Lower Extremity Injury Risk Research Articles

Women’s Collegiate Volleyball Players Exhibit Kinetic Asymmetries during Sport-Specific Tasks

Women’s volleyball demands frequent lateral movements and vertical jumps. Repetitive lateral movements in the same direction could lead to biomechanical asymmetries and a potential increased risk of lower extremity injury. PURPOSE:To identify and analyze biomechanical asymmetries in collegiate women’s volleyball players during sport-specific lateral and vertical jumping tasks. METHODS: Nineteen female collegiate volleyball players were analyzed using standard 3D motion capture techniques during a drop vertical jump (DVJ) from a 30-cm box and a reactive jump (REACT) task. For the REACT, participants began in an athletic stance awaiting a directional cue on a screen placed in front of them. Once directed, participants were instructed to jump laterally and then vertically as high and fast as possible to mimic a volleyball block. Repeated measures MANOVA models were used to identify asymmetries in kinematic and kinetic measures in the DVJ and REACT task (α=0.05). Paired t-tests identified asymmetries in reaction time during the REACT task. Limb symmetry indices (LSI) were calculated for significant findings. RESULTS:Significant kinetic asymmetries were identified for both the DVJ (p=0.01) and REACT (p=0.003) tasks, but no kinematic asymmetries were found in either task (p>0.05). During the DVJ, participants exhibited asymmetrical knee abduction (LSI=81%, p=0.03), ankle dorsiflexion (LSI=94%, p=0.03), and ankle inversion (LSI=30%, p=0.001) external joint moments and vertical ground reaction forces (LSI=93%, p=0.04). During the REACT task, participants exhibited asymmetrical ankle dorsiflexion (LSI=85%, p=0.03), and ankle inversion (LSI=73%, p=0.001) external joint moments. There were no differences in reaction times between the two limbs (p>0.05). CONCLUSIONS:Collegiate women’s volleyball players exhibit significant asymmetry in the knee and ankle during jumping and landing tasks. Interestingly, asymmetries were identified in kinetic variables but not kinematic variables. These findings indicate that screening, injury prevention and rehabilitation practices cannot solely rely on visual observation to identify lower extremity asymmetry in this athletic population.

The Influence Of Concussion History On Landing Biomechanics In Adolescent Athletes: A Pilot Investigation.

Sport-related concussion (SRC) is now classified as a major public health concern affecting millions of athletes each year. Recent evidence suggests that previously concussed athletes are at greater risk for lower extremity (LE) injury beyond the resolution of traditional SRC assessment batteries. The current literature has yet to elucidate the biomechanical movement patterns of sport-specific activities that may provide rationale for LE injury risk following SRC. PURPOSE: To examine landing biomechanics in adolescent athletes who report a SRC history. METHODS: Three athletes with a SRC history (age: 11.3 ± 3.5 yrs; previous SRCs: 1.3 ± 0.6) and two athletes without a SRC history (age: 13.0 ± 4.2 yrs) completed drop-landings from 30 cm and 60 cm. Three dimensional kinematic data were measured via a 10-camera motion analysis system at 100 Hz, while kinetic data were collected at 1000 Hz with two adjacent force platforms. The preferred limb to initiate the drop-landing was used for data analysis in comparing landing mechanics between groups. Five landing trials were collected to ensure landing performance stability. The independent variables were group (concussion, control) and landing height (30, 60 cm), while the dependent variables included maximum vertical ground reaction force (vGRF), loading rate, and knee joint kinematic parameters during the landing tasks. RESULTS: Athletes with a previous SRC demonstrated a 7.9% increase (4.22 BWs vs 3.89 BWs) in maximum vGRF and 14.7% increase in loading rate (109.2 BWs / sec vs 93.2 BWs / sec) from the 60 cm height compared to control athletes. Additionally, previously concussed athletes demonstrated an 8.8 degrees (-4.9° vs 3.9°) and 11.2 degrees (-8.1° vs 3.1°) increase in knee abduction angle from the 30 cm and 60 cm heights compared to control athletes. Knee sagittal plane range of motion was decreased by 56.2% (52.0° vs 81.2°) from the 30 cm height and 30.3% (62.3° vs 81.1°) from the 60 cm height in athletes with a previous SRC. CONCLUSIONS: Preliminary analysis highlights that previously concussed adolescent athletes demonstrate landing mechanics that may increase LE injury risk. Specifically, athletes with a SRC history demonstrate sagittal and frontal plane knee motion during landings that are associated with greater risk of an anterior cruciate ligament injury.

Explaining Upper or Lower Extremity Crossover Effects of Visuomotor Choice Reaction Time Training.

