Contact: Wyatt DuBois
wed112@psu.edu
814-863-3798
Penn State

That’s what three researchers found when they analyzed over/under lines and the results of more than 190 National Football League games played in 2010 and the impacts of several variables used to set the betting line.

“This may mean that bettors place too much emphasis on recent information,” says Tracy D. Rishel, associate professor of management at Susquehanna University in Selinsgrove, PA.

Rishel, and two economists from Randolph Macon College — C. Barry Pfitzner and Steven D. Lang — presented a paper on their results in October in Myrtle Beach, SC at the annual meeting of the Southeast Institute for Operations Research and Management Sciences.

“We are able to explain about two-thirds of the variance in the over/under betting line for individual games with the variables we examined,” reports Susquehanna University’s Rishel. “The data are very consistent across two years study; both 2010 and research we did earlier on the 2008 NFL season.”

The over/under line set by bookmakers, is an attempt to predict the number of points to be scored by both teams in the next game. Bettors can choose the “over” meaning that they think more points will be scored than the odds makers predict. Or they can select the “under,” meaning that they win if fewer points are scored than are forecast in the betting line.

Another element that proved important in predicting where odds makers would set the over/under line was whether the game was played in a domed stadium with the roof closed. The dome factor, however, was not significant in predicting the number of actual points scored in the 2010 season although a statistically significant relationship was found for the 2008 season.

“The dome effect may have captured the effect of teams that played in home domed stadiums, were also high scoring teams for the 2008 season, but were not quite so productive in 2010. Other explanations are equally plausible,” says Rishel.

As expected, the researchers found, using multivariate regression analysis, that offense vs. defense matchups play large roles in setting the over/under line. They play a lesser but still noticeable role in predicting scores.

“Matchups count,” notes Rishel. “Examination of yards gained on offense matched against yards surrendered on defense, was highly statistically significant in the placement of the betting line.”

The work by Rishel, Pfitzner and Lang could be a cautionary tale for football bettors.

“The line, as expected, is much easier to predict than the actual points scored,” says Rishel. “The outcomes and points scored are not easily predicted which is ‘why they play the games.’”

In their analysis, the researchers made no allowance for injuries or for weather in games played outdoors.

Their study is titled: “The Determinants of Scoring in 2010 NFL Games and the Over/Under Line.”

Contact: Laura Snyder
laura@dickjonescomm.com
814-766-3565
Dick Jones Communications

The study – published online Nov. 4 by the Journal of Neurosurgery: Spine – compared head injury risks of two early 20th Century leatherhead helmets with 11 top-of – the-line 21st Century polycarbonate helmets.

In their biomechanics lab, Cleveland Clinic researchers conducted impact tests, crashing helmets together at severities on par with 95 percent of on-field collisions (75 g-forces or less) in collegiate and high school football games. For this study, researchers analyzed hits that are common in games and practices – hits that taken separately may not seem perilous but when added together may lead to serious long-term injury.

For many of the impacts and angles studied in the lab, the researchers found that leather helmets offered similar, or even better, protection than modern helmets.

“The point of this study is not to advocate for a return to leather helmets but, rather, to test the notion that modern helmets must be more protective than older helmets simply because ‘newer must be better,’” said lead researcher Adam Bartsch, Ph.D., Director of the Spine Research Lab in Cleveland Clinic’s Center for Spine Health. “Unlike cars, in which seat belts, airbags and crumple zones make the choice between a 1920′s Model T and modern mini-van a no-brainer, these results tell us that modern helmets have ample room to improve safety against many typical game-like hits.”

Though head and neck injuries were greatly reduced after football helmet standards and rule changes were instituted in 1970′s and 1980′s, the incidence of concussions have continued to increase. In fact, concussions are the leading cause of brain damage in sports, particularly in football. Estimates suggest that up to 40 percent of football players experience a concussion each year, with more than half of these going unreported.

