Forward step down test - clinical rating is correlated with joint angles of the pelvis and hip: an observational study.

BACKGROUND: Clinical methods for assessing quality of movement and functional tests are important to clinicians. Typical deviations from normal kinematics during the clinical test of Forward Step Down Test (FSDT) are pelvic tilt and hip adduction which are associated with the risk of knee pain. OBJECTIVES: (1) to examine the correlation between clinical assessment of the FSDT and joint angle measurements of pelvis, hip, knee and ankle joints in males and females; (2) to examine the differences in joint angles between individuals rated as good, fair or poor in a FSDT performance test. METHODS: Ninety-two healthy individuals performing FSDT were video-taped with two-dimensional digital video cameras. The clinical assessment of the FSDT was rated by two experienced physical therapists as good, fair, or poor based on a Crossley et al. (2011) validated scale. Measurements of pelvic drop, hip adduction and knee valgus were taken using Image J software. RESULTS: Out of 177 lower limbs, 74 (37 in each limb) were clinically rated as "good/fair" (41.80%) while 103 (52 in the dominant leg and 51 in the non-dominant leg) were rated as "poor" (58.19%). No significant differences were observed between dominant and non-dominant legs or between males and females in clinical rating of the FSDT. Pelvic drop angle was significantly higher and hip adduction angle was significantly lower for "poor" clinical rating compared to "good/fair" in both dominant and non-dominant legs (p < 0.001) in males and females. Females demonstrated higher pelvic drop, lower hip adduction and higher knee valgus angles compared with males (p < 0.05). CONCLUSIONS: This study showed that the clinical rating of FSDT is correlated with joint angle measurements suggesting that this assessment can be utilized in clinical practice. Individuals with poor quality performance of FSDT showed higher pelvic drop and hip adduction movement. Further studies examining different populations with diverse disorders or pathologies are essential.

Knee wobbling during the single-leg-squat-and-hold test reflects dynamic knee instability in patients with anterior cruciate ligament injury.

We propose using the single-leg squat-and-hold (SLSH) task with kinematic analysis to objectively measure dynamic knee stability after anterior cruciate ligament (ACL) injury. There are three objectives of this study: to compare the knee kinematics of ACL-deficient patients and healthy controls by capturing knee wobbling during the SLSH task, to detect kinematic changes after ACL reconstruction, and to correlate the kinematic variables with self-reported knee function. Twenty-five ACL-deficient participants and 18 healthy matched participants were recruited. The knee kinematics involving both the magnitudes and frequency of motion fluctuation was captured during SLSH by 3D motion analysis system (Vicon). Compared to the limbs of the control participants, the ACL involved limbs exhibited a greater range of flexion-extension (4.33 ± 1.96 vs. 2.73 ± 1.15; p = 0.005) and varus-valgus (2.52 ± 0.99 vs. 1.36 ± 0.42; p < 0.001). It also inhibited higher frequency of flexion-extension (4.87 ± 2.55 vs. 2.68 ± 1.23; p = 0.003) and varus-valgus (3.83 ± 2.59 vs. 1.42 ± 0.55; p < 0.001). The range of flexion-extension (4.50 ± 2.24 vs. 2.90 ± 1.01; p = 0.018), frequency of flexion-extension (4.58 ± 2.53 vs. 3.05 ± 1.80; p = 0.038) and varus-valgus (3.46 ± 2.11 vs. 1.80 ± 1.23; p = 0.022) was reduced after ACL reconstruction. Increased frequency of knee varus-valgus was correlated with lower IKDC score (r = -0.328; p = 0.034). Knee wobbling was more prominent in ACL-deficient patients, which was associated with poor knee function. SLSH task with kinematic analysis appears to be a potential assessment method for monitoring dynamic knee stability after ACL injury.

ACL deficiency influences medio-lateral tibial alignment and knee varus-valgus during in vivo activities.