Current evidence indicates a strong relation between improved visuomotor choice reaction time (VMRT) and a reduced risk of lower extremity injury, making both lower- and upper extremity VMRT training paradigms valuable to athletes. This investigation studied as yet unconfirmed crossover effects of upper extremity training on lower extremity performance; and we evaluated underlying relevant perceptual and cognitive adaptations. In this three-armed, randomized, controlled intervention, we used a computerized training device to compare participants receiving four weeks of upper (n = 12) and lower (n = 12) extremity VMRT training with a control group (n = 13) of healthy participants. Collectively, our participants had a mean age of 24.6 years (SD = 2.2), a mean height of 173 cm (SD = 10), and a mean weight of 69.6 kg (SD = 12.1); 57% (n = 21) were female and 43% (n = 16) were male. We assessed participants' upper and lower extremity VMRT performance and domain-specific perceptual and cognitive abilities before and after intervention and analyzed differences between their before and after performances. Lower extremity training enhanced VMRT performances for both lower extremity and crossover upper extremity. Upper extremity training improved VMRT for upper extremity and increased cognitive choice reaction performance but yielded no crossover effects to lower extremity. We found no effects of VMRT training on other domain-specific cognitive performance markers (attention, executive function, memory, or working memory). VMRT training modulated only task-specific cognitive performance and induced crossover effects from lower extremity training to upper extremity performance but not vice versa.

Postural Stability Under Dual-Task Conditions: Development of a Post-Concussion Assessment for Lower-Extremity Injury Risk.

Concussions are consequence of sports participation. Recent reports indicate there is an increased risk of lower-extremity musculoskeletal injury when returning to sport after concussion suggesting that achieving "normal" balance may not fully indicate the athlete is ready for competition. The increased risk of injury may indicate the need to refine a screening tool for clearance. Assess the between-session reliability and the effects of adding a cognitive task to static and dynamic postural stability testing in a healthy population. Clinical laboratory. Twelve healthy subjects (6 women; age 22.3 [2.9]y, height 174.4 [7.5]cm, weight 70.1 [12.7]kg) participated in this study. Subjects underwent static and dynamic postural stability testing with and without the addition of a cognitive task (Stroop test). Test battery was repeated 10 days later. Dynamic postural stability testing consisted of a forward jump over a hurdle with a 1-legged landing. A stability index was calculated. Static postural stability was also assessed with and without the cognitive task during single-leg balance. Variability of each ground reaction force component was averaged. Interclass correlation coefficients (ICC2,1) were computed to determine the reliability. Standard error of measure, mean standard error, mean detectable change, and 95% confidence interval were all calculated. Mean differences between sessions were low, with the majority of variables having moderate to excellent reliability (static .583-.877, dynamic .581-.939). The addition of the dual task did not have any significant effect on reliability of the task; however, generally, the ICC values improved (eyes open .583-.770, dual task .741-.808). The addition of a cognitive load to postural stability assessments had moderate to excellent reliability in a healthy population. These results provide initial evidence on the feasibility of dual-task postural stability testing when examining risk of lower-extremity musculoskeletal injury following return to sport in a concussed population.

Landing Kinematics, Sports Performance, and Isokinetic Strength in Adolescent Male Volleyball Athletes: Influence of Core Training.

Core control and strength are important for reducing the risk of lower-extremity injury. Current evidence on the effect of core training in male adolescent athletes is limited, and other investigations into the effects of core training often emphasized core strength only. To examine whether core training emphasizing both control and strength of the trunk and hip would improve joint kinematics during landing, sports performance, and lower-extremity muscle strength in adolescent male volleyball athletes. Single group pretest and posttest design. University laboratory. Sixteen male participants (age: 13.4 [1]y, height: 167.8 [8.6]cm, mass: 58.6 [13.9]kg, and volleyball experience: 3.8 [1.5]y) from a Division I volleyball team at a junior high school. Kinematics of the trunk and lower-extremity during box landing and spike jump landing tasks, volleyball-related sports performance, and isokinetic strength of hip and knee muscles were assessed before and after a 6-week core training program. After training, the participants demonstrated decreased trunk flexion angle (P = .01, Cohen's d = 0.78) during the box landing task and reduced the maximum knee internal rotation angle (P = .04, Cohen's d = 0.56) during the spike jump landing task. The average isokinetic strength of hip flexors and external rotators, and knee flexors and extensors also significantly increased (P = .001, Cohen's d = 0.98; P = .04, Cohen's d = 0.57; P = .02, Cohen's d = 0.66; P = .003, Cohen's d = 0.87, respectively); however, sports performance did not show significant changes. A more erect landing posture following training suggests that the core training program may be beneficial for improving core stability. The long-term effect of core training for knee injury prevention needs further investigation.