Cleveland Clinic researchers note that helmet safety standards – as measured by the Gadd Severity Index – are based solely on the risk of severe skull fracture and catastrophic brain injury, not concussion risk. So, while modern helmets may prevent severe head injuries, this study found that they frequently did not provide superior protection in typical on-field impacts when compared to leather helmets.

“Today’s safety standards are no longer state-of-the-art predictors of injury,” said Edward Benzel, M.D., Chair of Cleveland Clinic’s Department of Neurological Surgery. “Of course, preventing skull fractures is vitally important, but concussion prevention needs to be an integral part of the standards as well. Also, helmets need to protect against the cumulative effects of multiple lower impact blows that may not lead to a concussion immediately but may add up to cause severe long-term head, neck or brain injuries.”

The findings suggest that helmet testing should focus on both low- and high-energy impacts, not solely on potentially catastrophic high-energy impacts. This is especially true of youth football helmets, which are currently scaled-down versions of adult helmets. The lack of adequate knowledge surrounding adult helmet protectivity at low-energy impacts, as well as the current absence of any youth-specific helmet testing standards, may have serious brain health implications for the 3 million youths participating in tackle football in the United States each year.

The leatherhead study is one of several projects Cleveland Clinic is undertaking to better detect and prevent brain injuries across a wide range of sports, including football, boxing, hockey and soccer. Teams of researchers are working to make safer youth football helmets (through a grant from NFL Charities); create an Intelligent Mouthguard that measures the number and severity of hits to the head among athletes; produce a blood test that can diagnose concussions; and develop an iPad app that uses the device’s built-in gyroscope to quantitatively capture pre- and post-game measures of balance, memory and cognition. In Las Vegas, the Cleveland Clinic Lou Ruvo Center for Brain Health has launched a landmark study with professional fighters that will help determine whether MRIs of the brain, along with other tests, can detect subtle changes in brain health that correlate with impaired thinking and functioning. The research teams draw from their experiences of caring for thousands of professional, amateur and youth athletes every year on the sidelines and in clinic.

About Cleveland Clinic

Celebrating its 90th anniversary, Cleveland Clinic is a nonprofit multispecialty academic medical center that integrates clinical and hospital care with research and education. It was founded in 1921 by four renowned physicians with a vision of providing outstanding patient care based upon the principles of cooperation, compassion and innovation. Cleveland Clinic has pioneered many medical breakthroughs, including coronary artery bypass surgery and the first face transplant in the United States. U.S.News & World Report consistently names Cleveland Clinic as one of the nation’s best hospitals in its annual “America’s Best Hospitals” survey. About 2,800 full-time salaried physicians and researchers and 11,000 nurses represent 120 medical specialties and subspecialties. Cleveland Clinic Health System includes a main campus near downtown Cleveland, nine community hospitals and 15 Family Health Centers in Northeast Ohio, Cleveland Clinic Florida, the Lou Ruvo Center for Brain Health in Las Vegas, Cleveland Clinic Canada, and opening in 2013, Cleveland Clinic Abu Dhabi. In 2010, there were 4 million visits throughout the Cleveland Clinic health system and 155,000 hospital admissions. Patients came for treatment from every state and from more than 100 countries. Visit us at http://www.clevelandclinic.org/. Follow us at www.twitter.com/ClevelandClinic.

“We think when you’re under pressure, that your attention goes inward naturally. Suddenly it means so much, you want to make sure everything’s working properly,” says Rob Gray, of the University of Birmingham, the author of the new article. And that is exactly when things go wrong. Something about paying attention to what you’re doing makes it not work right.

Of course, athletes know that they should just relax and do their usual thing, but it’s not very helpful to tell someone to just relax. The goal for psychological scientists, Gray says, is to figure out what actually happens when someone starts paying too much attention to their body. “Focusing on what you’re doing makes you mess up, but why? How do your movements change? How can we focus on correcting those issues instead of telling you to stop trying so hard?”

