Effects of Aging on Patellofemoral Joint Stress during Stair Negotiation on Challenging Surfaces.

This study examined the effect of age and surface on patellofemoral joint (PFJ) stress magnitude and waveform during stair ascent and descent tasks. A total of 12 young and 12 older adults had knee biomechanics quantified while they ascended and descended stairs on normal, slick, and uneven surfaces. The peak of stance (0-100%) PFJ stress and associated components were submitted to a two-way repeated measures ANOVA, while the PFJ stress waveform was submitted to statistical parametric mapping two-way ANOVA. During stair ascent, older adults exhibited greater PFJ stress waveforms, from 55 to 59% and 74 to 84% of stance (p < 0.001) as well as greater PFJ stress-time integral across stance (p = 0.003), and later peak PFJ stress, than young adults (p = 0.002). When ascending on the uneven surface, participants exhibited smaller PFJ stress from 9 to 24% of stance compared to the normal surface, but greater PFJ stress from 75 to 88% and from 63 to 68% of stance (p < 0.001) as well as greater PFJ stress-time integrals compared to normal and slick surfaces (p < 0.032). During stair descent, older adults exhibited a smaller PFJ contact area range (p = 0.034) and peak knee flexion angle (p = 0.022) than young adults. When descending on the slick surface, participants exhibited smaller PFJ stress from 5 to 18% of stance, but greater stress, from 92 to 98% of stance (both: p < 0.001), compared to the normal surface. Negotiating slick and uneven stairs may produce knee biomechanics that increase PFJ stress, and the larger, later PFJ stress exhibited by older adults may further increase their risk of PFJ pain.

Knee muscle strength and steadiness for individuals with anterior cruciate ligament reconstruction and knee osteoarthritis.

BACKGROUND: Strength and neuromuscular decrements following knee musculoskeletal injury may accelerate knee osteoarthritis development. This study assessed isometric knee extensor and flexor strength and steadiness between individuals with knee injury, i.e., ligament reconstruction, and knee osteoarthritis to healthy age-matched controls. METHODS: Four cohorts (1: knee injury and 2: age-matched controls, and 3: radiographic knee osteoarthritis and 4: age-matched controls) were recruited. Participants performed maximal voluntary isometric knee extensor and flexor contractions. Then, strength (e.g., peak and rate of torque development) and steadiness (e.g., peak power, mean, and median frequency) were derived from each raw torque-time curve and associated power spectral density. A Kruskal-Wallis H test and Spearman's rho correlation analysis assessed cohort differences and association between knee extensor and flexor strength and steadiness. FINDINGS: The young adult control and knee injury cohorts exhibited greater knee extensor and flexor strength than the older, knee osteoarthritis cohort (p < 0.043). The knee injury cohort, despite being as strong as their healthy counterparts, were significantly less steady with a 92% increase in peak power frequency (p = 0.046). The osteoarthritis cohort exhibited 157% less total power compared to the knee injury and young control cohorts (p < 0.019). Knee extensor and flexor peak torque, rate of torque development, and mean torque exhibit a significant, positive relation with total power (p < 0.018). INTERPRETATION: Individuals with knee injury and disease may exhibit weaker or less steady knee musculature, predisposing them to degenerative joint disease. Clinicians may need to restore knee extensor and flexor steadiness to facilitate better joint neuromuscular control.

Effect of age on ankle biomechanics and tibial compression during stair descent.

