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John McCleve, Luke Donovan, Christopher D. Ingersoll, Charles Armstrong, and Neal R. Glaviano

and provide a perceived sense of security and confidence with dynamic postural stability. 25 However, based on our findings, the application of FRT did not have any effect on lower extremity biomechanics during gait in active individuals with CAI. Conflicting to our findings, application of FRT and

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Jae P. Yom, Kathy J. Simpson, Scott W. Arnett, and Cathleen N. Brown

One potential ACL injury situation is due to contact with another person or object during the flight phase, thereby causing the person to land improperly. Conversely, athletes often have flight-phase collisions but do land safely. Therefore, to better understand ACL injury causation and methods by which people typically land safely, the purpose of this study was to determine the effects of an in-flight perturbation on the lower extremity biomechanics displayed by females during typical drop landings. Seventeen collegiate female recreational athletes performed baseline landings, followed by either unexpected laterally-directed perturbation or sham (nonperturbation) drop landings. We compared baseline and perturbation trials using paired-samples t tests (P < .05) and 95% confidence intervals for lower-extremity joint kinematics and kinetics and GRF. The results demonstrated that perturbation landings compared with baseline landings exhibited more extended joint positions of the lower extremity at initial contact; and, during landing, greater magnitudes for knee abduction and hip adduction displacements; peak magnitudes of vertical and medial GRF; and maximum moments of ankle extensors, knee extensors, and adductor and hip adductors. We conclude that a lateral in-flight perturbation leads to abnormal GRF and angular motions and joint moments of the lower extremity.

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Randy J. Schmitz, John C. Cone, Timothy J. Copple, Robert A. Henson, and Sandra J. Shultz

Context:

Potential biomechanical compensations allowing for maintenance of maximal explosive performance during prolonged intermittent exercise, with respect to the corresponding rise in injury rates during the later stages of exercise or competition, are relatively unknown.

Objective:

To identify lower-extremity countermovement-jump (CMJ) biomechanical factors using a principal-components approach and then examine how these factors changed during a 90-min intermittent-exercise protocol (IEP) while maintaining maximal jump height.

Design:

Mixed-model design.

Setting:

Laboratory.

Participants:

Fifty-nine intermittent-sport athletes (30 male, 29 female) participated in experimental and control conditions.

Interventions:

Before and after a dynamic warm-up and every 15 min during the 1st and 2nd halves of an individually prescribed 90-min IEP, participants were assessed on rating of perceived exertion, sprint/cut speed, and 3-dimensional CMJ biomechanics (experimental). On a separate day, the same measures were obtained every 15 min during 90 min of quiet rest (control).

Main Outcome Measures:

Univariate piecewise growth models analyzed progressive changes in CMJ performance and biomechanical factors extracted from a principal-components analysis of the individual biomechanical dependent variables.

Results:

While CMJ height was maintained during the 1st and 2nd halves, the body descended less and knee kinetic and energetic magnitudes decreased as the IEP progressed.

Conclusions:

The results indicate that vertical-jump performance is maintained along with progressive biomechanical changes commonly associated with decreased performance. A better understanding of lower-extremity biomechanics during explosive actions in response to IEP allows us to further develop and individualize performance training programs.

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Christopher A. DiCesare, Adam W. Kiefer, Scott Bonnette, and Gregory D. Myer

:10.1177/0363546508314425 10.1177/0363546508314425 18359820 8. Hopper AJ , Haff EE , Joyce C , Lloyd RS , Haff GG . Neuromuscular training improves lower extremity biomechanics associated with knee injury during landing in 11–13 year old female netball athletes: a randomized control

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Evangelos Pappas, Karl F. Orishimo, Ian Kremenic, Marijeanne Liederbach, and Marshall Hagins

Retrospective studies have suggested that dancers performing on inclined (“raked”) stages have increased injury risk. One study suggests that biomechanical differences exist between flat and inclined surfaces during bilateral landings; however, no studies have examined whether such differences exist during unilateral landings. In addition, little is known regarding potential gender differences in landing mechanics of dancers. Professional dancers (N = 41; 14 male, 27 female) performed unilateral drop jumps from a 30 cm platform onto flat and inclined surfaces while extremity joint angles and moments were identified and analyzed. There were significant joint angle and moment effects due to the inclined flooring. Women had significantly decreased peak ankle dorsiflexion and hip adduction moment compared with men. Findings of the current study suggest that unilateral landings on inclined stages create measurable changes in lower extremity biomechanical variables. These findings provide a preliminary biomechanical rationale for differences in injury rates found in observational studies of raked stages.

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Lindsay Hunter, Quinette Abigail Louw, and Sjan-Mari van Niekerk

Context:

Iliotibial-band syndrome (ITBS) is a common overuse running injury. There is inconclusive evidence to support current management strategies, and few advances have been made in the past few years. New management approaches should thus be developed and evaluated.

Objective:

To assess the effects of a real-time running-retraining program on lower-extremity biomechanics, pain while running, and function.

Design:

Single-subject experimental study.

Setting:

University motion-analysis laboratory.

Participant:

Female recreational runner with ITBS.

