Sagittal Plane Knee Biomechanics and Vertical Ground Reaction Forces Are Modified Following ACL Injury Prevention Programs: A Systematic Review

Influences of fatigue and anticipation on female soccer players' biomechanical characteristics during 180° pivot turn: implication for risk and prevention of anterior cruciate ligament injury

Introduction

Athletes' capability to perform activities with body rotation could be weakened by fatigue accumulation. Making pivot turning in unanticipated scenarios after fatigue may greatly challenge athletes' ability to adapt rational motion strategies, elevating the risk of anterior cruciate ligament (ACL) injury. This study aimed to investigate the effects of fatigue and anticipation on biomechanical risk factors of ACL injury during 180° pivot turns in female soccer players.

Methods

Twenty-one female soccer players were selected as participants. The participants performed anticipated turning maneuver before the fatigue intervention. The participants sprinted along the runway, decelerated and planted their foot on the force plate, and then executed a 180° pivot turn. For unanticipated tests, the pivot turn was mixed with side/cross-cuts, which were indicated to the participant using a custom-designed light system. The tests were repeated by the participant after receiving a fatigue intervention. Lower-limb joint angles and moments were characterized. Peak ground reaction forces (GRFs) and GRF loading rates were determined. Two-way repeated measures analysis of variance was applied to examine the effects of fatigue and anticipation on the variables of interest.

Results

Compared to the anticipated conditions, the approach speed was significantly lower in the unanticipated tests (P < 0.0001). Lower-limb kinematics showed varied angular patterns across conditions: greater hip joint variations in flexion, abduction, and internal rotation during unanticipated turns; consistent knee joint flexion and ankle plantarflexion with dorsiflexion observed mid-turn. Significant interactions (P = 0.023 to P = 0.035) between fatigue and anticipation influenced hip joint angles. Anticipation effects were notable at initial contact and peak ground reaction force, increasing hip, knee, and ankle joint angles (P < 0.0001 to P = 0.012). Participants showed consistent ground reaction force (GRF) patterns during pivot turns across fatigue and anticipation conditions, with the first peak occurring approximately 10% into the turn period. Significant interaction effects (P = 0.016) between fatigue and anticipation were observed for knee flex/extension moments at the first peak vertical GRF. Anticipation significantly increased first peak vertical (P < 0.0001), anteroposterior (P < 0.0001), and mediolateral (P < 0.0001) GRFs. Fatigue increased first peak vertical (P = 0.022), anteroposterior (P = 0.018), and mediolateral (P = 0.019) GRFs. Post-fatigue, participants exhibited reduced first peak GRFs and loading rates compared to pre-fatigue conditions, with higher rates observed in unanticipated turns (vertical GRF: P = 0.030; anteroposterior GRF: P < 0.0001).

Conclusion

Female soccer players' lower-limb Biomechanical characterization could be greatly affected by the change of anticipatory scenarios. With the associated increase of GRF, the risk of their ACL injury might be elevated. Fatigue affected female soccer players' abilities on movement performances, but the interaction of these two factors could potentially weaken their knee's functions during pivot turns. Cognitive training on unanticipated tasks may be important for rehabilitation training after ACL injury.

Injury Prevention Programmes Fail to Change Most Lower Limb Kinematics and Kinetics in Female Team Field and Court Sports: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

BACKGROUND

One mechanism by which exercise interventions may be effective in reducing anterior cruciate ligament (ACL) injury risk is through changes in lower limb biomechanics. Understanding how training programmes affect lower-limb kinematics and kinetics may help refine injury prevention programmes.

OBJECTIVE

The aim of this systematic review and meta-analysis was to assess the effect of injury prevention programmes on kinematics and kinetics during tasks related to ACL injury in female team field and court sports.

DATA SOURCES

Five databases were searched in October 2022.

ELIGIBILITY CRITERIA

Randomised controlled trials assessing the effect of injury prevention programmes compared with usual training/no training on lower limb kinematics and kinetics in female team field and court sports were eligible for review.

RESULTS

Sixteen studies were included. A total of 976 female athletes were included. Most of the studies included interventions with multiple components (12/16). Commonly used components were plyometrics (12/16), strength (8/16), and balance/stability (7/16). Thirteen studies had routine training or sham interventions as the control group and three studies had no training. Very low certainty evidence suggests that injury prevention programmes increase knee flexion angles (mean difference = 3.1° [95% confidence interval 0.8-5.5]); however, very low to low certainty evidence suggests no effect on hip flexion angles/moments, knee flexion moments, hip adduction angles/moments, knee adduction angles/moments, hip internal rotation angles/moments, ankle dorsiflexion angles, and ground reaction forces, compared with usual training/no training.

CONCLUSION

Injury prevention programmes may be effective in increasing knee flexion angles during dynamic landing and cutting tasks but may have no effect on other lower limb biomechanical variables. As such, the benefits of injury prevention programmes may be mediated by factors other than altered biomechanics and/or may happen through other biomechanical measures not included in this review.

Establishing Normal Variances and Expectations for Quadriceps Limb Symmetry Index Benchmarks Based on Time from Surgery After Anterior Cruciate Ligament Reconstruction

The anticipated timeline for muscle strength as well as return to running and sports are some of the most common inquiries by patients undergoing anterior cruciate ligament reconstruction. Despite the popularity of this procedure, the answers to these inquiries are not well described in the literature. The purpose of this study was to evaluate the range of quadriceps strength percentage and function benchmarks at various points after anterior cruciate ligament reconstruction surgery based on sex, age, and graft.

Design

Observational Cohort Study.

Methods

Patients who underwent anterior cruciate ligament reconstruction (ACLR) were evaluated at various points after their surgery with handheld dynamometer assessments. Additional hop and balance testing was performed and patients were evaluated for clearance for running and sport via a physical therapist directed functional movement assessment (FMA). The progression of quadriceps symmetry throughout the postoperative period was examined with multi-level models, estimates of time to reach 70%, 80%, and 90% quadriceps symmetry were obtained from the fitted model.