BACKGROUND: Stress fracture is a concern among older adults, as age-related decrements in ankle neuromuscular function may impair their ability to attenuate tibial compressive forces experienced during daily locomotor tasks, such as stair descent. Yet, it is unknown if older adults exhibit greater tibial compression than their younger counterparts when descending stairs. RESEARCH QUESTION: Do older adults exhibit differences in ankle biomechanics that alter their tibial compression during stair descent compared to young adults, and is there a relation between tibial compression and specific changes in ankle biomechanics? METHODS: Thirteen young (18-25 years) and 13 older (> 65 years) adults had ankle joint biomechanics and tibial compression quantified during a stair descent. Discrete ankle biomechanics (peak joint angle and moment, and joint stiffness) and tibial compression (maximum and impulse) measures were submitted to an independent t-test, while ankle joint angle and moment, and tibial compression waveforms were submitted to an independent statistical parametric mapping t-test to determine group differences. Pearson correlation coefficients (r) determined the relation between discrete ankle biomechanics and tibial compression measures for all participants, and each group. RESULTS: Older adults exhibited smaller maximum tibial compression (p = 0.004) from decreases in peak ankle joint angle and moment between 17 % and 34 % (p = 0.035), and 20-31 % of stance (p < 0.001) than young adults. Ankle biomechanics exhibited a negligible to weak correlation with tibial compression for all participants, with peak ankle joint moment and maximum tibial compression (r = -0.48 ±â€¯0.32) relation the strongest. Older adults typically exhibited a stronger relation between ankle biomechanics and tibial compression (e.g., r = -0.48 ±â€¯0.47 vs r = -0.27 ±â€¯0.52 between peak ankle joint moment and maximum tibial compression). SIGNIFICANCE: Older adults altered ankle biomechanics and decreased maximum tibial compression to safely execute the stair descent. Yet, specific alterations in ankle biomechanics could not be identified as a predictor of changes in tibial compression.

Balloon atrial septostomy versus left atrial cannulation for left heart decompression in children with dilated cardiomyopathy and myocarditis on extracorporeal membrane oxygenation: An ELSO registry analysis.

INTRODUCTION: In children with myocarditis or dilated cardiomyopathy (DCM) on extracorporeal membrane oxygenation (ECMO) for cardiogenic shock, it is often necessary to decompress the left heart to minimize distension and promote myocardial recovery. We compare outcomes in those who underwent balloon atrial septostomy (BAS) versus direct left atrial (LA) drainage for left heart decompression in this population. METHODS: Retrospective study of the Extracorporeal Life Support Organization (ELSO) multicenter registry of patients ≤ 18 years with myocarditis or DCM on ECMO who underwent LA decompression. Descriptive and univariate statistics assessed association of patient factors with decompression type. Multivariable logistic regression sought independent associations with outcomes. RESULTS: 369 pediatric ECMO runs were identified. 52% myocarditis, 48% DCM, overall survival 74%. 65% underwent BAS and 35% LA drainage. Patient demographics including age, weight, gender, race/ethnicity, diagnosis, pre-ECMO pH, mean airway pressure, and arrest status were similar. 89% in the BAS group were peripherally cannulated onto ECMO, versus 3% in the LA drainage group (p < .001). On multivariable analysis, LA drainage (OR 3.96; 95% CI, 1.47-10.711; p = .007), renal complication (OR 2.37; 95% CI, 1.41-4.01; p = .001), cardiac complication (OR 3.14; 95% CI, 1.70-5.82; p < .001), and non-white race/ethnicity (OR 1.75; 95% CI, 1.04-2.94; p = .035) were associated with greater odds of mortality. There was a trend toward more episodes of pulmonary hemorrhage in BAS (n = 17) versus LA drainage group (n = 3), p = .08. Comparing only those with central cannulation, LA drainage group was more likely to be discontinued from ECMO due to recovery (72%) versus the BAS group (48%), p = .032. CONCLUSIONS: In children with myocarditis or DCM, there was a three times greater likelihood for mortality with LA drainage versus BAS for LA decompression. When adjusted for central cannulation groups only, there was better recovery in the LA drainage group and no difference in mortality. Further prospective evaluation is warranted.

Association of Digoxin Use With Transplant-Free Interstage Survival in Infants Palliated With a Stage 1 Hybrid Procedure.

Background Digoxin prescription in patients with single-ventricle physiology after stage 1 palliation is associated with reduced interstage death. Prior literature has primarily included patients having undergone the Norwood procedure. We sought to determine if digoxin prescription at discharge in infants following hybrid stage 1 palliation was associated with improved transplant-free interstage survival. Methods and Results A retrospective multicenter cohort analysis was conducted using data from the National Pediatric Cardiology Quality Improvement Collaborative registry data from 2008 to 2021. Infants with functional single ventricles and aortic arch obstruction discharged home after the hybrid stage 1 palliation hospitalization were included. Patients were excluded if they had supraventricular tachycardia or conversion to Norwood operation. The primary outcome was transplant-free survival. Multivariable logistic regression analysis including a propensity score for digoxin use identified associations between digoxin use and interstage death or transplant. Of 259 included infants from 45 sites, 158 (61%) had hypoplastic left heart syndrome. Forty-nine percent had a gestational age ≤38 weeks, 18% had a birth weight <2.5 kg, and 58% had a preoperative risk factor. Of the 259 subjects, 129 (50%) were discharged on digoxin. Interstage death or transplant occurred in 30 (23%) patients in the no-digoxin group compared with 18 (14%) in the digoxin group (P=0.06). With multivariate analysis, discharge digoxin prescription was associated with a lower risk of interstage death or transplant (adjusted odds ratio, 0.48 [95% CI, 0.24-0.93]; P=0.03). Conclusions In infants with single-ventricle physiology who underwent hybrid stage 1 palliation, digoxin prescription at hospital discharge was associated with improved interstage transplant-free survival.

