Jan 29, 2015
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Uncovering Sprinters’ Secrets The mystery behind the origins of elite sprinters’ speed is closer to being solved thanks to research conducted at Southern Methodist University’s Locomotor Performance Laboratory. Two different studies, one published in the June 2014 issue of The Journal of Experimental Biology and the other in the September 2014 issue of the Journal of Applied Physiology, found that sprinters generate speed through distinct limb dynamics that increase ground forces upon impact.

Most explain the biomechanics of running with the spring mass model, which says that in each running step, the body is caught by the leg and propelled upwards. When the legs are engaged in this running motion, they interact with the ground much like a compression pogo stick. However, SMU researchers discovered that sprinters’ legs apply force to the ground in a much different manner.

“Our studies show that elite sprinters don’t use their legs to just bounce off the ground as most other runners do,” Ken Clark, MS, doctoral student at SMU and lead author of both studies, told Science Daily. “The top sprinters have developed a wind-up and delivery mechanism to augment impact forces.”

For both studies, researchers observed 14 athletes–seven top 100- and 200-meter sprinters as well as seven collegiate athletes from speed-intensive sports, such as football, lacrosse, and soccer. Both groups were composed of four males and three females. Using a high-speed force treadmill, the participants’ footfalls were measured at speeds ranging from three to 11 meters per second.

The research deduced that non-sprinters conformed to the spring mass model, while the top sprinters did not. Instead, members of the latter group struck the ground with firm, rapid punches and decelerated their feet and ankles in just over two-hundredths of a second after their feet touched the ground. Additionally, elite sprinters ran in an upright posture, causing them to have shorter ground-contact times and larger vertical forces.

“We found that [the sprinters] applied greater ground forces with a common and apparently characteristic pattern that resulted from the same basic gait features,” said Peter Weyand, PhD, coauthor of the studies and Director of the SMU Locomotor Lab, told Science Daily. “The motion of their limbs in the air is distinct; so even though the duration of their limb-swing at top speed does not differ from other runners, the force delivery mechanism differs markedly.

“The [sprinters] cock the knee high before driving the foot into the ground, while maintaining a stiff ankle,” he added. “These actions elevate the ground forces by stopping the lower leg abruptly upon impact.”

Clark hopes the study will offer training insights for all athletes. “It is our hope that our results can translate in evidence-based approaches to training speed,” he said.

Both studies can be found by searching their titles, “Foot Speed, Foot Strike, and Footwear: Linking Gait Mechanics and Running Ground Reaction Forces,” and, “Are Running Speeds Maximized with Simple-Spring Stance Mechanics?” at: www.ncbi.nlm.nih.gov/pubmed.

When Concussion Symptoms Persist

For athletes who are having trouble recovering from a sport-related concussion, a new study by researchers at the University of Calgary may provide hope. It found that athletes with persistent symptoms who received eight weeks of therapies addressing the spine and inner ear were more likely to receive return-to-play clearance than those who did not.

In the study, which was published in the September 2014 issue of the British Journal of Sports Medicine, researchers evaluated 31 athletes ages 12 to 30 who still reported symptoms of dizziness, neck pain, and/or headaches about seven weeks following a concussion. All participants received postural education, range-of-motion exercises, and cognitive and physical rest, but 15 athletes also underwent cervical spine and vestibular rehabilitation.

The cervical spine treatments included manual therapy of the cervical and thoracic spine, craniovertebral flexor and extensor retraining exercises, and sensorimotor retraining movements. Vestibular rehabilitation consisted of gaze stabilization, adaptation activities, standing balance actions, dynamic balance exercises, and canalith repositioning maneuvers.

Eleven of the 15 athletes (73 percent) who experienced cervical spine and vestibular therapy were cleared to return to sport within the eight-week term of the study, while only one of the remaining 14 athletes (seven percent) received such clearance. A sports medicine physician who was unaware of which athletes received each protocol conducted the evaluations.

The researchers theorized that continued symptoms of dizziness, neck pain, or headaches reflected problems with balance and cervical spine function, and thus rehabilitation in these areas facilitated the recovery process. “There are a variety of different techniques to help the brain compensate for problems in the vestibular system,” lead researcher Kathryn Schneider, PhD, Assistant Professor of Kinesiology at the University of Calgary, told the Toronto Globe and Mail. “They can be walking on different surfaces. Then we have them catching a ball while walking. If there’s debris in the inner ear [wax, skin cells] we do a series of head positions to use gravity to help get the debris out.”

However, the report noted the reasons behind the improved recovery were not assessed as part of the study. As this is the first investigation into the use of cervical spine and vestibular treatment for athletes having trouble recovering from a concussion, further research is needed in this area.

To view the abstract of the study, search its title, “Cervicovestibular Rehabilitation in Sport-Related Concussion: A Randomised Controlled Trial,” at: bjsm.bjm.com.

Reducing Fatigue in Basketball Players

In the final quarter of a tightly contested basketball game, it is often the less fatigued squad that claims the victory. One way to ensure a team has energy left for the final minutes may be by taking a carbohydrate or sodium bicarbonate supplement, according to recent research published in the March 2014 issue of the International Journal of Sport Nutrition and Exercise Metabolism.

The study, conducted by researchers from the University of Bath and Westmont College in Santa Barbara, Calif., evaluated 17 male basketball athletes with more than four years of playing experience as they underwent a basketball simulation. This protocol consisted of a specific game situation drill, a simulated game featuring four 15-minute quarters, and finished with another game situation. During the simulated contest, players had their rate of perceived exertion measured after the 11th minute of each quarter.

The athletes were divided into two groups, with each undergoing the basketball simulation twice. The first time, 10 athletes took either 75 grams of sucrose or a placebo 45 minutes prior to exercise, while the other seven took 2×0.2 grams per kilogram of bodyweight of sodium bicarbonate or a placebo both 90 and 20 minutes before the protocol. In the second round, the placebo groups switched and took the respective supplements.

According to the study, both the sucrose and sodium bicarbonate, which researchers called “common pre-exercise nutritional interventions,” had a positive effect on the players. This was especially true during the fourth quarter of the simulated game by offsetting fatigue in a manner that allowed the athletes to better maintain their sprinting performance in comparison to the placebo group.

“Within the context of this design, ingestion of carbohydrate and/or sodium bicarbonate shortly before basketball has the potential to offset fatigue and thus improve performance late in exercise,” the researchers concluded.

To view the full text of the study, search its title, “Effect of Carbohydrate or Sodium Bicarbonate Ingestion on Performance During a Validated Basketball Simulation Test,” at: www.ncbi.nlm.nih.gov/pubmed.


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