Results

A total of 164 patients were evaluated. Patients either received bone-tendon-bone (BTB) autograft (n=118) or BTB allograft (n=46) for their ACL graft. Average age was 31.1 years-of-age (SD: 13.6). Males undergoing ACLR using BTB autograft (n=53) were able to achieve 80% quadriceps symmetry earlier than females (n=65) (5.7 months vs 7.1 months), were cleared to return to run sooner (5.6 months vs 6.8 months) and passed an FMA exam earlier (8.5 months vs 10 months). Males undergoing ACLR with allograft (n=13) were able to achieve 80% quadriceps symmetry earlier than females (n=33) (3.9 months vs 5.4 months) and were cleared to run sooner (4.5 months vs 5.8 months).

Conclusion

Patients undergoing BTB autograft obtain 80% quadriceps symmetry at an average of 5.7 months for males and 7.1 months for females. Individuals under the age of 25 obtain their quadriceps symmetry faster and are cleared to return to running faster than individuals over 25. Male sex is associated with decreased amount of time to obtain clearance for running and for full activity. Male sex is associated with decreased amount of time to regain quadriceps symmetry however this was not significant.

Level of Evidence

4 (Case series).

Peak instantaneous PlayerLoad metrics highlight movement strategy deficits in professional male soccer players

To investigate the influence of task, limb dominance and previous injury on single leg hop task performance and loading response, 25 professional male soccer players completed anterior, medial and lateral hop tests with an accelerometer at mid-calf. Performance outcome was defined as hop distance with loading response defined as the magnitude of, and time to peak instantaneous planar PlayerLoad. The performance was sensitive to task and previous injury (P < 0.001) but not limb dominance, with no evidence of bilateral asymmetry (P = 0.668). Despite impaired performance, previously injured players did not exhibit lower peak instantaneous PlayerLoad after impact in any plane (P ≥ 0.110). There was however a significantly (P = 0.001) longer time to peak medio-lateral loading after impact in previously injured players' affected limb. This observation was exacerbated when the injury was to the non-dominant limb (P = 0.041). Lower-limb accelerometry enhances understanding of movement strategy beyond task outcome, with practical implications in player screening and objective rehabilitation.

Estimating vertical ground reaction forces during gait from lower limb kinematics and vertical acceleration using wearable inertial sensors

One of the most important forces generated during gait is the vertical ground reaction force (vGRF). This force can be measured using force plates, but these can limit the scope of gait analysis. This paper presents a method to estimate the vGRF using inertial measurement units (IMU) and machine learning techniques. Four wearable IMUs were used to obtain flexion/extension angles of the hip, knee, and ankle joints, and an IMU placed over the C7 vertebra to measure vertical acceleration. We trained and compared the performance of two machine learning algorithms: feedforward neural networks (FNN) and random forest (RF). We investigated the importance of the inputs introduced into the models and analyzed in detail the contribution of lower limb kinematics and vertical acceleration to model performance. The results suggest that the inclusion of vertical acceleration increases the root mean square error in the FNN, while the RF appears to decrease it. We also analyzed the ability of the models to construct the force signal, with particular emphasis on the magnitude and timing of the vGRF peaks. Using the proposed method, we concluded that FNN and RF models can estimate the vGRF with high accuracy.

Anterior cruciate ligament failure and management

Anterior cruciate ligament (ACL) reconstruction failure can be defined as abnormal knee function due to graft insufficiency with abnormal laxity or failure to recreate a functional knee according to the expected outcome. Traumatic ruptures have been reported as the most common reason for failure. They are followed by technical errors, missed concomitant knee injuries, and biological failures. An in-depth preoperative examination that includes a medical history, clinical examinations, advanced imaging, and other appropriate methods is of utmost importance. There is still no consensus as to the ideal graft, but autografts are the favorite choice even in ACL revision. Concomitant meniscal treatment, ligamentous reconstruction, and osteotomies can be performed in the same surgical session to remove anatomical or biomechanical risk factors for the failure. Patient expectations should be managed since outcomes after ACL revision are not as good as those following primary ACL reconstruction.

Neuromechanical Consequences of Eccentric Load Reduction During the Performance of Weighted Jump Squats

PURPOSE

To quantify the acute effects of a spectrum of eccentric load reductions on neuromechanical adjustments during the performance of weighted jump squats (WJSs).

METHODS

On separate days, 16 well-trained participants performed WJS trials with various eccentric load reductions (0% [body mass only], 25%, 50%, 75%, and 100% [standard WJS] of concentric load) with a mechanical braking unit, while concentric load was set at 30% of peak isometric squat force in all trials. A force platform and a motion-capture system were used to assess neuromuscular performance.

RESULTS

Peak power output was 6.2% (4.7%) higher when load was reduced by 50% versus 0% (55.4 [7.8] vs 51.9 [7.6] W/kg; P = .001). Compared with no braking (0.326 [0.059] m), jump height was ∼13% to 17% higher for all eccentric load reduction conditions (all P < .001). Vertical ground reaction forces were progressively lower for 25%, 50%, 75%, and 100% loading conditions (-22.1% [14.6%], -32.3% [10.8%], -42.0% [13.2%], and -46.1% [14.7%]; all P ≤ .001) in reference to body mass only.

CONCLUSION

Eccentric load reduction is advantageous compared with traditional isoinertial loading for improving both jump height and peak power output during the concentric portion of maximal-effort WJS. This practice also decreases mechanical constraints in the lower extremities, which may become beneficial for load-compromised individuals.

Can a knee sleeve influence ground reaction forces and knee joint power during a step-down hop in participants following anterior cruciate ligament reconstruction? A secondary analysis

PURPOSE

Elastic knee sleeves are often worn following anterior cruciate ligament (ACL) reconstruction. The study aimed to define immediate and 6-week effects of wearing a knee sleeve on ground reaction forces (GRF) and knee joint power during a step-down hop task.

