Dissemination and Implementation Strategies of Lower Extremity Preventive Training Programs in Youth: A Clinical Review

Context:

Neuromuscular preventive training programs effectively reduce injury and improve performance in youth athletes. However, program effectiveness is directly linked to program compliance, fidelity, and dosage. Preventive training programs are not widely adopted by youth sport coaches. One way to promote widespread dissemination and compliance is to identify implementation strategies that influence program adoption and maintenance. It is unknown how previously published programs have followed the elements of an implementation framework. The objective of this review was to evaluate how elements of the 7 steps of implementation, developed by Padua et al, have been performed in the evidence of lower extremity preventive training programs.

Evidence Acquisition:

A systematic review of the literature from 1996 through September 2016 was conducted using electronic databases. Investigations that documented implementation of a sport team-based neuromuscular preventive training program in youth athletes and measured lower extremity injury rates were included.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

A total of 12 studies met the inclusion criteria and were reviewed. Information regarding the completion of any of the 7 steps within the implementation framework developed by Padua et al was extracted. None of the 12 articles documented completion of all 7 steps. While each study addressed some of the 7 steps, no study addressed maintenance or an exit strategy for youth athletes. Program implementation appears limited in obtaining administrative support, utilizing an interdisciplinary implementation team, and monitoring or promoting fidelity of the intervention.

Conclusion:

Despite strong evidence supporting the effectiveness of preventive training programs in youth athletes, there is a gap between short-term improvements and long-term implementation strategies. Future interventions should include all 7 steps of the implementation framework to promote transparent dissemination of preventive training programs.

Biochemical markers of cartilage metabolism are associated with walking biomechanics 6-months following anterior cruciate ligament reconstruction

The purpose of our study was to determine the association between biomechanical outcomes of walking gait (peak vertical ground reaction force [vGRF], vGRF loading rate [vGRF-LR], and knee adduction moment [KAM]) 6 months following anterior cruciate ligament reconstruction (ACLR) and biochemical markers of serum type-II collagen turnover (collagen type-II cleavage product to collagen type-II C-propeptide [C2C:CPII]), plasma degenerative enzymes (matrix metalloproteinase-3 [MMP-3]), and a pro-inflammatory cytokine (interleukin-6 [IL-6]). Biochemical markers were evaluated within the first 2 weeks (6.5 ± 3.8 days) following ACL injury and again 6 months following ACLR in eighteen participants. All peak biomechanical outcomes were extracted from the first 50% of the stance phase of walking gait during a 6-month follow-up exam. Limb symmetry indices (LSI) were used to normalize the biomechanical outcomes in the ACLR limb to that of the contralateral limb (ACLR/contralateral). Bivariate correlations were used to assess associations between biomechanical and biochemical outcomes. Greater plasma MMP-3 concentrations after ACL injury and at the 6-month follow-up exam were associated with lesser KAM LSI. Lesser KAM was associated with greater plasma IL-6 at the 6-month follow-up exam. Similarly, lesser vGRF-LR LSI was associated with greater plasma MMP-3 concentrations at the 6-month follow-up exam. Lesser peak vGRF LSI was associated with higher C2C:CPII after ACL injury, yet this association was not significant after accounting for walking speed. Therefore, lesser biomechanical loading in the ACLR limb, compared to the contralateral limb, 6 months following ACLR may be related to deleterious joint tissue metabolism that could influence future cartilage breakdown. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2288-2297, 2017.

Epidemiology of Hip Flexor and Hip Adductor Strains in National Collegiate Athletic Association Athletes, 2009/2010-2014/2015

BACKGROUND

Little research has examined the rates and patterns of hip flexor or hip adductor strains in student-athletes in the National Collegiate Athletic Association (NCAA).

PURPOSE

To describe the epidemiology of hip flexor and adductor strains in NCAA athletes during the 2009/2010-2014/2015 academic years.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Rates and patterns of hip flexor and adductor strains in collegiate sports were examined in a convenience sample of NCAA varsity teams from 25 sports. Rates and distributions of strains by mechanism, recurrence, and participation restriction time were examined. Injury rate ratios (IRRs) and proportion ratios were calculated to compare rates within and between sports by event type, sex, mechanism, recurrence, and participation restriction time.

RESULTS

A total of 770 hip flexor and 621 hip adductor strains were reported, resulting in overall injury rates of 1.60 and 1.29 per 10,000 athlete-exposures (AEs), respectively. In men, the rate of hip flexor strains was 1.81 per 10,000 AEs, and that for hip adductor strains was 1.71 per 10,000 AEs. In women, the rate of hip flexor strains was 1.59 per 10,000 AEs, and the rate of hip adductor strains was 1.15 per 10,000 AEs. The highest rates of strains were found in men's soccer and men's ice hockey (range, 2.47-3.77 per 10,000 AEs). Most hip flexor and hip adductor strains occurred in practice, but both had higher rates in competition. In sex-comparable sports, hip flexor strain rates did not differ between the sexes (IRR = 1.14; 95% CI, 0.96-1.36), but the rate of hip adductor strains was higher in men than women (IRR = 1.49; 95% CI, 1.22-1.81). Noncontact was the most common mechanism for both types of strains (hip flexor strains, 59.4%; hip adductor strains, 62.5%); 10.1% of hip flexor strains and 11.1% of hip adductor strains were recurrent. The highest rates of recurrence of both types of strain were found in men's and women's ice hockey (range, 16.0%-30.6%). Most hip flexor and hip adductor strains resulted in <1 week of participation restriction (hip flexor strains, 83.8%; hip adductor strains, 82.9%).

CONCLUSION

The NCAA sports with the highest rates of hip flexor and hip adductor strains were men's soccer and men's ice hockey. In sex-comparable sports, men had a higher rate of hip adductor, but not hip flexor, strains. Recurrence rates were remarkably high in ice hockey. Male sports teams, especially soccer and ice hockey, should place an emphasis on prevention programs for hip adductor strains. Secondary prevention programs involving thorough rehabilitation and strict return-to-play criteria should be developed and implemented to curb the high recurrence rate of these injuries, particularly in ice hockey.

Association of Injury History and Incident Injury in Cadet Basic Military Training

PURPOSE

This study aimed to determine the association between injury history at enrollment and incident lower extremity (LE) injury during cadet basic training among first-year military cadets.

METHODS

Medically treated LE injuries during cadet basic training documented in the Defense Medical Surveillance System were ascertained in a prospective cohort study of three large US military academies from 2005 to 2008. Both acute injuries (International Classification of Disease, Ninth Revision, codes in the 800-900s, including fracture, dislocations, and sprains/strains) and injury-related musculoskeletal injuries (International Classification of Disease, Ninth Revision, codes in the 700s, including inflammation and pain, joint derangement, stress fracture, sprain/strain/rupture, and dislocation) were included. Risk ratio (RR) and 95% confidence interval (CI) were computed using multivariate log-binomial models stratified by gender.

RESULTS

During basic training, there were 1438 medically treated acute and 1719 musculoskeletal-related LE injuries in the 9811 cadets. The most frequent LE injuries were sprains/strains (73.6% of acute injuries) and inflammation and pain (89.6% of musculoskeletal-related injuries). The overall risk of incident LE injury was 23.2% (95% CI = 22.3%-24.0%). Cadets with a history of LE injury were at increased risk for incident LE injury. This association was identical in males (RR = 1.74, 95% CI = 1.55-1.94) and females (RR = 1.74, 95% CI = 1.52-1.99). In site-specific analyses, strong associations between injury history and incident injury were observed for hip, knee ligament, stress fracture, and ankle sprain. Injury risk was greater (P < 0.01) for females (39.1%) compared with males (18.0%). The elevated injury risk in females (RR = 2.19, 95% CI = 2.04-2.36) was independent of injury history (adjusted RR = 2.09, 95% CI = 1.95-2.24).

CONCLUSION

Injury history upon entry to the military is associated with the incidence of LE injuries sustained during cadet basic training. Prevention programs targeted at modifiable factors in cadets with a history of LE injury should be considered.