Gray has found that baseball players that are under pressure have fewer hits because their swing varies more under pressure than at normal times. Other researchers have found that climbers move less fluidly when they’re higher up on a wall than when they’re near the ground, which suggests that their joints move less freely when they’re more anxious.

The research shows that there are particular things that go wrong when someone is under pressure — changing the angle of the club head when putting or throwing with more force. If those things can be identified, a coach could work on the particular problems.

One way to do it might be with analogies, Gray says. For example, a golfer who grips the club too tight when she’s nervous might benefit from an instruction like “imagine you have an open tube of toothpaste between your hands and the contents must not be pushed out.” This would both address the problem and get her attention away from how well she’s doing.

For more information about this study, please contact: Rob Gray at r.gray.2@bham.ac.uk.

Current Directions in Psychological Science, a journal of the Association for Psychological Science, publishes concise reviews on the latest advances in theory and research spanning all of scientific psychology and its applications. For a copy of “Links Between Attention, Performance Pressure, and Movement in Skilled Motor Action” and access to other Current Directions in Psychological Science research findings, please contact Divya Menon at 202-293-9300 or dmenon@psychologicalscience.org.

The Auburn Eagles, a local, Montgomery County, Va., youth team consisting of 6 to 8 year old boys, has participated in the study since August. The helmets of the child football players are instrumented with custom 12 accelerometer arrays that measure how a child’s head responds to impact. Each time a player impacts his head, data are recorded and wirelessly downloaded to a computer on the sideline.

The technology is similar to what Virginia Tech has used since 2003 to instrument its collegiate football team. “The research conducted with the Virginia Tech football team has led to a better understanding of head impacts in football and how they relate to concussions,” said Stefan Duma (http://www.sbes.vt.edu/duma.php), the Virginia Tech professor of biomedical engineering and department head of the Virginia Tech – Wake Forest University School of Biomedical Engineering and Sciences (SBES) that directs this project.

Furthermore, this research has led to the development of the National Impact Database (http://www.sbes.vt.edu/nid), which contains the first safety rating system ever available for adult football helmets (STAR Evaluation System). Similar developments for youth football are anticipated from the current study with the Auburn Eagles.

“Based on eight years of studying head impacts experienced by Virginia Tech football players, we were able to quantify exposure for adult football players relative to impact location, severity, and frequency,” Duma said. “Unfortunately, we cannot translate the adult exposure to the youth helmets because the impact conditions of youth football are completely unknown. To solve this problem, we are applying the same approach that we have used with the Virginia Tech football team to a youth football team,” Duma added.

The instrumentation wasn’t compatible with the older helmets that were initially provided for the youth team, so Virginia Tech purchased new helmets for the entire team. “The kids are very excited about wearing the same technology in their helmets that the Virginia Tech football team has worn over the last eight years,” said Ray Daniel, the graduate student whose master’s thesis will be focused on the study.

“The parents, kids, and coaches have been very cooperative and are all excited about being part of this important study that will lead to better design guides for youth football helmets,” added Daniel, who performs the daily duties for the study and who is at every practice and game. All players and parents have consented to the study in accordance with the Virginia Tech Institutional Review Board procedures.

To date, over 400 head impacts experienced by the youth football team have been collected and analyzed. “Not only are the impacts generally less severe in youth football when compared to adults, but the frequency of the most severe impacts is substantially lower,” Duma said. While most of the impacts collected have been of very low severity; surprisingly, a few impacts are approaching impact levels associated with concussion in adult football players. The goal of this study is to completely quantify and characterize the head impact conditions of youth football, which will provide guidelines to aide manufacturers in designing better helmets for children.

“We have a unique opportunity to quantify the distribution of head impacts experienced by youth players, which no one has ever looked at before,” said Steven Rowson (http://www.cib.vt.edu/people/bios/faculty_bios/bio_rowson.html), research assistant professor of biomedical engineering and creator of the STAR Evaluation System for football helmets. Rowson, who also helped design the sensors that are currently in the youth helmets, added, “By knowing these impact distributions, we can develop a safety rating system for youth football helmets that will supplement the National Impact Database. This not only educates consumers on relative helmet safety, but also provides improved design criteria for helmet manufacturers.”