PURPOSE: The role of the anterior cruciate ligament (ACL) in knee biomechanics in vivo and under weight-bearing is still unclear. The purpose of this study was to compare the tibiofemoral kinematics of ACL-deficient knees to healthy contralateral ones during the execution of weight-bearing activities. METHODS: Eight patients with isolated ACL injury and healthy contralateral knees were included in the study. Patients were asked to perform a single step forward and a single leg squat first with the injured knee and then with the contralateral one. Knee motion was determined using a validated model-based tracking process that matched subject-specific MRI bone models to dynamic biplane radiographic images, under the principles of Roentgen stereophotogrammetric analysis (RSA). Data processing was performed in a specific software developed in Matlab. RESULTS: Statistically significant differences (p < 0.05) were found for single leg squat along the frontal plane: ACL-deficient knees showed a more varus angle, especially at the highest knee flexion angles (40°-50° on average), compared to the contralateral knees. Furthermore, ACL-deficient knees showed tibial medialization along the entire task, while contralateral knees were always laterally aligned. This difference became statistically relevant (p < 0.05) for knee flexion angles included between 0° and about 30°. CONCLUSION: ACL-deficient knees showed an abnormal tibial medialization and increased varus angle during single leg squat when compared to the contralateral knees. These biomechanical anomalies could cause a different force distribution on tibial plateau, explaining the higher risk of early osteoarthritis in ACL deficiency. The clinical relevance of this study is that also safe activities used in ACL rehabilitation protocols are significantly altered in ACL deficiency. LEVEL OF EVIDENCE: III.

Dynamic knee valgus in competitive alpine skiers: Observation from youth to elite and influence of biological maturation.

Numerous studies investigated the association between dynamic knee valgus and injury risk in post-pubertal and elite athletes; however, normative reference scores for competitive alpine skiers and observations on the development process throughout and beyond athletes' growth spurt are lacking. Thus, the aim of this study was to describe the dynamic knee valgus of competitive alpine skiers during drop jump landings (DJ) and single-leg squats (SLS) with respect to sex, sportive level, and biological maturation. Thirty-seven elite and 104 youth competitive alpine skiers around the growth spurt (U15) were examined for their maximal medial knee displacement (MKD) during DJ and SLS by a marker-based 3D motion analysis evaluating dynamic knee valgus. Additionally, skiers' age, anthropometry and biological maturation were assessed. MKD of youth and elite alpine skiers during DJ was comparable and did not improve with increasing training age. Female U15 skiers (on average further matured) had significantly larger MKD values during DJ than male U15 skiers (less matured) (P < .01). Moreover, MKD during DJ was directly associated with the athlete's individual biological maturation status. MKD values obtained from DJ significantly differed from those obtained during SLS (P < .01). The gender-specific difference in MKD values during DJ and their relationship with maturity offset highlight the fundamental changes to the neuromuscular control system during the growth spurt. Thus, biological maturation needs to be considered as a confounding factor for knee valgus screening. Caution is required when evaluating MKD by using high- and low-dynamic tasks, as corresponding information can differ.

Validity of a New 3-D Motion Analysis Tool for the Assessment of Knee, Hip and Spine Joint Angles during the Single Leg Squat.

AIM: Study concurrent validity of a new sensor-based 3D motion capture (MoCap) tool to register knee, hip and spine joint angles during the single leg squat. DESIGN: Cross-sectional. SETTING: University laboratory. PARTICIPANTS: Forty-four physically active (Tegner ≥ 5) subjects (age 22.8 (±3.3)) Main outcome measures: Sagittal and frontal plane trunk, hip and knee angles at peak knee flexion. The sensor-based system consisted of 4 active (triaxial accelerometric, gyroscopic and geomagnetic) sensors wirelessly connected with an iPad. A conventional passive tracking 3D MoCap (OptiTrack) system served as gold standard. RESULTS: All sagittal plane measurement correlations observed were very strong for the knee and hip (r = 0.929-0.988, p < 0.001). For sagittal plane spine assessment, the correlations were moderate (r = 0.708-0.728, p < 0.001). Frontal plane measurement correlations were moderate in size for the hip (ρ = 0.646-0.818, p < 0.001) and spine (ρ = 0.613-0.827, p < 0.001). CONCLUSIONS: The 3-D MoCap tool has good to excellent criterion validity for sagittal and frontal plane angles occurring in the knee, hip and spine during the single leg squat. This allows bringing this type of easily accessible MoCap technology outside laboratory settings.

