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  • Author: Timothy E. Hewett x
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Kevin R. Ford, Gregory D. Myer, Laura C. Schmitt, Timothy L. Uhl and Timothy E. Hewett

The purpose of this study was to identify alterations in preparatory muscle activation patterns across different drop heights in female athletes. Sixteen female high school volleyball players performed the drop vertical jump from three different drop heights. Surface electromyography of the quadriceps and hamstrings were collected during the movement trials. As the drop height increased, muscle activation of the quadriceps during preparatory phase also increased (p < .05). However, the hamstrings activation showed no similar increases relative to drop height. Female athletes appear to preferentially rely on increased quadriceps activation, without an increase in hamstrings activation, with increased plyometric intensity. The resultant decreased activation ratio of the hamstrings relative to quadriceps before landing may represent altered dynamic knee stability and may contribute to the increased risk of ACL injury in female athletes.

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Kathryn R. Glaws, Thomas J. Ellis, Timothy E. Hewett and Stephanie Di Stasi

Context: Six months is the expected time frame to return to sport (RTS) after hip arthroscopy for femoroacetabular impingement syndrome (FAIS). Objective: The primary aims of this study were to (1) report the RTS rate of physically active individuals 6 months after arthroscopic surgery for FAIS and (2) compare the self-reported hip function between those who were able to RTS against those who had not. Design: Cohort study. Setting: The Ohio State University Wexner Medical Center. Patients: A total of 42 physically active individuals scheduled for hip arthroscopy for FAIS. Main Outcome Measures: Self-reported function, including preinjury and current activity levels and ability to participate in sport, were collected on 42 individuals with FAIS prior to surgery and at 6-month follow-up. Participants were allocated into 2 groups based on self-reported RTS status at 6-month follow-up. Separate 2-way analyses of variance were used to test the interaction of groups (those who did/did not RTS). Main effects were reported in the absence of statistically significant interactions (P ≤ .05). Results: Altogether, 28 of 42 participants (66%) returned for 6-month follow-up; 5 of the 14 participants (35.7%) lost to follow-up underwent contralateral hip surgery within the study time frame. At the 6-month follow-up, 16 of the remaining 28 participants (57.1%) reported that they had returned to sport, 5 of whom returned at their prior level of participation. There was no statistically significant interaction of group and time for either hip outcome score subscale (P ≥ .20). Self-reported hip function improved over time, regardless of group (P ≤ .001). Participants in the yRTS group demonstrated higher hip outcome score-sport scores than did the nRTS group, regardless of time (P = .04). Conclusions: Though just over half of participants returned to sport 6 months after hip arthroscopy for FAIS, only 18% returned to their previous level of sports participation. Participants who returned to sport reported better function than those who did not, but self-reported hip function improved over time regardless of group. The most commonly reported reasons for not returning to sport were weakness (69.6%), fear (65.2%), and pain (56.5%).

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Constantine P. Nicolozakes, Daniel K. Schneider, Benjamin D. Roewer, James R. Borchers and Timothy E. Hewett

Context: The functional movement screen (FMS™) is used to identify movement asymmetries and deficiencies. While obesity has been reported to impede movement, the correlation between body mass index (BMI), body fat percentage (BF%), and FMS™ in athletes is unknown. Objective: To determine if there is a relationship between BMI, BF%, and FMS™ scores in a sample of National Collegiate Athletic Association Division I football athletes. Design: Cross-sectional study. Setting: Biodynamics laboratory. Participants: A total of 38 male freshman football players (18.0 [0.7] y, 185.3 [5.5] cm, and 103.9 [20.3] kg). Interventions: Height, weight, and BF% were collected, and subjects underwent the FMS™ conducted by a certified athletic trainer. Main Outcome Measures: The dependent variables were BMI, BF%, composite FMS™ score, and 7 individual FMS™ test scores. Subjects were grouped as normal BMI (BMI < 30 kg/m2) or obese (BMI ≥ 30 kg/m2). A composite FMS™ score of ≤14 and an individual FMS™ score of ≤1 were classified as cutoffs for poor movement performance. Results: A negative correlation between composite FMS™ score and BMI approached significance (P = .07, ρ = .296). A negative correlation between composite FMS™ score and BF% was significant (P = .01, ρ = −.449). There was a significant difference in the number of obese subjects scoring below the composite FMS™ cutoff (χ 2 = 5.179, P = .02) and the individual FMS™ cutoff on the deep squat (χ 2 = 6.341, P = .01), hurdle step (χ 2 = 9.870, P = .002), and in-line lunge (χ 2 = 5.584, P = .02) when compared with normal BMI subjects. Conclusions: Increased BF% and BMI relate to lower composite FMS™ and individual FMS™ test scores, indicating potentially poor movement patterns in larger National Collegiate Athletic Association football athletes. Future research should focus on examining lower extremity–specific FMS™ tasks individually from composite FMS™ scores.

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Randon Hall, Kim Barber Foss, Timothy E. Hewett and Gregory D. Myer

Objectives:

To determine if sport specialization increases the risk of anterior knee pain in adolescent female athletes.

Design:

Retrospective cohort epidemiology study.

