Does It Matter? Isometric or Isokinetic Assessment of Quadriceps Strength Symmetry 9 Months After ACLR in Collegiate Athletes.

BACKGROUND: Greater quadriceps strength symmetry is associated with better outcomes after anterior cruciate ligament reconstruction (ACLR). Isometric and isokinetic assessments of quadriceps strength inform therapeutic exercise prescription and return-to-sport decisions. It is unclear whether isometric and isokinetic measures provide similar information post-ACLR. HYPOTHESIS: Quadriceps strength symmetry is similar between isometric and isokinetic assessments. Isokinetic and isometric strength symmetries have similar associations to functional knee kinetics and self-reported knee function. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: NCAA Division I athletes (N = 35), 8.9 ± 2.5 months post-ACLR completed isometric and isokinetic quadriceps strength assessments, countermovement jumps (CMJs), and treadmill running. Self-reported knee function was assessed using the International Knee Documentation Committee Subjective Knee Form (IKDC). Agreement between isometric and isokinetic strength symmetry was assessed using Bland-Altman analysis, with associations to functional knee kinetics and IKDC assessed using Pearson correlations and linear regressions. RESULTS: Mean difference in quadriceps strength symmetry between isokinetic and isometric assessments was 1.0% (95% limits of agreement of -25.1% to 23.0%). Functional knee kinetics during running and CMJ were moderately to strongly associated with isometric strength symmetry (r = 0.64-0.80, P < 0.01) and moderately associated with isokinetic strength symmetry (r = 0.41-0.58, P < 0.01). IKDC scores were weakly to moderately associated with isometric (r = 0.39, P = 0.02) and isokinetic (r = 0.49, P < 0.01) strength symmetry. CONCLUSION: Isokinetic and isometric assessments of quadriceps strength symmetry in collegiate athletes 9 months post-ACLR demonstrated strong agreement. Quadriceps strength symmetry is associated with functional knee kinetic symmetry post-ACLR. CLINICAL RELEVANCE: Considerable individual variation suggests mode of contraction should be consistent throughout postoperative assessment. Isometric strength symmetry may be a better indicator of functional knee kinetic symmetry, while isokinetic strength symmetry may be associated more closely with patient-reported outcomes.

Effect of Running Speed on Knee Biomechanics in Collegiate Athletes Following Anterior Cruciate Ligament Reconstruction.

INTRODUCTION: Athletes post-anterior cruciate ligament reconstruction (ACLR) demonstrate altered surgical knee running kinematics and kinetics compared to the non-surgical limb and healthy controls. The effect of running speed on biomechanics has not been formally assessed in athletes post-ACLR. The purpose of this study was to characterize how knee biomechanics change with running speed between 3.5-7 (EARLY) and 8-13 (LATE) months post-ACLR. METHODS: Fifty-five Division I collegiate athletes post-ACLR completed running analyses (EARLY: n = 40, LATE: n = 41, both: n = 26) at 2.68, 2.95, 3.35, 3.80 and 4.47 m/s. Linear mixed effects models assessed the influence of limb, speed, time post-ACLR, and their interactions on knee kinematics and kinetics. RESULTS: A significant limb*speed interaction was detected for peak knee flexion, knee flexion excursion, and rate of knee extensor moment (p-values <0.02), controlling for time. From 3.35 to 4.47 m/s knee flexion excursion decreased -2.3° (95% CI: -3.6, -1.0) in the non-surgical limb and -1.0° (95% CI: -2.3, -0.3) in the surgical limb. Peak vertical ground reaction force, peak knee extensor moment, and knee negative work increased similarly with speed for both limbs (p-values <0.002). A significant limb*time interaction was detected for all variables (p-values <0.001). Accounting for running speed, improvements in all surgical limb biomechanics were observed from EARLY to LATE (p-values <0.001), except for knee flexion at initial contact (p = 0.12), but between-limb differences remained (p-values <0.001). CONCLUSIONS: Surgical and non-surgical knee biomechanics increase similarly with speed in collegiate athletes at EARLY and LATE, with the exception of peak knee flexion, knee flexion excursion, and rate of knee extensor moment. Surgical knee biomechanics improved from EARLY and LATE, but significant between-limb differences persisted.

Diffusion tensor imaging of hamstring muscles after acute strain injury and throughout recovery in collegiate athletes.