METHODS

Using a cross-over design, we estimated GRF and knee kinematics and kinetics during a step-down hop for 30 participants following ACL reconstruction (median 16 months post-surgery) with and without wearing a knee sleeve. In a subsequent randomised clinical trial, participants in the 'Sleeve Group' (n = 9) wore the sleeve for 6 weeks at least 1 hour daily, while a 'Control Group' (n = 9) did not wear the sleeve. We compared the following outcomes using statistical parametric mapping (SPM): (1) GRF and knee joint power trajectories between three conditions at baseline (uninjured side, unsleeved injured and sleeved injured side); (2) GRF and knee joint power trajectories within-participant changes from baseline to follow-up between groups. We also compared discrete peak GRFs and power, rate of (vertical) force development, and mean knee joint power in the first 5% of stance phase.

RESULTS

SPM showed no differences for GRF for the (unsleeved) injured compared to the uninjured sides; when wearing the sleeve, injured side mean power in the first 5% of stance increased significantly from a concentric to an eccentric power. Discrete variables showed lower peak anterior (propulsive) GRF, mean power in the first 5% of stance, peak eccentric and concentric power for the injured compared to the uninjured sides. After six weeks, a directional change for vertical GRF differed showed slightly decreased forces for the Control Group and increased forces for the Sleeve Group.

CONCLUSION

Wearing a knee sleeve on the anterior cruciate ligament injured knee improved knee power during the first 5% of stance during the step-down hop. No consistent changes were observed for ground reaction forces for SPM and discrete variable analyses. Wearing the knee sleeve at least one hour daily for 6-weeks lead to a directional change of increased vertical GRF for the Sleeve Group at follow-up.

TRIAL REGISTRATION

The trial was prospectively registered with the Australia New Zealand Clinical Trials Registry No: ACTRN12618001083280, 28/06/2018. https: //anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375347&isClinicalTrial=False.

Automated Landing Error Scoring System Performance and the Risk of Bone Stress Injury in Military Trainees

CONTEXT

Lower extremity bone stress injuries (BSIs) place a significant burden on the health and readiness of the US Armed Forces.

OBJECTIVE

To determine if preinjury baseline performance on an expanded and automated 22-item version of the Landing Error Scoring System (LESS-22) was associated with the incidence of BSIs in a military training population.

DESIGN

Prospective cohort study.

SETTING

US Military Academy at West Point, NY.

PATIENTS OR OTHER PARTICIPANTS

A total of 2235 incoming cadets (510 females [22.8%]).

MAIN OUTCOME MEASURE(S)

Multivariable Poisson regression models were used to produce adjusted incidence rate ratios (IRRs) to quantify the association between preinjury LESS scores and BSI incidence rate during follow-up and were adjusted for pertinent risk factors. Risk factors were included as covariates in the final model if the 95% CI for the crude IRR did not contain 1.00.

RESULTS

A total of 54 BSIs occurred during the study period, resulting in an overall incidence rate of 0.07 BSI per 1000 person-days (95% CI = 0.05, 0.09). The mean number of exposure days was 345.4 ± 61.12 (range = 3-368 days). The final model was adjusted for sex and body mass index and yielded an adjusted IRR for a LESS-22 score of 1.06 (95% CI = 1.002, 1.13; P = .04), indicating that each additional LESS error documented at baseline was associated with a 6.0% increase in the incidence rate of BSI during the follow-up period. In addition, 6 individual LESS-22 items, including 2 newly added items, were significantly associated with the BSI incidence.

CONCLUSIONS

We provided evidence that performance on the expanded and automated version of the LESS was associated with the BSI incidence in a military training population. The automated LESS-22 may be a scalable solution for screening military training populations for BSI risk.

Inter-limb asymmetry of kinetic and electromyographic during walking in patients with chronic ankle instability

After an initial ankle sprain, a relevant number of participants develop chronic ankle instability (CAI). Compensatory strategies in patients with CAI may change the inter-limb symmetry needed for absorbing movement-related forces. Accordingly, an increased risk of injury can occur. The present study aimed to compare the inter-limb asymmetry of kinetic and electromyography between individuals with CAI and without a history of an ankle sprain (Non-CAI) during walking. In this cross-sectional study, fifty-six athletes (28 CAI; 28 Non-CAI) participated. Participants walked at a comfortable pace over level ground while vertical ground reaction force (vGRF) and muscle activity of the tibialis anterior, peroneus longus, medial gastrocnemius, and gluteus medius were recorded. Inter-limb asymmetry during walking was calculated for each of the variables. Patients with CAI exhibited a greater inter-limb asymmetry of the first peak of vGRF, time to peak vGRF, and loading rate (P < 0.001), as well as presenting a greater inter-limb asymmetry of peroneus longus activity (contact phase) (P = 0.003) and gluteus medius activity (midstance/propulsion phase) (P = 0.010) compared to the Non-CAI group. No other differences in vGRF or muscles activity were observed between the groups. Our findings indicate that patients with CAI walk with greater inter-limb asymmetry in vGRF and muscle activity in different phases of the gait cycle compared to Non-CAI group. Our results could inform future studies on gait training aimed to reduce asymmetry during walking in patients with CAI.

Examining the Dynamic Nature of Anterior Cruciate Ligament Injury Risk Factors in Women's Collegiate Soccer

CONTEXT

Anterior cruciate ligament (ACL) injuries are a common and devastating injury in women's soccer. Several risk factors for ACL injury have been identified, but have not yet been examined as potentially dynamic risk factors, which may change throughout a collegiate soccer season.

DESIGN

Prospective cohort study.

METHODS

Nine common clinical screening assessments for ACL injury risk, consisting of range of motion, movement quality, and power, were assessed in 29 Division I collegiate women's soccer players. Preseason and midseason values were compared for significant differences. Change scores for each risk factor were also correlated with cumulative training loads during the first 10 weeks of a competitive soccer season.

RESULTS

Hip external rotation range of motion and power had statistically significant and meaningful differences at midseason compared with preseason, indicating they are dynamic risk factors. There were no significant associations between the observed risk factor changes and cumulative training load.

CONCLUSIONS

Hip external rotation range of motion and power are dynamic risk factors for ACL injury in women's collegiate soccer athletes. Serial screening of these risk factors may elucidate stronger associations with injury risk and improve prognostic accuracy of screening tools.