Impact of Routine Gastrocnemius Stretching on Ankle Dorsiflexion Flexibility and Injury Rates in High School Basketball Athletes.

Background:Achilles tightness exacerbates a variety of foot and ankle conditions while increasing the risk of lower extremity injuries. The correlation between Achilles tightness and lower extremity injury rates in a young, athletic population is unknown.Purpose:To evaluate the impact of routine gastrocnemius stretching on ankle flexibility and lower extremity injury rates in youth basketball athletes.Study Design:Cohort study; Level of evidence, 3.Methods:A prospective cohort study enrolling 8 high school basketball teams (4 male teams, 4 female teams) was conducted over a 3-month sporting season. Two schools (2 male teams, 2 female teams) were assigned to a daily gastrocnemius stretching protocol. Two control schools (2 male teams, 2 female teams) followed no protocol. Passive ankle dorsiflexion was measured bilaterally in both groups at 4 time points: preseason, 1 month and 2 months after the start of the season, and postseason (3 months from the start of the season). The number of injuries sustained during the season and the number of games missed because of a lower extremity injury were recorded. Differences in dorsiflexion flexibility measurements and injury rates were analyzed between the protocol and control groups.Results:A total of 106 athletes (46 male, 60 female) were included in the study. The protocol group included 51 athletes (mean age, 15.7 ± 1.2 years) versus 55 athletes (mean age, 16.2 ± 1.0 years) in the control group. Athletes undergoing routine gastrocnemius stretching had significantly higher ankle dorsiflexion flexibility measurements compared with control athletes at all time points (P < .05 for each time point) while also demonstrating a significant increase in dorsiflexion between the preseason and postseason time points (P = .04). No significant difference in injury rates was appreciated between the protocol and control groups, and no difference in dorsiflexion flexibility measurements was appreciated between injured and uninjured athletes.Conclusion:The implementation of a gastrocnemius stretching protocol in youth basketball athletes increased ankle dorsiflexion over a single season without decreasing the injury incidence relative to controls in our study. Because the size of our study limited statistical power, a confirmation of the results in a larger study is required.

Match Play-induced Changes in Landing Biomechanics with Special Focus on Fatigability.

Growing evidence exists that match-related fatigue induces biomechanical alterations that might increase lower extremity injury risk. Fatigue studies often use match simulation protocols that expose all subjects to a standardized demand (e.g., a fixed distance/time). In those studies, the induced level of fatigue depends then on subjects' fatigability. If between-subject variability in fatigability is high, this might confound overall fatigue effects. Therefore, the first aim was to investigate whether a fatigue protocol with fixed demand causes alterations in landing patterns. Second, we assessed the relationship between fatigability and landing patterns as we hypothesized that athletes with high fatigability would show movement patterns that involve greater injury risk. Eighteen athletes performed three different unilateral landing tasks before and after a match simulation protocol while muscle activation (vastus medialis, vastus lateralis, hamstrings medialis, hamstrings lateralis, gastrocnemius medialis, gastrocnemius lateralis, and gluteus medius) and landing kinematics and kinetics of the hip, knee, and ankle joint were recorded. Furthermore, RPE was administered to measure fatigability. ANOVA analyses were conducted to investigate fatigue effects on landing patterns. Correlation analyses assessed the relationship between fatigability (postfatigue RPE) and landing patterns. The ANOVA analyses did not show any overall postfatigue alterations in landing patterns. However, correlation analyses showed an association between fatigability and landing patterns. Athletes who had higher RPE scores showed smaller postfatigue knee flexion angles and smaller pre- and postfatigue knee abduction angles across different landing tasks. The fixed demand protocol did not cause overall alterations in landing patterns. When fatigability was taken into account, high fatigability was related with less optimal landing patterns.

THE MODIFIED STAR EXCURSION BALANCE AND Y-BALANCE TEST RESULTS DIFFER WHEN ASSESSING PHYSICALLY ACTIVE HEALTHY ADOLESCENT FEMALES

The modified Star Excursion Balance Test (mSEBT) and Y-Balance Test (YBT) are two common methods for clinical assessment of dynamic balance. Clinicians often use only one of these test methods and one outcome factor when screening for lower extremity injury risk. Dynamic balance scores are known to vary by age, sex and sport. The physically active adolescent female is at high risk for sustaining lower extremity injuries, specifically to the anterior cruciate ligament (ACL). Thus clarity regarding the use of dynamic balance testing results in adolescent females is important. To date, no studies have directly compared the various outcome factors between these two dynamic balance tests for this population. To determine if there was an association between the mSEBT and YBT scores for measured reach distances, calculated composite score and side-to-side limb asymmetry in the ANT direction in physically active healthy adolescent females. Cross-sectional study. Twenty-five healthy, physically active female adolescents (mean age, 14.0 ± 1.3 years) participated. Reach distances, a composite score and side-to-side limb asymmetry for the mSEBT and YBT, for each limb, were compared and examined for correlation. There were significant differences and moderate to excellent relationships between the measured reach directions between the mSEBT and the YBT. Injury risk classification, based on limb asymmetry in the anterior reach direction, differed between the tests. However, the calculated composite scores from the two tests did not differ. Performance scores on a particular reach direction should not be used interchangeably between the mSEBT and YBT in physically active adolescent females, and should not be compared to previously reported values for other populations. Level 3.

