Knee-Friendly Landings Reduce Force By 56 Percent

Anterior cruciate ligament injuries are a common and debilitating problem, especially for female athletes. A new study from UC Davis shows that changes in training can reduce shear forces on knee joints and could help cut the risk of developing ACL tears.

"We focused on an easy intervention, and we were amazed that we could reduce shear load in 100 percent of the volunteers," said David Hawkins, professor of neurobiology, physiology and behavior at UC Davis. Hawkins conducted the study at the UC Davis Human Performance Laboratory with graduate student Casey Myers.

The anterior cruciate ligament lies in the middle of the knee and provides stability to the joint. Most ACL injuries do not involve a collision between players or a noticeably bad landing, said Sandy Simpson, UC Davis women's basketball coach.

"It almost always happens coming down from a rebound, catching a pass or on a jump-stop lay-up," Simpson said. "It doesn't have to be a big jump."

Hawkins and Myers worked with 14 female basketball players from UC Davis and local high schools. They fitted them with instruments and used digital cameras to measure their movements and muscle activity, and calculated the forces acting on their knee joints as they practiced a jump-stop movement, similar to a basketball drill.

First, they recorded the athletes making their normal movement. Then they instructed them in a modified technique: Jumping higher to land more steeply; landing on their toes; and bending their knees more deeply before taking off again.

After learning the new technique, all 14 volunteers were able to reduce the force passed up to the knee joint through the leg bone (the tibial shear force) by an average of 56 percent. At the same time, the athletes in the study actually jumped an inch higher than before, without losing speed.

Hawkins recommends warm-ups that exercise the knee and focusing on landing on the toes and balls of the feet. The study does not definitively prove that these techniques will reduce ACL injuries, Hawkins said: that would require a full clinical trial and follow-up. But the anecdotal evidence suggests that high tibial shear forces are associated with blown knees.

Hawkins and Myers shared their findings with Simpson and other UC Davis women's basketball and soccer coaches, as well as with local youth soccer coaches.  The research was published online Aug. 3 in the Journal of Biomechanics.

Simpson said that the team had tried implementing some changes during last year's preseason, but had found it difficult to continue the focus once the full regular season began. In live play, athletes quickly slip back to learned habits and "muscle memory" takes over, he noted. More intensive off-court training and practice would be needed to change those habits, he said.

"We will be talking about this again this season," Simpson said. Implementing the techniques in youth leagues, while children are still learning how to move, might have the most impact, he said.

Source: University of California - Davis - Health System

See also: Barefoot Is Better and For Rock Climbers, Endurance Is Key To Performance

Sports Science Gym Bag - 12-8-09

Wow, what are the odds that I lead off this week's Gym Bag with a Tiger Woods story?  Don't worry, this article has no mention of Escalades, golddiggers or mothers-in-law.  Plus, plenty of other great stuff from the sports science world.


The Tiger Woods Effect

 Success is intimidating. When we compete against someone who's supposed to be better than us, we start to get nervous, and then we start to worry, and then we start to make stupid mistakes. That, at least, is the lesson of a new working paper by Jennifer Brown, a professor at the Kellogg school.
Brown demonstrated this psychological flaw by analyzing data from every player in every PGA tournament from 1999 to 2006. The reason she chose golf is that Tiger Woods is an undisputed superstar, the most intimidating competitor in modern sports. (In 2007, Golf Digest noted that Woods finished with 19.62 points in the World Golf Ranking, more than twice as many as his closest rival. This meant that "he had enough points to be both No. 1 and No. 2.") Brown also notes that "golf is an excellent setting in which to examine tournament theory and superstars in rank-order events, since effort relates relatively directly to scores and performance measures are not confounded by team dynamics." In other words, every golfer golfs alone...

Vince Young
The underlying assumption of the Wonderlic test is that players who are better at math and logic problems will make better decisions in the pocket. At first glance, this seems like a reasonable conjecture. No other position in sports requires such extreme cognitive talents. A successful quarterback will need to memorize hundreds of offensive plays and dozens of different defensive formations. They'll need to spend hours studying game tape of their opponents so that, when they're on the field, they can put that knowledge to use. In many instances, quarterbacks are even responsible for changing the play at the line of scrimmage. They are like a coach with shoulder pads...