Relationship Between Cognitive Performance and Lower Extremity Biomechanics: Implications for Sports-Related Concussion

Background

Collegiate athletes with prior sports-related concussion (SRC) are at increased risk for lower extremity (LE) injuries; however, the biomechanical and cognitive mechanisms underlying the SRC-LE injury relationship are not well understood.

Purpose

To examine the association between cognitive performance and LE land-and-cut biomechanics among collegiate athletes with and without a history of SRC and to determine the association among multiple cognitive testing batteries in the same athlete cohort.

Study Design

Controlled laboratory study.

Methods

A cohort of 20 collegiate athletes with prior SRC (9 men, 11 women; mean ± standard deviation [SD] age, 20.5 ± 1.3 years; mean ± SD time since last SRC, 461 ± 263 days) and 20 matched controls (9 men, 11 women; mean ± SD age, 19.8 ± 1.3 years) completed land-and-cut tasks using the dominant and nondominant limbs. LE biomechanical variables and a functional visuomotor reaction time (FVMRT) were collected during each trial. Athletes also completed the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) and Senaptec Sensory Station assessments.

Results

In the SRC cohort, Pearson correlation coefficients indicated slower FVMRT was moderately correlated with decreased dominant limb (r = -0.512) and nondominant limb (r = -0.500) knee flexion, while increased dominant limb knee abduction moment was moderately correlated with decreased ImPACT Visual Memory score (r = -0.539) and slower ImPACT Reaction Time (r = 0.515). Most computerized cognitive measures were not associated with FVMRT in either cohort (P > .05).

Conclusion

Decreased reaction time and working memory performance were moderately correlated with decreased sagittal plane knee motion and increased frontal plane knee loading in collegiate athletes with a history of SRC. The present findings suggest a potential unique relationship between cognitive performance and LE neuromuscular control in athletes with a history of SRC injury. Last, we determined that computerized measures of cognitive performance often utilized for SRC management are dissimilar to sport-specific cognitive processes.

Clinical Relevance

Understanding the relationship between cognitive performance and LE biomechanics in athletes with prior SRC may inform future clinical management strategies. Future research should prospectively assess cognitive and biomechanical measures, along with LE injury incidence, to identify mechanisms underlying the SRC-LE injury relationship.

Effect of isolated hip abductor fatigue on single-leg landing mechanics and simulated ACL loading

BACKGROUND

Altered movement biomechanics are a risk factor for ACL injury. While hip abductor weakness has been shown to negatively impact landing biomechanics, the role of this musculature and injury risk is not clear. The aim of this musculoskeletal simulation study was to determine the effect of hip abductor fatigue-induced weakness on ACL loading, force production of lower extremity muscles, and lower extremity biomechanics during single-leg landing.

METHODS

Biomechanical data from ten healthy adults were collected before and after a fatigue protocol and used to derive subject-specific estimates of muscle forces and ACL loading using a 5-degree of freedom (DOF) model.

RESULTS

There were no significant differences in knee joint angles and ACL loading between pre and post-fatigue. However, there were significant differences, due to fatigue, in lateral trunk flexion angle, total excursion of trunk, muscle forces, and joint moments.

CONCLUSION

Altered landing mechanics, due to hip abductor fatigue-induced weakness, may be associated with increased risk of ACL injury during single-leg landings. Clinical assessment or screening of ACL injury risk will benefit from subject-specific musculoskeletal models during dynamic movements. Future study considering the type of the fatigue protocols, cognitive loads, and various tasks is needed to further identify the effect of hip abductor weakness on lower extremity landing biomechanics.

Twelve-Week Quadriceps Strength as A Predictor of Quadriceps Strength At Time Of Return To Sport Testing Following Bone-Patellar Tendon-Bone Autograft Anterior Cruciate Ligament Reconstruction

BACKGROUND

Restoration of quadriceps strength following anterior cruciate ligament reconstruction (ACL-R) continues to challenge both patients and clinicians. Failure to adequately restore quadriceps strength has been linked to decreased patients' self-reported outcomes and an increased risk for re-injury. Early identification of quadriceps strength deficits may assist in tailoring early interventions to better address impairments.

PURPOSE

The purpose of this study was to assess the relationship between early (12 weeks following ACL-R) isokinetic peak torque and isokinetic peak torque at time of return to sport (RTS) testing.

STUDY DESIGN

Cohort Study.

METHODS

A total of 120 participants (males = 55; females =65) were enrolled in the study (age = 16.1±1.4 yrs; height = 1.72±10.5 m; mass = 70.7±16.3 kg). All participants were level 1 or 2 cutting and pivoting sport athletes who underwent a primary bone-patellar tendon-bone autograft ACL-R. Participants were tested at two time points: 12 weeks following surgery and again at time of RTS testing. A linear regression model was carried out to investigate the relationship between age, sex, and isokinetic peak torque at 12 weeks following ACL-R and isokinetic peak torque at time of RTS testing.

RESULTS

When 12-week isokinetic peak torque was entered first for the hierarchy regression analysis, this factor was predictive of the peak torque at the time of RTS testing, F(1, 118) = 105.6, p < 0.001, R 2 = 0.472, indicating that the 12-week quadriceps strength accounted for 47% of the variance in the quadriceps strength at the time of RTS testing. When age and sex were added in the regression analysis, both factors only added 0.8% of variance for the quadriceps strength at the time of RTS testing.

CONCLUSION

Isokinetic peak torque at 12 weeks following surgery was shown to be a significantly strong predictor (47%) for isokinetic quadriceps strength recovery at time of RTS. This finding underscores the importance of early restoration of quadriceps strength and that while non-modifiable factors such as sex and age are important, early restoration of quadriceps strength most strongly influences late stage quadriceps strength.

LEVEL OF EVIDENCE

3.

Effects of a neuromuscular training program using external focus attention cues in male athletes with anterior cruciate ligament reconstruction: a randomized clinical trial

Background

Athletes who have undergone anterior cruciate ligament (ACL) reconstruction often exhibit persistent altered biomechanics and impaired function. Neuromuscular training programs appear to be effective for reducing high-risk landing mechanics and preventing primary ACL injuries; however, there have been few attempts to examine their effects in athletes who have undergone ACL reconstruction. The purpose of our study was to examine the effects of a neuromuscular training program that emphasizes external focus of attention cuing on biomechanics, knee proprioception, and patient-reported function in athletes who had undergone ACL reconstruction and completed conventional post-operative rehabilitation.