Walking Speed As a Potential Indicator of Cartilage Breakdown Following Anterior Cruciate Ligament Reconstruction

OBJECTIVE

To determine whether or not self-selected walking speed associates with serum biomarkers of cartilage (collagen and proteoglycan) breakdown in anterior cruciate ligament reconstructed (ACLR) individuals.

METHODS

Twenty individuals with a history of a primary unilateral ACLR participated in this cross-sectional study. Resting blood was collected from each participant prior to completing 5 walking gait trials at a self-selected comfortable speed. Walking speed was evaluated in a 3-dimensional motion capture laboratory and determined from the velocity of the pelvic center of mass. Sera were assessed for collagen type II cleavage product (C2C) and proteoglycan (aggrecan) concentrations using commercially available specific enzyme-linked immunosorbent assays. Pearson's product-moment (r) and Spearman's (ρ) correlations were used to evaluate associations between walking speed and biomarkers of cartilage breakdown metabolism. Partial correlations were used to determine whether covariates influenced associations between walking speed and biomarkers of cartilage breakdown.

RESULTS

ACLR individuals with a slower walking speed demonstrated higher concentrations of serum C2C (r = -0.52, P = 0.02), while there was no significant association between walking speed and aggrecan concentrations (ρ = -0.29, P = 0.31). After accounting for the variance associated with stance phase duration, ACLR individuals with a slower walking speed still demonstrated greater serum C2C concentrations (partial r = -0.53, P = 0.02).

CONCLUSION

ACLR individuals who habitually walk slower may experience a greater degree of collagen breakdown, suggesting that walking speed may be a future useful clinical indicator for identifying individuals with higher levels of cartilage breakdown and preradiographic osteoarthritic joint changes.

Quadriceps rate of torque development and disability in individuals with anterior cruciate ligament reconstruction

BACKGROUND

The purpose of this study was to determine associations between self-reported function (International Knee Documentation Committee Index), isometric quadriceps strength and rate of torque development in individuals with a unilateral anterior cruciate ligament reconstruction.

METHODS

Forty-one individuals [31% male, BMI mean 25 (SD 4) kg/m², months post anterior cruciate ligament reconstruction mean 49 (SD 40)] completed the self-reported function and isometric quadriceps function testing. Rate of torque development was assessed at 0-100ms (early), 100-200ms (late) ms, and peak following the onset of contraction. Associations were examined between rate of torque development, strength, and self-reported function. Linear regression was used to determine the unique amount of variance explained by the combination of rate of torque development and strength.

FINDINGS

Higher rate of torque development 100-200ms is weakly associated with higher self-reported function in individuals with a unilateral anterior cruciate ligament reconstruction (r=0.274, p=0.091); however, rate of torque development 100-200ms does not predict a significant amount of variance in self-reported function after accounting for strength (ΔR²=0.003, P=0.721).

INTERPRETATION

Quadriceps strength has a greater influence on self-reported function compared to rate of torque development in individuals with an anterior cruciate ligament reconstruction with time from surgery.

Visual Utilization During Postural Control in Anterior Cruciate Ligament- Deficient and -Reconstructed Patients: Systematic Reviews and Meta-Analyses

OBJECTIVE

To determine whether anterior cruciate ligament-deficient (ACL-D) individuals and individuals with a reconstructed anterior cruciate ligament (ACL-R) rely more heavily on visual information to maintain postural control.

DATA SOURCES

PubMed, CINAHL, and SPORTDiscus databases were searched from their earliest available date to May 24, 2016, using a combination of keywords.

STUDY SELECTION

Articles were included if they reported any instrumented static single-leg balance outcome in both a patient and control sample. The means and SDs of these outcomes must have been reported with both eyes open and eyes closed.

DATA EXTRACTION

Sample sizes, means, and SDs of single-leg balance measures for each group's eyes open and eyes closed testing conditions were extracted. The methodological quality of included studies was independently evaluated by multiple authors using an adapted version of the Quality Index.

DATA SYNTHESIS

Effect sizes were calculated by dividing the differences in change between eyes closed and eyes open in the ACL-D and control group and the ACL-R and control group by the pooled SD from the eyes closed trials for each analysis. Significant differences between the ACL-D and control group (effect size, -1.66; 95% confidence interval [CI], -2.90 to -.41) were noted. The ACL-R and control group were not different (effect size, -.61; 95% CI, -2.17 to .95).

CONCLUSIONS

ACL-D individuals but not individuals with ACL-R demonstrate a greater reliance on visual information during single-leg stance compared with healthy individuals.

Epidemiology of Quadriceps Strains in National Collegiate Athletic Association Athletes, 2009-2010 Through 2014-2015

CONTEXT

  Few researchers have examined the rates and patterns of quadriceps strains in student-athletes in the National Collegiate Athletic Association (NCAA).

OBJECTIVE

  To describe the epidemiology of quadriceps strains in 25 NCAA sports during the 2009-2010 through 2014-2015 academic years.

DESIGN

  Descriptive epidemiology study.

SETTING

  Convenience sample of NCAA programs from 25 sports during the 2009-2010 through 2014-2015 academic years. Patients or Other Particpants:  Collegiate student-athletes participating in men's and women's NCAA athletics during the 2009-2010 through 2014-2015 academic years.

MAIN OUTCOME MEASURE(S)

  Aggregate quadriceps strain injury and exposure data from the NCAA Injury Surveillance Program during the 2009-2010 through 2014-2015 academic years were analyzed. Quadriceps strain injury rates and injury rate ratios (IRRs) were reported with 95% confidence intervals (CIs).

RESULTS

  Overall, 517 quadriceps strains were reported, resulting in an injury rate of 1.07/10 000 athlete-exposures (AEs). The sports with the highest overall quadriceps strain rates were women's soccer (5.61/10 000 AEs), men's soccer (2.52/10 000 AEs), women's indoor track (2.24/10 000 AEs), and women's softball (2.15/10 000 AEs). Across sex-comparable sports, women had a higher rate of quadriceps strains than men overall (1.97 versus 0.65/10 000 AEs; IRR = 3.03; 95% CI = 2.45, 3.76). The majority of quadriceps strains were sustained during practice (77.8%). However, the quadriceps strain rate was higher during competition than during practice (1.29 versus 1.02/10 000 AEs; IRR = 1.27; 95% CI = 1.03, 1.56). Most quadriceps strains occurred in the preseason (57.8%), and rates were higher during the preseason compared with the regular season (2.29 versus 0.63/10 000 AEs; IRR = 3.60; 95% CI = 3.02, 4.30). Common injury mechanisms were noncontact (63.2%) and overuse (21.9%). Most quadriceps strains restricted participation by less than 1 week (79.3%).

CONCLUSIONS

  Across 25 sports, higher quadriceps strain rates were found in women versus men, in competitions versus practices, and in the preseason versus the regular season. Most quadriceps strains were minor in severity, although further surveillance is needed to better examine the risk factors associated with incidence and severity.

Sagittal plane kinematics predict kinetics during walking gait in individuals with anterior cruciate ligament reconstruction

BACKGROUND

Alterations in mechanical loading following anterior cruciate ligament reconstruction may lead to the development of knee osteoarthritis. Feedback that cues a change in knee kinematics during walking gait may influence mechanical loading, yet it remains unknown if knee kinematics predict kinetics during walking gait. Our aim was to determine if sagittal plane knee kinematics predict kinetics during walking gait in anterior cruciate ligament reconstructed individuals.

METHODS

Forty-one individuals with a history of primary, unilateral anterior cruciate ligament reconstruction completed a motion capture walking gait analysis. Hierarchical linear regression analyses were used in order to determine the amount of variance in the kinetic variables of interest (peak vertical ground reaction force, instantaneous and linear vertical ground reaction force loading rate) that was individually predicted by the kinematic variables of interest (knee flexion angle at heelstrike, peak knee flexion angle, and knee flexion excursion).

FINDINGS

Knee flexion excursion of the injured limb significantly predicted 11% of the variance in peak vGRF of the injured limb after accounting for gait speed and peak knee flexion angle (ΔR²=0.11, P=0.004). After accounting for gait speed and knee flexion angle at heelstrike, knee flexion excursion significantly predicted 16% of the variance in the injured limb peak vertical ground reaction force (ΔR²=0.16, P=0.001). No kinematic variable predicted vertical ground reaction force loading rate.

