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Archive for March, 2010

Motion Control Shoe Delays Fatigue of Shank Muscles in Runners With Overpronating Feet

Wednesday, March 31st, 2010

Abstract

Background The motion control shoe is a well-developed technology in running shoe design for controlling excessive rearfoot pronation and plantar force distribution. However, there is little information on the leg muscle activation with different shoe conditions.

Hypothesis The motion control shoe can prevent excessive shank muscle activation and delay fatigue.

Study Design Controlled laboratory study.

Methods Twenty female recreational runners with excessive rearfoot pronation were tested with running 10 km on a treadmill on 2 days. Participants wore either a motion control running shoe or neutral running shoe on each day. Activities of their right tibialis anterior and peroneus longus were recorded with surface electromyography. The normalized root-mean-square electromyography and median frequency were compared between the 2 shoe conditions.

Results Significant positive correlations were found between the root-mean-square eletromyography and running mileage in both the tibialis anterior and peroneus longus in the neutral shoe condition (P <.001). The median frequency dropped in both shoe conditions with mileage, but paired t tests revealed a significantly larger drop in the neutral shoe (P < .001 for peroneus longus, P = .074 for tibialis anterior).

Conclusion The motion control shoe may facilitate a more stable activation pattern and higher fatigue resistance of the tibialis anterior and peroneus longus in individuals with excessive rearfoot pronation during running.

Clinical Relevance The motion control shoe may increase the running endurance, thus reduce overuse injuries, in athletes with unstable feet during long-distance running.

Posted in Injury Prevention | Email Us

Shoe-Surface Friction Influences Movement Strategies During a Sidestep Cutting Task

Wednesday, March 31st, 2010

Abstract

Background Increasing the coefficient of friction of the shoe-surface interaction has been shown to lead to increased incidence of anterior cruciate ligament (ACL) injuries, but the causes for this increase are unknown. Previous studies indicate that specific biomechanical measures during landing are associated with an increased risk for ACL injury.

Hypothesis At foot contact during a sidestep cutting task, subjects use different movement strategies for shoe-surface conditions with a high coefficient of friction (COF) relative to a low friction condition. Specifically, the study tested for significant differences in knee kinematics, external knee moments, and the position of the center of mass for different COFs.

Study Design Controlled laboratory study.

Methods Twenty-two healthy subjects (11 male) were evaluated performing a 30° sidestep cutting task on a low friction surface (0.38) and a high friction surface (0.87) at a constant speed. An 8-camera markerless motion capture system combined with 2 force plates was used to measure full-body kinematics, kinetics, and center of mass.

Results At foot contact, subjects had a lower knee flexion angle (P = .01), lower external knee flexion moment (P < .001), higher external knee valgus moment (P < .001), and greater medial distance of the center of mass from the support limb (P < .001) on the high friction surface relative to the low friction surface.

Conclusion The high COF shoe-surface condition was associated with biomechanical conditions that can increase the risk of ACL injury. The higher incidence of ACL injury observed on high friction surfaces could be a result of these biomechanical changes. The differences in the biomechanical variables were the result of an anticipated stimulus due to different surface friction, with other conditions remaining constant.

Clinical Relevance The risk analysis of ACL injury should consider the biomechanical movement changes that occur for a shoe-surface condition with high friction.

Posted in Clinical Research | Email Us

Natural History of Concussion in Sport, Markers of Severity and Implications for Management

Wednesday, March 31st, 2010

Abstract

Background Evidence-based clinical data are required for safe return to play after concussion in sport.

Purpose The objective of this study was to describe the natural history of concussion in sport and identify clinical features associated with more severe concussive injury, using return-to-sport decisions as a surrogate measure of injury severity.

Study Design Cohort study (prognosis); Level of evidence, 3.

Methods Male elite senior, elite junior, and community-based Australian Rules football players had preseason baseline cognitive testing (Digit Symbol Substitution Test, Trail-Making Test–Part B, and CogSport computerized test battery). Players were recruited into the study after a concussive injury sustained while playing football. Concussed players were tested serially until all clinical features of their injury had resolved.

Results Of 1015 players, 88 concussions were observed in 78 players. Concussion-associated symptoms lasted an average of 48.6 hours (95% confidence interval, 39.5–57.7 hours) with delayed return to sport correlated with ≥4 symptoms, headache lasting ≥60 hours, or self-reported “fatigue/fogginess.” Cognitive deficits using the Digit Symbol Substitution Test and Trail-Making Test–part B recovered concomitantly with symptoms, but computerized test results recovered 2 to 3 days later and remained impaired in 35% of concussed players after symptom resolution.

Conclusion Delayed return to sport was associated with initially greater symptom load, prolonged headache, or subjective concentration deficits. Cognitive testing recovery varied, taking 2 to 3 days longer for computerized tests, suggesting greater sensitivity to impairment. Therefore, symptom assessment alone may be predictive of but may underestimate time to complete recovery, which may be better estimated with computerized cognitive testing.

Posted in Clinical Research | Email Us