The Effect of Functional Knee Braces on Muscular Contributions to Joint Rotational Stiffness in Anterior Cruciate Ligament-Deficient and -Reconstructed Patients.

Functional knee braces are frequently prescribed by physicians to ameliorate the function of individuals with anterior cruciate ligament (ACL) injuries. These braces have been shown in the literature to potentially enhance knee stability by augmenting muscle activation patterns and the timing of muscle response to perturbations. However, very few techniques are available in the literature to quantify how those modifications in lower-limb muscle activity influence stability of the knee. The aim of the present study was to quantify the effect of an off-the-shelf functional knee brace on muscle contributions to knee joint rotational stiffness in ACL-deficient and ACL-reconstructed patients. Kinematic, electromyography, and kinetic data were incorporated into an electromyography-driven model of the lower extremity to calculate individual and total muscle contributions to knee joint rotational stiffness about the flexion-extension axis, for 4 independent variables: leg condition (contralateral uninjured, unbraced ACL injured, and braced ACL injured); knee flexion (5°-10°, 20°-25°, and 30°-35°); squat stability condition (stable and unstable); and injury status (ACL deficient and ACL reconstructed). Participants had significantly higher (P < .05, η2 = .018) total knee joint rotational stiffness values while wearing the brace compared with the control leg. A 2-way interaction effect between stability and knee flexion (P < .05, η2 = .040) for total joint rotational stiffness was also found.

The Role of Lumbopelvic-Hip Complex Stability in Softball Throwing Mechanics.

CONTEXT: Studies have found that a 20% reduction in energy generation from the lumbopelvic-hip complex during overhead throws leads to a 34% increase in load on the shoulder. OBJECTIVE: The purpose of this study was to assess the effects of lumbopelvic-hip complex stability, via the single leg squat assessment, on throwing mechanics of softball athletes. DESIGN: Prospective cohort study. SETTING: Laboratory setting. PARTICIPANTS: A total of 50 softball athletes (164.0 [104.0] cm, 65.6 [11.3] kg, 16.3 [3.8] y, 8.61 [3.62] y of experience) performed 3 overhead throws and a single leg squat on each leg. INTERVENTION: Four stability groups were derived: (1) stable on both legs (bilateral stability), (2) unstable on the throwing side leg (TS instability) and stable on the nonthrowing side leg, (3) unstable on the nonthrowing side leg (NTS instability) and stable on the throwing side leg, and (4) unstable on both legs (bilateral instability). All throws were analyzed across 4 throwing events: foot contact (FC), maximum external shoulder rotation (MER), ball release (BR), and maximum internal shoulder rotation (MIR). MAIN OUTCOME MEASURES: Mann-Whitney U tests revealed significant differences between the bilateral stability and the TS instability groups in trunk flexion at BR; the bilateral stability and the NTS instability groups in trunk flexion at BR, shoulder horizontal abduction at FC, shoulder rotation at FC, and pelvis flexion at MIR; the TS instability and the bilateral instability groups in trunk rotation at FC; and the NTS instability and the bilateral instability groups in trunk flexion at MER and shoulder rotation at FC. CONCLUSION: These findings demonstrate the different mechanisms in which energy can be lost through lumbopelvic-hip complex instability as evident in throwing mechanics. The findings from this study suggest that the current methods used for classification could act as a tool for coaches, physicians, and athletic trainers when assessing their athletes' injury susceptibility.

Evaluating gluteus maximus maximal voluntary isometric contractions for EMG normalization in male rugby players.

[Purpose] The aim of this study was to determine the highest electromyography (EMG) amplitude of the gluteus maximus from closed and open kinetic gluteal maximal voluntary isometric contractions (MVICs). [Participants and Methods] Ten healthy male rugby players performed three MVIC techniques that included, in random order: single leg squat, prone hip extension and standing gluteal squeeze. EMG signals were recorded from the inferior and superior regions of gluteus maximus of the dominant leg, and were normalized to the prone hip extension. [Results] For statistical analysis the EMG of both gluteus maximus regions were pooled together. The standing gluteal squeeze revealed a significantly lower EMG compared to single leg squat and prone hip extension. However, there was no significant difference in gluteal EMG activity between single leg squat and prone hip extension. [Conclusion] There is no distinct advantage for either single leg squat or prone hip extension in eliciting maximum EMG activity. Future research should compare the present positions with other MVICs that are commonly prescribed or have been demonstrated to produce high EMG amplitudes.