Methods

Twenty-four male athletes who had undergone primary, unilateral, hamstring autograft ACL reconstruction and completed conventional post-operative rehabilitation were randomly allocated to an experimental group (n = 12) who took part in an 8-week neuromuscular training program or a control group (n = 12) who continued a placebo program. The neuromuscular training program included lower extremity strengthening and plyometric exercises, balance training, and movement pattern re-training. Biomechanics during single-leg landing, knee proprioception, and patient-reported function were assessed before and after the 8-week training period.

Results

Athletes in the experimental group demonstrated increased trunk, hip, and knee flexion angles and decreased knee abduction, internal rotation angles and knee valgus during landing following the intervention. Further, the experimental group decreased their peak knee extension and abduction moments and vertical ground reaction force on landing post-intervention. International Knee Documentation Committee questionnaire (IKDC) scores increased in the experimental group following training. The control group demonstrated no changes in any variable over the same time period.

Conclusions

Neuromuscular training with external focus of attention cueing improved landing biomechanics in patients after ACL reconstruction. Neuromuscular training programs beneficially mitigate second ACL injury risk factors and should be emphasized during and after traditional post-operative rehabilitation.

Trial registration

Current Controlled Trials using the IRCT website with ID number of, IRCT20180412039278N1 “Prospectively registered” at 21/12/2018.

THE INFLUENCE OF ATTENTIONAL FOCUS ON LANDING STIFFNESS IN FEMALE ATHLETES: A CROSS-SECTIONAL STUDY

BACKGROUND

Anterior cruciate ligament injury prevention often involves instructing athletes to reduce landing stiffness. Instructions promoting an external focus appear to result in superior motor performance for a wide range of tasks; however, the effect of attentional focus on landing stiffness has not been examined.

HYPOTHESIS/PURPOSE

The purpose of this study was to compare the influence of instructions promoting an internal focus vs. those promoting an external focus on landing stiffness. It was hypothesized that both types of instructions would reduce landing stiffness vs. landings performed prior to instruction. It was also hypothesized that participants would demonstrate a greater reduction in landing stiffness when provided with instructions promoting an external focus.

STUDY DESIGN

Cross-sectional, quasi-experimental.

METHODS

Sixteen female athletes (basketball, soccer, volleyball) completed drop landings while force and kinematic data were collected. Participants first performed drop landings with their typical technique (baseline). They then received instructions promoting an internal focus and an external focus before performing additional drop landings. Peak force, time-to-peak force, leg stiffness, and hip, knee, and ankle sagittal plane angles were analyzed.

RESULTS

Both types of instructions resulted in lower landing forces, less leg stiffness, and greater hip and knee flexion versus at baseline. However, athletes demonstrated more knee flexion at the time of the peak force (59.4 ± 9.6 ° vs. 56.0 ± 9.5 °) and less leg stiffness (69.5 ± 17.9 Nkg^-1/m vs. 84.0 ± 38.1 Nkg^-1/m) when provided with instructions promoting an external focus, compared to when they were provided with instructions promoting an internal focus.

CONCLUSION

Instructions promoting an external focus appear to result in a greater reduction in landing stiffness. Clinicians should consider providing instructions promoting an external focus when training athletes to reduce lower extremity stiffness during drop landings. The findings from this study may help to inform clinicians involved in movement pattern re-training for female athletes.

LEVEL OF EVIDENCE

Level 3b.

The Relationship Between Vertical Ground Reaction Force, Loading Rate, and Sound Characteristics During a Single-Leg Landing

Context:Landing kinetic outcomes are associated with injury risk and may be persistently altered after anterior cruciate ligament injury or reconstruction. However, it is challenging to assess kinetics clinically. The relationship between sound characteristics and kinetics during a limited number of functional tasks has been supported as a potential clinical alternative.Objective:To assess the relationship between kinetics and sound characteristics during a single-leg landing task.Design:ObservationalSetting:Laboratory.Participants:There was total of 26 healthy participants (15 males/11 females, age = 24.8 [3.6] y, height = 176.0 [9.1] cm, mass = 74.9 [14.4] kg, Tegner Activity Scale = 6.1 [1.1]).Intervention:Participants completed single-leg landings onto a force plate while audio characteristics were recorded.Main Outcome Measures:Peak vertical ground reaction force, linear loading rate, instantaneous loading rate, peak sound magnitude, sound frequency were measured. Means and SDs were calculated for each participant’s individual limbs. Spearman rho correlations were used to assess the relationships between audio characteristics and kinetic outcomes.Results:Peak sound magnitude was positively correlated with normalized peak vertical ground reaction force (ρ = .486,P = .001); linear loading rate (ρ = .491,P = .001); and instantaneous loading rate (ρ = .298,P = .03). Sound frequency was negatively correlated with instantaneous loading rate (ρ = −.444,P = .001).Conclusions:Peak sound magnitude may be more helpful in providing feedback about an individual’s normalized vertical ground reaction force and linear loading rate, and sound frequency may be more helpful in providing feedback about instantaneous loading rate. Further refinement in sound measurement techniques may be required before these findings can be applied in a clinical population.

Hop-Stabilization Training and Landing Biomechanics in Athletes With Chronic Ankle Instability: A Randomized Controlled Trial

CONTEXT

Hopping exercises are recommended as a functional training tool to prevent lower limb injury, but their effects on lower extremity biomechanics in those with chronic ankle instability (CAI) are unclear.

OBJECTIVE

To determine if jump-landing biomechanics change after a hop-stabilization intervention.

DESIGN

Randomized controlled clinical trial.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-eight male collegiate basketball players with CAI were divided into 2 groups: hop-training group (age = 22.78 ± 3.09 years, mass = 82.59 ± 9.51 kg, height = 187.96 ± 7.93 cm) and control group (age = 22.57 ± 2.76 years, mass = 78.35 ± 7.02 kg, height = 185.69 ± 7.28 cm).