Association of Functional Movement Screen and Y-Balance Test Scores With Injury in High School Athletes.

Lisman, P, Hildebrand, E, Nadelen, M, and Leppert, K. Association of functional movement screen and Y-Balance Test scores with injury in high school athletes. J Strength Cond Res 35(7): 1930-1938, 2021-The purpose of this study was to determine the association between functional movement screen (FMS) and Y-Balance Test (YBT) performance and lower extremity injury in a sample of male high school athletes. A total of 124 high school football (n = 89), lacrosse (n = 25), and baseball (n = 10) players underwent FMS and YBT before the start of their competitive seasons. Time loss lower extremity injury incidence data were tracked by each team's certified athletic trainer and used for analysis. Receiver operating characteristic (ROC) curves were calculated to determine the optimal cutpoints for FMS composite score (CS) and YBT measures, including CS and reach distance asymmetry for anterior, posteromedial, and posterolateral directions, for predicting injury. No cutpoints on the ROC curves maximized sensitivity and specificity; therefore, FMS CS and YBT measures (CS and asymmetry) were analyzed as continuous variables. Logistic regression models adjusted for age and sport revealed no significant associations between FMS CS and lower extremity injury (odds ratio [OR] = 0.99; 95% confidence interval [CI] = 0.83-1.20). Similar findings were found for YBT asymmetry in all directions (ORs ranged from 0.98 to 1.08) and CS (OR = 0.99; 95% CI = 0.95-1.04). There were also no significant associations between the presence of asymmetry and low score (score of 1) on any individual FMS test and injury. Overall, FMS and YBT were not associated with increased risk of lower extremity injury in this sample of high school athletes. These findings do not support the use of FMS and YBT as stand-alone injury risk assessments in high school athletes.

RELIABILITY AND STABILITY OF THE Y BALANCE TEST IN HEALTHY EARLY ADOLESCENT FEMALE ATHLETES

BACKGROUND/PURPOSE: Adolescent females are at an increased risk of lower extremity injuries and may be partially explained by the interaction of peak rates of skeletal growth, an immature neuromuscular system, and deficits in muscle strength and recruitment patterns. Reliable tests of dynamic stability can help identify athletes with balance deficits and assess changes in limb function after injury. Sophisticated measures of dynamic postural control, such as stabilometry, are able to detect subtle deficits in young athletes, but are expensive and may not be readily available in a clinical setting. The Y Balance Test (YBT) is a low-cost, clinical measure of dynamic postural control that mimics the demands of sports requiring unilateral balance. It requires the athlete to dynamically balance on each leg while performing a maximal reach with the other limb in three different directions: anterior (ANT), posteromedial (PM), and posterolateral (PL). The athlete is required to maintain unilateral balance during the test as maximal reach distance is measured to the nearest 0.5 cm. Though the YBT has been predicative of injury in the adult population, studies are lacking regarding the utility in adolescents. The purpose of this study was to estimate the inter- and intra- rater reliability and stability of the YBT in early adolescent females over a one-month period. METHODS: Twenty-five female athletes (mean age 12.7 ± 0.6 years) participated. Subjects were tested at their respective practice facilities and participated in various sporting activities (Figure 1). Two novice raters with minimal training in YBT administration were randomly selected from a pool of five. The raters simultaneously assessed each subject’s YBT performance and were blinded to each other’s results. A second testing session was performed approximately one month later (n=21, mean 32.3± 9.6 days) by the same two raters, blinded to previous measurements (Figure 2). The time interval was chosen to mimic a typical duration between reassessments in standard clinical care. Maximum reach distances and composite (COMP) scores were collected on both limbs and normalized to leg length (Figure 3). Intraclass correlation coefficients (ICC) were calculated for between rater (ICC 2,1) and between session (ICC 3,1) agreement. Measurement error and minimal detectable change (MDC) values were calculated for clinical interpretation. RESULTS: There was a significant increase in height (p=0.016) and weight (p=0.003) from day 1 to day 2 of testing. Interrater reliability was excellent for all corrected reach directions and COMP scores of the right limb (ICC 0.973- 0.998) and left limb (ICC 0.960-0.999) except for the day 1 left ANT reach which was good (ICC 0.811) (Figure 4). Intrarater (test-retest) reliability were moderate to excellent for the right limb (ICC 0.681- 0.908) and moderate to good for left limb (ICC 0.714 - 0.811). Standard error of measurement (SEM) percentages were all less than 2% of all respective mean reach distances. MDC values for the right and left limbs ranged between 2.02-3.62% and 2.77-3.63%, respectively (Figure 5). CONCLUSIONS/SIGNIFICANCE: The early adolescent female is a unique population, where dynamic balance deficits are escalated by the interaction of an immature neuromuscular system, peak maturational growth rates, and emergence of sex specific differences. The incidence of ACL injuries is greatest during the high school years and recommendations support the implementation of targeted neuromuscular interventions prior to the time of this peak injury risk. The YBT is a reliable and stable tool to assess dynamic balance in early adolescent females and may be utilized by clinicians, physical education teachers, and coaches to help identify high risk individuals, mitigate the risk of injury, and determine functional improvements. The time span between testing sessions in the current study was longer than previous work in attempt to improve external validity by mimicking a typical time interval between outcome measure reassessments performed in a clinical setting. Between session reliability measures were lower than previous studies in adults and highlights the unique performance variation with dynamic balance tasks in the female preadolescent population. This is exemplified by the anthropometric changes that occurred over just a one month interval. This study supports the reliability and stability of the YBT in healthy early adolescent females and can be administered by those with minimal YBT training. Though the YBT has been shown to be predicative of injury in adults and is often included in return to sport functional test batteries after injury, future studies are needed to further understand its utility in this high-risk early adolescent female population. [Figure: see text]