OBJECTIVE: To identify the region of interest (ROI) to represent injury and observe between-limb diffusion tensor imaging (DTI) microstructural differences in muscle following hamstring strain injury. MATERIALS AND METHODS: Participants who sustained a hamstring strain injury prospectively underwent 3T-MRI of bilateral thighs using T1, T2, and diffusion-weighted imaging at time of injury (TOI), return to sport (RTS), and 12 weeks after RTS (12wks). ROIs were using the hyperintense region on a T2-weighted sequence: edema, focused edema, and primary muscle injured excluding edema (no edema). Linear mixed-effects models were used to compare diffusion parameters between ROIs and timepoints and limbs and timepoints. RESULTS: Twenty-four participants (29 injuries) were included. A significant ROI-by-timepoint interaction was detected for all diffusivity measures. The edema and focused edema ROIs demonstrated increased diffusion at TOI compared to RTS for all diffusivity measures (p-values < 0.006), except λ1 (p-values = 0.058-0.12), and compared to 12wks (p-values < 0.02). In the no edema ROI, differences in diffusivity measures were not observed (p-values > 0.82). At TOI, no edema ROI diffusivity measures were lower than the edema ROI (p-values < 0.001) but not at RTS or 12wks (p-values > 0.69). A significant limb-by-timepoint interaction was detected for all diffusivity measures with increased diffusion in the involved limb at TOI (p-values < 0.001) but not at RTS or 12wks (p-values > 0.42). Significant differences in fractional anisotropy over time or between limbs were not detected. CONCLUSION: Hyperintensity on T2-weighted imaging used to define the injured region holds promise in describing muscle microstructure following hamstring strain injury by demonstrating between-limb differences at TOI but not at follow-up timepoints.

Ultrasound shear wave seeds reduced following hamstring strain injury but not after returning to sport.

OBJECTIVES: The purpose of the study was to investigate differences in ultrasound shear wave speed (SWS) between uninjured and injured limbs following hamstring strain injury (HSI) at time of injury (TOI), return to sport (RTS), and 12 weeks after RTS (12wks). METHODS: This observational, prospective, cross-sectional design included male and female collegiate athletes who sustained an HSI. SWS imaging was performed at TOI, RTS, and 12wks with magnetic resonance imaging. SWS maps were acquired by a musculoskeletal-trained sonographer at the injury location of the injured limb and location-matched on the contralateral limb. The average SWS from three 5 mm diameter Q-boxes on each limb were used for analysis. A linear mixed effects model was performed to determine differences in SWS between limbs across the study time points. RESULTS: SWS was lower in the injured limb compared to the contralateral limb at TOI (uninjured - injured limb difference: 0.23 [0.05, 0.41] m/s, p = 0.006). No between-limb differences in SWS were observed at RTS (0.15 [-0.05, 0.36] m/s, p = 0.23) or 12wks (-0.11 [-0.41, 0.18] m/s, p = 0.84). CONCLUSIONS: The SWS in the injured limb of collegiate athletes after HSI was lower compared to the uninjured limb at TOI but not at RTS or 12 weeks after RTS. CRITICAL RELEVANCE STATEMENT: Hamstring strain injury with structural disruption can be detected by lower injured limb shear wave speed compared to the uninjured limb. Lack of between-limb differences at return to sport may demonstrate changes consistent with healing. Shear wave speed may complement traditional ultrasound or MRI for monitoring muscle injury. KEY POINTS: • Ultrasound shear wave speed can non-invasively measure tissue elasticity in muscle injury locations. • Injured limb time of injury shear wave speeds were lower versus uninjured limb but not thereafter. • Null return to sport shear wave speed differences may correspond to structural changes associated with healing. • Shear wave speed may provide quantitative measures for monitoring muscle elasticity during recovery.

Association of quantitative diffusion tensor imaging measures with time to return to sport and reinjury incidence following acute hamstring strain injury.