Surface, but Not Age, Impacts Lower Limb Joint Work during Walking and Stair Ascent.

Older adults often suffer an accidental fall when navigating challenging surfaces during common locomotor tasks, such as walking and ascending stairs. This study examined the effect of slick and uneven surfaces on lower limb joint work in older and younger adults while walking and ascending stairs. Fifteen young (18-25 years) and 12 older (>65 years) adults had stance phase positive limb and joint work quantified during walking and stair ascent tasks on a normal, slick, and uneven surface, which was then submitted to a two-way mixed model ANOVA for analysis. The stair ascent required greater limb, and hip, knee, and ankle work than walking (all p < 0.001), with participants producing greater hip and knee work during both the walk and stair ascent (both p < 0.001). Surface, but not age, impacted positive limb work. Participants increased limb (p < 0.001), hip (p = 0.010), and knee (p < 0.001) positive work when walking over the challenging surfaces, and increased hip (p = 0.015), knee (p < 0.001), and ankle (p = 0.010) work when ascending stairs with challenging surfaces. Traversing a challenging surface during both walking and stair ascent tasks required greater work production from the large proximal hip and knee musculature, which may increase the likelihood of an accidental fall in older adults.

Right ventricular dysfunction in patients with acute respiratory distress syndrome receiving venovenous extracorporeal membrane oxygenation.

Acute respiratory distress syndrome is characterized by non-cardiogenic pulmonary edema, decreased pulmonary compliance, and abnormalities in gas exchange, especially hypoxemia. Patients with acute respiratory distress syndrome (ARDS) who receive support with venovenous (V-V) extracorporeal membrane oxygenation (ECMO) usually have severe lung disease. Many patients with ARDS have associated pulmonary vascular injury which can result in elevated pulmonary vascular resistance and right heart dysfunction. Since V-V ECMO relies upon preserved cardiac function, right heart failure has important implications for patient evaluation, management, and outcomes. Worsening right heart function complicates ARDS and disease processes. Given the increasing use of ECMO to support patients with ARDS, an understanding of right ventricular-ECMO and cardiopulmonary interactions is essential for the clinician. A narrative review of the manifestations of right heart dysfunction, as well as diagnosis and management strategies for the patient with ARDS on ECMO, is provided.

Improvement in Multidisciplinary Provider Rounding (Surgical Rounds) in the Pediatric Cardiac ICU: An Application of Lean Methodology.

OBJECTIVES: Provider-only, combined surgical, and medical multidisciplinary rounds ("surgical rounds") are essential to achieve optimal outcomes in large pediatric cardiac ICUs. Lean methodology was applied with the aims of identifying areas of waste and nonvalue-added work within the surgical rounds process. Thereby, the goals were to improve rounding efficiency and reduce rounding duration while not sacrificing critical patient care discussion nor delaying bedside rounds or surgical start times. DESIGN: Single-center improvement science study with observational and interventional phases from February 2, 2021, to July 31, 2021. SETTING: Tertiary pediatric cardiac ICU. PARTICIPANTS: Cardiothoracic surgery and cardiac intensive care team members participating in daily "surgical" rounds. INTERVENTIONS: Implementation of technology automation, creation of work instructions, standardization of patient presentation content and order, provider training, and novel role assignment. MEASUREMENTS AND MAIN RESULTS: Sixty-one multidisciplinary rounds were observed (30 pre, 31 postintervention). During the preintervention period, identified inefficiencies included prolonged preparation time, redundant work, presentation variability and extraneous information, and frequent provider transitions. Application of targeted interventions resulted in a 26% decrease in indexed rounds duration (2.42 vs 1.8 min; p = 0.0003), 50% decrease in indexed rounds preparation time (0.53 vs 0.27 min; p < 0.0001), and 66% decrease in transition time between patients (0.09 vs 0.03 min; p < 0.0001). The number of presenting provider changes also decreased (9 vs 4; p < 0.0001). Indexed discussion duration did not change (1 vs 0.98 min; p = 0.08) nor did balancing measures (bedside rounds and surgical start times) change (8.5 vs 9 min; p = 0.89 and 38 vs 22 min; p = 0.09). CONCLUSIONS: Lean methodology can be effectively applied to multidisciplinary rounds in a joint cardiothoracic surgery/cardiac intensive care setting to decrease waste and inefficiency. Interventions resulted in decreased preparation time, transition time, presenting provider changes, total rounds duration indexed to patient census, and anecdotal improvements in provider satisfaction.