2018 JOSPT Award Recipients.

During the American Physical Therapy Association's Combined Sections Meeting in Washington, DC in January 2019, JOSPT recognized the authors of the most outstanding research and clinical practice manuscripts published in JOSPT during 2018. The 2018 George J. Davies-James A. Gould Excellence in Clinical Inquiry Award was presented to Joseph R. Kardouni, PT, PhD; Tracie L. Shing, MPH; Craig J. McKinnon, MPH; Dennis E. Scofield, MAEd; and Susan P. Proctor, DSc for their July 2018 article, "Risk for Lower Extremity Injury After Concussion: A Matched Cohort Study in Soldiers." The 2018 JOSPT Excellence in Research Award was presented to Kathryn J. Schneider, PT, PhD; Willem H. Meeuwisse, MD, PhD; Luz Palacios-Derflingher, PhD; and Carolyn A. Emery, PT, PhD for their December 2018 article, "Changes in Measures of Cervical Spine Function, Vestibulo-ocular Reflex, Dynamic Balance, and Divided Attention Following Sport-Related Concussion in Elite Youth Ice Hockey Players." J Orthop Sports Phys Ther 2019;49(3):117. doi:10.2519/jospt.2019.0101.

Lower extremity biomechanics and muscle activity differ between ‘new’ and ‘dead’ pointe shoes in professional ballet dancers

ABSTRACT The purpose of this study was to compare lower extremity (LE) biomechanics and muscle activity between ‘new’ and ‘dead’ pointe shoes in professional female ballet dancers performing relevé and arabesque. We compared sway area, peak ankle moments, and tibialis anterior and medial gastrocnemius muscle activation amplitudes. Nine ballet dancers participated (age = 22.2 ± 2.2 years, height = 163.2 ± 6.3 cm, body mass = 50.8 ± 6.5 kg) executed three trials of relevé and arabesque on pointe shoes under two conditions: ‘dead’ (108–144 training hours) and ‘new’ (3–36 training hours). While wearing ‘dead’ pointe shoes, dancers had significantly higher sway area during both relevé and arabesque (p = 0.017 and 0.028, respectively). Dancers exhibit significantly higher tibialis anterior activation (root mean square, %maximum voluntary contraction) during arabesque while wearing ‘dead’ pointe shoes (p = 0.043). No significant differences were identified in other dependent variables. The increased sway area and tibialis anterior muscle activity when wearing ‘dead’ pointe shoes during relevé and arabesque movements demonstrates that using ‘dead’ shoes is more demanding. Our findings provide quantitative evidence of possible deleterious biomechanical changes when wearing dead pointe shoes that may increase LE injury risk in dancers.