Hamstring strain injuries (HSI) are a common occurrence in athletics and complicated by limited prognostic indicators and high rates of reinjury. Assessment of injury characteristics at the time of injury (TOI) may be used to manage athlete expectations for time to return to sport (RTS) and mitigate reinjury risk. Magnetic resonance imaging (MRI) is routinely used in soft tissue injury management, but its prognostic value for HSI is widely debated. Recent advancements in musculoskeletal MRI, such as diffusion tensor imaging (DTI), have allowed for quantitative measures of muscle microstructure assessment. The purpose of this study was to determine the association of TOI MRI-based measures, including the British Athletic Muscle Injury Classification (BAMIC) system, edema volume, and DTI metrics, with time to RTS and reinjury incidence. Negative binomial regressions and generalized estimating equations were used to determine relationships between imaging measures and time to RTS and reinjury, respectively. Twenty-six index injuries were observed, with five recorded reinjuries. A significant association was not detected between BAMIC score and edema volume at TOI with days to RTS (p-values ≥ 0.15) or reinjury (p-values ≥ 0.13). Similarly, a significant association between DTI metrics and days to RTS was not detected (p-values ≥ 0.11). Although diffusivity metrics are expected to increase following injury, decreased values were observed in those who reinjured (mean diffusivity, p = 0.016; radial diffusivity, p = 0.02; principal effective diffusivity eigenvalues, p-values = 0.007-0.057). Additional work to further understand the directional relationship observed between DTI metrics and reinjury status and the influence of external factors is warranted.

Cross cultural adaptation, reliability and validity of the Persian version of the university of Wisconsin running injury and recovery index.

BACKGROUND: The University of Wisconsin Running Injury and Recovery Index (UWRI) was developed to evaluate running ability after a running-related injury. The aim of this study was to translate and cross-culturally adapt the UWRI into Persian (UWRI-Persian) and to investigate its psychometric properties in patients with a running-related injury. METHODS: The UWRI-Persian was translated using the Beaton guidelines. One hundred and seventy-three native Persian patients with running-related injuries were participated in the study. The exploratory factor analysis was carried out using the principal component analysis method with Varimax rotation. The construct validity of the UWRI-Persian was evaluated using the Pearson correlation with the pain self-efficacy questionnaire (PSEQ), Tampa scale for Kinesiophobia (TKS), and visual analogue scale (VAS). Test-retest reliability was tested among 64 patients who completed the form again after seven days. RESULTS: The UWRI-Persian showed excellent internal consistency for total score (α = 0.966). An excellent internal consistency (α = 0.922) was shown for psychological response and good internal consistency (α = 0.887) for running progression. The interclass correlation coefficient for the UWRI-Persian total scores was 0.965 (95% CI, 0.942 to 0.979), indicating high intra-rater reliability. The UWRI-Persian showed a moderate correlation with the PSEQ (r = 0.425) and the TSK (r = 0.457) and a weak correlation with the VAS (r = 0.187). These findings suggest no floor or ceiling effects. CONCLUSIONS: The UWRI is a reliable and valid tool for Persian-speaking patients with running-related injuries. The UWRI was successfully translated from English to Persian and demonstrated good to excellent internal consistency, validity and reliability with no floor or ceiling effects.

MRI radiomics for hamstring strain injury identification and return to sport classification: a pilot study.

OBJECTIVE: To determine if MRI-based radiomics from hamstring muscles are related to injury and if the features could be used to perform a time to return to sport (RTS) classification. We hypothesize that radiomics from hamstring muscles, especially T2-weighted and diffusion tensor imaging-based features, are related to injury and can be used for RTS classification. SUBJECTS AND METHODS: MRI data from 32 athletes at the University of Wisconsin-Madison that sustained a hamstring strain injury were collected. Diffusion tensor imaging and T1- and T2-weighted images were processed, and diffusion maps were calculated. Radiomics features were extracted from the four hamstring muscles in each limb and for each MRI modality, individually. Feature selection was performed and multiple support vector classifiers were cross-validated to differentiate between involved and uninvolved limbs and perform binary (≤ or > 25 days) and multiclass (< 14 vs. 14-42 vs. > 42 days) classification of RTS. RESULT: The combination of radiomics features from all diffusion tensor imaging and T2-weighted images provided the most accurate differentiation between involved and uninvolved limbs (AUC ≈ 0.84 ± 0.16). For the binary RTS classification, the combination of all extracted radiomics offered the most accurate classification (AUC ≈ 0.95 ± 0.15). While for the multiclass RTS classification, the combination of features from all the diffusion tensor imaging maps provided the most accurate classification (weighted one vs. rest AUC ≈ 0.81 ± 0.16). CONCLUSION: This pilot study demonstrated that radiomics features from hamstring muscles are related to injury and have the potential to predict RTS.