Peak patellar tendon force progressions during heavy load single-leg squats on level ground and decline board.

BACKGROUND: Progressive tendon loading programs for patellar tendinopathy typically include single-leg squats with heavy weights either on level ground or on a decline board. Changes in patellar tendon force due to variations of the heavy load single-leg squat have not yet been objectively quantified. The objective of this study was to investigate the influence of the mass of an external weight and the use of a decline board on the peak patellar tendon force during a heavy load single-leg squat. METHODS: Twelve healthy participants performed single-leg back squats on a decline board and level ground at 70%, 80% and 90% of their one repetition maximum. Three-dimensional kinematics and ground reaction forces were measured and the peak patellar tendon force was calculated using musculoskeletal modelling. A two-way repeated measures ANOVA determined the main effects for the mass of the external weights and the use of a decline board as well as their interaction effect. FINDINGS: Peak patellar tendon forces were significantly higher on the decline board compared to level ground (p < 0.05). Neither on the decline board, nor on level ground did the peak patellar tendon force increase significantly when increasing the external weights (p > 0.05). INTERPRETATION: Progression in peak patellar tendon forces during a heavy load single-leg squat can only be obtained with a decline board. Increasing the mass of the external weight from 70% to 90% of the one repetition maximum does not result in a progressively higher peak patellar tendon force.

Lower limb muscles' thicknesses are weakly associated with dynamic knee valgus during single-leg squat in women with patellofemoral pain.

INTRODUCTION: Patellofemoral pain (PFP) patients often show an altered lower limb alignment during the single-leg squat (SLS). There is evidence that proximal and distal-to-the-knee muscle alterations can modify the lower limb alignment in PFP patients. However, we observed a lack of studies investigating the possible association between the thickness and strength of proximal and distal-to-the-knee muscles and lower limb alignment during SLS in women with PFP. Therefore, this study aimed to investigate the association between the thickness and strength of lower limb muscles and dynamic knee valgus (DKV) during SLS in women with PFP. METHODS: Cross-sectional study, where fifty-five women with PFP were submitted to the following evaluations: (1) muscle thickness (MT) of Gluteus Medius (GMed), Gluteus Maximus (GMax), Vastus Lateralis (VL), and Tibialis Anterior (TA); (2) isometric peak torque of hip abductors, hip external rotators, knee extensors, and foot inversors; and (3) DKV during SLS. RESULTS: There was a significant negative association between GMax's MT and DKV (r = -0.32; p = 0.01), and between TA's MT and DKV (r = -0.28; p = 0.03). No significant correlations were observed between isometric torques and DKV. Regression analysis found that GMax's MT explained 10% of the DKV's variance during SLS. DISCUSSION: Poor lower limb alignment during SLS is weakly associated with proximal and distal-to-the-knee muscle thicknesses, with no association with isometric torque in PFP women. CONCLUSION: Our results suggest that other factors besides strength and muscle thicknesses may explain and improve lower limb alignment in women with PFP.

Dependence on visual information in patients with ACL injury for multi-joint coordination during single-leg squats: a case control study.