INTERPRETATION

Altering knee flexion excursion may be useful as a future therapeutic target for modifying peak vertical ground reaction force during walking gait following anterior cruciate ligament reconstruction.

Acute Lower Extremity Injury Rates Increase after Concussion in College Athletes

Dynamic postural control deficits and disrupted cortical pathways have been reported to persist beyond an athlete's return to activity after concussion, potentially increasing the risk of acute lower extremity musculoskeletal injury.

PURPOSE

This study aimed to investigate acute lower extremity musculoskeletal injury rates before and after concussion in athletes with concussion and their matched control.

METHODS

College athletes with concussion (n = 44; age, 20.0 ± 1.2 yr) were physician-diagnosed. Nonconcussed college athletes (n = 58; age, 20.5 ± 1.3 yr) were matched to individuals with concussion. Acute lower extremity musculoskeletal injury data were collected for 2 yr (±1 yr of the diagnosed concussion) using electronic medical records. Control participants' 2-yr window for exposure and musculoskeletal injury data were anchored to their match's concussion injury date. Pre- and postconcussion musculoskeletal injury rates were calculated for 90-, 180-, and 365-d periods for both study cohorts. Risk ratios were calculated to determine differences within and between groups for all periods.

RESULTS

Within 1 yr after concussion, the group with concussion was 1.97 (95% confidence interval (CI), 1.19-3.28; P = 0.01) times more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than before concussion and 1.64 times (95% CI, 1.07-2.51; P = 0.02) more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than their matched nonconcussed cohort over the same period. Up to 180 d after concussion, the group with concussion was 2.02 (95% CI, 1.08-3.78; P = 0.02) times more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than before concussion.

CONCLUSIONS

Previous literature has identified dynamic postural control deficits along with increased motor evoked potential latency and decreased amplitude after concussion, suggesting that the brain may be unable to effectively coordinate movement. Our findings underscore the need to explore functional movement and dynamic postural control assessments in postconcussion injury assessment protocols.

Static and dynamic single leg postural control performance during dual-task paradigms

Combining dynamic postural control assessments and cognitive tasks may give clinicians a more accurate indication of postural control under sport-like conditions compared to single-task assessments. We examined postural control, cognitive and squatting performance of healthy individuals during static and dynamic postural control assessments in single- and dual-task paradigms. Thirty participants (female = 22, male = 8; age = 20.8 ± 1.6 years, height = 157.9 ± 13.0 cm, mass = 67.8 ± 20.6 kg) completed single-leg stance and single-leg squat assessments on a force plate individually (single-task) and concurrently (dual-task) with two cognitive assessments, a modified Stroop test and the Brooks Spatial Memory Test. Outcomes included centre of pressure speed, 95% confidence ellipse, squat depth and speed and cognitive test measures (percentage of correct answers and reaction time). Postural control performance varied between postural control assessments and testing paradigms. Participants did not squat as deep and squatted slower (P < 0.001) during dual-task paradigms (≤12.69 ± 3.4 cm squat depth, ≤16.20 ± 4.6 cm · s^-1 squat speed) compared to single-task paradigms (14.57 ± 3.6 cm squat depth, 19.65 ± 5.5 cm · s^-1 squat speed). The percentage of correct answers did not change across testing conditions, but Stroop reaction time (725.81 ± 59.2 ms; F_2,58 = 7.725, P = 0.001) was slowest during single-leg squats compared to baseline (691.64 ± 80.1 ms; P = 0.038) and single-task paradigms (681.33 ± 51.5 ms; P < 0.001). Dynamic dual-task assessments may be more challenging to the postural control system and may better represent postural control performance during dynamic activities.

Sex Differences in the Incidence of Anterior Cruciate Ligament, Medial Collateral Ligament, and Meniscal Injuries in Collegiate and High School Sports: 2009-2010 Through 2013-2014

BACKGROUND

Previous research has noted sex-based differences in anterior cruciate ligament (ACL) injury rates in young athletes, while little is known about medial collateral ligament (MCL) and meniscal injury rates in this population. The objective of this study was to compare injury rates for traumatic knee injuries (ie, ACL, MCL, and meniscal injuries) in collegiate and high school (HS) varsity student-athletes across multiple sports.

HYPOTHESIS

Knee injury rates vary by sex and across different sports and levels of competition.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Injury and athlete-exposure data were utilized from the National Athletic Treatment, Injury and Outcomes Network (NATION) and National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP) during the 2009-2010 to 2013-2014 academic years. Analyses focused on ACL, MCL, and meniscal injuries. Injury rates and injury rate ratios (IRRs) with 95% CIs were calculated for basketball, ice hockey, lacrosse, soccer, and baseball/softball.

RESULTS

The ACL injury rate was higher for female than male athletes at the collegiate (IRR, 2.49; 95% CI, 1.81-3.41) and HS (IRR, 2.30; 95% CI, 1.67-3.18) levels. At the collegiate level, the highest ACL IRR comparing female to male athletes was reported in softball/baseball (IRR, 6.61; 95% CI, 1.48-29.55). At the HS level, the highest ACL IRR was reported in basketball (IRR, 3.68; 95% CI, 1.91-7.10). The MCL injury rate was higher for female than male athletes at the HS level (IRR, 2.11; 95% CI, 1.25-3.56) but lower for female than male athletes at the collegiate level (IRR, 0.73; 95% CI, 0.59-0.92). The meniscal injury rate was lower for female than male athletes at the HS level (IRR, 0.47; 95% CI, 0.31-0.71), while no differences by sex were seen at the collegiate level (IRR, 1.35; 95% CI, 0.90-2.02).

CONCLUSION

Knee injury rates varied by sex across 5 different sports in the HS and collegiate settings. Female athletes sustained ACL injuries at a higher rate than male athletes at both the HS and collegiate levels in these 5 sports; however, there was not a distinct sex disparity in MCL and meniscal injuries. Future studies should examine the rates of concomitant and recurrent injuries to inform injury prevention and rehabilitation programs.

Certified Athletic Trainers' Knowledge and Perceptions of Posttraumatic Osteoarthritis After Knee Injury

CONTEXT

  Posttraumatic osteoarthritis (PTOA) is a specific phenotype of osteoarthritis (OA) that commonly develops after acute knee injury, such as anterior cruciate ligament (ACL) or meniscal injury (or both). Athletic trainers (ATs) are well positioned to educate patients and begin PTOA management during rehabilitation of the acute injury, yet it remains unknown if ATs currently prioritize long-term outcomes in patients with knee injury.

OBJECTIVE

  To investigate ATs' knowledge and perceptions of OA and its treatment after ACL injury, ACL reconstruction, or meniscal injury or surgery.

DESIGN

  Cross-sectional study.

PATIENTS OR OTHER PARTICIPANTS

  An online survey was administered to 2000 randomly sampled certified ATs. We assessed participants' perceptions of knee OA, the risk of PTOA after ACL or meniscal injury or surgery, and therapeutic management of knee OA.

RESULTS

  Of the 437 ATs who responded (21.9%), the majority (84.7%) correctly identified the definition of OA, and 60.3% indicated that they were aware of PTOA. A high percentage of ATs selected full meniscectomy (98.9%), meniscal tear (95.4%), ACL injury (90.2%), and partial meniscectomy (90.1%) as injuries that would increase the risk of developing OA. Athletic trainers rated undertaking strategies to prevent OA development in patients after ACL injury or reconstruction (73.8%) or meniscal injury or surgery (74.7%) as extremely or somewhat important. Explaining the risk of OA to patients with an ACL or meniscal injury was considered appropriate by 98.8% and 96.8% of respondents, respectively; yet a lower percentage reported that they actually explained these risks to patients after an ACL (70.8%) or meniscal injury (80.6%).

CONCLUSIONS

  Although 84.7% of ATs correctly identified the definition of OA, a lower percentage (60.3%) indicated awareness of PTOA. These results may reflect the need to guide ATs on how to educate patients regarding the long-term risks of ACL and meniscal injuries and how to implement strategies that may prevent PTOA.