UN calls for football tax to fund education for poor children 
The United Nations today launches an appeal to FIFA football leagues, including the Premier League, to place a small levy on sponsorship revenues that would help get 2 million children in poor countries into school over the next five years...

Pushing Past the Pain of Exertion
LAST November, Kara Goucher ran the ING New York City Marathon, her first 26.2-mile race. Even though she was an Olympian who had placed 10th in the 10,000 meter race in 2008 in Beijing — running the equivalent of 6.2 miles — she felt fear.  “I was really scared I wouldn’t be able to handle the pain for that long,” said Ms. Goucher, 31, who had never run more than 18 miles at a time before training for the marathon. “Now I was asking myself to run eight miles farther, a lot faster. It was daunting.”

Coaching and science: What's the big deal and who cares for the science?
"As promised, today begins a series of posts on coaching and science, and how the science can be, should be, and sometimes is, and often is not, applied to athlete preparation. Obviously, it comes with an endurance focus, but there's no reason why sprint coaches and team sport coaches can also not glean some information from this.
This is a series that was inspired by my visit to the US Olympic Center in Colorado Springs. I was lucky enough to be invited there by Prof Randy Wilber of the USOC, who had organized a symposium on altitude training. The symposium brought together scientists, coaches, athletes and mangers from 22 different countries, and included 32 Olympic athletes, and numerous sporting codes, Summer and Winter Olympics among them..."

Belichick had the numbers on his side
Among the countless criticisms hurled at Patriots coach Bill Belichick for his decision to go for it on fourth down Sunday night, former Colts coach Tony Dungy summed up the most popular when, speaking on NBC, he said, “You have got to play the percentages and punt the ball.’’ What Dungy did not realize, though, is that “the percentages’’ dictated that Belichick do exactly what he did...

Short Heels and Long Toes: A Surprising Recipe for Speed
Track coaches have long claimed that the best sprinters are born, not made. Now, new research on the biomechanics of sprinting suggests that at least part of elite athletes’ impressive speed comes from the natural shape of their foot and ankle bones.
Using ultrasound imaging, researchers compared the feet of 12 top college sprinters with those of 12 mere mortals. Surprisingly, the athletes had particularly short heels and longer-than-average toes — features that actually put them at a mechanical disadvantage when running.
“What we found is that sprinters actually had less mechanical advantage than the non-sprinter subjects that we tested,” said biomechanics researcher Stephen Piazza of Penn State University, co-author of the study published Friday in the Journal of Experimental Biology. “This was surprising to us because we expected that sprinters needed all the help they could get.”

Usain Bolt Can Be Even Faster, Researchers Claim

Well, maybe Usain Bolt was right after all.  As discussed in our Physiology of Speed story, Bolt predicted he could run 100 meters in 9.54 seconds, lowering his own world record of 9.69 seconds.

Earlier this week, he almost got there running a 9.58 at the World Championships in Berlin.

Now, researchers from Tilburg University in the Netherlands say he could shave another 3/100ths of a second off and hit the tape at 9.51 seconds.

Using the "extreme value theory", Professor of Statistics John Einmahl and former student Sander Smeets have calculated the fastest possible times for men and women.  Between 1991 and 2008, they chronicled the best times for 762 male sprinters and 469 female sprinters.  They did not trust the data prior to 1991 as possibly being tainted by doping athletes (not that's its gotten much better since then.)

For females, their current world record, set by Florence Griffith-Joyner, of 10.49 seconds could be theoretically lowered to 10.33 seconds.

Extreme value theory is a branch of statistics that tries to predict extreme events such as 100-year floods or major stock market movements that deviate signficantly from the median.  With less statistical confidence (95% confidence), Einmahl estimates the men could get to 9.21 while the women could run a 9.88.

To make this statistical postulating a reality, Bolt needs to find the secret competitive edge that will shave these tenths and hundredths of seconds away. Scientists at the Research Institute of Wildlife Ecology in Austria claim sunflower oil may be the super fuel that is missing.

They found that mice fed a diet high in sunflower oil, which contains n-6 polyunsaturated fatty acids, were 6.3% faster in sprint races against mice fed a diet rich in linseed oil, which is high in n-3 fatty acids.