BACKGROUND: The influence of vision on multi-joint control during dynamic tasks in anterior cruciate ligament (ACL) deficient patients is unknown. Thus, the purpose of this study was to establish a new method for quantifying neuromuscular control by focusing on the variability of multi-joint movement under conditions with different visual information and to determine the cutoff for potential biomarkers of injury risk in ACL deficient individuals. METHODS: Twenty-three ACL deficient patients and 23 healthy subjects participated in this study. They performed single-leg squats under two different conditions: open eyes (OE) and closed eyes (CE). Multi-joint coordination was calculated with the coupling angle of hip flexion, hip abduction and knee flexion. Non-linear analyses were performed on the coupling angle. Dependence on vision was compared between groups by calculating the CE/OE index for each variable. Cutoff values were calculated using ROC curves with ACL injury as the dependent variable and significant variables as independent variables. RESULTS: The sample entropy of the coupling angle was increased in all groups under the CE condition (P < 0.001). The CE/OE index of coupling angle variability during the descending phase was higher in ACL deficient limbs than in the limbs of healthy participants (P = 0.036). The CE/OE index of sample entropy was higher in the uninjured limbs of ACL deficient patients than in the limbs of healthy participants (P = 0.027). The cutoff value of the CE/OE index of sample entropy was calculated to be 1.477 (Sensitivity 0.957, specificity 0.478). CONCLUSION: ACL deficient patients depended on vision to control multiple joint movements not only on the ACL deficient side but also on the uninjured side during single leg squat task. These findings underscore the importance of considering visual dependence in the assessment and rehabilitation of neuromuscular control in ACL deficient individuals.

A comprehensive two-dimensional scoring system to assess the single-leg squat task in football players.

BACKGROUND: The single-leg squat (SLS) is a safe and widespread functional test commonly performed in the mid-stages of rehabilitation after severe knee injuries. The use of reliable objective measures has been advocated to improve the quality of SLS assessment. The aim of this study was to describe a qualitative whole-body scoring system based on two-dimensional (2D) video analysis during SLS test and validate it against three-dimensional (3D) kinetics and kinematics. METHODS: Thirty-four competitive football (soccer) players performed a series of SLS tasks. 3D kinematics and kinetics were collected through infrared cameras, and 2D video analysis was performed through a scoring system with sub-scores ranging from 0/2 (non-adequate movement) to 2/2 (adequate movement) based on frontal and lateral planes objective measurements. 3D kinematics and kinetics were grouped according to the results of the 2D evaluation and compared through the analysis of variance (P < 0.05). RESULTS: Higher hip adduction, hip internalrotation, and knee valgus collapse were found in trials rated 0/2 or 1/2 compared with theone rated 2/2 in the limb stability score. Hip flexion and hip/knee moment ratio were lower in those scoring 0/2 comparedwith those scoring 2/2 in the movement strategy criterion. A low total score was associated with higherknee valgus collapse and lower hip/knee extensor moment ratio. Compensatory strategieswere found in frontal plane scores. CONCLUSIONS: The 2D scoring system described was strongly associated with kinematics and kinetics from gold-standard 3D motion capture and might represent a valid tool to describe the movement quality of an SLS task.

Dynamic Functional Ability in Lacrosse Players in Relation to Development of Sport-Related Onset of Musculoskeletal Pain.

Background: Unlike other sports, the relationship between performance deficits and pain/injury in lacrosse players has not been well-investigated. Purpose: The purposes of this study were to: 1) determine whether age and sex differences exist in dynamic physical function tests and drop jump performance among lacrosse players, and 2) determine whether pre-seasonal physical function scores predict onset of either lower extremity or low back pain over time. Study Design: Prospective observational study. Methods: Lacrosse players (N=128) were stratified into three groups: 12-14.9 yrs, 15-18 yrs and >18 yrs. Thomas test (hip flexibility), Ober's test (iliotibial band tightness), and Ely's test (rectus femoris tightness) were performed. Landing Error Scoring System (LESS) scores were collected while players performed drop jumps. Sagittal and frontal plane movement from 2D video during single and double legged squats was assessed. Musculoskeletal pain symptoms or injury were tracked for six months. Age bracket, sex and physical function scores were entered into logistic regression models to determine risk factors that predicted onset of lower extremity pain and low back pain onset. Results: LESS scores and single-leg squat movement quality test scores were lowest in the 12-14.9 yr groups and highest in the >18 yr group (all p<0.05). Single leg squat performance score increased the odds risk (OR) for lower extremity pain (OR=2.62 [95% CI 1.06-6.48], p=.038) and LESS scores elevated risk for low back pain onset over six months (OR = 2.09 [95% CI 1.07- 4.06], p= .031). Conclusions: LESS scores and single legged squat performance may help identify lacrosse players at risk for musculoskeletal pain or injury onset. Detecting these pertinent biomechanical errors and subsequently developing proper training programs could help prevent lower extremity and low back pain onset. Level of Evidence: III.