Is consumer behaviour towards footwear predisposing for lower extremity injuries in runners and walkers? A prospective study

BackgroundRunners and walkers often suffer from lower extremity injuries. Little is known about the relationship between their consumer behaviour towards footwear and the development of those injuries. Therefore, the aim of this study was to investigate if consumer behaviour towards footwear is a risk factor for lower extremity injuries.MethodsA prospective cohort study was set-up in leisure-time walkers and runners. Potential risk factors in consumer behaviour were obtained by means of a baseline questionnaire related to the acquisition of current walking or running shoes. Information on injuries sustained during a 24 week period after the baseline questionnaire was obtained in 104 runners and 104 walkers using a 2-weekly questionnaire. Binary logistic regression analysis was used to identify risk factors for lower extremity injuries in the consumer behaviour.ResultsForty- nine (24%) subjects suffered a self-reported lower extremity injury. 35 injuries occurred in runners and 14 among walkers.Undergoing a gait analysis before buying shoes was associated with an increased occurrence of lower extremity injuries (odds ratio (OR) 4.76). A protective factor was caring a lot about the right fitting of the shoes (OR 0.11).ConclusionRunners and walkers should pay attention to the correct size when buying footwear to diminish the risk of lower extremity injury. Buying footwear after a gait analysis increased the risk of a lower extremity injury in runners and walkers, however, this might be associated with the increased risk that was already present because of previous injury.Trial registrationThis trial was not registered since this was an observational study and no intervention took place.

Y-Balance test asymmetry is greater in collegiate athletes with a history of concussion

Athletes with a history of concussion (HC) are at an increased risk of sustaining lower extremity injuries. It is unclear if these individuals exhibit dynamic postural control deficits associated with lower extremity injury risk. The purpose of this study was to determine if collegiate athletes with a HC demonstrate differences in Y-Balance Test (YBT) performance compared to athletes with no history of concussion (NHC). A total of 116 varsity and club athletes from a Division-I university participated. Forty participants reported a HC (female/male: 31/9, age: 20.0 ± 1.4 years, height: 169.3 ± 13.1 cm, mass: 68.4 ± 14.0 kg) while 76 reported NHC (female/male: 60/16, age: 20.0 ± 1.7 years, height: 168.5 ± 12.9 cm, mass: 68.7 ± 14.6 kg). Individuals with a current concussion or lower extremity injury, or a history of lower extremity surgery were excluded. Participants completed the YBT anterior reach direction barefoot on both limbs. The YBT was completed by maximally reaching anteriorly, maintaining balance, and returning to the starting position without errors. Participants completed 4 practice trials and 3 test trials. Reach distances were averaged and normalized to leg length. Between-limb asymmetry was calculated as the absolute difference between the left and right limbs. Separate independent t-tests examined group differences in normalized reach distances and asymmetry. The proportion of participants in each group with &gt;4 cm of asymmetry was compared using a χ2 test. Alpha was set at 0.05 for all analyses. No group differences were identified in normalized reach distances for the left (HC: 61.4% ± 9.2%, NHC: 60.8% ± 6.2%, p = 0.88, ES = 0.08) or right (HC: 61.4% ± 6.2%, NHC: 60.2% ± 6.8%, p = 0.51, ES = 0.17) limbs. However, a greater proportion of HC participants demonstrated &gt;4 cm asymmetry (HC: 40.0%, NHC: 19.7%; p = 0.02) and these participants exhibited greater asymmetry (HC: 3.87 ± 3.69 cm, NHC: 2.40 ± 2.13 cm, p = 0.03; ES = 0.53). Athletes with a HC exhibited greater asymmetry compared to athletes with NHC. Anterior reach asymmetries of &gt;4 cm are associated with greater lower extremity injury risk. The YBT may provide a clinical technique to further explore the relationship between concussion and lower extremity injury.

Basketball Players' Dynamic Performance Across Competition Levels.

Bullock, GS, Arnold, TW, Plisky, PJ, and Butler, RJ. Basketball players' dynamic performance across competition levels. J Strength Cond Res 32(12): 3537-3542, 2018-Dynamic balance is an integral component in screening lower extremity injury risk. Previous research has identified the need to create sport- and competition level-specific dynamic balance injury cut points. The purpose of this study was to determine if dynamic balance differences exist, using the Lower Quarter Y Balance Test (YBT-LQ), across varying competition levels (middle school, high school, college, and professional), in basketball players. Subjects were participating at the middle school (MS; n = 88), high school (HS; n = 105), college (COL; n = 46), and professional levels (PRO; n = 41). Statistical analysis was completed with a series of analysis of variance tests. Tukey post hoc tests were used to identify specific group-to-group differences if statistical significance (p ≤ 0.05) was observed. Effect size indices (ESI) were also calculated to provide an estimate of the clinical relevance. In the anterior reach, HS basketball players performed statistically better than the MS and COL (p < 0.01, ESI = 0.58) athletes, and all these groups performed better than the PRO basketball players (p < 0.01, ESI = 1.72). For the posteromedial, posterolateral reach directions and the composite score, the HS, COL, and PRO basketball players were not significantly different from each other; however, the HS group did reach further than the MS group (p < 0.01-0.02, ESI = 0.40-0.55). The PRO basketball players exhibited a lower asymmetrical total score compared with MS, HS, and COL players (p < 0.01-0.02, ESI = 0.52-0.68). Different competition levels displayed varying dynamic balance strategies. Creating basketball competition levels normative values for dynamic balance could help define injury risk cut points.