This work has implications that are not limited to improved helmets in football, but also has applications towards improved head protection in other sports, as well as advancements in automobile safety designs. Funding for this project is provided by the National Highway Traffic Safety Administration (NHTSA) and the Institute for Critical Technology and Applied Science (ICTAS) at Virginia Tech.

Contact: Lynn Nystrom
tansy@vt.edu
540-231-4371
Virginia Tech

This October, the Journal of Quantitative Analysis in Sports will feature the article: An Estimate of How Hitting, Pitching, Fielding, and Base-stealing Impact Team Winning Percentages in Baseball. In it, University of Delaware Professor Charles (Charlie) Pavitt defines the perfect “formula” for MLB teams to use to build the ultimate winning team.

Pavitt found hitting accounts for more than 45% of teams’ winning records, fielding for 25% and pitching for 25%. And, the impact of stolen bases is greatly overestimated.

He crunched hitting, pitching, fielding and base-stealing records for every MLB team over a 48-year period from 1951-1998 with a method no other researcher has used in this area. In statistical parlance, he used a conceptual decomposition of offense and defense into its component parts and then analyzed recombinations of the parts in intuitively meaningful ways.

He also found something many MLB teams don’t know: the ability to steal bases is just not that important to the overall winning record of a professional baseball team.

As major league baseball’s playoffs kick off and “Moneyball” plays in movie theatres nationwide, Pavitt is available for interviews.

Contact: Meredith Chapman
mchapman@udel.edu
302-831-8749
University of Delaware

The study, led by Joseph J. Crisco, professor of orthopaedics in the Warren Alpert Medical School of Brown University and director of the bioengineering laboratory at Rhode Island Hospital, documented 286,636 head blows among 314 players in the 2007-09 seasons. Crisco said the new data on the magnitude, frequency, and location of head blows amounts to a measure of each player’s head impact exposure. Ultimately it can help doctors understand the biomechanics of how blows to the head result in injury.

“This allows us to quantify what the exposure is,” Crisco said. “It is the exposure that we need to build upon, so that we can then start understanding what the relationships are with acute and chronic head injury.”

The study appears online in advance in the Journal of Biomechanics.

Concussions and other head injuries have become a source of elevated concern in football and other sports in recent years, with various leagues revising policies to protect players better. In part based on seeing this new data, said Robin Harris, Ivy League executive director, league officials announced earlier this year that full-contact practices would be limited to two a week.

Hits by position

The new study documents the nature of head blows by player position. Players on the three teams wore helmets equipped with wireless sensors that measured acceleration in various directions. That data allowed the team of researchers from Brown, Dartmouth, Virginia Tech, and sensor-maker Simbex to discern how hard the hit was, how often each player was hit, and where on the helmet they were hit.

Crisco devised the algorithm that Simbex’s Head Impact Telemetry System uses to measure head impacts. The system’s development and this study were funded by the National Institute of Child Health and Human Development and the National Operating Committee on Standards for Athletic Equipment.

The data on head acceleration and hit direction are used to calculate a composite score of exposure called HITsp that researchers believe might be a good predictor of concussion. On average, running backs had the highest HITsp, 36.1, followed by quarterbacks with 34.5 and linebackers at 32.6. Offensive and defensive linemen had the lowest HITsp numbers, with 29.0 and 28.9 respectively, but along with linebackers, they were hit on the head most often. Doctors worry not only about hit severity, but also hit frequency, because repeated head impacts may cause “subconcussive” neurological damage over time.

By analyzing head impacts by position, Crisco said, researchers can help football league officials and equipment designers begin to think about ways to make players safer.