Preinjury Knee and Ankle Mechanics during Running Are Reduced among Collegiate Runners Who Develop Achilles Tendinopathy.

INTRODUCTION: Achilles tendinopathies (AT) are common in runners, but prospective data assessing running mechanics associated with developing AT are limited. Asymmetry in running mechanics is also considered a risk factor for injury, although it is unknown if the problematic mechanics occur on the injured limb only or are present bilaterally. PURPOSE: This study aimed to prospectively identify differences in preinjury running biomechanics in collegiate runners who did and did not develop AT and determine if between-limb asymmetries were associated with which limb developed AT. METHODS: Running gait data were obtained preseason on healthy collegiate cross-country runners, and AT incidence was prospectively recorded each year. Spatiotemporal, ground reaction forces, and joint kinematics and kinetics were analyzed. Linear mixed-effects models assessed differences in biomechanics between those who did and did not develop AT during the subsequent year. Generalized linear mixed-effects models determined if the asymmetry direction was associated with which limb developed an AT, with odds ratios (OR) and 95% confidence intervals (95% CI) reported. RESULTS: Data from 106 runners were analyzed and 15 developed AT. Preinjury biomechanics of runners who developed AT showed less peak knee flexion (noninjured: 45.9° (45.2°-46.6°), injured: 43.2° (41.5°-44.9°), P < 0.001), ankle dorsiflexion (noninjured: 28.7° (28.0°-30.2°), injured: 26.0° (23.8°-28.3°), P = 0.01), and knee extensor moment (noninjured: -2.18 (N·m)·kg -1 (-2.24 to -2.12 (N·m)·kg -1 ), injured: -2.00 (N·m)·kg -1 (-2.17 to -1.84 (N·m)·kg -1 ), P = 0.02). The limb demonstrating less peak knee flexion had greater odds of sustaining an AT (OR, 1.29 (1.00-1.65), P = 0.05). CONCLUSIONS: Knee and ankle kinematics, in addition to knee kinetics, were associated with developing an AT. Monitoring these mechanics may be useful for prospectively identifying runners at risk of developing AT.

Risk Factors for Running-Related Injury in High School and Collegiate Cross-country Runners: A Systematic Review.

OBJECTIVE: To summarize and describe risk factors for running-related injuries (RRIs) among high school and collegiate cross-country runners. DESIGN: Descriptive systematic review. LITERATURE SEARCH: Four databases (Scopus, SPORTDiscus, CINAHL, Cochrane) were searched from inception to August 2023. STUDY SELECTION CRITERIA: Studies assessing RRI risk factors in high school or collegiate runners using a prospective design with at least 1 season of follow-up were included. DATA SYNTHESIS: Results across each study for a given risk factor were summarized and described. The NOS and GRADE frameworks were used to evaluate quality of each study and certainty of evidence for each risk factor. RESULTS: Twenty-four studies were included. Overall, study quality and certainty of evidence were low to moderate. Females or runners with prior RRI or increased RED-S (relative energy deficiency in sport) risk factors were most at risk for RRI, as were runners with a quadriceps angle of >20° and lower step rates. Runners with weaker thigh muscle groups had increased risk of anterior knee pain. Certainty of evidence regarding training, sleep, and specialization was low, but suggests that changes in training volume, poorer sleep, and increased specialization may increase RRI risk. CONCLUSION: The strongest predictors of RRI in high school and collegiate cross-country runners were sex and RRI history, which are nonmodifiable. There was moderate certainty that increased RED-S risk factors increased RRI risk, particularly bone stress injuries. There was limited evidence that changes in training and sleep quality influenced RRI risk, but these are modifiable factors that should be studied further in this population. J Orthop Sports Phys Ther 2024;54(2):1-13. Epub 16 November 2023. doi:10.2519/jospt.2023.11550.

Changes in Sleep, Stress, and Fatigue Were Not Prospectively Associated With Running-Related Injuries Among High School Cross Country Runners.