Intersession reliability of quadriceps corticospinal excitability: A functional transcranial magnetic stimulation study.

Recording transcranial magnetic stimulation-derived measures during a closed kinetic chain task can serve as a functional technique to assess corticomotor function, which may have implications for activities of daily living or lower extremity injury in physically active individuals. Given the novelty of TMS use in this way, our purpose was to first determine the intersession reliability of quadriceps corticospinal excitability during a single-leg squat. We used a descriptive laboratory study to assess 20 physically active females (22.1 ± 2.5 years, 1.7 ± 0.7 m, 66.3 ± 13.6 kg, Tegner Activity Scale: 5.90 ± 1.12) over a 14-day period. Two-way mixed effects Intraclass Correlation Coefficients (3,1) (ICC) for absolute agreement were used to assess intersession reliability. The active motor threshold (AMT) and normalized motor evoked potential (MEP) amplitudes were assessed in the vastus medialis of each limb. The dominant limb AMTs demonstrated moderate-to-good reliability (ICC = 0.771, 95% CI = 0.51-0.90; p < 0.001). The non-dominant limb AMTs (ICC = 0.364, 95% CI = 0.00-0.68, p = 0.047), dominant limb MEPs (ICC = 0.192, 95% CI = 0.00-0.71; p = 0.340), and non-dominant limb MEPs (ICC = 0.272, 95% CI = 0.00-0.71; p = 0.235) demonstrated poor-to-moderate reliability. These findings may provide insight into corticomotor function during activities requiring weight-bearing, single-leg movement. However, variability in agreement suggests further work is warranted to improve the standardization of this technique prior to incorporating in clinical outcomes research.

Association of Changes in Hip and Knee Kinematics During a Single-Leg Squat With Changes in Patient-Reported Outcomes at 6 Months and 1 Year After Hip Arthroscopy.

BACKGROUND: Previous studies have demonstrated alterations in squat kinematics in patients with femoroacetabular impingement syndrome (FAIS). Little is known about the effects of arthroscopic hip surgery on biomechanics during a single-leg squat (SLS) in these patients. PURPOSE/HYPOTHESIS: The purpose of this study was to determine if (1) lower extremity dynamic range of motion (ROM) during an SLS task improves after hip arthroscopy for FAIS and (2) correlations exist between changes in patient-reported outcomes (PROs) and changes in lower extremity dynamic ROM during an SLS after hip arthroscopy for FAIS. It was hypothesized that dynamic hip ROM would improve after hip arthroscopy and that hip dynamic ROM would be associated with changes in PRO scores at both 6 months and 1 year. STUDY DESIGN: Descriptive laboratory study. METHODS: Patients with FAIS performed 3 SLSs that were analyzed using a 20-camera motion capture system. Dynamic ROMs were calculated in 3 planes for the hip, knee, ankle, and pelvic segments. Squat depth was calculated as the change in vertical center of mass during the squat cycle. PROs including the Hip Outcome Score-Activities of Daily Living (HOS-ADL), Hip Outcome Score-Sports (HOS-Sports), International Hip Outcome Tool-12, and visual analog scale for pain scores were collected preoperatively and at the time of postoperative testing. Paired-samples t tests were used to compare kinematic variables pre- and postoperatively. Correlations were used to compare changes in PROs with changes in kinematics. All statistical analysis was performed using SPSS Version 26. RESULTS: Fifteen patients were tested preoperatively and at a mean of 9 months postoperatively. All PRO measures improved postoperatively at 6 months and 1 year. Squat depth and sagittal plane hip and knee dynamic ROMs were significantly improved postoperatively. Positive correlations existed between changes in (1) hip ROM with the 6-month HOS-ADL score (r = 0.665) and (2) knee ROM with the 6 month (r = 0.590) and 1-year (r = 0.565) HOS-Sports scores. CONCLUSION: Dynamic sagittal plane hip and knee ROMs improve after hip arthroscopy for FAIS. These improvements demonstrate strong correlations with improvements in some but not all postoperative PROs. CLINICAL RELEVANCE: The current study sought to better understand the role of dynamic movement in the diagnosis and treatment of FAIS. These findings indicate that dynamic ROM and squat depth can, similarly to PROs, serve as biomarkers for patient function both before and after hip arthroscopic surgery.