Musculoskeletal adaptation of young and older adults in response to challenging surface conditions.

Over 36 million adults over 65 years of age experience accidental falls each year. The underlying neuromechanics (whole-body function) and driving forces behind accidental falls, as well as the effects of aging on the ability of the musculoskeletal system to adapt, are poorly understood. We evaluated differences in kinematics (lower extremity joint angles and range of motion), kinetics (ground reaction force), and electromyography (muscle co-contraction), due to changes in surface conditions during gait in 14 older adults with a history of falling and 14 young adults. We investigated the impact of challenging surfaces on musculoskeletal adaptation and compared the mechanisms of adaptation between age-groups. Older adults displayed greater hip and knee flexion and range of motion during gait, reduced initial vertical loading, and 13 % greater knee muscle co-contraction during early stance compared to young adults. Across age groups, the presence of an uneven challenging surface increased lower-limb flexion compared to an even surface. On a slick surface, older adults displayed 30 % greater ankle muscle co-contraction during early stance as compared to young adults. Older adults respond to challenging surfaces differently than their younger counterparts, employing greater flexion during early stance. This study underscores the need for determining lower-limb musculoskeletal adaptation strategies during gait and assessing how these strategies change with age, risk of accidental falls, and environmental surfaces to reduce the risk of accidental falls.

Tibial compression during sustained walking with body borne load.

This study determined if sustained walking with body borne load increases tibial compression, and whether increases in tibial compression are related to vertical GRFs. Thirteen participants had tibial compression and vertical GRF measures quantified while walking at 1.3 m/s for 60 min with body borne load. Each tibial compression (maximum and impulse) and GRF measure (peak, impulse, impact peak and loading rate) were submitted to a RM ANOVA to test the main effect and interaction between load (0, 15, and 30 kg) and time (minute 0, 30 and 60), and correlation analyses determined the relation between tibial compression and vertical GRF measures for each load and time. Each tibial compression and GRF measure increased with the addition of body borne load (all: p < 0.001). Time impacted impact peak (p = 0.034) and loading rate (p = 0.017), but no other GRF or tibial compression measure (p > 0.05). Although both tibial compression and vertical GRFs increased with load, vertical GRF measures exhibited negligible to weak (r: -0.37 to 0.35), and weak to moderate (r: -0.62 to 0.59) relation with maximum and impulse of tibial compression with each body borne load. At each time point, GRF measures exhibited negligible to weak (r: -0.39 to 0.27), and weak to moderate (r: -0.53 to 0.65) relation with maximum and impulse of tibial compression, respectively. Walking with body borne load increased tibial compression, and may place compressive forces on the tibia that lead to stress fracture. But, increases in tibial compression may not stem from concurrent increases in vertical GRFs.

Digoxin Associated With Greater Transplant-Free Survival in High- vs Low-Risk Interstage Patients.