The Effects of an Injury Prevention Program on Landing Biomechanics Over Time

BACKGROUND

Knowledge is limited regarding how long improvements in biomechanics remain after completion of a lower extremity injury prevention program.

PURPOSE

To evaluate the effects of an injury prevention program on movement technique and peak vertical ground-reaction forces (VGRF) over time compared with a standard warm-up (SWU) program.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 1104 incoming freshmen (age range, 17-22 years) at a military academy in the United States volunteered to participate. Participants were cluster-randomized by military company to either the Dynamic Integrated Movement Enhancement (DIME) injury prevention program or SWU. A random subsample of participants completed a standardized jump-landing task at each time point: immediately before the intervention (PRE), immediately after (POST), and 2 (POST2M), 4 (POST4M), 6 (POST6M), and 8 months (POST8M) after the intervention. VGRF data collected during the jump-landing task were normalized to body weight (%BW). The Landing Error Scoring System (LESS) was used to evaluate movement technique during the jump landing. The change scores (Δ) for each variable (LESS, VGRF) between the group's average value at PRE and each time point were calculated. Separate univariate analyses of variance were performed to evaluate group differences.

RESULTS

The results showed a greater decrease in mean (±SD) VGRF in the DIME group compared with the SWU group at all retention time points: POST2M (SWU [Δ%BW], -0.13 ± 0.82; DIME, -0.62 ± 0.91; P = .001), POST4M (SWU, -0.15 ± 0.98; DIME,-0.46 ± 0.64; P = .04), POST6M (SWU, -0.04 ± 0.96; DIME, -0.53 ± 0.83; P = .004), and POST8M (SWU, 0.38 ± 0.95; DIME, -0.11 ± 0.98; P = .003), but there was not a significant improvement in the DIME group between PRE and POST8M (Δ%BW, -0.11 ± 0.98). No group differences in Δ LESS were observed.

CONCLUSION

The study findings demonstrated that an injury prevention program performed as a warm-up can reduce vertical ground-reaction forces compared with a standard warm-up but a maintenance program is likely necessary in order for continued benefit.

CLINICAL RELEVANCE

Injury prevention programs may need to be performed constantly, or at least every sport season, in order for participants to maintain the protective effects against injury.

Greater Mechanical Loading During Walking Is Associated With Less Collagen Turnover in Individuals With Anterior Cruciate Ligament Reconstruction

BACKGROUND

Individuals who have sustained an anterior cruciate ligament (ACL) injury and undergo ACL reconstruction (ACLR) are at higher risk of developing knee osteoarthritis. It is hypothesized that altered knee loading may influence the underlying joint metabolism and hasten development of posttraumatic knee osteoarthritis.

PURPOSE

To explore the associations between serum biomarkers of cartilage metabolism and peak vertical ground-reaction force (vGRF) and vGRF loading rate in the injured and uninjured limbs of individuals with ACLR.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Patients with a history of a primary unilateral ACLR who had returned to unrestricted physical activity (N = 19) participated in the study. Resting blood was collected from each participant before completing 5 walking gait trials at a self-selected comfortable speed. Peak vGRF was extracted for both limbs during the first 50% of the stance phase of gait, and the linear vGRF loading rate was determined between heel strike and peak vGRF. Sera were assessed for collagen breakdown (collagen type II cleavage product [C2C]) and synthesis (collagen type II C-propeptide [CPII]), as well as aggrecan concentrations, via commercially available specific enzyme-linked immunosorbent assays. Pearson product-moment correlations (r) and Spearman rank-order correlations (ρ) were used to evaluate associations between loading characteristics and biomarkers of cartilage metabolism.

RESULTS

Lower C2C:CPII ratios were associated with higher peak vGRF in the injured limb (ρ = -0.59, uncorrected P = .007). There were no significant associations between peak vGRF or linear vGRF loading rate and CPII, C2C, or aggrecan serum concentrations.

CONCLUSION

Lower C2C:CPII ratios were associated with higher peak vGRF in the ACLR limb during gait, suggesting that higher peak loading in the ACLR limb is related to lower type II collagen breakdown relative to type II collagen synthesis.

CLINICAL RELEVANCE

These data suggest that type II collagen synthesis may be higher relative to the amount of type II collagen breakdown in the ACLR limb with higher lower extremity loading. Future study should determine if metabolic compensations to increase collagen synthesis may affect the risk of developing osteoarthritis after ACLR.

Altered knee and ankle kinematics during squatting in those with limited weight-bearing-lunge ankle-dorsiflexion range of motion

CONTEXT

Ankle-dorsiflexion (DF) range of motion (ROM) may influence movement variables that are known to affect anterior cruciate ligament loading, such as knee valgus and knee flexion. To our knowledge, researchers have not studied individuals with limited or normal ankle DF-ROM to investigate the relationship between those factors and the lower extremity movement patterns associated with anterior cruciate ligament injury.

OBJECTIVE

To determine, using 2 different measurement techniques, whether knee- and ankle-joint kinematics differ between participants with limited and normal ankle DF-ROM.

DESIGN

Cross-sectional study.

SETTING

Sports medicine research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Forty physically active adults (20 with limited ankle DF-ROM, 20 with normal ankle DF-ROM).

MAIN OUTCOME MEASURE(S)

Ankle DF-ROM was assessed using 2 techniques: (1) nonweight-bearing ankle DF-ROM with the knee straight, and (2) weight-bearing lunge (WBL). Knee flexion, knee valgus-varus, knee internal-external rotation, and ankle DF displacements were assessed during the overhead-squat, single-legged squat, and jump-landing tasks. Separate 1-way analyses of variance were performed to determine whether differences in knee- and ankle-joint kinematics existed between the normal and limited groups for each assessment.

RESULTS

We observed no differences between the normal and limited groups when classifying groups based on nonweight-bearing passive-ankle DF-ROM. However, individuals with greater ankle DF-ROM during the WBL displayed greater knee-flexion and ankle-DF displacement and peak knee flexion during the overhead-squat and single-legged squat tasks. In addition, those individuals also demonstrated greater knee-varus displacement during the single-legged squat.

CONCLUSIONS

Greater ankle DF-ROM assessed during the WBL was associated with greater knee-flexion and ankle-DF displacement during both squatting tasks as well as greater knee-varus displacement during the single-legged squat. Assessment of ankle DF-ROM using the WBL provided important insight into compensatory movement patterns during squatting, whereas nonweight-bearing passive ankle DF-ROM did not. Improving ankle DF-ROM during the WBL may be an important intervention for altering high-risk movement patterns commonly associated with noncontact anterior cruciate ligament injury.

Trunk and Lower Extremity Kinematics During Stair Descent in Women With or Without Patellofemoral Pain

CONTEXT

There is limited evidence indicating the contribution of trunk kinematics to patellofemoral pain (PFP). A better understanding of the interaction between trunk and lower extremity kinematics in this population may provide new avenues for interventions to treat PFP.

OBJECTIVE

To compare trunk and lower extremity kinematics between participants with PFP and healthy controls during a stair-descent task.

DESIGN

Cross-sectional study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty women with PFP (age = 22.2 ± 3.1 years, height = 164.5 ± 9.2 cm, mass = 63.5 ± 13.6 kg) and 20 healthy women (age = 21.0 ± 2.6 years, height = 164.5 ± 7.1 cm, mass = 63.8 ± 12.7 kg).

INTERVENTION(S)

Kinematics were recorded as participants performed stair descent at a controlled velocity.

MAIN OUTCOME MEASURE(S)

Three-dimensional joint displacement of the trunk, hip, and knee during the stance phase of stair descent for the affected leg was measured using a 7-camera infrared optical motion-capture system. Pretest and posttest pain were assessed using a visual analogue scale. Kinematic differences between groups were determined using independent-samples t tests. A 2 × 2 mixed-model analysis of variance (group = PFP, control; time = pretest, posttest) was used to compare knee pain.

RESULTS

We observed greater knee internal-rotation displacement for the PFP group (12.8° ± 7.2°) as compared with the control group (8.9° ± 4.4°). No other between-groups differences were observed for the trunk, hip, or other knee variables.