BACKGROUND: Running-related injuries (RRI) are common among adolescent runners; however, our understanding of RRI risk factors in this population is limited. Sleep, stress, and fatigue are risk factors in other youth sports but have not been studied in high school runners. This study prospectively assessed the effect of changes in sleep duration and quality, stress, and fatigue on RRI among high school cross country runners. HYPOTHESIS: Less and poorer quality sleep and greater stress and fatigue, compared with the previous week, would be associated with RRI. STUDY DESIGN: Prospective, observational study. LEVEL OF EVIDENCE: Level 2b. METHODS: Runners completed a preseason demographics and injury history survey and daily surveys regarding sleep duration and quality, stress, fatigue, and current RRI. Values were summed within each week, and change scores were calculated relative to the previous week. Runners completing ≥75% of daily surveys were analyzed; sensitivity analyses for those completing ≥50% and ≥90% were also conducted. Generalized estimating equations assessed the association between change in each predictor, including its interaction with sex, and RRI, controlling for year in school, previous RRI, and repeated observations. RESULTS: A total of 434 runners enrolled in the study; 161 (37%) completed ≥75% of daily surveys. No associations between change in sleep duration, sleep quality, or fatigue and RRI were observed (P values ≥0.24). A significant change in stress × sex interaction with RRI was observed (P < 0.01). Associations among boys (P = 0.06) and girls (P = 0.07) were marginally significant. Sensitivity results were similar. CONCLUSION: Short-term changes in sleep duration, quality, and fatigue were not associated with RRI, but a significant interaction between change in stress and sex suggests that stress may influence RRI risk in high school cross country runners. CLINICAL RELEVANCE: Large changes in stress levels should be monitored throughout the season, as these changes may precede RRI occurrence in this population.

Validity of Inertial Measurement Units to Measure Lower-Limb Kinematics and Pelvic Orientation at Submaximal and Maximal Effort Running Speeds.

Inertial measurement units (IMUs) have been validated for measuring sagittal plane lower-limb kinematics during moderate-speed running, but their accuracy at maximal speeds remains less understood. This study aimed to assess IMU measurement accuracy during high-speed running and maximal effort sprinting on a curved non-motorized treadmill using discrete (Bland-Altman analysis) and continuous (root mean square error [RMSE], normalised RMSE, Pearson correlation, and statistical parametric mapping analysis [SPM]) metrics. The hip, knee, and ankle flexions and the pelvic orientation (tilt, obliquity, and rotation) were captured concurrently from both IMU and optical motion capture systems, as 20 participants ran steadily at 70%, 80%, 90%, and 100% of their maximal effort sprinting speed (5.36 ± 0.55, 6.02 ± 0.60, 6.66 ± 0.71, and 7.09 ± 0.73 m/s, respectively). Bland-Altman analysis indicated a systematic bias within ±1° for the peak pelvic tilt, rotation, and lower-limb kinematics and -3.3° to -4.1° for the pelvic obliquity. The SPM analysis demonstrated a good agreement in the hip and knee flexion angles for most phases of the stride cycle, albeit with significant differences noted around the ipsilateral toe-off. The RMSE ranged from 4.3° (pelvic obliquity at 70% speed) to 7.8° (hip flexion at 100% speed). Correlation coefficients ranged from 0.44 (pelvic tilt at 90%) to 0.99 (hip and knee flexions at all speeds). Running speed minimally but significantly affected the RMSE for the hip and ankle flexions. The present IMU system is effective for measuring lower-limb kinematics during sprinting, but the pelvic orientation estimation was less accurate.

Preseason Vertical Center of Mass Displacement During Running and Bone Mineral Density Z-Score Are Risk Factors for Bone Stress Injury Risk in Collegiate Cross-country Runners.

OBJECTIVES: To (1) assess relationships between running biomechanics, bone health, and bone stress injuries (BSIs), and (2) determine which variables constitute the most parsimonious BSI risk model among collegiate cross-country runners. DESIGN: Prospective, observational cohort study. METHODS: Running gait and bone mineral density (BMD) data from healthy collegiate cross-country runners were collected at preseason over 6 seasons. A generalized estimating equation model with backward selection was used to develop the most parsimonious model for estimating BSI risk, controlling for sex, running speed, and prior BSI. The variables assessed were spatiotemporal, ground reaction force, and joint kinematics, based on previous literature. Quasi-likelihood under the independence model criterion values and R2 values were used to select the best-fitting model. RESULTS: Data from 103 runners were included in the analysis. The best-fitting model included vertical center of mass (COM) displacement and BMD z-score. Injury risk increased with greater vertical COM displacement (unit = 0.5 cm; relative risk [RR] = 1.14; 95% confidence interval [CI]: 1.01, 1.29; P = .04) and decreased with greater BMD z-score (unit = 0.5; RR = 0.83; 95% CI: 0.72, 0.95; P = .007). The model performed similarly when step rate was included instead of vertical COM displacement. CONCLUSION: Vertical COM displacement and BMD z-score contributed to the best model for estimating risk the risk of bone stress injury in cross-country runners. Step rate was also an important variable for assessing injury risk. J Orthop Sports Phys Ther 2023;53(12):1-8. Epub 20 October 2023. doi:10.2519/jospt.2023.11860.