BACKGROUND: Digoxin has been associated with reduced interstage mortality for patients with functional single ventricles with aortic hypoplasia or ductal-dependent systemic circulation. The NEONATE (type of stage 1 palliation operation, postoperative extracorporeal membrane oxygenation, discharge with opiates, no digoxin at discharge, postoperative arch obstruction, moderate to severe tricuspid regurgitation without an oxygen requirement, and extra oxygen required at discharge in patients with moderate to severe tricuspid regurgitation) score can stratify patients by risk of death or transplantation (DTx) on the basis of clinical factors. The study investigators suspected a variable transplant-free survival benefit of digoxin in high-risk vs low-risk patients. METHODS: National Pediatric Cardiology Quality Improvement Collaborative patients discharged after stage 1 palliation with complete data were categorized as high- or low-risk on the basis of a modified NEONATE score. The primary outcome of DTx was evaluated. A mixed-effect regression evaluated associations between digoxin prescription and risk factors. RESULTS: A total of 1199 patients were included; 399 (33%) were high risk. Baseline demographics were similar between the cohorts. Blalock-Taussig shunt or a hybrid operation, postoperative extracorporeal membrane oxygenation, opiate prescription, and significant tricuspid regurgitation or arch obstruction were more common in high-risk patients. The odds of DTx were 65% lower in high-risk patients prescribed digoxin compared with patients who were not (P = .001). Digoxin prescription was associated with 60.8% lower DTx in the high-risk cohort (7.8% vs 19.9%; P = .001). There was no significant difference in the DTx rate according to digoxin prescription in the low-risk cohort (4.7% vs 5.7%; P = .46). Blalock-Taussig shunt, aortic arch obstruction, and significant tricuspid regurgitation were most strongly associated with deriving a benefit from digoxin. CONCLUSIONS: Digoxin use is associated with significant improvement in transplant-free survival in high-risk but not in low-risk interstage patients. A tailored approach to the use of digoxin in interstage patients may be warranted.

Sex and Stride Impact Joint Stiffness During Loaded Running.

This study determined changes in lower limb joint stiffness when running with body-borne load, and whether they differ with stride or sex. Twenty males and 16 females had joint stiffness quantified when running (4.0 m/s) with body-borne load (20, 25, 30, and 35 kg) and 3 stride lengths (preferred or 15% longer and shorter). Lower limb joint stiffness, flexion range of motion (RoM), and peak flexion moment were submitted to a mixed-model analysis of variance. Knee and ankle stiffness increased 19% and 6% with load (P < .001, P = .049), but decreased 8% and 6% as stride lengthened (P = .004, P < .001). Decreased knee RoM (P < .001, 0.9°-2.7°) and increased knee (P = .007, up to 0.12 N.m/kg.m) and ankle (P = .013, up to 0.03 N.m/kg.m) flexion moment may stiffen joints with load. Greater knee (P < .001, 4.7°-5.4°) and ankle (P < .001, 2.6°-7.2°) flexion RoM may increase joint compliance with longer strides. Females exhibited 15% stiffer knee (P = .025) from larger reductions in knee RoM (4.3°-5.4°) with load than males (P < .004). Stiffer lower limb joints may elevate injury risk while running with load, especially for females.

Effects of prolonged load carriage on angular jerk of frontal and sagittal knee motion.

BACKGROUND: During training, service members routinely walk with heavy body borne loads for long periods of time. These loads alter knee biomechanics and may produce jerky knee motions that reportedly increase joint loading and risk of musculoskeletal injury. Yet, it is unknown if service members use jerky knee motions during prolong walking with body borne load. RESEARCH QUESTION: To quantify the effects of body borne load and duration of walking on the jerkiness of sagittal and frontal plane knee motion. METHODS: Eighteen participants had angular jerk of knee motion quantified while they walked (1.3 m/s) for 60-min with three body borne loads (0, 15, and 30 kg). Peak and cost of angular jerk for sagittal and frontal plane knee motion was quantified and submitted to a repeated measures linear model to test the main effects and interaction of load (0, 15, and 30 kg) and time (0, 15, 30, 45, and 60 min). RESULTS: Body borne load increased peak and cost of angular jerk for sagittal plane knee motion up to 35 % and 110 %, respectively, and frontal plane knee motion up to 20 % and 51 %, respectively (all p<0.001), while jerk cost of frontal plane knee motion (p=0.001) increased 31 % after walking 45 min. SIGNIFICANCE: Body borne load produced large (between 20 % and 110 %), incremental increases in angular jerk for both sagittal and frontal plane knee motion; whereas, duration of walking led to a 31 % increase in jerkiness of frontal plane knee motion. Service members who often walking for long periods of time with heavy body borne loads may have greater risk of developing musculoskeletal injury and disease due to large increases in jerky knee motions.