INTERVENTION(S)

A 6-week supervised hop-stabilization training program that consisted of 18 training sessions.

MAIN OUTCOME MEASURE(S)

Lower extremity kinetics and kinematics during a jump-landing task and self-reported function were assessed before and after the 6-week training program.

RESULTS

The hop-stabilization program resulted in improved self-reported function (P < .05), larger sagittal-plane hip- and knee-flexion angles, and greater ankle dorsiflexion (P < .05) relative to the control group. Reduced frontal-plane joint angles at the hip, knee, and ankle as well as decreased ground reaction forces and a longer time to peak ground reaction forces were observed in the hopping group compared with the control group after the intervention (P < .05).

CONCLUSIONS

The 6-week hop-stabilization training program altered jump-landing biomechanics in male collegiate basketball players with CAI. These results may provide a potential mechanistic explanation for improvements in patient-reported outcomes and reductions in injury risk after ankle-sprain rehabilitation programs that incorporate hop-stabilization exercises.

Visual-Motor Control of Drop Landing After Anterior Cruciate Ligament Reconstruction

CONTEXT

  Visual feedback is crucial in the control of human movement. When vision is obstructed, alterations in landing neuromuscular control may increase movements that place individuals at risk for injury. Anterior cruciate ligament (ACL) injury may further alter the motor-control response to alterations in visual feedback. The development of stroboscopic glasses that disrupt visual feedback without fully obscuring it has enabled researchers to assess visual-motor control during movements that simulate the dynamic demands of athletic activity.

OBJECTIVE

  To investigate the effect of stroboscopic visual-feedback disruption (SVFD) on drop vertical-jump landing mechanics and to determine whether injury history influenced the effect.

DESIGN

  Cohort study.

SETTING

  Movement-analysis laboratory.

PATIENTS OR OTHER PARTICIPANTS

  A total of 15 participants with ACL reconstruction (ACLR; 7 men, 8 women; age = 21.41 ± 2.60 years, height = 1.72 ± 0.09 m, mass = 69.24 ± 15.24 kg, Tegner Activity Scale score = 7.30 ± 1.30, time since surgery = 36.18 ± 26.50 months, hamstrings grafts = 13, patellar tendon grafts = 2) and 15 matched healthy control participants (7 men, 8 women; age = 23.15 ± 3.48 years, height = 1.73 ± 0.09 m, mass = 69.98 ± 14.83 kg, Tegner Activity Scale score = 6.77 ± 1.48).

INTERVENTION(S)

  Drop vertical-jump landings under normal and SVFD conditions.

MAIN OUTCOME MEASURE(S)

  The SVFD effect for knee sagittal- and frontal-plane excursions, peak moments, and vertical ground reaction force were calculated during landing and compared with previously established measurement error and between groups.

RESULTS

  The SVFD altered knee sagittal-plane excursion (4.04° ± 2.20°, P = .048) and frontal-plane excursion (1.98° ± 1.53°, P = .001) during landing above within-session measurement error. Joint-moment difference scores from full vision to the SVFD condition were not greater than within-session error. We observed an effect of ACLR history only for knee flexion (ACLR group = 3.12° ± 3.76°, control group = -0.84° ± 4.45°; P = .001). We did not observe an effect of side or sex.

CONCLUSIONS

  The SVFD altered sagittal- and frontal-plane landing knee kinematics but did not alter moments. Anterior cruciate ligament reconstruction may induce alterations in sagittal-plane visual-motor control of the knee. The group SVFD effect was on a level similar to that of an in-flight perturbation, motor-learning intervention, or plyometric-training program, indicating that visual-motor ability may contribute to knee neuromuscular control on a clinically important level. The individual effects of the SVFD indicated possible unique sensorimotor versus visual-motor movement strategies during landing.

Hip and Knee Kinematics and Kinetics During Landing Tasks After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis

OBJECTIVE

  To evaluate the current evidence concerning kinematic and kinetic strategies adopted during dynamic landing tasks by patients with anterior cruciate ligament reconstruction (ACLR).

DATA SOURCES

  PubMed, Web of Science.

STUDY SELECTION

  Original research articles that evaluated kinematics or kinetics (or both) during a landing task in those with a history of ACLR were included.

DATA EXTRACTION

  Methodologic quality was assessed using the modified Downs and Black checklist. Means and standard deviations for knee or hip (or both) kinematics and kinetics were used to calculate Cohen d effect sizes and corresponding 95% confidence intervals between the injured limb of ACLR participants and contralateral or healthy matched limbs. Data were further stratified by landing tasks, either double- or single-limb landing. A random-effects-model meta-analysis was used to calculate pooled effect sizes and 95% confidence intervals.

DATA SYNTHESIS

  The involved limbs of ACLR patients demonstrated clinically and significantly lower knee-extension moments during double-legged landing compared with healthy contralateral limbs and healthy control limbs (Cohen d range = -0.81 to -1.23) and decreased vertical ground reaction forces when compared with healthy controls, regardless of task (Cohen d range = -0.39 to -1.75).

CONCLUSIONS

  During single- and double-legged landing tasks, individuals with ACLR demonstrated meaningful reductions in injured-limb knee-extension moments and vertical ground reaction forces. These findings indicate potential unloading of the injured limb after ACLR, which may have significant implications for secondary ACL injury and long-term joint health.

The Association Between Serum Biomarkers of Collagen Turnover and Subsequent Anterior Cruciate Ligament Rupture

BACKGROUND

No study has attempted to associate the levels of preinjury serum biomarkers of collagen turnover with the subsequent risk of anterior cruciate ligament (ACL) injury.

HYPOTHESIS

Preinjury serum biomarkers of collagen turnover would be associated with the subsequent risk of ACL injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

We conducted a case-control study with 45 ACL-injured cases and 45 controls matched for sex, age, height, and weight. In addition to the matching criteria, controls had no history of major joint injury. Baseline preinjury serum samples were obtained from the Department of Defense Serum Repository for all subjects. Samples were assessed for 2 serum biomarkers of collagen synthesis (CPII and CS846) and 2 markers of collagen degradation (C1,2C and C2C) through commercially available enzyme-linked immunosorbent assay (ELISA) kits. All ELISAs were performed in triplicate. Conditional logistic regression models were used to analyze the data.