A hierarchical clustering approach for examining the relationship between pelvis-proximal femur geometry and bone stress injury in runners.

Bone stress injury (BSI) risk in runners is multifactorial and not well understood. Unsupervised machine learning approaches can potentially elucidate risk factors for BSI by identifying groups of similar runners within a population which differ in BSI incidence. Here, a hierarchical clustering approach is used to identify groups of collegiate cross country runners based on 2-dimensional frontal plane pelvis and proximal femur geometry, which was extracted from dual-energy X-ray absorptiometry scans and dimensionally reduced by principal component analysis. Seven distinct groups were identified using the cluster tree, with the initial split being highly related to female-male differences. Visual inspection revealed clear differences between groups in pelvis and proximal femur geometry, and groups were found to differ in lower body BSI incidence during the subsequent academic year (Rand index = 0.53; adjusted Rand index = 0.07). Linear models showed between-cluster differences in visually identified geometric measures. Geometric measures were aggregated into a pelvis shape factor based on trends with BSI incidence, and the resulting shape factor was significantly different between clusters (p < 0.001). Lower shape factor values, corresponding with lower pelvis height and ischial span, and greater iliac span and trochanteric span, appeared to be related to increased BSI incidence. This trend was dominated by the effect observed across clusters of male runners, indicating that geometric effects may be more relevant to BSI risk in males, or that other factors masked the relationship in females. More broadly, this work outlines a methodological approach for distilling complex geometric differences into simple metrics that relate to injury risk.

The Influence of Quadriceps Strength and Rate of Torque Development on the Recovery of Knee Biomechanics During Running After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: After anterior cruciate ligament reconstruction (ACLR), altered surgical knee biomechanics during running is common. Although greater quadriceps strength is associated with more symmetrical running knee kinetics after ACLR, abnormal running mechanics persist even after resolution of quadriceps strength deficits. As running is a submaximal effort task characterized by limited time to develop knee extensor torque, quadriceps rate of torque development (RTD) may be more closely associated with recovery of running knee mechanics than peak torque (PT). PURPOSE: To assess the influence of recovery in quadriceps PT and RTD symmetry on knee kinematic and kinetic symmetry during running over the initial 2 years after ACLR. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 39 Division I collegiate athletes (106 testing sessions; 19 female) completed serial isometric performance testing and running analyses between 3 and 24 months after ACLR. Athletes performed maximal and rapid isometric knee extension efforts with each limb to assess PT and RTD between-limb symmetry indices (PTLSI and RTDLSI), respectively. Peak knee flexion difference (PKFDIFF) and peak knee extensor moment limb symmetry index (PKEMLSI) during running were computed. Multivariable linear mixed-effects models assessed the influence of PTLSI and RTDLSI on PKFDIFF and PKEMLSI over the initial 2 years after ACLR. RESULTS: Significant main effects of RTDLSI (P < .001) and time (P≤ .02) but not PTLSI (P≥ .24) were observed for both PKFDIFF and PKEMLSI models. For a 10% increase in RTDLSI, while controlling for PTLSI and time, a 0.9° (95% CI, 0.5°-1.3°) reduction in PKFDIFF and a 3.5% (95% CI, 1.9%-5.1%) increase in PKEMLSI are expected. For every month after ACLR, a 0.2° (95% CI, 0.1°-0.4°) reduction in PKFDIFF and a 1.3% (95% CI, 0.6%-2.0%) increase in PKEMLSI are expected, controlling for PTLSI and RTDLSI. CONCLUSION: Quadriceps RTDLSI was more strongly associated with symmetrical knee biomechanics during running compared with PTLSI or time throughout the first 2 years after ACLR.