Intervention:

Nine real-time running-retraining sessions were implemented based on the biomechanical alterations of the participant's symptomatic lower limb, including pelvic and knee movement in the transverse plane, as well as foot movement in the frontal plane. Real-time visual feedback of the pelvic-rotation angle was provided during the running-retraining sessions.

Main Outcome Measurements:

3-dimensional lower-extremity running kinematics, pain on a verbal analog scale while running on a treadmill, and the Lower Extremity Functional Scale (LEFS).

Results:

Pelvic external rotation decreased, although the aim was to increase pelvic external rotation and knee rotation. The foot-progression angle improved after the intervention and at 1-mo follow-up. There was a 12.5% improvement in running time, and the pain score while running improved by 50% postintervention; these improvements were maintained at 1-mo follow-up. The mean LEFS score, indicative of function, improved by 8.75% and by 10% at the end of the intervention and at 1-mo follow-up, respectively.

Conclusion:

The real-time running-retraining program improved pain while running, as well as function, and was effective in addressing the lower-limb biomechanical alterations of the knee and foot in a female runner with ITBS. The application, effectiveness, and feasibility of real-time training should be addressed in larger studies in the future.

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Matthew D. Milewski, Sylvia Õunpuu, Matthew Solomito, Melany Westwell, and Carl W. Nissen

Documentation of the lower extremity motion patterns of adolescent pitchers is an important part of understanding the pitching motion and the implication of lower extremity technique on upper extremity loads, injury and performance. The purpose of this study was to take the initial step in this process by documenting the biomechanics of the lower extremities during the pitching cycle in adolescent pitchers and to compare these findings with the published data for older pitchers. Three-dimensional motion analysis using a comprehensive lower extremity model was used to evaluate the fast ball pitch technique in adolescent pitchers. Thirty-two pitchers with a mean age of 12.4 years (range 10.5–14.7 years) and at least 2 years of experience were included in this study. The pitchers showed a mean of 49 ± 12° of knee flexion of the lead leg at foot contact. They tended to maintain this position through ball release, and then extended their knee during the follow through phase (ball release to maximal internal glenohumeral rotation). The lead leg hip rapidly progressed into adduction and flexion during the arm cocking phase with a range of motion of 40 ± 10° adduction and 30 ± 13° flexion. The lead hip mean peak adduction velocity was 434 ± 83°/s and flexion velocity was 456 ± 156°/s. Simultaneously, the trailing leg hip rapidly extended approaching to a mean peak extension of –8 ± 5° at 39% of the pitch cycle, which is close to passive range of motion constraints. Peak hip abduction of the trailing leg at foot contact was –31 ± 12°, which also approached passive range of motion constraints. Differences and similarities were also noted between the adolescent lower extremity kinematics and adult pitchers; however, a more comprehensive analysis using similar methods is needed for a complete comparison.

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Hayley M. Ericksen and Rachele E. Vogelpohl

Anterior cruciate ligament (ACL) injury in female athletes is common. Team sport athletes experience more ACL injuries than ballet and modern dancers. Examining biomechanical differences between these two groups may help to explain the discrepancy in ACL injury rates. The purpose of this study was to examine lower extremity kinematic differences between collegiate dancers and National Collegiate Athletic Association Division I soccer athletes during a rebound jump-landing task. Peak hip, knee, and ankle kinematics were collected during a jump-landing task. Results showed more knee flexion and less ankle eversion in the dancers compared to the soccer athletes. Differences in training and strategies used during landing may explain the kinematic differences between groups.

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Chris J. Hass, Elizabeth A. Schick, John W. Chow, Mark D. Tillman, Denis Brunt, and James H. Cauraugh

Epidemiological evidence suggests the incidence of injury in female athletes is greater after the onset of puberty and that landing from a jump is a common mechanism of knee injury. This investigation compared lower extremity joint kinematics and joint resultant forces and moments during three types of stride jump (stride jump followed by a static landing; a ballistic vertical jump; and a ballistic lateral jump) between pre- and postpubescent recreational athletes to provide some insight into the increased incidence of injury. Sixteen recreationally active postpubescent women (ages 18–25 years) and 16 recreationally active prepubescent girls (ages 8–11 years) participated in this study. High speed 3D videography and force plate data were used to record each jumper’s performance of the stride jumps, and an inverse dynamic procedure was used to estimate lower extremity joint resultant forces and moments and power. These dependent variables were submitted to a 2 × 3 (Maturation Level × Landing Sequence) MANOVA with repeated measures on the last factor. The findings indicated that postpubescents landed with the knee more extended (4.4°) and had greater extension moments (approximately 30% greater hip and knee extension moments) and powers (40% greater knee power). Further, the post-pubescent athletes had greater knee anterior/posterior forces as well as medio-lateral resultant forces. The differences found between the two groups suggest there may be anatomical and physiological changes with puberty that lead to differences in strength or neuromuscular control which influence the dynamic restraint system in these recreational athletes. A combination of these factors likely plays a role in the increased risk of injury in postpubescent females.

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Denise L. Massie and Annetta Haddox