RESULTS

Univariate results suggested that both biomarkers for collagen degradation (C1,2C and C2C) were significantly associated with the subsequent likelihood of ACL injury. Serum C2C and C1,2C concentration at baseline were associated with odds ratios (ORs) of 2.05 (95% CI, 1.30-3.23; P = .001) and 3.02 (95% CI, 1.60-5.71; P = .002), respectively. Baseline serum CPII concentrations were also associated with subsequent ACL injury. Serum CPII concentration at baseline was associated with an OR of 4.41 (95% CI, 1.87-10.38; P = .001). Baseline serum CS846 levels approached significance (OR = 0.77; 95% CI, 0.57-1.03; P = .080). Multivariable models suggested that preinjury CPII and C2C concentrations at baseline are important indicators of subsequent ACL injury risk.

CONCLUSION

Preinjury differences in serum biomarker levels of collagen turnover suggest that collagen metabolism in individuals who go on to tear an ACL may be different when compared with a matched control group with no history of major joint injury. These differences may be reflective of different preinjury biochemical and/or biomechanical risk profiles or genetic factors that subsequently affect both collagen metabolism and ACL injury risk.

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.

A Systematic Summary of Systematic Reviews on the Topic of the Anterior Cruciate Ligament

BACKGROUND

There has been a substantial increase in the amount of systematic reviews and meta-analyses published on the anterior cruciate ligament (ACL).

PURPOSE

To quantify the number of systematic reviews and meta-analyses published on the ACL in the past decade and to provide an overall summary of this literature.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review of all ACL-related systematic reviews and meta-analyses published between January 2004 and September 2014 was performed using PubMed, MEDLINE, and the Cochrane Database. Narrative reviews and non-English articles were excluded.

RESULTS

A total of 1031 articles were found, of which 240 met the inclusion criteria. Included articles were summarized and divided into 17 topics: anatomy, epidemiology, prevention, associated injuries, diagnosis, operative versus nonoperative management, graft choice, surgical technique, fixation methods, computer-assisted surgery, platelet-rich plasma, rehabilitation, return to play, outcomes assessment, arthritis, complications, and miscellaneous.

CONCLUSION

A summary of systematic reviews on the ACL can supply the surgeon with a single source for the most up-to-date synthesis of the literature.

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.

Landing Technique and Performance in Youth Athletes After a Single Injury-Prevention Program Session

CONTEXT

Injury-prevention programs (IPPs) performed as season-long warm-ups improve injury rates, performance outcomes, and jump-landing technique. However, concerns regarding program adoption exist. Identifying the acute benefits of using an IPP compared with other warm-ups may encourage IPP adoption.

OBJECTIVE

To examine the immediate effects of 3 warm-up protocols (IPP, static warm-up [SWU], or dynamic warm-up [DWU]) on jump-landing technique and performance measures in youth athletes.

DESIGN

Randomized controlled clinical trial.

SETTING

Gymnasiums.

PATIENTS OR OTHER PARTICIPANTS

Sixty male and 29 female athletes (age = 13 ± 2 years, height = 162.8 ± 12.6 cm, mass = 37.1 ± 13.5 kg) volunteered to participate in a single session.

INTERVENTION(S)

Participants were stratified by age, sex, and sport and then were randomized into 1 protocol: IPP, SWU, or DWU. The IPP consisted of dynamic flexibility, strengthening, plyometric, and balance exercises and emphasized proper technique. The SWU consisted of jogging and lower extremity static stretching. The DWU consisted of dynamic lower extremity flexibility exercises. Participants were assessed for landing technique and performance measures immediately before (PRE) and after (POST) completing their warm-ups.

MAIN OUTCOME MEASURE(S)

One rater graded each jump-landing trial using the Landing Error Scoring System. Participants performed a vertical jump, long jump, shuttle run, and jump-landing task in randomized order. The averages of all jump-landing trials and performance variables were used to calculate 1 composite score for each variable at PRE and POST. Change scores were calculated (POST - PRE) for all measures. Separate 1-way (group) analyses of variance were conducted for each dependent variable (α < .05).

RESULTS

No differences were observed among groups for any performance measures (P > .05). The Landing Error Scoring System scores improved after the IPP (change = -0.40 ± 1.24 errors) compared with the DWU (0.27 ± 1.09 errors) and SWU (0.43 ± 1.35 errors; P = .04).

CONCLUSIONS

An IPP did not impair sport performance and may have reduced injury risk, which supports the use of these programs before sport activity.

A resistance band increased internal hip abduction moments and gluteus medius activation during pre-landing and early-landing

An increased knee abduction angle during jump-landing has been identified as a risk factor for anterior cruciate ligament injuries. Activation of the hip abductors may decrease the knee abduction angle during jump-landing. The purpose of this study was to examine the effects of a resistance band on the internal hip abduction moment and gluteus medius activation during the pre-landing (100ms before initial contact) and early-landing (100ms after initial contact) phases of a jump-landing-jump task. Thirteen male and 15 female recreational athletes (age: 21.1±2.4yr; mass: 73.8±14.6kg; height: 1.76±0.1m) participated in the study. Subjects performed jump-landing-jump tasks with or without a resistance band applied to their lower shanks. During the with-band condition, subjects were instructed to maintain their movement patterns as performing the jump-landing task without a resistance band. Lower extremity kinematics, kinetics, and gluteus medius electromyography (EMG) were collected. Applying the band increased the average hip abduction moment during pre-landing (p<0.001, Cohen׳s d (d)=2.8) and early-landing (p<0.001, d=1.5), and the average gluteus medius EMG during pre-landing (p<0.001, d=1.0) and early-landing (p=0.003, d=0.55). Applying the band decreased the initial hip flexion angle (p=0.028, d=0.25), initial hip abduction angle (p<0.001, d=0.91), maximum knee flexion angle (p=0.046, d=0.17), and jump height (p=0.004, d=0.16). Applying a resistance band provides a potential strategy to train the strength and muscle activation for the gluteus medius during jump-landing. Additional instructions and feedback regarding hip abduction, hip flexion, and knee flexion may be required to minimize negative changes to other kinematic variables.