Influence of ultrasound machine settings on quantitative measures derived from spatial frequency analysis of muscle tissue.

BACKGROUND: Ultrasound is a powerful tool for diagnostic purposes and provides insight into both normal and pathologic tissue structure. Spatial frequency analysis (SFA) methods characterize musculoskeletal tissue organization from ultrasound images. Both sonographers in clinical imaging and researchers may alter a minimized range of ultrasound settings to optimize image quality, and it is important to know how these small adjustments of these settings affect SFA parameters. The purpose of this study was to investigate the effects of making small adjustments in a typical default ultrasound machine setting on extracted spatial frequency parameters (peak spatial frequency radius (PSFR), Mmax, Mmax%, and Sum) in the biceps femoris muscle. METHODS: Longitudinal B-mode images were collected from the biceps femoris muscle in 36 participants. The window depth, foci locations, and gain were systematically adjusted consistent with clinical imaging procedures for a total of 27 images per participant. Images were analyzed by identifying a region of interest (ROI) in the middle portion of the muscle belly in a template image and using a normalized two-dimensional cross-correlation technique between the template image and subsequent images. The ROI was analyzed in the frequency domain using conventional SFA methods. Separate linear mixed effects models were run for each extracted parameter. RESULTS: PSFR was affected by modifications in focus location only (p < 0.001) with differences noted between all locations. Mmax% was influenced by the interaction of gain and focus location (p < 0.001) but was also independently affected by increasing window depth (p < 0.001). Both Mmax and Sum parameters were sensitive to small changes in machine settings with the interaction of focus location and window depth (p < 0.001 for both parameters) as well as window depth and gain (p < 0.001 for both) influencing the extracted values. CONCLUSIONS: Frequently adjusted imaging settings influence some SFA statistics. PSFR and Mmax% appear to be most robust to small changes in image settings, making them best suited for comparison across individuals and between studies, which is appealing for the clinical utility of the SFA method.

The effects of hip- vs. knee-dominant hamstring exercise on biceps femoris morphology, strength, and sprint performance: a randomized intervention trial protocol.

BACKGROUND: The hamstrings are an important muscle group that contribute to horizontal force during sprint acceleration and are also the most injured muscle group in running-based sports. Given the significant time loss associated with hamstrings injury and impaired sprinting performance following return to sport, identifying exercises that drive adaptations that are both protective of strain injury and beneficial to sprint performance is important for the strength and conditioning professional. This paper describes the study protocol investigating the effects of a 6-week training program using either the hip-dominant Romanian deadlift (RDL) or the knee-dominant Nordic hamstring exercise (NHE) on hamstring strain injury risk factors and sprint performance. METHODS: A permuted block randomized (1:1 allocation) intervention trial will be conducted involving young, physically-active men and women. A target sample size of 32 will be recruited and enrolled participants will undergo baseline testing involving extended-field-of-view ultrasound imaging and shear wave elastography of the biceps femoris long head muscle, maximal hamstrings strength testing in both the RDL and NHE, and on-field sprint performance and biomechanics. Participants will complete the 6-week training intervention using either the RDL or NHE, according to group allocation. Baseline testing will be repeated at the end of the 6-week intervention followed by 2 weeks of detraining and a final testing session. The primary outcome will be regional changes in fascicle length with secondary outcomes including pennation angle, muscle cross sectional area, hamstring strength, and maximal sprint performance and biomechanics. An exploratory aim will determine changes in shear wave velocity. DISCUSSION: Despite extensive research showing the benefits of the NHE on reducing hamstring strain injury risk, alternative exercises, such as the RDL, may offer similar or potentially even greater benefits. The findings of this study will aim to inform future researchers and practitioners investigating alternatives to the NHE, such as the RDL, in terms of their effectiveness in reducing rates of hamstring strain injury in larger scale prospective intervention studies. TRIAL REGISTRATION: The trial is prospectively registered on ClinicalTrials.gov (NCT05455346; July 15, 2022).

Cross-Cultural Adaptation of the University of Wisconsin Running Injury and Recovery Index in Turkish Runners.