“It will allow us to begin to understand how to control the exposures,” Crisco said. Controlling head impact exposure is critical, he added, because there are currently no treatments for acute or chronic brain injuries, and helmets cannot prevent injuries for all players in all situations.

One possibility could include rule changes. Another could include designing helmets for specific positions.

Crisco and his colleagues are now analyzing data about concussions during the three seasons to determine how and whether head impact exposure is associated with injury. He recently co-authored another paper about male and female collegiate hockey players, which reported that although women were diagnosed with more concussions, they sustained fewer and less severe head impacts.

Although Crisco’s analysis is still underway, his insights into head impact exposure led him and co-author Richard Greenwald, a Dartmouth engineer, to write a commentary earlier this year in Current Sports Medicine Reports, in which they argued that intentional use of the head in sports must be curbed.

“We propose the adoption of rules – or in some sports, we champion the enforcement of existing rules – that eliminate intentional head contact in helmeted sports,” they wrote. “When coupled with education that leads to modified tackling, blocking, or checking techniques, these rules will reduce head impact exposure and have the potential to reduce the incidence and severity of brain injury.”

Crisco, a former college football and lacrosse player, said he is passionate about contact sports and believes they have many benefits.

“Hitting is an essential component,” he said. “But intentional hitting with your head was never part of any sport and is poor technique.”

In addition to Crisco and Greenwald, other authors of the paper are Bethany Wilcox of Brown; Jonathan Beckwith and Jeffrey Chu of Simbex; Stefan Duma and Steve Rowson of Virginia Tech and Wake Forest; and Ann-Christine Duhaime, Arthur Maerlender, and Thomas McAllister of Dartmouth.

Contact: David Orenstein
david_orenstein@brown.edu
401-863-1862
Brown University

New research findings provide an answer. Analysis of 3.5 million pitches from 2004 to 2008 found that minority pitchers scale back their performance to overcome racial/ethnic favoritism toward whites by MLB home plate umpires, said Johan Sulaeman, a financial economist at Southern Methodist University in Dallas and a study author.

The study found that minority pitchers reacted to umpire bias by playing it safe with the pitches they throw in a way that actually harmed their performance, said Sulaeman, a labor and discrimination expert.

Specifically, minority pitchers limited the umpires’ discretion to call their pitch a “ball” by throwing squarely across the plate in the strike zone more often. Unfortunately for the pitcher, such throws are also easier for batters to hit.

The finding builds on an earlier study that discovered Major League Baseball’s home plate umpires called strikes more often for pitchers in their same ethnic group – except when the plate was electronically monitored by cameras, Sulaeman said.

While the earlier finding surprised the researchers, they said, the latest results are even more surprising.

Since most MLB umpires are white, the overall effect is that umpire bias pushes performance measures of minorities downward, said Sulaeman, an expert in labor economics and discrimination.

The findings have important implications for measuring the extent of discrimination not only in baseball, but also in labor markets generally, say the authors.

“In MLB, as in so many other fields of endeavor, power belongs disproportionately to members of the majority – white – group,” the authors write.

Findings draw on analysis of pitching in QuesTec-monitored parks

Sulaeman and his co-authors analyzed 3.5 million pitches by Major League Baseball pitchers from 2004 to 2008. All parks are now monitored, but during those four years about one-third of major league ballparks were monitored with computers and cameras to check the accuracy of the umpires’ ball and strike calls.

Four cameras tracked and recorded the location of each pitch, with umpires and pitchers aware that QuesTec was the primary mechanism for gauging umpire performance. MLB considers an ump’s performance sub-standard if more than 10 percent of his calls differ from QuesTec.

Of the 3.5 million pitches, umpire and pitcher were the same race – usually white – for about two-thirds of the 1.89 million pitches that were called strikes or balls. About 89 percent of umpires and 70 percent of pitchers were white.