CONCLUSIONS

We observed no difference in trunk kinematics between groups but did note differences in knee internal-rotation displacement. These findings contribute to the current knowledge of altered movement in those with PFP and provide direction for exercise interventions.

The Landing Error Scoring System as a Screening Tool for an Anterior Cruciate Ligament Injury-Prevention Program in Elite-Youth Soccer Athletes

CONTEXT

Identifying neuromuscular screening factors for anterior cruciate ligament (ACL) injury is a critical step toward large-scale deployment of effective ACL injury-prevention programs. The Landing Error Scoring System (LESS) is a valid and reliable clinical assessment of jump-landing biomechanics.

OBJECTIVE

To investigate the ability of the LESS to identify individuals at risk for ACL injury in an elite-youth soccer population.

DESIGN

Cohort study.

SETTING

Field-based functional movement screening performed at soccer practice facilities.

PATIENTS OR OTHER PARTICIPANTS

A total of 829 elite-youth soccer athletes (348 boys, 481 girls; age = 13.9 ± 1.8 years, age range = 11 to 18 years), of whom 25% (n = 207) were less than 13 years of age.

INTERVENTION(S)

Baseline preseason testing for all participants consisted of a jump-landing task (3 trials). Participants were followed prospectively throughout their soccer seasons for diagnosis of ACL injuries (1217 athlete-seasons of follow-up).

MAIN OUTCOME MEASURE(S)

Landings were scored for "errors" in technique using the LESS. We used receiver operator characteristic curves to determine a cutpoint on the LESS. Sensitivity and specificity of the LESS in predicting ACL injury were assessed.

RESULTS

Seven participants sustained ACL injuries during the follow-up period; the mechanism of injury was noncontact or indirect contact for all injuries. Uninjured participants had lower LESS scores (4.43 ± 1.71) than injured participants (6.24 ± 1.75; t1215 = -2.784, P = .005). The receiver operator characteristic curve analyses suggested that 5 was the optimal cutpoint for the LESS, generating a sensitivity of 86% and a specificity of 64%.

CONCLUSIONS

Despite sample-size limitations, the LESS showed potential as a screening tool to determine ACL injury risk in elite-youth soccer athletes.

The effects of 2 landing techniques on knee kinematics, kinetics, and performance during stop-jump and side-cutting tasks

BACKGROUND

Anterior cruciate ligament injuries (ACL) commonly occur during jump landing and cutting tasks. Attempts to land softly and land with greater knee flexion are associated with decreased ACL loading. However, their effects on performance are unclear.

HYPOTHESIS

Attempts to land softly will decrease peak posterior ground-reaction force (PPGRF) and knee extension moment at PPGRF compared with a natural landing during stop-jump and side-cutting tasks. Attempts to land with greater knee flexion at initial ground contact will increase knee flexion at PPGRF compared with a natural landing during both tasks. In addition, both landing techniques will increase stance time and lower extremity mechanical work as well as decrease jump height and movement speed compared with a natural landing during both tasks.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 18 male and 18 female recreational athletes participated in the study. Three-dimensional kinematic and kinetic data were collected during stop-jump and side-cutting tasks under 3 conditions: natural landing, soft landing, and landing with greater knee flexion at initial ground contact.

RESULTS

Attempts to land softly decreased PPGRF and knee extension moment at PPGRF compared with a natural landing during stop-jump tasks. Attempts to land softly decreased PPGRF compared with a natural landing during side-cutting tasks. Attempts to land with greater knee flexion at initial ground contact increased knee flexion angle at PPGRF compared with a natural landing during both stop-jump and side-cutting tasks. Attempts to land softly and land with greater knee flexion at initial ground contact increased stance time and lower extremity mechanical work, as well as decreased jump height and movement speed during both stop-jump and side-cutting tasks.

CONCLUSION

Although landing softly and landing with greater knee flexion at initial ground contact may reduce ACL loading during stop-jump and side-cutting tasks, the performance of these tasks decreased, as indicated by increased stance time and mechanical work as well as decreased jump height and movement speed.

CLINICAL RELEVANCE

Training effects tested in laboratory environments with the focus on reducing ACL loading may be reduced in actual competition environments when the focus is on athlete performance. The effects of training programs for ACL injury prevention on lower extremity biomechanics in athletic tasks may need to be evaluated in laboratories as well as in actual competitions.

Seven steps for developing and implementing a preventive training program: lessons learned from JUMP-ACL and beyond

Musculoskeletal injuries during military and sport-related training are common, costly and potentially debilitating. Thus, there is a great need to develop and implement evidence-based injury prevention strategies to reduce the burden of musculoskeletal injury. The lack of attention to implementation issues is a major factor limiting the ability to successfully reduce musculoskeletal injury rates using evidence-based injury prevention programs. We propose 7 steps that can be used to facilitate successful design and implementation of evidence-based injury prevention programs within the logical constraints of a real-world setting by identifying implementation barriers and associated solutions. Incorporating these 7 steps along with other models for behavioral health interventions may improve the overall efficacy of military and sport-related injury prevention programs.

Consortium for health and military performance and American College of Sports Medicine Summit: utility of functional movement assessment in identifying musculoskeletal injury risk

Prevention of musculoskeletal injuries (MSKI) is critical in both civilian and military populations to enhance physical performance, optimize health, and minimize health care expenses. Developing a more unified approach through addressing identified movement impairments could result in improved dynamic balance, trunk stability, and functional movement quality while potentially minimizing the risk of incurring such injuries. Although the evidence supporting the utility of injury prediction and return-to-activity readiness screening tools is encouraging, considerable additional research is needed regarding improving sensitivity, specificity, and outcomes, and especially the implementation challenges and barriers in a military setting. If selected current functional movement assessments can be administered in an efficient and cost-effective manner, utilization of the existing tools may be a beneficial first step in decreasing the burden of MSKI, with a subsequent focus on secondary and tertiary prevention via further assessments on those with prior injury history.

Improper trunk rotation sequence is associated with increased maximal shoulder external rotation angle and shoulder joint force in high school baseball pitchers

BACKGROUND

In a properly coordinated throwing motion, peak pelvic rotation velocity is reached before peak upper torso rotation velocity, so that angular momentum can be transferred effectively from the proximal (pelvis) to distal (upper torso) segment. However, the effects of trunk rotation sequence on pitching biomechanics and performance have not been investigated.

PURPOSE

The aim of this study was to investigate the effects of trunk rotation sequence on ball speed and on upper extremity biomechanics that are linked to injuries in high school baseball pitchers. The hypothesis was that pitchers with improper trunk rotation sequence would demonstrate lower ball velocity and greater stress to the joint.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Three-dimensional pitching kinematics data were captured from 72 high school pitchers. Subjects were considered to have proper or improper trunk rotation sequences when the peak pelvic rotation velocity was reached either before or after the peak upper torso rotation velocity beyond the margin of error (±3.7% of the time from stride-foot contact to ball release). Maximal shoulder external rotation angle, elbow extension angle at ball release, peak shoulder proximal force, shoulder internal rotation moment, and elbow varus moment were compared between groups using independent t tests (α < 0.05).

RESULTS

Pitchers with improper trunk rotation sequences (n = 33) demonstrated greater maximal shoulder external rotation angle (mean difference, 7.2° ± 2.9°, P = .016) and greater shoulder proximal force (mean difference, 9.2% ± 3.9% body weight, P = .021) compared with those with proper trunk rotation sequences (n = 22). No other variables differed significantly different between groups.

CONCLUSION

High school baseball pitchers who demonstrated improper trunk rotation sequences demonstrated greater maximal shoulder external rotation angle and shoulder proximal force compared with pitchers with proper trunk rotation sequences.

CLINICAL RELEVANCE

Improper sequencing of the trunk and torso alter upper extremity joint loading in ways that may influence injury risk. As such, exercises that reinforce the use of a proper trunk rotation sequence during the pitching motion may reduce the stress placed on the structures around the shoulder joint and lead to the prevention of injuries.