Kiss goodbye to the 'kissing knees': no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes.

The aim of this study was to investigate if frontal plane knee and hip control in single-leg squats or vertical drop jumps with an overhead target were associated with future non-contact anterior cruciate ligament (ACL) injury in elite female athletes. Of the 429 handball and 451 football athletes (age 21.5 ± 4.0 years, height 169.6 ± 6.4 cm, body weight 67.1 ± 8.0 kg), 722 non-injured and 56 non-contact ACL injured participants were eligible for analysis. We calculated lateral pelvic tilt, frontal plane knee projection angle, medial knee position, and side-to-side asymmetry in these from 2D videos recorded at baseline, and recorded any new ACL injuries prospectively. None of the aforementioned variables in either screening task were different or could discriminate between injured and non-injured athletes (all p values >.05 and Cohen's d values < .27). Two-dimensional video assessment of frontal plane knee and hip control during both a single-leg squat and vertical drop jump was unable to identify individuals at increased risk of non-contact ACL injury, thus should not be used for screening.

Changes to balance dynamics following a high-intensity run are associated with future injury occurrence in recreational runners.

Background: Fatigue is associated with increased injury risk along with changes in balance control and task performance. Musculoskeletal injury rates in runners are high and often result from an inability to adapt to the demands of exercise and a breakdown in the interaction among different biological systems. This study aimed to investigate whether changes in balance dynamics during a single-leg squat task following a high-intensity run could distinguish groups of recreational runners who did and did not sustain a running-related injury within 6 months. Methods: Thirty-one healthy recreational runners completed 60 s of single-leg squat before and after a high-intensity run. Six months after the assessment, this cohort was separated into two groups of 13 matched individuals with one group reporting injury within this period and the other not. Task performance was assessed by the number of repetitions, cycle time, amplitude, and speed. To evaluate balance dynamics, the regularity and temporal correlation structure of the center of mass (CoM) displacements in the transverse plane was analyzed. The interaction between groups (injury, non-injured) and time (pre, post) was assessed through a two-way ANOVA. Additionally, a one-way ANOVA investigated the percent change difference of each group across time. Results: The injured group presented more regular (reduced entropy; 15.6%) and diffusive (increased short-term persistence correlation; 5.6%) CoM displacements after a high-intensity run. No changes were observed in the non-injured group. The within-subject percent change was more sensitive in demonstrating the effects of fatigue and distinguishing the groups, compared to group absolute values. No differences were observed in task performance. Discussion: Runners who were injured in the future demonstrate changes in balance dynamics compared to runners who remain injury-free after fatigue. The single-leg squat test adopted appears to be a potential screening protocol that provides valuable information about balance dynamics for identifying a diminished ability to respond to training and exercise.

Reliability and Measurement Error of the Qualitative Analysis of Single Leg Loading (QASLS) Tool For Unilateral Tasks.