Methods:

Female basketball, soccer, and volleyball players (N = 546) were recruited from a single county public school district in Kentucky consisting of 5 middle schools and 4 high schools. A total of 357 multisport and 189 single-sport (66 basketball, 57 soccer, and 66 volleyball) athlete subjects were included due to their diagnosis of patellofemoral pain (PFP) on physical exam. Testing consisted of a standardized history and physician-administered physical examination to determine the presence of PFP. This study compared self-reported multisport athletes with sport-specialized athletes participating in only 1 sport. The sports-participation data were normalized by sport season, with each sport accounting for 1 season of exposure. Incidence rate ratios and 95% confidence intervals (CI) were calculated and used to determine significant differences between athletes who specialized in sport in early youth and multisport athletes.

Results:

Specialization in a single sport increased the relative risk of PFP incidence 1.5-fold (95% CI 1.0−2.2, P = .038) for cumulative PFP diagnoses. Specific diagnoses such as Sinding Larsen Johansson/patellar tendinopathy (95% CI 1.5−10.1, P = .005) and Osgood Schlatter disease (95% CI 1.5−10.1, P = .005) demonstrated a 4-fold greater relative risk in single-sport compared with multisport athletes. Incidence of other specific PFP diagnoses such as fat pad, plica, trauma, pes anserine bursitis, and iliotibial-band tendonitis was not different between single-sport and multisport participants (P > .05).

Conclusion:

Early sport specialization in female adolescents is associated with increased risk of anterior knee-pain disorders including PFP, Osgood Schlatter, Sinding Larsen-Johansson compared with multisport athletes.

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Jensen L. Brent, Gregory D. Myer, Kevin R. Ford, Mark V. Paterno and Timothy E. Hewett

Context:

As high school female athletes demonstrate a rate of noncontact anterior cruciate ligament (ACL) injury 3–6 times higher than their male counterparts, research suggests that sagittal-plane hip strength plays a role in factors associated with ACL injuries.

Objective:

To determine if gender or age affect hip-abductor strength in a functional standing position in young female and male athletes.

Design:

Prospective cohort design.

Setting:

Biomechanical laboratory.

Participants:

Over a 3-y time period, 852 isokinetic hip-abduction evaluations were conducted on 351 (272 female, 79 male) adolescent soccer and basketball players.

Intervention:

Before testing, athletes were secured in a standing position, facing the dynamometer head, with a strap secured from the uninvolved side and extending around the waist just above the iliac crest. The dynamometer head was positioned in line with the body in the coronal plane by aligning the axis of rotation of the dynamometer with the center of hip rotation. Subjects performed 5 maximum-effort repetitions at a speed of 120°/s. The peak torque was recorded and normalized to body mass. All test trials were conducted by a single tester to limit potential interrater test error.

Main Outcome Measure:

Standing isokinetic hip-abduction torque.

Results:

Hip-abduction torque increased in both males and females with age (P < .001) on both the dominant and nondominant sides. A significant interaction of gender and age was observed (P < .001), which indicated that males experienced greater increases in peak torque relative to body weight than did females as they matured.

Conclusions:

Males exhibit a significant increase in normative hip-abduction strength, while females do not. Future study may determine if the absence of similar increased relative hip-abduction strength in adolescent females, as they age, may be related to their increased risk of ACL injury compared with males.

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Kevin R. Ford, Christopher A. DiCesare, Gregory D. Myer and Timothy E. Hewett

Context: Biofeedback training enables an athlete to alter biomechanical and physiological function by receiving biomechanical and physiological data concurrent with or immediately after a task. Objective: To compare the effects of 2 different modes of real-time biofeedback focused on reducing risk factors related to anterior cruciate ligament injury. Design: Randomized crossover study design. Setting: Biomechanics laboratory and sports medicine center. Participants: Female high school soccer players (age 14.8 ± 1.0 y, height 162.6 ± 6.8 cm, mass 55.9 ± 7.0 kg; n = 4). Intervention: A battery of kinetic- or kinematic-based real-time biofeedback during repetitive double-leg squats. Main Outcome Measures: Baseline and posttraining drop vertical jumps were collected to determine if either feedback method improved high injury risk landing mechanics. Results: Maximum knee abduction moment and angle during the landing was significantly decreased after kinetic-focused biofeedback (P = .04). The reduced knee abduction moment during the drop vertical jumps after kinematic-focused biofeedback was not different (P = .2). Maximum knee abduction angle was significantly decreased after kinetic biofeedback (P < .01) but only showed a trend toward reduction after kinematic biofeedback (P = .08). Conclusions: The innovative biofeedback employed in the current study reduced knee abduction load and posture from baseline to posttraining during a drop vertical jump.

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Gregory D. Myer, Kevin R. Ford and Timothy E. Hewett

Edited by Tricia J. Hubbard

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Benjamin W. Stroube, Gregory D. Myer, Jensen L. Brent, Kevin R. Ford, Robert S. Heidt Jr. and Timothy E. Hewett

Context:

Anterior cruciate ligament (ACL) injuries are prevalent in female athletes. Specific factors have possible links to increasing a female athlete’s chances of suffering an ACL injury. However, it is unclear if augmented feedback may be able to decrease possible risk factors.

