 pitchers from five MLB teams: the Los Angeles Dodgers, New York Mets, Philadelphia Phillies, San Francisco Giants and Tampa Bay Rays. Sleep preference was determined using a modified version of the Morningness-Eveningness Questionnaire (MEQ). It identifies a person's tendency to be either a morning type who prefers to go to bed and wake up early, or an evening type who prefers to stay up late at night and wake up late in the day. Ten participants were found to be evening types, and eight were morning types.
The study used the players' statistics from the 2009 season, which provided about 728 early innings and 845 late innings for analysis. Game start times were adjusted for travel using the principle that for every time zone crossed, it takes 24 hours to adjust.
"These results are important as they are potentially giving insight into an entirely new way to grade or classify an athlete, in this specific case a pitcher," said Winter. "This study may provide insight as to which pitchers would be best in a given situation based upon when the game is being played. For example, a critical game being played in the evening might be a better situation to pitch an evening-type pitcher versus a day-type pitcher."
Winter also has studied the effect of travel across time zones on the performance of MLB teams. At SLEEP 2008 he presented the initial findings of a 10-year retrospective study that was later published in the September 2009 issue of the International Journal of Sports Physiology and Performance. He found that teams traveling from Western time zones to Eastern time zones were 14 percent more likely to win than teams traveling from east to west. Teams also won more than 60 percent of the games in which they had a three-hour "circadian advantage.
Pitchers who are 'morning types' appear to have an advantage over night owls
A Major League Baseball pitcher's natural sleep preference might affect how he performs in day and night games, according to a research abstract that will be presented Wednesday, June 9, 2010, in San Antonio, Texas, at SLEEP 2010, the 24th annual meeting of the Associated Professional Sleep Societies LLC.
Results indicate that pitchers who were morning types performed statistically better overall than those who were evening types. In early games that started before 7 p.m., the earned run average (ERA) of pitchers who were morning types (3.06) was lower than the average ERA of pitchers who were evening types (3.49); however, in games that started at 7 p.m. or later, pitchers who were evening types performed slightly better (4.07 ERA) than morning types (4.15 ERA).
"We were surprised to see that chronotype did affect pitching," said principal investigator and lead author W. Christopher Winter, MD, medical director of the Martha Jefferson Hospital Sleep Medicine Center in Charlottesville, Va. "We were also surprised to see that pitchers who were more 'morning type' seemed to do better overall."
Individual pitchers showed a trend toward higher ERAs in the late games. According to Winter, this supports previous research showing that the peak performance time for most athletes is between mid-afternoon and early evening.
The study involved 18 pitchers from five MLB teams: the Los Angeles Dodgers, New York Mets, Philadelphia Phillies, San Francisco Giants and Tampa Bay Rays. Sleep preference was determined using a modified version of the Morningness-Eveningness Questionnaire (MEQ). It identifies a person's tendency to be either a morning type who prefers to go to bed and wake up early, or an evening type who prefers to stay up late at night and wake up late in the day. Ten participants were found to be evening types, and eight were morning types.
The study used the players' statistics from the 2009 season, which provided about 728 early innings and 845 late innings for analysis. Game start times were adjusted for travel using the principle that for every time zone crossed, it takes 24 hours to adjust.
"These results are important as they are potentially giving insight into an entirely new way to grade or classify an athlete, in this specific case a pitcher," said Winter. "This study may provide insight as to which pitchers would be best in a given situation based upon when the game is being played. For example, a critical game being played in the evening might be a better situation to pitch an evening-type pitcher versus a day-type pitcher."
Winter also has studied the effect of travel across time zones on the performance of MLB teams. At SLEEP 2008 he presented the initial findings of a 10-year retrospective study that was later published in the September 2009 issue of the International Journal of Sports Physiology and Performance. He found that teams traveling from Western time zones to Eastern time zones were 14 percent more likely to win than teams traveling from east to west. Teams also won more than 60 percent of the games in which they had a three-hour "circadian advantage.
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