Risk of Lower Extremity Injury in a Military Cadet Population After a Supervised Injury-Prevention Program

CONTEXT

 Specific movement patterns have been identified as possible risk factors for noncontact lower extremity injuries. The Dynamic Integrated Movement Enhancement (DIME) was developed to modify these movement patterns to decrease injury risk.

OBJECTIVE

 To determine if the DIME is effective for preventing lower extremity injuries in US Military Academy (USMA) cadets.

DESIGN

 Cluster-randomized controlled trial.

SETTING

 Cadet Basic Training at USMA.

PATIENTS OR OTHER PARTICIPANTS

 Participants were 1313 cadets (1070 men, 243 women).

INTERVENTION(S)

 Participants were cluster randomized to 3 groups. The active warm-up (AWU) group performed standard Army warm-up exercises. The DIME groups were assigned to a DIME cadre-supervised (DCS) group or a DIME expert-supervised (DES) group; the former consisted of cadet supervision and the latter combined cadet and health professional supervision. Groups performed exercises 3 times weekly for 6 weeks.

MAIN OUTCOME MEASURE(S)

 Cumulative risk of lower extremity injury was the primary outcome. We gathered data during Cadet Basic Training and for 9 months during the subsequent academic year. Risk ratios and 95% confidence intervals (CIs) were calculated to compare groups.

RESULTS

 No differences were seen between the AWU and the combined DIME (DCS and DES) groups during Cadet Basic Training or the academic year. During the academic year, lower extremity injury risk in the DES group decreased 41% (relative risk [RR] = 0.59; 95% CI = 0.38, 0.93; P = .02) compared with the DCS group; a nonsignificant 25% (RR = 0.75; 95% CI = 0.49, 1.14; P = .18) decrease occurred in the DES group compared with the AWU group. Finally, there was a nonsignificant 27% (RR = 1.27; 95% CI = 0.90, 1.78; P = .17) increase in injury risk during the academic year in the DCS group compared with the AWU group.

CONCLUSIONS

 We observed no differences in lower extremity injury risk between the AWU and combined DIME groups. However, the magnitude and direction of the risk ratios in the DES group compared with the AWU group, although not statistically significant, indicate that professional supervision may be a factor in the success of injury-prevention programs.

The influences of sex and posture on joint energetics during drop landings

Previous observations suggest that females utilize a more erect initial landing posture than males with sex differences in landing posture possibly related to sex-specific energy absorption (EA) strategies. However, sex-specific EA strategies have only been observed when accompanied by sex differences in initial landing posture. This study (a) investigated the potential existence of sex-specific EA strategies; and (b) determined the influences of sex and initial landing posture on the biomechanical determinants of EA. The landing biomechanics of 80 subjects were recorded during drop landings in Preferred, Flexed, and Erect conditions. No sex differences in joint EA were identified after controlling for initial landing posture. Males and females exhibited greater ankle EA during Erect vs Flexed landings with this increase driven by 12% greater ankle velocity, but no change in ankle extensor moment. No differences in hip and knee EA were observed between conditions. However, to achieve similar knee EA, subjects used 7% greater mean knee extensor moment but 9% less knee angular velocity during Flexed landings. The results suggest that sex-specific EA strategies do not exist, and that the magnitude of knee joint EA can be maintained by modulating the relative contributions of joint moment and angular velocity to EA.

Neuromuscular fatigue alters postural control and sagittal plane hip biomechanics in active females with anterior cruciate ligament reconstruction

BACKGROUND

Females with history of anterior cruciate ligament (ACL) injury and subsequent ligament reconstruction are at high risk for future ACL injury. Fatigue may influence the increased risk of future injury in females by altering lower extremity biomechanics and postural control.

HYPOTHESIS

Fatigue will promote lower extremity biomechanics and postural control deficits associated with ACL injury.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Fourteen physically active females with ACL reconstruction (mean age, 19.64 ± 1.5 years; mean height, 163.52 ± 6.18 cm; mean mass, 62.6 ± 13.97 kg) volunteered for this study. Postural control and lower extremity biomechanics were assessed in the surgical limb during single-leg balance and jump-landing tasks before and after a fatigue protocol. Main outcome measures were 3-dimensional hip and knee joint angles at initial contact, peak angles, joint angular displacements and peak net joint moments, anterior tibial shear force, and vertical ground reaction force during the first 50% of the loading phase of the jump-landing task. During the single-leg stance task, the main outcome measure was center of pressure sway speed.

RESULTS

Initial contact hip flexion angle decreased (t = -2.82, P = 0.01; prefatigue, 40.98° ± 9.79°; postfatigue, 36.75° ± 8.61°) from pre- to postfatigue. Hip flexion displacement (t = 2.23, P = 0.04; prefatigue, 45.19° ± 14.1°; postfatigue, 47.48° ± 14.21°) and center of pressure sway speed (t = 3.95, P < 0.05; prefatigue, 5.18 ± 0.96 cm/s; postfatigue, 6.20 ± 1.72 cm/s) increased from pre- to postfatigue. There was a trending increase in hip flexion moment (t = 2.14, P = 0.05; prefatigue, 1.66 ± 0.68 Nm/kg/m; postfatigue, 1.91 ± 0.62 Nm/kg/m) from pre- to postfatigue.

CONCLUSION

Fatigue may induce lower extremity biomechanics and postural control deficits that may be associated with ACL injury in physically active females with ACL reconstruction.

CLINICAL RELEVANCE

Rehabilitation and maintenance programs should incorporate activities that aim to improve muscular endurance and improve the neuromuscular system's tolerance to fatiguing exercise in efforts to maintain stability and safe landing technique during subsequent physical activity.

Prevalence of freestyle biomechanical errors in elite competitive swimmers

Background:

Poor freestyle stroke biomechanics is a suggested risk factor for shoulder pain and pathology, but this has not been proven in biomechanical or clinical studies. Furthermore, the prevalence of these theoretical errors has not been identified, which would help coaches, athletic trainers, and researchers determine the most appropriate errors to focus on and develop interventions.

Hypothesis:

The majority of swimmers will present with at least 1 freestyle stroke error.

Study Design:

Cross-sectional study.

Level of Evidence:

Level 4.

Methods:

Stroke biomechanics for 31 swimmers from a collegiate swimming team were captured using underwater/above-water cameras. Each video was evaluated for biomechanical errors: a dropped elbow during the pull-through phase, a dropped elbow during the recovery phase, an eyes-forward head-carrying angle, incorrect hand position during hand entry, incorrect hand entry angle, incorrect pull-through pattern, and inadequate body roll. Error prevalence was calculated, and relationships among the errors were evaluated using chi-square statistics.

Results:

A dropped elbow during the pull-through phase (61.3%) and a dropped elbow during the recovery phase (53.2%) had the highest prevalence. A dropped elbow during the recovery phase was significantly associated with a thumb-first hand entry angle (P = 0.027) and incorrect hand entry position (P = 0.009). An eyes-forward head-carrying angle was associated with an incorrect pull-through pattern (P = 0.047).

Conclusion:

Biomechanical errors potentially detrimental to the shoulder are prevalent among swimmers. Many of the errors were interrelated, suggesting that one error may lead to other errors.

Clinical Relevance:

These errors highlight the need for proper stroke instruction and evaluation to decrease the risk of shoulder injury in competitive swimmers.

Effect of fatigue on landing performance assessed with the landing error scoring system (less) in patients after ACL reconstruction. A pilot study

BACKGROUND

Fatigue has been shown to affect performance of hop tests in patients after anterior cruciate ligament reconstruction (ACLR) compared to uninjured controls (CTRL). This may render the hop test less sensitive in detecting landing errors. The primary purpose of this study was to investigate the effect of lower extremity fatigue on landing performance assessed with the Landing Error Scoring System (LESS) in patients after ACLR compared to a CTRL group. It is plausible that fatigue would have an effect on confidence and risk appraisal in the ACLR group. The secondary purpose was to determine the relationship between psychological responses and LESS scores after fatigue.