Effects of prolonged walking with body borne load on knee adduction biomechanics.

BACKGROUND: Soldiers that suffer a service-related knee musculoskeletal injury routinely develop joint osteoarthritis. Knee osteoarthritis is a substantial and costly problem among soldiers, yet it is unknown how body borne load and duration of walking impact knee adduction biomechanics linked to progression and severity of osteoarthritis. RESEARCH QUESTION: This study determined the adaptations in magnitude and variability of knee adduction joint angle (KAA) and moment (KAM) during prolonged walking with body borne load. METHODS: Thirteen recreationally active participants had knee biomechanics quantified while walking over-ground for 60-min at 1.3 m/s with three body borne loads (0, 15, and 30 kg). Magnitude and variability of KAA and KAM measures were quantified and submitted to a RM ANOVA to test the main effect and interactions between load (0, 15 and 30 kg) and time (0, 15, 30, 45 and 60 min). RESULTS: Body borne load increased peak KAM (p < 0.001), whereas time increased peak and range of KAA (both: p < 0.001). Specifically, peak KAM increased with each addition of body borne load (all: p < 0.025), and peak and range of KAA increased after 30 min of walking (both: p < 0.040). Neither body borne load, nor time had a significant effect on KAA or KAM variability (both: p > 0.05). SIGNIFICANCE: Prolonged walking with heavy body borne load increased knee adduction biomechanics related to osteoarthritis. Adding heavy body borne load increased in peak KAM whereas duration of walking increased KAA, knee biomechanics that may increase loading of the medial knee joint compartment and risk of OA at the joint.

Lower-Limb Biomechanics Differ Between Sexes During Maximal Loaded Countermovement Jumps.

ABSTRACT: Fain, AC, Semore, KD, Lobb, NJ, and Brown, TN. Lower-limb biomechanics differ between sexes during maximal loaded countermovement jumps. J Strength Cond Res 35(2): 325-331, 2021-To improve military personnel's operational performance, this study determined the impact of heavy, military body-borne load on vertical jump performance. Twenty men and 17 women had lower-limb work and power quantified during a series of countermovement jumps with 4 body-borne loads (20, 25, 30, and 35 kg). For each jump, subjects stood in athletic position with feet shoulder-width apart, then squatted down and immediately performed a maximal-effort vertical jump. Subjects performed 3 successful jumps with each load. During each jump, limb and hip, knee and ankle work and power, each joint's contribution to limb work, as well as jump height and center of mass velocity were quantified. Each dependent measure was submitted to a 2-way repeated-meausres analysis of variance, with alpha level 0.05. Body-borne load reduced jump height (p = 0.001) but increased ankle work (p < 0.001). To jump higher (p < 0.001) with a greater center of mass velocity (p = 0.001), men produced more limb work (p < 0.001), hip (p = 0.001; p < 0.001), knee (p < 0.001; p < 0.001), and ankle (p < 0.001; p < 0.001) joint power and work. But, women produced a greater percentage of work at the ankle (p = 0.020) than men. Military practitioners may target different training adaptations to improve male and female personnel operational performance because lower-limb biomechanics differ between sexes during loaded vertical jumps.

Association Between Knee Anatomic Metrics and Biomechanics for Male Soldiers Landing With Load.

BACKGROUND: Anterior cruciate ligament (ACL) injury is a military occupational hazard that may be attributed to an individual's knee biomechanics and joint anatomy. This study sought to determine if greater flexion when landing with load resulted in knee biomechanics thought to decrease ACL injury risk and whether knee biomechanics during landing relate to knee anatomic metrics. HYPOTHESIS: Anatomic metrics regarding the slope and concavity of the tibial plateau will exhibit a significant relation to the increased anterior shear force on the knee and decreased knee flexion posture during landing with body-borne load. STUDY DESIGN: Descriptive laboratory study. METHODS: Twenty male military personnel completed a drop landing task with 3 load conditions: light (~6 kg), medium (15% body weight), and heavy (30% body weight). Participants were divided into groups based on knee flexion exhibited when landing with the heavy load (high- and low-Δflexion). Tibial slopes and depth were measured on weightbearing volumetric images of the knee obtained with a prototype cone beam computed tomography system. Knee biomechanics were submitted to a linear mixed model to evaluate the effect of landing group and load, with the anatomic metrics considered covariates. RESULTS: Load increased peak proximal anterior tibial shear force (P = .034), knee flexion angle (P = .024), and moment (P = .001) during landing. Only the high flexion group increased knee flexion (P < .001) during weighted landings with medium and heavy loads. The low flexion group used greater knee abduction angle (P = .030) and peak proximal anterior tibial shear force (P = .034) when landing with load. Anatomic metrics did not differ between groups, but ratio of medial-to-lateral tibial slope and medial tibial depth predicted peak proximal anterior tibial shear force (P = .009) and knee flexion (P = .034) during landing, respectively. CONCLUSION: Increasing knee flexion is an attainable strategy to mitigate risk of ACL injury, but certain individuals may be predisposed to knee forces and biomechanics that load the ACL during weighted landings. CLINICAL RELEVANCE: The ability to screen individuals for anatomic metrics that predict knee flexion may identify soldiers and athletes who require additional training to mitigate the risk of lower extremity injury.