Assessing Lower Extremity Injury Risk in a Mid-Atlantic Drum Corps Using the Weight Bearing Lunge Test

With athletic training’s expansion into non-traditional settings it is important to assess if screening tools can provide value in range of settings. Currently, there is a dearth of information regarding specific models for injury risk assessment in Drum Corps patients. The Weight Bearing Lunge Test (WBLT) has been used to evaluate those at risk for suffering a lower extremity injury (LEI) in a traditional athletic population. This practice based research is an attempt to apply current evidence of injury risk assessment in the traditional settings to performing arts. The purpose of our investigation was to determine the effect of WBLT motion on LEI in Drum Corps. All participating Drum Corps members were measured using the WBLT during the preseason screening process. Injury record keeping was completed through electronic medical records (EMR) and all LEI were recorded over two consecutive, 85 day seasons. The average of the maximal distance in centimeters of the great toe from the wall indicated the WBLT Average (WBLTAv). WBLT Asymmetry (WBLTAsy) was the absolute difference between limbs. T-tests were used to determine if there was a significant difference between those who sustained a LEI (Injured) and those who did not (Uninjured) for WBLTAv and WBLTAsy. For dependent measures associated with significant group differences, receiver operator characteristic curves (ROC) were performed to examine injury risk using area under the curve (AUC). Lastly, cut-off scores that produced the maximal values of sensitivity and specificity were identified. Alpha level was set a priori at p 0.75cm) measures were more likely to sustain a LEI during a competitive drum corps season. This data demonstrates that the WBLT could be viable as a screening tool in the marching arts and provides initial cut-off values.

Lower Extremity Horizontal Work But Not Vertical Power Predicts Lower Extremity Injury in Female Collegiate Dancers.

Ambegaonkar, JP, Schock, CS, Caswell, SV, Cortes, N, Hansen-Honeycutt, J, and Wyon, MA. Lower extremity horizontal work but not vertical power predicts lower extremity injury in female collegiate dancers. J Strength Cond Res 32(7): 2018-2024, 2018-Dancers often perform powerful and explosive movements that require adequate lower extremity (LE) activity in horizontal and vertical directions. We examined whether these measures were interrelated and whether they predicted LE injury status in dancers using binary logistic regressions and receiver operator characteristic (ROC) curve analyses. Forty-three collegiate female dancers (18 ± 0.7 years; 162.6 ± 5.9 cm; 59.4 ± 7.1 kg) performed single leg hop (SLH, m) and vertical jump (VJ, cm) tests. Single leg hop and VJ distances were used to calculate SLH norm (as a % of body height) and vertical power (vPower, watts). Lower extremity injuries and dance exposure hours (DEhrs) were recorded for 16 weeks. Dancers had 51 injuries resulting in a 3.7/1,000 DEhr injury incidence rate (95% confidence interval [CI]: 2.7-4.7). Twenty dancers were injured, whereas 23 remained injury free. Injured dancers had significantly lower SLH norm than noninjured dancers (t = 2.7, p = 0.009, 85.2 ± 11.2% vs. 76.8 ± 8.4%, respectively), but vPower was similar (t = 0.6, p = 0.53, injured = 2,632.0 ± 442.9 watts, noninjured = 2,722.7 ± 480.0 watts). SLH norm, but not vPower significantly predicted injury status χ(1,43) = 5.9, p = 0.02. Specifically, an SLH norm cut-off value of 78.2% identified dancers at injury risk (area under the curve = 0.73, SE = 0.08, p = 0.01, 95% CI = 0.57-0.89, sensitivity = 0.75, specificity = 0.70). However, vPower was not able to identify dancers at risk (p = 0.36). vPower had moderate relationships with SLH norm (r = 0.31, p = 0.04). Compared with injured dancers, noninjured dancers had greater SLH norm but similar vPower. Only SLH norm predicted injury status in female collegiate dancers. Thus, the SLH test may possibly predict LE injury risk in dancers. Strength and conditioning coaches can prospectively use baseline SLH test screenings to identify dancers whose SLH is less than 78.2% of their height because these dancers may have increased probability of LE injury risk. Coaches can then include horizontal direction exercises when designing training programs and examine whether these programs reduce LE injury risk in female collegiate dancers.

A comparison of the free moment pattern between normal and hyper-pronated aligned feet in female subjects during the stance phase of gait.