CONTEXT: The University of Wisconsin Running Injury and Recovery Index (UWRI) was developed to evaluate the key elements that runners use to self-assess their own running ability following common running-related injuries. The aim of this study was to translate and culturally adapt the UWRI and to evaluate the psychometric properties of its Turkish version (UWRI-Tr) in runners. DESIGN: Prospective cohort study. METHODS: The study included 129 runners. The UWRI-Tr, the Lower Extremity Functional Scale, the Oswestry Disability Index, the Hip Outcome Score, the International Knee Documentation Committee Subjective Knee Evaluation Form, and the Foot and Ankle Ability Measure were applied for the validation purposes. Internal consistency, reliability, construct validity, and discriminant validity of the UWRI-Tr were tested. RESULTS: The test-retest reliability of the UWRI-Tr was excellent with an intraclass correlation coefficient of .85 and a Cronbach α value of .84. There was a small to strong correlation among the UWRI-Tr and Lower Extremity Functional Scale (r = .278), Oswestry Disability Index (r = -.744), Hip Outcome Score (r = .684), The International Knee Documentation Committee Subjective Knee Evaluation Form (r = .758), and Foot and Ankle Ability Measure (r = .498 and .767), indicating that its construct validity was appropriate for use with Turkish runners. CONCLUSIONS: The UWRI-Tr was shown to be a valid and reliable tool to use in clinical and research settings as a sport-specific measurement tool.

Preferred temporal-spatial parameters, physical maturation, and sex are related to vertical and braking forces in adolescent long-distance runners.

For adults, increasing cadence reduces ground reaction forces, but a lower preferred cadence does not predispose adults to experience higher ground reaction forces. Pubertal growth and motor control changes influence running mechanics, but it is unknown if preferred cadence or step length are associated with ground reaction forces for pre-adolescent and adolescent runners. Pre-adolescent and adolescent runners underwent an overground running analysis at a self-selected speed. Mixed model multiple linear regressions investigated the associations of preferred cadence, step length, physical maturation, and sex on ground reaction forces, while accounting for running speed and leg length. Running with a lower preferred cadence or longer preferred step length was associated with larger peak braking and vertical forces (p ≤ .01), being less physically mature was associated with larger vertical impact peak force and vertical loading rate (p ≤ .01), and being a male was associated with larger loading rates (p ≤ .01). A lower preferred cadence or longer preferred step length were associated with higher braking and vertical forces and being less physically mature or a male were associated with higher loading rates. An intervention to increase cadence/decrease step length could be considered if ground reaction forces are a concern for an adolescent runner.

Quadriceps Performance and Running Biomechanics Influence Femur BMD Changes after ACL Reconstruction in Collegiate Athletes.

PURPOSE: Reduced bone mineral density of the distal femur (BMD DF ) can persist long term after anterior cruciate ligament reconstruction (ACLR), even in athletes who return to high levels of competition. These deficits may have implications for the onset and progression of knee osteoarthritis. It is unknown if clinically modifiable factors are associated with losses in BMD DF . This study evaluated the potential influence of knee extensor peak torque (PT), rate of torque development (RTD), as well as peak knee flexion (PKF) angle and peak knee extensor moment (PKEM) during running, on longitudinal changes in BMD DF post-ACLR. METHODS: After ACLR, 57 Division I collegiate athletes underwent serial whole-body dual-energy x-ray absorptiometry (DXA) scans between 3 and 24 months post-ACLR. Of these, 43 athletes also had isometric knee extensor testing (21 female, 105 observations), and 54 had running analyses (26 female, 141 observations). Linear mixed-effects models, controlling for sex, assessed the influence of surgical limb quadriceps performance (PT and RTD), running mechanics (PKF and PKEM), and time post-ACLR on BMD DF (5% and 15% of femur length). Simple slope analyses were used to explore interactions. RESULTS: Athletes with RTD less than 7.20 (N·m)·kg -1 ·s -1 (mean) at 9.3 months post-ACLR demonstrated significant decreases in 15% BMD DF over time ( P = 0.03). Athletes with PKEM during running less than 0.92 (N·m)·kg -1 (-1 SD below mean) at 9.8 months post-ACLR demonstrated significant decreases in 15% BMD DF over time ( P = 0.02). Significant slopes were not detected at -1 SD below the mean for PT (1.75 (N·m)·kg -1 , P = 0.07) and PKF (31.3°, P = 0.08). CONCLUSIONS: Worse quadriceps RTD and running PKEM were associated with a greater loss of BMD DF between 3 and 24 months post-ACLR.