Anterior cruciate ligament prevention strategies: are they effective in young athletes - current concepts and review of literature

PURPOSE OF REVIEW

Participation in sports is on the rise, with young athletes training year round and specializing at earlier ages, predisposing them to sports-related injuries. Once thought to be rare, injuries of the anterior cruciate ligament (ACL) are being seen with a greater frequency in the paediatric population. Numerous preventive training programmes have been developed. The purpose of this review is to discuss risk factors and the effectiveness of preventive programmes in the young athlete.

RECENT FINDINGS

Most ACL prevention programmes take a multifaceted approach, targeting dynamic neuromuscular and proprioceptive deficits. Focus often lies on noncontact mechanisms of injury, jump and landing techniques, and improving movement patterns during pivoting, cutting and change in direction. However, the effectiveness of these programmes in skeletally immature athletes needs to be evaluated.

SUMMARY

Early specialization and increased demand for peak performance at a time of major physiological change, lack of physical fitness and neuromuscular deficits have contributed to an increase in ACL injuries in young athletes. Various preventive training programmes have been developed, but their effectiveness is debatable. We encourage young athletes to partake in preseason training programmes focused on strengthening, neuromuscular and proprioceptive training units under the appropriate supervision of qualified personnel.

Retention of movement pattern changes after a lower extremity injury prevention program is affected by program duration

BACKGROUND

Changes in movement patterns have been repeatedly observed immediately after completing a lower extremity injury prevention program. However, it is not known if movement pattern changes are maintained after discontinuing the training program.

HYPOTHESIS

The ability to maintain movement pattern changes after training has ceased may be influenced by the program's duration. The authors hypothesized that among individuals who completed either a 3-month or 9-month training program and who demonstrated immediate movement pattern changes, only those who completed the 9-month training program would maintain movement pattern changes after a 3-month period of no longer performing the exercises.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 140 youth soccer athletes from 15 separate teams volunteered to participate. Athletes' movement patterns were assessed using the Landing Error Scoring System (LESS) at pretest, posttest, and 3 months after ceasing the program (retention test). Eighty-four of the original 140 participants demonstrated improvements in their LESS scores between pretest and posttest (change in LESS score >0) and were included in the final analyses for this study (n = 84; 20 boys and 64 girls; mean age, 14 ± 2 years; age range, 11-17 years). Teams performed 3-month (short-duration group) and 9-month (extended-duration group) injury prevention programs. The exercises performed were identical for both groups. Teams performed the programs as part of their normal warm-up routine.

RESULTS

Although both groups improved their total LESS scores from pretest to posttest, only the extended-duration training group retained their improvements 3 months after ceasing the injury prevention program (F(2,137) = 3.38; P = .04).

CONCLUSION

Results suggest that training duration may be an important factor to consider when designing injury prevention programs that facilitate long-term changes in movement control.

Rationale and implementation of anterior cruciate ligament injury prevention warm-up programs in female athletes

The sex disparity in anterior cruciate ligament (ACL) injury risk and the subsequent adverse effects on knee joint health, psychosocial well-being, and financial costs incurred have produced a surge in research on risk factors and interventions designed to decrease this disparity and overall incidence. Biomechanical and neuromuscular differences have been identified throughout the trunk and lower extremity that may increase noncontact ACL injury risk in female athletes. Evidence demonstrates that many risk factors are modifiable with intervention programs and that athletic performance measures can be enhanced. No universally accepted ACL injury prevention program currently exists, and injury prevention programs are diverse. Anterior cruciate ligament injury prevention programs introduced in a warm-up format offer multiple benefits, primarily, improved compliance based on improved practicality of implementation. However, drawbacks of warm-up style formats also exist, most notably that a lack of equipment and resources may preclude measurable improvements in athletic performance that foster improved compliance among participants. The purpose of this review is to analyze the current literature researching possible biomechanical and neuromuscular risk factors in noncontact ACL injury in female athletes and the most effective means of implementing critical elements of a program to decrease ACL injury risk in female athletes while improving athletic performance. Hip and hamstring training, core stabilization, plyometrics, balance, agility, neuromuscular training with video and verbal feedback to modify technique, and stretching appear to be essential components of these programs. Further research is critical to determine ideal training program volume, intensity, duration, and frequency.

Integrated injury prevention program improves balance and vertical jump height in children

Implementing an injury prevention program to athletes under age 12 years may reduce injury rates. There is limited knowledge regarding whether these young athletes will be able to modify balance and performance measures after completing a traditional program that has been effective with older athletes or whether they require a specialized program for their age. The purpose of this study was to compare the effects of a pediatric program, which was designed specifically for young athletes, and a traditional program with no program in the ability to change balance and performance measures in youth athletes. We used a cluster-randomized controlled trial to evaluate the effects of the programs before and after a 9-week intervention period. Sixty-five youth soccer athletes (males: n = 37 mass = 34.16 +/- 5.36 kg, height = 143.07 +/- 6.27 cm, age = 10 +/- 1 yr; females: n = 28 mass = 33.82 +/- 5.37 kg, height = 141.02 +/- 6.59 cm) volunteered to participate and attended 2 testing sessions in a research laboratory. Teams were cluster-randomized to either a pediatric or traditional injury prevention program or a control group. Change scores for anterior-posterior and medial-lateral time-to-stabilization measures and maximum vertical jump height and power were calculated from pretest and post-test sessions. Contrary with our original hypotheses, the traditional program resulted in positive changes, whereas the pediatric program did not result in any improvements. Anterior-posterior time-to-stabilization decreased after the traditional program (mean change +/- SD = -0.92 +/- 0.49 s) compared with the control group (-0.49 +/- 0.59 s) (p = 0.003). The traditional program also increased vertical jump height (1.70 +/- 2.80 cm) compared with the control group (0.20 +/- 0.20 cm) (p = 0.04). There were no significant differences between control and pediatric programs. Youth athletes can improve balance ability and vertical jump height after completing an injury prevention program. Training specificity appears to affect improvements and should be considered with future program design.