Objective:

To compare the effects of task-specific feedback on a repeated tuck-jump maneuver.

Design:

Double-blind randomized controlled trial.

Setting:

Sports-medicine biodynamics center.

Patients:

37 female subjects (14.7 ± 1.5 y, 160.9 ± 6.8 cm, 54.5 ± 7.2 kg).

Intervention:

All athletes received standard off-season training consisting of strength training, plyometrics, and conditioning. They were also videotaped during each session while running on a treadmill at a standardized speed (8 miles/h) and while performing a repeated tuck-jump maneuver for 10 s. The augmented feedback group (AF) received feedback on deficiencies present in a 10-s tuck jump, while the control group (CTRL) received feedback on 10-s treadmill running.

Main Outcome Measures:

Outcome measurements of tuck-jump deficits were scored by a blinded rater to determine the effects of group (CTRL vs AF) and time (pre- vs posttesting) on changes in measured deficits.

Results:

A significant interaction of time by group was noted with the task-specific feedback training (P = .03). The AF group reduced deficits measured during the tuck-jump assessment by 23.6%, while the CTRL training reduced deficits by 10.6%.

Conclusions:

The results of the current study indicate that task-specific feedback is effective for reducing biomechanical risk factors associated with ACL injury. The data also indicate that specific components of the tuck-jump assessment are potentially more modifiable than others.

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Nicholas M. Edwards, Gregory D. Myer, Heidi J. Kalkwarf, Jessica G. Woo, Philip R. Khoury, Timothy E. Hewett and Stephen R. Daniels

Objective:

Evaluate effects of local weather conditions on physical activity in early childhood.

Methods:

Longitudinal prospective cohort study of 372 children, 3 years old at enrollment, drawn from a major US metropolitan community. Accelerometer-measured (RT3) physical activity was collected every 4 months over 5 years and matched with daily weather measures: day length, heating/cooling degrees (degrees mean temperature < 65°F or ≥ 65°F, respectively), wind, and precipitation. Mixed regression analyses, adjusted for repeated measures, were used to test the relationship between weather and physical activity.

Results:

Precipitation and wind speed were negatively associated with total physical activity and moderate-vigorous physical activity (P < .0001). Heating and cooling degrees were negatively associated with total physical activity and moderate-vigorous physical activity and positively associated with inactivity (all P < .0001), independent of age, sex, race, BMI, day length, wind, and precipitation. For every 10 additional heating degrees there was a 5-minute daily reduction in moderatevigorous physical activity. For every additional 10 cooling degrees there was a 17-minute reduction in moderate-to-vigorous physical activity.

Conclusions:

Inclement weather (higher/lower temperature, greater wind speed, more rain/snow) is associated with less physical activity in young children. These deleterious effects should be considered when planning physical activity research, interventions, and policies.

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Gregory D. Myer, Nathaniel A. Bates, Christopher A. DiCesare, Kim D. Barber Foss, Staci M. Thomas, Samuel C. Wordeman, Dai Sugimoto, Benjamin D. Roewer, Jennifer M. Medina McKeon, Stephanie L. Di Stasi, Brian W. Noehren, Michael McNally, Kevin R. Ford, Adam W. Kiefer and Timothy E. Hewett

Context:

Due to the limitations of single-center studies in achieving appropriate sampling with relatively rare disorders, multicenter collaborations have been proposed to achieve desired sampling levels. However, documented reliability of biomechanical data is necessary for multicenter injury-prevention studies and is currently unavailable.

Objective:

To measure the reliability of 3-dimensional (3D) biomechanical waveforms from kinetic and kinematic variables during a single-leg landing (SLL) performed at 3 separate testing facilities.

Design:

Multicenter reliability study.

Setting:

3 laboratories.

Patients:

25 female junior varsity and varsity high school volleyball players who visited each facility over a 1-mo period.

Intervention:

Subjects were instrumented with 43 reflective markers to record 3D motion as they performed SLLs. During the SLL the athlete balanced on 1 leg, dropped down off of a 31-cm-high box, and landed on the same leg. Kinematic and kinetic data from both legs were processed from 2 trials across the 3 laboratories.

Main Outcome Measures:

Coefficients of multiple correlations (CMC) were used to statistically compare each joint angle and moment waveform for the first 500 ms of landing.

Results:

Average CMC for lower-extremity sagittal-plane motion was excellent between laboratories (hip .98, knee .95, ankle .99). Average CMC for lower-extremity frontal-plane motion was also excellent between laboratories (hip .98, knee .80, ankle .93). Kinetic waveforms were repeatable in each plane of rotation (3-center mean CMC ≥.71), while knee sagittal-plane moments were the most consistent measure across sites (3-center mean CMC ≥.94).

Conclusions:

CMC waveform comparisons were similar relative to the joint measured to previously published reports of between-sessions reliability of sagittal- and frontal-plane biomechanics performed at a single institution. Continued research is needed to further standardize technology and methods to help ensure that highly reliable results can be achieved with multicenter biomechanical screening models.