Effect of Sex and Ankle Brace Design on Knee Biomechanics During a Single-Leg Cut.

BACKGROUND: Despite success at preventing ankle sprain, prophylactics that restrict ankle plantarflexion motion may produce deleterious knee biomechanics and increase injury risk. PURPOSE: To determine if ankle prophylactics that restrict plantar- and dorsiflexion motion produce changes in knee biomechanics during a single-leg cut and whether those changes differ between sexes. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 17 male and 17 female participants performed a single-leg cut with 4 conditions: Ankle Roll Guard (ARG), lace-up brace, nonelastic tape, and an unbraced control. Peak stance knee flexion, abduction, and internal rotation joint angle and moment; total knee reaction moment (TKM) and its components (sagittal, frontal, and transverse); and ankle plantarflexion and inversion range of motion (ROM) and peak stance joint moments were tested with a repeated measures analysis of variance to determine the main effect and interaction of condition and sex. RESULTS: Brace and tape restricted plantarflexion ROM as compared with ARG and control (all P < .001). With the brace, women had increased peak knee abduction angle versus ARG (P = .012) and control (P = .009), and men had decreased peak knee internal rotation moment as compared with ARG (P = .032), control (P = .006), and tape (P = .003). Although the restrictive tape decreased inversion ROM when compared with ARG (P = .004) and brace (P = .017), it did not change knee biomechanics. Neither brace nor tape produced significant changes in TKM or components, yet sagittal TKM increased with ARG versus control (P = .016). Women exhibited less ankle inversion ROM (P = .003) and moment (P = .049) than men, while men exhibited significantly greater frontal TKM (P = .022) and knee internal rotation moment with the ARG (P = .029), control (P = .007), and tape (P = .016). CONCLUSION: Prophylactics that restrict ankle plantarflexion motion may elicit knee biomechanical changes during a single-leg cut, but these changes may depend on prophylactic design and user's sex and may increase women's injury risk. CLINICAL RELEVANCE: Sex-specific ankle prophylactic designs may be warranted to reduce knee injury during sports.

Effectiveness of Novel Ankle Prophylactic Compared With Lace-Up Brace or Tape.

CONTEXT: Conventional ankle prophylactics restrict harmful ankle inversion motions that lead to injury. But these existing prophylactics also limit other ankle motions, potentially leading to detriments in functional joint capacity. The ankle roll guard (ARG) may alleviate the prevailing issues of existing ankle prophylactics and prevent harmful ankle inversion, while allowing other joint motions. OBJECTIVE: This technical report sought to compare the ARG's ability to prevent ankle inversion, but not restrict other ankle motions with existing prophylactics. DESIGN: Repeated-measures study. SETTING: Motion capture laboratory. PARTICIPANTS: Thirty participants. INTERVENTION: Each participant had dominant limb ankle kinematics recorded during 5 successful trials of a sudden inversion event and 30-cm drop landing task with each of 4 conditions (ARG, ASO ankle stabilizer [brace], closed-basket weave athletic tape [tape], and unbraced [control]). MAIN OUTCOME MEASURES: Peak ankle inversion angle, range of inversion motion (ROM), and time to peak inversion during the sudden inversion event, and ankle plantar- and dorsiflexion ROM during the drop landing were submitted to a 1-way repeated-measures analysis of variance to test the main effect of prophylaxis. RESULTS: Participants exhibited greater inversion ROM with control compared with tape (P = .001), and greater plantar- and dorsiflexion ROM with ARG and control compared with brace (P = .02, P = .001) and tape (P = .02, P < .001). It took significantly longer to reach peak ankle inversion with brace and tape compared with ARG (P < .001, P = .001) and control (P = .01, P = .01). No significant difference in peak ankle inversion was observed between any condition (P > .05). CONCLUSION: The ARG may prevent ankle inversion angles where injury is thought to occur (reportedly >41°), but is less restrictive than existing prophylactics. The less restrictive ARG may make its use ideal during rehabilitation as it allows ankle plantar- and dorsiflexion motions, while preventing inversion related to injury.