METHODS

Twelve patients following ACLR (6 males, 6 females) who were tested at 10 ± 2.4 months after surgery participated in the current study and were compared to 10 subjects in the control group (5 males, 5 females). Subjects performed a jump-landing task and the landing was assessed using the Landing Error Scoring System (LESS) both before and after fatigue. Digital video camcorders recorded frontal and sagittal plane views of the subject performing the task. The LESS was scored using video replay. Psychological responses in the ACLR group were assessed with the ACL-RSI questionnaire.

RESULTS

Patients after ACLR had a median LESS of 6.5 which reflects a poor result (LESS >6) in the pre-fatigue condition compared to controls who had a LESS of 2.5 which is considered excellent (≤4). In the post-fatigue condition, median LESS in patients after ACLR increased to 7.0 whereas in the control group the LESS increased to 6.0 both of which reflect a poor result. The median increase in LESS was larger in the control (2.0) group compared to patients after ACLR (1.0) but the difference was not significant (p=0.165).

CONCLUSIONS

Patients after ACLR have higher LESS scores at baseline compared to a control group. Fatigue resulted in an increase in scores on the LESS in both groups.

LEVEL OF EVIDENCE

3b.

Jump-landing biomechanics and knee-laxity change across the menstrual cycle in women with anterior cruciate ligament reconstruction

CONTEXT

Of the individuals able to return to sport participation after an anterior cruciate ligament(ACL) injury, up to 25% will experience a second ACL injury. This population may be more sensitive to hormonal fluctuations, which may explain this high rate of second injury.

OBJECTIVE

To examine changes in 3-dimensional hip and knee kinematics and kinetics during a jump landing and to examine knee laxity across the menstrual cycle in women with histories of unilateral noncontact ACL injury.

DESIGN

Controlled laboratory study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 20 women (age = 19.6 ± 1.3 years, height = 168.6 ± 5.3 cm, mass = 66.2 ± 9.1 kg) with unilateral, noncontact ACL injuries.

INTERVENTION(S)

Participants completed a jump-landing task and knee-laxity assessment 3 to 5 days after the onset of menses and within 3 days of a positive ovulation test.

MAIN OUTCOME MEASURE(S)

Kinematics in the uninjured limb at initial contact with the ground during a jump landing, peak kinematics and kinetics during the loading phase of landing, anterior knee laxity via the KT-1000, peak vertical ground reaction force, and blood hormone concentrations (estradiol-β-17, progesterone, free testosterone).

RESULTS

At ovulation, estradiol-β-17 (t = -2.9, P = .009), progesterone (t = -3.4, P = .003), and anterior knee laxity (t = -2.3, P = .03) increased, and participants presented with greater knee-valgus moment (Z = -2.6, P = .01) and femoral internal rotation (t = -2.1, P = .047). However, during the menses test session, participants landed harder (greater peak vertical ground reaction force; t = 2.2, P = .04), with the tibia internally rotated at initial contact (t = 2.8, P = .01) and greater hip internal-rotation moment (Z = -2.4, P = .02). No other changes were observed across the menstrual cycle.

CONCLUSIONS

Knee and hip mechanics in both phases of the menstrual cycle represented a greater potential risk of ACL loading. Observed changes in landing mechanics may explain why the risk of second ACL injury is elevated in this population.

Comparison of integrated and isolated training on performance measures and neuromuscular control

Traditional weight training programs use an exercise prescription strategy that emphasizes improving muscle strength through resistance exercises. Other factors, such as stability, endurance, movement quality, power, flexibility, speed, and agility are also essential elements to improving overall functional performance. Therefore, exercises that incorporate these additional elements may be beneficial additions to traditional resistance training programs. The purpose of the study was to compare the effects of an isolated resistance training program (ISO) and an integrated training program (INT) on movement quality, vertical jump height, agility, muscle strength and endurance, and flexibility. The ISO program consisted of primarily upper and lower extremity progressive resistance exercises. The INT program involved progressive resistance exercises, and core stability, power, and agility exercises. Thirty subjects were cluster randomized to either the ISO (n = 15) or INT (n = 15) training program. Each training group performed their respective programs 2 times per week for 8 weeks. The subjects were assessed before (pretest) and after (posttest) the intervention period using the following assessments: a jump-landing task graded using the Landing Error Scoring System (LESS), vertical jump height, T-test time, push-up and sit-up performance, and the sit-and-reach test. The INT group performed better on the LESS test (pretest: 3.90 ± 1.02, posttest: 3.03 ± 1.02; p = 0.02), faster on the T-test (pretest: 10.35 ± 1.20 seconds, posttest: 9.58 ± 1.02 seconds; p = 0.01), and completed more sit-ups (pretest: 40.20 ± 15.01, posttest: 46.73 ± 14.03; p = 0.045) and push-ups (pretest: 40.67 ± 13.85, posttest: 48.93 ± 15.17; p = 0.05) at posttest compared with pretest, and compared with the ISO group at posttest. Both groups performed more push-ups (p = 0.002), jumped higher (p < 0.001), and reached further (p = 0.008) at posttest compared with that at pretest. Performance enhancement programs should use an integrated approach to exercise selection to optimize performance and movement technique benefits.

Trunk and hip biomechanics influence anterior cruciate loading mechanisms in physically active participants

BACKGROUND

Excessive trunk motion and deficits in neuromuscular control (NMC) of the lumbopelvic hip complex are risk factors for anterior cruciate ligament (ACL) injury. However, the relationship between trunk motion, NMC of the lumbopelvic hip complex, and triplanar knee loads during a sidestep cutting task has not been examined.

PURPOSE

To determine if there is an association between multiplanar trunk motion, NMC of the lumbopelvic hip complex, and triplanar knee loads with ACL injury during a sidestep cutting task.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The hip and knee biomechanics and trunk motion of 30 participants (15 male, 15 female) were analyzed during a sidestep cutting task using an optoelectric camera system interfaced to a force plate. Trunk and lower extremity biomechanics were calculated from the kinematic and ground-reaction force data during the first 50% of the stance time during the cutting task. Pearson product moment correlation coefficients were calculated between trunk and lower extremity biomechanics. Multiple linear regression analyses were carried out to determine the amount of variance in triplanar knee loading explained by trunk motion and hip moments.

RESULTS

A greater internal knee varus moment (mean, 0.11 ± 0.12 N·m/kg*m) was associated with less transverse-plane trunk rotation away from the stance limb (mean, 20.25° ± 4.42°; r = -0.46, P = .011) and a greater internal hip adduction moment (mean, 0.33 ± 0.25 N·m/kg*m; r = 0.83, P < .05). A greater internal knee external rotation moment (mean, 0.11 ± 0.08 N·m/kg*m) was associated with a greater forward trunk flexion (mean, 7.62° ± 5.28°; r = 0.42, P = .020) and a greater hip internal rotation moment (mean, 0.15 ± 0.16 N·m/kg*m; r = 0.59, P = .001). Trunk rotation and hip adduction moment explained 81% (P < .05) of the variance in knee varus moment. Trunk flexion and hip internal rotation moment explained 48% (P < .05) of the variance in knee external rotation moment.

CONCLUSION

Limited trunk rotation displacement toward the new direction of travel and hip adduction moment are associated with an increased internal knee varus moment, while a combined increase in trunk flexion displacement and hip internal rotation moment is associated with a higher internal knee external rotation moment.

CLINICAL RELEVANCE

Prevention interventions for ACL injury should encourage trunk rotation toward the new direction of travel and limit excessive trunk flexion while adjusting frontal- and transverse-plane hip NMC.

Scapular bracing and alteration of posture and muscle activity in overhead athletes with poor posture

CONTEXT

Overhead athletes commonly have poor posture. Commercial braces are used to improve posture and function, but few researchers have examined the effects of shoulder or scapular bracing on posture and scapular muscle activity.

OBJECTIVE

To examine whether a scapular stabilization brace acutely alters posture and scapular muscle activity in healthy overhead athletes with forward-head, rounded-shoulder posture (FHRSP).

DESIGN

Randomized controlled clinical trial.

SETTING

Applied biomechanics laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty-eight healthy overhead athletes with FHRSP.