Background: Excessive range of adductory free moment of the ground reaction force may potentially increase the risk of lower extremity injuries by applying a higher torsional load transmitted to the proximal parts.Objective: It was hypothesized that the free moment pattern might be different between hyper-pronated and normal feet subjects. Moreover, a correlation would exist between peak adduction free moment and peak ankle-foot complex abduction at the stance phase of walking.Material and Methods: In this cross sectional study, thirty female participants were divided into two groups of asymptomatic hyper-pronated and normal feet. Kinetic and kinematic data were collected using a single force plate and a six-camera motion analysis system during three successful free speed walking trials. Ensemble average curves were extracted from the time normalized individual trials of the stance phase for both free moment and peak ankle-foot complex abduction parameters.Results: Significant differences in peak adductory free moment, peak ankle-foot complex eversion and peak ankle-foot complex abduction were found between normal and hyper-pronated groups (4.90±0.97 Vs. 5.94±0.88, P < 0.01), (3.30±0.95 Vs. 6.28±1.47, P < 0.01) and (4.52±1.16 Vs. 8.23±2.52, P < 0.01) respectively. A significant positive correlation was found between the peak adduction free moment and peak ankle-foot complex abduction in both groups, which was more strongly positive in hyper-pronated group (r = 0.745, p < 0.01 for normal group and r = 0.900, p < 0.01 for hyper-pronated group).Conclusion: As a good measure of torque which is transmitted to the lower extremity, may free moment be a useful biomechanical indicator for both clinical and research purposes.

Investigation of knee control as a lower extremity injury risk factor: A prospective study in youth football.

This prospective study in youth football examined the relationship between frontal plane knee projection angle (FPKPA) during the single-leg squat and sustaining an acute lower extremity injury or acute non-contact lower extremity injury. Secondly, side-to-side asymmetry in FPKPA and sex as injury risk factors were explored. In addition, we investigated the influence of age, sex, and leg dominance on the FPKPA. A total of 558 youth football players (U11 to U14) participated in the single-leg squat test and prospective injury registration. FPKPA was not found as a risk factor for injuries at this age. There was no difference in the mean FPKPA between sexes. However, FPKPA was associated with age; oldest subjects displayed the smallest FPKPA. Among boys, the frontal plane knee control improved by age. Among girls, the relationship between age and FPKPA was not as clear, but the oldest girls displayed the smallest mean FPKPA in the study (12.2°±8.3°). The FPKPA was greater on the dominant kicking leg compared to the non-dominant support leg (P<.001 for boys, P=.001 for girls). However, side-to-side asymmetry in FPKPA was not associated with future injuries. In conclusion, frontal plane knee control in the single-leg squat was not associated with lower extremity injuries among young football players. As the single-leg squat to 90° knee flexion was too demanding for many subjects, easier single-leg squat test procedure or a different movement control test, such as a double-legged squat, could be more suitable for the young football players.

Risk for Lower Extremity Injury After Concussion: A Matched Cohort Study in Soldiers.

Background Rates of lower extremity musculoskeletal injury are reportedly higher in professional and collegiate athletes following concussions. However, there is a paucity of evidence on this relationship in individuals who are not high-level athletes. Objectives To examine the risk of acute lower extremity musculoskeletal injury in soldiers within 2 years of an incident concussion, compared to matched nonconcussed soldiers. Methods This was a matched-cohort study that used the medical encounter and personnel data of active-duty US Army soldiers from 2005 to 2011. Incident concussions were identified using International Classification of Diseases-Ninth Revision codes in medical encounter data of all soldiers from 2005 to 2009. One nonconcussed soldier in the US Army during the same month was matched by age, sex, rank, length of service, deployment status, and military career field to each concussed soldier. Hazard ratio (HR) and 95% confidence interval (CI) were calculated for the risk of lower extremity injury within 2 years of the incident concussion. Monthly HRs were compared to identify differences in injury rates between the groups, and an HR for the period of greatest difference was also calculated. Results A total of 23 044 individuals (11 522 concussed and 11 522 nonconcussed) were included in the study. Within 2 years of concussion, the hazard of lower extremity injury was 38% greater in concussed compared to nonconcussed soldiers (HR, 1.38; 95% CI: 1.30, 1.46), while the 15-month hazard was 45% greater (HR, 1.45; 95% CI: 1.36, 1.56). Conclusion The rate of lower extremity musculoskeletal injury among this population of physically active adults is higher following concussion, and the risk remains elevated for more than a year following injury. Level of Evidence Prognosis, level 2b. J Orthop Sports Phys Ther 2018;48(7):533-540. Epub 8 May 2018. doi:10.2519/jospt.2018.8053.