The researchers looked not only at the race of umpires, pitchers and batters, but also: effects for each pitcher, umpire and batter; presence or absence of QuesTec; importance of the at-bat; when the pitch would terminate the at-bat; whether the pitch came early or later in the game; importance of the game; racial demographics of the neighborhood around the park; umpire age and experience; pitch characteristics, including horizontal pitch distance and pitch height; and whether the throw was a fastball, curveball, slider or cutter.

The study controlled for inning, pitch count, pitcher score advantage and whether the pitcher was playing at home or visiting.

Findings: Minimal direct impact, but significant indirect influence

The researchers found:

• In non-monitored parks, the percentage of called pitches that are strikes is higher when the race of both umpire and pitcher match than when it does not. This is true not only of whites, but also Hispanics and blacks.
• In QuesTec parks, if the race of the pitcher and umpire match, the likelihood that a called pitch is ruled a strike is reduced by more than one percentage point relative to the same setup in non-QuesTec parks. This implies umpires implicitly allow their apparent favoritism to be expressed when not being monitored, the study authors say.
• Implicit monitoring – for example, an important pitch viewed by a big crowd – also dramatically alters umpire behavior. On the other hand, white and minority umpires at poorly attended games appear to favor pitchers of the same race by calling more strikes.
• Umpires favor pitchers of the same race only when the pitch won’t terminate the batter’s plate appearance.
• Little evidence was found to indicate the umpire is influenced by the race of either the batter or the catcher.
• A higher strike percentage showed umpires exhibited same-race favoritism in non-QuesTec parks. A lower strike percentage indicated negative bias toward pitchers of different races in QuesTec parks.
• There is some weak evidence that bias is more likely among younger and less experienced umpires.
• Favoritism was a significant factor for pitches thrown to the edge of the strike zone – where umpires have the most discretion – but not for pitches inside or outside the strike zone. In QuesTec parks, the umpire and pitcher having the same race has virtually no effect on pitch location. In non-QuesTec parks, pitches to the edges significantly increase when umpire and pitcher share the same race. The finding suggests pitchers gamble on the fact that this region can reasonably be called as either balls or strikes and therefore offers them an advantage.
• In QuesTec parks, matched race is associated with a slight preference for hard-to-hit and hard-to-call curveball pitches. In non-QuesTec parks, that preference quadruples.

The researchers concluded:

• The direct effects on pitch outcomes are small. The indirect effect on players’ strategies may have larger impacts on the outcomes of plate appearances and games.
• From the starting pitcher’s perspective, a racial match with the umpire helped his statistics by yielding fewer earned runs, fewer hits and fewer home runs.
• Because the majority of umpires are white, teams with minority pitchers have a distinct disadvantage in non-monitored parks.
• There is no evidence that visiting managers adjusted their pitching lineups to minimize exposure of their minority pitchers to the subjective bias of a white umpire.
• In parks without QuesTec, pitchers of the same race threw pitches that allowed umpires the most discretion, apparently to maximize their advantage stemming from the umpires’ favoritism.
• A batter who swings is less likely to get a hit when the umpire and pitcher match.
• Applying the effects of favoritism, and given that the average salary of starting pitchers in MLB was $4.8 million in 2006, the findings suggest minority pitchers were underpaid relative to white pitchers by between $50,000 and $400,000 a year.

“If a pitcher expects favoritism, he will incorporate this advantage into his strategy, perhaps throwing pitches that allow the umpire more discretion,” the authors write. “If the batter expects such pitches to be called strikes, he is forced to swing at worse pitches, which reduces the likelihood of getting a hit.”

Not just Major League Baseball; a factor in all work environments

How many minority pitchers have had their pitching records diminished by this phenomenon is impossible to say, Sulaeman said, adding that one can only guess at the impact over decades of professional baseball. But discovery of the indirect effect of racial bias in MLB pointedly demonstrates how discrimination alters the behavior of a discriminated group, say the authors.

In any workplace where pay is based on measured productivity, the findings of small direct and larger indirect effects of favoritism and negative bias have important implications for measuring the extent of wage discrimination not only in baseball, but also in labor markets generally, say the authors.