Background: Movement quality assessment is popular within clinical and sporting practice, due to the contribution diminished or suboptimal movement quality is believed to have on musculoskeletal (MSK) injury risk. Various movement quality assessments exist, many are limited to bilateral or jumping movements evaluation. Qualitative analysis of single leg loading (QASLS) is a new clinical assessment tool for unilateral tasks that utilizes a dichotomous scoring system of ten questions relating to the segmental body regions of the trunk, lower and upper limb. Purpose: To determine the intra and inter-rater, within- and between-session reliability of the QASLS tool during two unilateral movement tasks, and provide insight to measurement error and smallest detectable difference (SDD). Study Design: Reliability Study. Methods: Fifteen healthy females (mean age 19 years SD2; height 167 cm, +/- 6; weight 56 kg, +/- 6) completed two unilateral tasks, single leg squat (SLS) and single leg landing (SLL), within session data collection occurred on the same day, with between session data collection occurring seven days later. Tasks were scored with the QASLS tool via video playback. Intra-Class correlation coefficients (ICCk,3) were used to measure within and between session reliability, and Kappa coefficients and percentage of exact agreement (PEA%) were used to determine intra and inter-rater reliability. Standard error of measurement (SEM) and the SDD for the compound score of each limb was calculated. Results: Within session reliability of QASLS scores was good (ICC = 0.82-0.86) for SLS and moderate (ICC = 0.67-0.87) for SLL. Between session reliability was moderate (ICC = 0.69-0.87) for SLS and excellent (ICC = 0.92-0.93) for SLL. SEM was less than 1 point, and SDD for compound score ranging from 1.0-2.5 points. Intra-rater agreement of compound QASLS score was near perfect (k = 0.85-100; PEA% 90-100%) and agreement of individual components was substantial- near perfect (k = 0.13-0.74; PEA% 78-100%). Inter-rater agreement for compound QASLS scores ranged from non-substantial (k = 0.13-0.74; PEA% 43.3-90%) for SLS and non-slight (k =0.03-0.17; PEA% 43.3-60%) for SLL. Conclusions: The QASLS movement analysis tool can be used to analyze movement quality during two unilateral loading tasks with moderate to excellent within and between session reliability. PEA% was acceptable for inter-rater agreement, however rater education training is recommended to develop more acceptable levels of reliability. Level of Evidence: 3.

Correlation between lower limb and trunk muscle endurance with drop vertical jump in the special military forces.

OBJECTIVE: Police officers, particularly the ones who are trained to be on "special forces", perform a wide range of hazardous and physically demanding activities when aiming to protect and serve. The purpose of this study was to investigate the association between lower limb and trunk muscle endurance with drop vertical jump (DVJ) height in a special military police force. METHODS: One hundred and three male military men (age: 36 ± 5.0 years; height: 1.76 ± 0.05 m; weight: 81.8 ± 9.7 kg) volunteered to take part in this study. SIX TESTS WERE PERFORMED: DVJ, McGill core battery (trunk flexion, trunk extension, and side bridge test-right and left), and single-leg squat repetitions. Correlations were analyzed using the Pearson correlation coefficient (r). The level of significance for all analyses was set at p ≤ 0.05. RESULTS: Single-leg squat repetitions were positively associated with DVJ height, contact time and flight time (p = 0.00093∗∗, p = 0.00085∗∗, and p = 0.00098∗∗ respectively). No correlation was observed between trunk muscle endurance and DVJ. CONCLUSION: Therefore, it was concluded that greater endurance of the lower limb muscles, as demonstrated by the single leg squat, was associated with better performance in a DVJ. Individuals should consider incorporating single leg squats into their fitness program to develop muscular endurance and possibly perform better in the DVJ.

Detection of knee wobbling as a screen to identify athletes who may be at high risk for ACL injury.

This study developed a method to detect knee wobbling (KW) at low knee flexion. KW consists of quick uncontrollable medio-lateral knee movements without knee flexion, which may indicate a risk of ACL injury. Ten female athletes were recorded while performing slow, single-leg squats. Using motion capture data, the ratio of the frontal angular velocity to sagittal angular velocity (F/S) was calculated. An 'F/S spike' was defined when the F/S ratio exceeded 100%. The number of F/S spikes was counted before and after low-pass filtering at different cut-off frequencies. Intraclass correlation coefficients for KW and filtered F/S spike were analysed. KWs per squat cycle showed a median (range) of 3 (2-8) times. F/S spikes before and after low-pass filtering at 3-, 6-, 10-, and 15-Hz were 51 (12-108), 2 (0-6), 3 (1-12), 5 (2-21), and 9 (3-33) times, respectively. KWs and F/S spikes on motion capture with 6-Hz, low-pass filtering were well correlated (r = 0 .76). Median percentages of valgus and varus F/S spikes were 71% and 29%, respectively. After 6Hz, low-pass filtering, the number of F/S spikes was strongly correlated with observed KWs. An F/S spike assessment may be used to objectively detect KW, including flexion and varus/valgus angular velocity.