INTERVENTION(S)

Participants were assigned randomly to 2 groups: compression shirt with no strap tension (S) and compression shirt with the straps fully tensioned (S + T). Posture was measured using lateral-view photography with retroreflective markers. Electromyography (EMG) of the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) in the dominant upper extremity was measured during 4 exercises (scapular punches, W's, Y's, T's) and 2 glenohumeral motions (forward flexion, shoulder extension). Posture and exercise EMG measurements were taken with and without the brace applied.

MAIN OUTCOME MEASURE(S)

Head and shoulder angles were measured from lateral-view digital photographs. Normalized surface EMG was used to assess mean muscle activation of the UT, MT, LT, and SA.

RESULTS

Application of the brace decreased forward shoulder angle in the S + T condition. Brace application also caused a small increase in LT EMG during forward flexion and Y's and a small decrease in UT and MT EMG during shoulder extension. Brace application in the S + T group decreased UT EMG during W's, whereas UT EMG increased during W's in the S group.

CONCLUSIONS

Application of the scapular brace improved shoulder posture and scapular muscle activity, but EMG changes were highly variable. Use of a scapular brace might improve shoulder posture and muscle activity in overhead athletes with poor posture.

Effect of excessive contralateral trunk tilt on pitching biomechanics and performance in high school baseball pitchers

BACKGROUND

There is a growing number of pitching-related upper extremity injuries among young baseball pitchers; however, there is a lack of data on the identification of injury prevention strategies, particularly the prevention of injuries through the instruction/modification of technique. The identification of technical parameters that are associated with increased joint loading is needed.

PURPOSE

To investigate the effects of excessive contralateral trunk tilt, a common technique identifiable by video observation, on pitching biomechanics and performance in high school baseball pitchers. The hypothesis was that this strategy is associated with greater joint loading and poor pitching performance.

STUDY DESIGN

Descriptive laboratory study; Level of evidence, 3.

METHODS

The 3-dimensional pitching biomechanics, ball speed, and frontal view of the pitching technique from 72 high school baseball pitchers were captured on video and analyzed. The videos were reviewed to determine if the pitcher's trunk was excessively contralaterally tilted at the instant of maximal shoulder external rotation by examining whether the side of the pitcher's head ipsilateral to the throwing limb deviated by more than a head width from a vertical line passing through the pitcher's stride foot ankle. Upper extremity kinetics and upper extremity/trunk kinematics between pitchers with and without excessive contralateral trunk tilt were compared using independent t tests.

RESULTS

Compared with pitchers who did not demonstrate excessive contralateral trunk tilt, those with excessive contralateral trunk tilt pitched at a higher ball speed (mean, 32.6 ± 2.2 vs 31.1 ± 2.9 m/s, respectively; P = .019) and experienced a greater elbow proximal force (mean, 103.9 ± 12.7 vs 93.2 ± 13.9 %weight, respectively; P = .001), shoulder proximal force (mean, 104.8 ± 14.1 vs 94.3 ± 15.5 %weight, respectively; P = .004), elbow varus moment (mean, 4.29 ± 0.73 vs 3.84 ± 0.8 %height*weight, respectively; P = .017), and shoulder internal rotation moment (mean, 4.21 ± 0.71 vs 3.75 ± 0.78 %height*weight, respectively; P = .011). Pitchers with excessive contralateral trunk tilt demonstrated less upper torso flexion at stride foot contact, less upper torso rotation, and greater upper torso contralateral flexion at maximal shoulder external rotation and ball release (P < .05).

CONCLUSION

Excessive contralateral trunk tilt is a strategy that is associated with higher ball speeds and increased joint loading.

CLINICAL RELEVANCE

Pitching with excessive contralateral trunk tilt, which can be identified through screening of the pitching technique, is associated with a benefit in performance and increased joint loading. Future study is warranted to determine if this strategy should be encouraged or discouraged by baseball coaches.

Lower extremity energy absorption and biomechanics during landing, part II: frontal-plane energy analyses and interplanar relationships

CONTEXT

Greater sagittal-plane energy absorption (EA) during the initial impact phase (INI) of landing is consistent with sagittal-plane biomechanics that likely increase anterior cruciate ligament (ACL) loading, but it does not appear to influence frontal-plane biomechanics. We do not know whether frontal-plane INI EA is related to high-risk frontal-plane biomechanics.

OBJECTIVE

To compare biomechanics among INI EA groups, determine if women are represented more in the high group, and evaluate interplanar INI EA relationships.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Participants included 82 (41 men, 41 women; age = 21.0 ± 2.4 years, height = 1.74 ± 0.10 m, mass = 70.3 ± 16.1 kg) healthy, physically active volunteers.

INTERVENTION(S)

We assessed landing biomechanics with an electromagnetic motion-capture system and force plate.

MAIN OUTCOME MEASURE(S)

We calculated frontal- and sagittal-plane total, hip, knee, and ankle INI EA. Total frontal-plane INI EA was used to create high, moderate, and low tertiles. Frontal-plane knee and hip kinematics, peak vertical and posterior ground reaction forces, and peak internal knee-varus moment (pKVM) were identified and compared across groups using 1-way analyses of variance. We used a χ (2) analysis to evaluate male and female allocation to INI EA groups. We used simple, bivariate Pearson product moment correlations to assess interplanar INI EA relationships.

RESULTS

The high-INI EA group exhibited greater knee valgus at ground contact, hip adduction at pKVM, and peak hip adduction than the low-INI EA group (P < .05) and greater peak knee valgus, pKVM, and knee valgus at pKVM than the moderate- (P < .05) and low- (P < .05) INI EA groups. Women were more likely than men to be in the high-INI EA group (χ(2) = 4.909, P = .03). Sagittal-plane knee and frontal-plane hip INI EA (r = 0.301, P = .006) and sagittal-plane and frontal-plane ankle INI EA were associated (r = 0.224, P = .04). No other interplanar INI EA relationships were found (P > .05).

CONCLUSIONS

Greater frontal-plane INI EA was associated with less favorable frontal-plane biomechanics that likely result in greater ACL loading. Women were more likely than men to use greater frontal-plane INI EA. The magnitudes of sagittal- and frontal-plane INI EA were largely independent.

Lower extremity energy absorption and biomechanics during landing, part I: sagittal-plane energy absorption analyses

CONTEXT

Eccentric muscle actions of the lower extremity absorb kinetic energy during landing. Greater total sagittal-plane energy absorption (EA) during the initial impact phase (INI) of landing has been associated with landing biomechanics considered high risk for anterior cruciate ligament (ACL) injury. We do not know whether groups with different INI EA magnitudes exhibit meaningful differences in ACL-related landing biomechanics and whether INI EA might be useful to identify ACL injury-risk potential.

OBJECTIVE

To compare biomechanical factors associated with noncontact ACL injury among sagittal-plane INI EA groups and to determine whether an association exists between sex and sagittal-plane INI EA group assignment to evaluate the face validity of using sagittal-plane INI EA to identify ACL injury risk.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 82 (41 men, 41 women; age = 21.0 ± 2.4 years, height = 1.74 ± 0.10 m, mass = 70.3 ± 16.1 kg) healthy, physically active individuals volunteered.

INTERVENTION(S)

We assessed landing biomechanics using an electromagnetic motion-capture system and force plate during a double-legged jump-landing task.

MAIN OUTCOME MEASURE(S)

Total INI EA was used to group participants into high, moderate, and low tertiles. Sagittal- and frontal-plane knee kinematics; peak vertical and posterior ground reaction forces (GRFs); anterior tibial shear force; and internal hip extension, knee extension, and knee varus moments were identified and compared across groups using 1-way analyses of variance. We used a χ (2) analysis to compare male and female representation in the high and low groups.

RESULTS

The high group exhibited greater knee-extension moment and posterior GRFs than both the moderate (P < .05) and low (P < .05) groups and greater anterior tibial shear force than the low group (P < .05). No other group differences were noted. Women were not represented more than men in the high group (χ(2) = 1.20, P = .27).

CONCLUSIONS

Greater sagittal-plane INI EA likely indicates greater ACL loading, but it does not appear to influence frontal-plane biomechanics related to ACL injury. Women were not more likely than men to demonstrate greater INI EA, suggesting that quantification of sagittal-plane INI EA alone is not sufficient to infer ACL injury-risk potential.