Sex and limb differences during a single-leg cut with body borne load.

BACKGROUND: Military personnel don body borne loads that produce maladaptive lower limb biomechanics, increasing risk of musculoskeletal injury during common training tasks. Female personnel have over twice the injury risk as males, but it is unknown if a sex dimorphism in lower limb biomechanics exists during common training-related tasks. RESEARCH QUESTION: To determine whether lower limb biomechanics exhibited during a single-leg cut with military body borne loads differ between sexes. METHODS: Sixteen females and 20 males had lower limb biomechanics quantified during five single-leg cuts off each limb with four loads (20, 25, 30 and 35 kg). Each cut required participants run 4 m/s, before planting their foot on a force platform and cut 45° towards the opposite limb. Lower limb biomechanics related to musculoskeletal injury were submitted to a repeated measures ANOVA to test for main and interaction effects of load, sex, and limb. RESULTS: During the cut, load increased peak proximal anterior tibial shear force (p < 0.001) and peak hip flexion (p = 0.010) and knee abduction (p = 0.045) moments, but decreased peak knee flexion angle (p = 0.032). Females exhibited greater peak proximal anterior tibial shear (p = 0.014), and peak hip adduction (p < 0.001) and knee external rotation (p = 0.001) moment than males. Dominant limb exhibited larger peak hip adduction (p = 0.002); whereas, the non-dominant limb exhibited greater peak hip internal (p = 0.002) and knee external (p = 0.007) rotation moments. Only the non-dominant limb increased peak knee abduction moment (p = 0.001) with additional load. SIGNIFICANCE: During the cut, adding body borne load produced maladaptive biomechanics that may increase knee musculoskeletal injury risk. Load increased peak proximal tibial shear and potential strain of knee's soft-tissues. Females exhibited a sex dimorphism in lower limb biomechanics that may further elevate their injury risk. Both limbs exhibited biomechanics that may increase injury risk, but only the non-dominant limb further increased injury risk with load.

Sex and stride length impact leg stiffness and ground reaction forces when running with body borne load.

This study quantified leg stiffness and vGRF measures for males and females using different stride lengths to run with four body borne loads (20, 25, 30, and 35 kg). Thirty-six participants (20 males and 16 females) ran at 4.0 m/s using either: their preferred stride length (PSL), or strides 15% longer (LSL) and shorter (SSL) than PSL. Leg stiffness and vGRF measures, including peak vGRF, impact peak and loading rate, were submitted to a RM ANOVA to test the main effect and interactions of load, stride length, and sex. Leg stiffness was greater with the 30 kg (p = 0.016) and 35 kg (p < 0.001) compared to the 20 kg load, but decreased as stride lengthened from SSL to PSL (p < 0.001) and PSL to LSL (p < 0.001). Males exhibited greater leg stiffness than females with SSL (p = 0.029). Yet, males decreased leg stiffness with each increase in stride length (p < 0.001; p < 0.001), while females only decreased leg stiffness between PSL and LSL (p = 0.014). Peak vGRF was greater with the addition of body borne load (p < 0.001) and increase in stride length (p < 0.001). Both impact peak and loading rate were greater with the 30 kg (p = 0.034; p = 0.043) and 35 kg (p = 0.004; p = 0.015) compared to the 20 kg load, and increased as stride lengthened from SSL to PSL (p = 0.001; p = 0.004) and PSL to LSL (p < 0.001; p < 0.001). Running with body borne load may elevate injury risk by increasing leg stiffness and vGRFs. Injury risk may further increase when using longer strides to run with body borne load.