Their research was presented in June at the Society for Experimental Biology Annual Meeting.

"The results of the current study on mice suggest that moderate differences in dietary n-6/n-3 polyunsaturated fatty acid intake can have a biologically meaningful effect on maximum running speed", says Dr Christopher Turbill, lead researcher. "The application of this research to the performance of elite athletes (specifically those in sports that involve short distance sprints, including cycling) is uncertain, but in my opinion certainly deserves some further attention" he said.

So, a little sunflower oil mixed into the pre-race Gatorade? It might work until world records start to fall and its added to the banned substance list.

The Physiology Of Speed

Usain Bolt, the triple Olympic gold medal sprinter from Jamaica, predicted last week that he could break his own world record of 9.69 seconds in the 100 meter sprint with a time as low as 9.54 seconds.  (8/15 update: he came very close running a 9.58 at the World Championships in Berlin.)

He claimed his coach told him its possible, so he believes him. His coach, Glen Mills, may have just finished reading some new research coming out of Duke University that showed sprinters and swimmers who are taller, heavier but more slender are the ones breaking world records.

At first glance, it may not make sense that bigger athletes would be faster. However, Jordan Charles, a recent engineering grad at Duke, plotted all of the world record holders in the 100 meter sprint and the 100 meter swim since 1900 against their height, weight and a measurement he called "slenderness."

World record sprinters have gained an average of 6.4 inches in height since 1900, while champion swimmers have shot up 4.5 inches, compared to the mere mortal average height gain of 1.9 inches.
During the same time, about 7/10 of a second have been shaved off of the 100-meter sprint while over 14 seconds have come off the 100-meter swim record.

What's going on
Charles applied the "constructal theory" he learned from his mentor Adrian Bejan, a mechanical engineering professor at Duke, that describes how objects move through their environment.

"Anything that moves, or anything that flows, must evolve so that it flows more and more easily," Bejan said. "Nature wants to find a smoother path, to flow more easily, to find a path with less resistance," he said. "The animal design never gets there, but it tries to be the least imperfect that it can be."

Their research is reported in the current online edition of the Journal of Experimental Biology.

For locomotion, a human needs to overcome two forces, gravity and friction. First, an athlete would need to lift his foot off the ground or keep his body at the water line without sinking. Second, air resistance for the sprinter and water resistance for the swimmer will limit speed.

So, the first step is actually weight lifting, which a bigger, stronger athlete will excel at. The second step is to move through the space with the least friction, which emphasizes the new slenderness factor.

By comparing height with a calculated "width" of the athlete, slenderness is a measurement of mass spread out over a long frame. The athlete that can build on more muscle mass over a aerodynamic frame will have the advantage.

The numbers
In swimming, legendary Hawaiian champion Duke Kahanamoku set the world record in 1912 with a time of 61.6 seconds with a calculated slenderness of 7.88. Some 96 years later, Eamon Sullivan lowered the world mark to 47.05 seconds at a slenderness factor of 8.29.

As the athletes’ slenderness factor has risen over the years, the winning times have dropped.  In 1929, Eddie Tolan's world-record 100 meter sprint of 10.4 seconds was achieved with a slenderness factor of 7.61. When Usain Bolt ran 9.69 seconds in the 2008 Olympics, his slenderness was also 8.29 while also being the tallest champion in history at 6-feet 5-inches.

“The trends revealed by our analysis suggest that speed records will continue to be dominated by heavier and taller athletes,” said Charles. “We believe that this is due to the constructal rules of animal locomotion and not the contemporary increase in the average size of humans.”

So, how fast did the original Olympians run? Charles used an anthropology finding for Greek and Roman body mass and plugged it into his formula.

“In antiquity, body weights were roughly 70 percent of what they are today,” Charles said. “Using our theory, a 100-meter dash that is won in 13 seconds would have taken about 14 seconds back then.”
Bolt puts his prediction to the test next month at the track and field world championships in Berlin. One of his main competitors is Asafa Powell, the previous world record holder, who is shorter and has a slenderness factor of 7.85. My money is on the Lightning Bolt.