Supervisory racial bias must be accounted for when generating measures of wage discrimination, the authors conclude.

The researchers’ earlier analysis of the data found that ethnic bias is virtually eliminated when an umpire knows his calls are being monitored with video cameras to check for accuracy.

“The good news is that all ballparks are now equipped with this technology, likely eliminating this subconscious bias,” said Sulaeman, assistant professor of finance in SMU’s Cox School.

Monitoring suppresses bias when evaluators are observed for bias

That isn’t the case, however, in other workplaces, where monitoring is not the norm, he said. As a result, supervisors have ample opportunity to subconsciously evaluate those of a different race more negatively, he said. Supervisors may be less prone to this subconscious bias if they know they are being monitored.

“When their decisions matter more, and when evaluators are themselves more likely to be evaluated by others, our results suggest that these preferences no longer manifest themselves,” the authors say.

The study, “Strike Three: Discrimination, Incentives and Evaluation,” is published in the current issue of the scholarly journal The American Economic Review.

In addition to Sulaeman, co-authors were Christopher A. Parsons, University of North Carolina at Chapel Hill; Michael C. Yates, Auburn University; and Daniel S. Hamermesh, University of Texas at Austin.

Contact: Margaret Allen
mallen@smu.edu
214-768-7664
Southern Methodist University

For the first time, several key rotational-biomechanic elements of the golf stroke in its entirety, from backswing to follow-through, were analyzed, and then the data were used to generate benchmark curves, said Jessica Rose, PhD, associate professor of orthopaedic surgery and senior author of the study. She and her fellow researchers found that swing biomechanics were highly consistent among a group of professional players. At certain phases of their swings, their movements were almost indistinguishable from one another.

“The set of biomechanical factors we examined were selected to capture the essential elements of power generation,” Rose said. The lead author of the study is former Stanford medical student David Meister, MD.

The findings, scheduled to be published online July 29 in the Journal of Applied Biomechanics, could be used to help improve golfers’ ability to hit the ball farther and do so without increasing their risks of injury. The authors point to studies showing that improper swing biomechanics is the leading cause of golf-related injuries. They also cite studies showing that 26-52 percent of golf-related complaints involve lower-back injuries, 6-10 percent involve shoulder injuries and 13-36 percent involve wrist injuries.

“Over-rotation is one of the leading causes of back injury,” Rose added.

Researchers collected data for the study using an array of eight special digital cameras in the Motion & Gait Analysis Laboratory at Lucile Packard Children’s Hospital at Stanford. Using the same precise technology they typically use to analyze gait and upper limb movement disorders, they recorded three-dimensional motion images of the golf swings of 10 professional and five amateur male players. Among the five non-professional golfers, one was a college-level amateur with a handicap of 4; two were amateurs with handicaps of 15 and 30, respectively; and two were novices. Most of the professional players were alumni of the Stanford Men’s Golf Team.

Although men were the exclusive subjects of this study, Rose said the findings likely extend to women, as well, but need to be examined.

Researchers analyzed several biomechanical elements of subjects’ golf swings, including S-factor (tilt of the shoulders), O-factor (tilt of the hips) and X-factor — the relative rotation of the hips to the shoulders, measured in degrees — which is considered key to power generation. Previous research has shown that pro golfers who hit the ball far generally have a larger peak X-factor than their peers, but this study is more extensive in that it considers X-factor in relation to other rotational biomechanics of the golf swing over the full duration of the motion.

Among the 10 pros in this study, peak X-factor during a hard swing was highly consistent, varying just 7.4 percent from a mean of 56 degrees. Their club speeds at impact with the ball also were highly consistent, varying just 5.9 percent from a mean of 79 mph. In contrast, peak X-factor of the three least skilled amateurs — the handicap-30 golfer and two novices — fell below the professional range: 48, 46 and 46 degrees, respectively. These smaller X-factor angles correlated with slower club speeds at impact: 68, 66 and 56 mph, respectively.

