April 2010

In the moment: sports medicine

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Soccer’s anti-aging formula

Soccer is already the world’s most popular sport, but new research could very well broaden its appeal even further. Multiple studies from Denmark suggest that playing soccer can improve bone mineral density and other musculoskeletal risk factors associated with falls and fractures.

“It is well known that the risk of falls and fractures increases with age as a result of weaker bones, poorer balance and attenuated ability to trigger rapid muscle force,” said Peter Krustrup, PhD, associate professor of exercise and sport sciences at the University of Copenhagen and primary investigator for the department’s soccer-specific research. “The present results suggest that soccer – and possibly other ball games – is an effective training method to reduce bone weakening that comes with increasing age.”

The Danish findings appear in a FIFA-sponsored special supplement to the April issue of the Scandinavian Journal of Medicine & Science in Sports, the most recent development in the ongoing health-focused public relations campaign being conducted by soccer’s international governing body (officially the Fédération Internationale de Football Association). FIFA last made medical headlines in December 2008 with the publication of a British Medical Journal study suggesting that a FIFA-developed exercise regimen could significantly reduce injury risk in soccer players.

In the current collection of findings, two separate studies found that playing soccer for one hour twice a week was associated with short- and long- term increases in volumetric bone mineral density in pre-menopausal women who had not done any training previously.

In women who were randomized to play soccer, 14 weeks of training were associated with significant increases in tibial vBMD, peak jump power, and maximal hamstring strength during fast and slow contractions. By comparison, women who were randomized to run twice a week demonstrated significant but less pronounced improvements in vBMD and no improvement in peak jump power or hamstring strength. Outcomes did not change significantly in control subjects.

“During soccer training and games, the players perform many sprints, turns, kicks, and tackles. This combination of actions helps achieve a variable bone impact that appears to provide a better stimulus to bone mineralization than running,” Krustrup said.

Of the 50 women randomized to the two training groups in the 14-week study, nine from the soccer group and 10 from the running group continued their training for 16 months. In the soccer group, whole body BMD at 16 months was 2.3% higher than at four months and 1.3% higher than at baseline, all significant differences. Similar changes were not seen in the running or control groups. Both training groups also experienced significant improvement in fast and slow eccentric muscle strength and rapid force capacity (the ability to generate force rapidly, as in response to a perturbation), which are both variables that have been linked to risk of falls in previous research.

But the musculoskeletal benefits of soccer aren’t just limited to women. A third study in the April supplement analyzed rapid muscle force characteristics, body composition, and postural stability in 18 elderly men (mean age of 70), 10 of whom had played soccer their entire lives. The researchers found significantly greater rates of force development and impulse, higher total lean body mass, and better single-leg balance in the lifelong soccer players than in the untrained subjects. Not only that, but the older soccer players demonstrated rates of force development and postural stability levels that were comparable to those of 49 untrained younger men (mean age 32).

“Seventy year old men who have played soccer most of their lives on a recreational basis have just as good balance and rapid muscle strength as untrained 30 year olds, and much better balance and muscle strength than their peers,” Krustrup said.

NFL athletes injure lower extremities more often on FieldTurf than on grass

Lower extremity injuries in professional football players occur at a higher rate in games played on FieldTurf than those played on natural grass, according to a National Football League study presented in March at the annual meeting of the American Academy of Orthopaedic Surgeons.

FieldTurf, an artificial surface believed to be more for- giving than its predecessor, AstroTurf, made its NFL debut in 2000. The researchers analyzed data from the NFL’s Injury Surveillance System from 2002 to 2008, by which time the surface was installed in 10 of 32 NFL stadiums. Lower extremity injuries in general occurred 17% more frequently on FieldTurf than on grass. Specifically, rates of anterior cruciate ligament injuries were 88% higher, and ankle eversion sprains resulting in more than seven days of lost time were 48% higher.

“We challenge the manufacturers to use this data to improve the surfaces,” said Elliott Hershman, MD, team orthopedist for the New York Jets and chairman of the NFL’s Injury and Safety Panel, who presented the findings at the AAOS meeting.

Analysis of pitching motion confirms contributions of muscles in both legs

There’s a reason that some of the best pitchers in major league baseball are known for their lower body strength. Research from Bowling Green State University confirms that the muscles of both legs are significantly activated during the better part of a pitcher’s throwing motion.

Investigators assessed lower extremity muscle activation in 11 baseball pitchers during the pitching motion, relative to maximal voluntary isometric contraction values. The muscles analyzed included the biceps femoris, rectus femoris, gluteus maximus, vastus medialis, and gastrocnemius. The pitching motion was divided into four phases.

In the trailing leg, the researchers identified moderate to high activity levels (38% to 172% of MVIC) during phase 2 (from maximum height of kick to front foot contact) and phase 3 (from foot contact to ball release). In the stride leg, moderate to high activity levels (23%  to 170% of MVIC) occurred during phases 2, 3 and 4 (from ball release to 0.5 seconds into follow-through).

The results were e-published in April by the Journal of Strength and Conditioning Research.

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