In addition, the study describes S-factor, a term coined by the researchers, for the first time. S-factor is the angle or tilt of the leading shoulder relative to the level position. The researchers found that peak S-factor occurred right after impact and was highly consistent among the pros, varying just 8.4 percent from a mean of 48 degrees. The handicap-15 player and two novices had lower S-factors of 42, 42 and 33 degrees, respectively, while S-factors of the handicap-4 player and handicap-30 players both fell within the professional range.

The study also found that peak free moment — the golfers’ turning force, or torque, measured using a special scale — was highly consistent among the pros, varying only 6.8 percent from a mean.

The authors conclude that peak free moment, X-factor and S-factor “are highly consistent, highly correlated to [club head speed at impact], and appear essential to golf swing power generation among professional golfers.”

In addition, the researchers found overall biomechanical differences between the professionals and amateurs. “For example, the peak free moment of Novice #1 was reduced and delayed compared with the professionals,” the authors note. “His X-factor was excessive in early backswing, but insufficient in downswing compared with professionals. Novice #2 had a reduced X-factor throughout backswing and downswing.” Both of these players had lower club speeds at impact than the pros did.

“A precise understanding of optimal rotational biomechanics during the golf swing may guide swing modifications to help prevent or aid in the treatment of injury,” they wrote.

Conrad Ray, the Knowles Family Director of Men’s Golf at Stanford University and a co-author of the study, said the findings give scientific backing to the elements of golf-swing form that professionals have long understood are vital for generating power. The study also helps to clarify some unresolved questions about golf-swing biomechanics, Ray said. “One question that always comes from students is, ‘What starts the downswing?’” he said. “People have had different answers. Some would say the hands, or others would say the shoulders or the lower body. But the study confirms that rotation of the hips initiates the downswing. So that, to me, is an interesting finding.”

Ray, who as the men’s head golf coach led the Cardinal to five appearances in the NCAA championships and its eighth national title, in 2007, said the study validates the importance of X-factor in generating club speed. “All golfers want to know how to hit the ball longer, and this study support that speed is really a factor of relative body rotation,” he said.

There were some limitations to the study. Although club speed at impact is a common measure for determining power generation, the authors note that they were unable to measure the outcome of the swings, such as distance and accuracy; measurements were made in a lab, with players hitting the ball into a net. “Down the road, it would be interesting to correlate ball data to the rotational biomechanics,” Ray said.

The other Stanford co-authors of the study are Amy Ladd, MD, professor of orthopaedic surgery; Erin Butler, who recently earned her PhD in bioengineering; Betty Zhao, MS, a recent graduate student in mechanical engineering; and Andrew Rogers, a former undergraduate student in human biology.

The study was supported in part by the Medical Scholars Research Program at the School of Medicine and Media-X at Stanford University.

In the fall, Rose and her colleagues plan to begin offering a service for analyzing golf swing biomechanics through Stanford Hospital & Clinics Sports Medicine Clinic.

The Stanford University School of Medicine consistently ranks among the nation’s top medical schools, integrating research, medical education, patient care and community service. For more news about the school, please visit http://mednews.stanford.edu. The medical school is part of Stanford Medicine, which includes Stanford Hospital & Clinics and Lucile Packard Children’s Hospital. For information about all three, please visit http://stanfordmedicine.org/about/news.html.

Contact: John Sanford
jsanford@stanfordmed.org
650-723-8309
Stanford University Medical Center

“When I heard the news about the tornadoes, not long after the Japan tsunami disaster, I knew I had to do something help them as well,” said Choi, who will distribute the funds through his through his K.J. Choi Foundation, which he started four years ago to help unprivileged children around the world.

“While winning The Players Championship was a defining point in my life, there were those who were going through their low point.  I want the victims of the tornadoes to know that their misfortunes will not be ignored.”