Sex-specific Injury Research Articles

Maternal Exposure to Polystyrene Nanoplastics Induces Sex-Specific Cardiotoxicity in Offspring Mice

Globally, plastic pollution threatens human health, particularly affecting the hearts of offspring exposed to maternal environmental factors early in development. Few studies have specifically addressed sex-specific cardiac injury in offspring resulting from maternal exposure to polystyrene nanoplastics (PS-NPs). This study investigates the potential cardiac injury in offspring following maternal exposure to 1 mg/L PS-NPs. Pregnant C57BL/6J mice were exposed to PS-NPs until 3 weeks postpartum to establish a maternal exposure model. Heart tissues were collected and weighed, and the transcriptomes of the offspring hearts were sequenced and analyzed using high-throughput RNA sequencing. Immunohistochemical staining was performed to assess the effects of PS-NPs on cardiac immune infiltration, fibrosis, and apoptosis in the offspring. PS-NPs caused a significant reduction in heart and body weight in female offspring compared to males. Additionally, PS-NPs induced sex-specific transcriptional reprogramming and metabolic disruptions in the offspring. PS-NPs also induced significant fibrosis, apoptosis, and increased CD68+ macrophage infiltration in offspring hearts. Notably, PS-NPs induced distinct cardiovascular diseases in the offspring. Fluid shear stress and atherosclerosis were significantly enriched in PS-NP-treated male offspring, while viral myocarditis was predominantly enriched in PS-NP-treated females. Our findings suggest that PS-NPs induce cardiotoxicity in offspring by disrupting metabolism, impairing immunity, and triggering fibrosis and apoptosis, with sex-specific differences. This study provides novel insights and a foundation for understanding sex-specific pharmacological differences and interventions in PS-NP-induced cardiovascular disease in offspring.

Female Tendons are from Venus and Male Tendons are from Mars, But Does it Matter for Tendon Health?

Tendons play fundamental roles in the execution of human movement and therefore understanding tendon function, health and disease is important for everyday living and sports performance. The acute mechanical behavioural and physiological responses to short-term loading of tendons, as well as more chronic morphological and mechanical adaptations to longer term loading, differ between sexes. This has led some researchers to speculate that there may be a sex-specific injury risk in tendons. However, the link between anatomical, physiological and biomechanical sex-specific differences in tendons and their contributory role in the development of tendon disease injuries has not been critically evaluated. This review outlines the evidence surrounding the sex-specific physiological and biomechanical responses and adaptations to loading and discusses how this evidence compares to clinical evidence on tendon injuries and rehabilitation in the Achilles and patellar tendons in humans. Using the evidence available in both sports science and medicine, this may provide a more holistic understanding to improve our ability to enhance human tendon health and performance in both sexes.

Sex differences in body composition and shock attenuation during running

Running-related impact shock is absorbed via biological tissue deformation. Given known sex differences in body composition, shock attenuation may also differ between sexes thereby influencing sex-specific running-related injury risk. This study examined sex differences in body composition and shock attenuation during running. Seventeen female (mean ± 1SD age: 34.7 ± 16.1) and twenty-one male runners (age: 29.0 ± 13.8) ran overground as inertial measurement units with triaxial accelerometers measured impact shock at the distal tibia and low-back. Frequency-domain axial and resultant shock attenuation were calculated between the low-back relative to the tibia using a transfer function of the power spectral density within 9–20, 21–35, and 36–50 Hz. Bone mineral density and content, fat and lean mass were measured in the lower extremity and pelvis/gynoid regions using dual x-ray absorptiometry. The association between sex and shock attenuation was tested using age-adjusted linear regression models, adjusted and unadjusted for body composition as a post-hoc analysis (α = 0.05). Body composition variables normalized to body mass were compared between sexes using independent samples t-tests (α = 0.05). Body composition differed between sexes (p-range: <0.001–0.01, Cohen’s d range: 0.17–2.41). Before adjusting for body composition, sex was not significantly associated with axial or resultant shock attenuation (p > 0.05), but adjusting for select body composition variables like lower extremity lean and bone mass revealed greater attenuation in females than males (β-range: −124.76 to −46.42, negative indicates greater attenuation; p-range = 0.004–0.04). Sex may not influence shock attenuation during running, but body composition must be accounted for to better understand this association and consequently sex-specific tissue capacities relative to applied loads.

Sex-Specific and Traumatic Brain Injury Effects on Dopamine Receptor Expression in the Hippocampus.

Traumatic brain injury (TBI) is a major health concern. Each year, over 50 million individuals worldwide suffer from TBI, and this leads to a number of acute and chronic health issues. These include affective and cognitive impairment, as well as an increased risk of alcohol and drug use. The dopaminergic system, a key component of reward circuitry, has been linked to alcohol and other substance use disorders, and previous research indicates that TBI can induce plasticity within this system. Understanding how TBI modifies the dopaminergic system may offer insights into the heightened substance use and reward-seeking behavior following TBI. The hippocampus, a critical component of the reward circuit, is responsible for encoding and integrating the spatial and salient aspects of rewarding stimuli. This study explored TBI-related changes in neuronal D2 receptor expression within the hippocampus, examining the hypothesis that sex differences exist in both baseline hippocampal D2 receptor expression and its response to TBI. Utilizing D2-expressing tdTomato transgenic male and female mice, we implemented either a sham injury or the lateral fluid percussion injury (FPI) model of TBI and subsequently performed a region-specific quantification of D2 expression in the hippocampus. The results show that male mice exhibit higher baseline hippocampal D2 expression compared to female mice. Additionally, there was a significant interaction effect between sex and injury on the expression of D2 in the hippocampus, particularly in regions of the dentate gyrus. Furthermore, TBI led to significant reductions in hippocampal D2 expression in male mice, while female mice remained mostly unaffected. These results suggest that hippocampal D2 expression varies between male and female mice, with the female dopaminergic system demonstrating less susceptibility to TBI-induced plasticity.

Protective Effects of Lrp2 Knockout Are Independent of Sex-Specific Renal Injury in Mice on Western Diet

Protective Effects of Lrp2 Knockout Are Independent of Sex-Specific Renal Injury in Mice on Western Diet

Elevation of Arginase-II in Podocytes Contributes to Age-Associated Albuminuria in Male Mice.

One of the manifestations of renal aging is podocyte dysfunction and loss, which are associated with proteinuria and glomerulosclerosis. Studies show a male bias in glomerular dysfunction and chronic kidney diseases, and the underlying mechanisms remain obscure. Recent studies demonstrate the role of an age-associated increase in arginase-II (Arg-II) in proximal tubules of both male and female mice. However, it is unclear whether Arg-II is also involved in aging glomeruli. The current study investigates the role of the sex-specific elevation of Arg-II in podocytes in age-associated increased albuminuria. Young (3-4 months) and old (20-22 months) male and female mice of wt and arginase-II knockout (arg-ii-/-) were used. Albuminuria was employed as a readout of glomerular function. Cellular localization and expression of Arg-II in glomeruli were analyzed using an immunofluorescence confocal microscope. A more pronounced age-associated increase in albuminuria was found in male than in female mice. An age-associated induction of Arg-II in glomeruli and podocytes (as demonstrated by co-localization of Arg-II with the podocyte marker synaptopodin) was also observed in males but not in females. Ablation of the arg-ii gene in mice significantly reduces age-associated albuminuria in males. Also, age-associated decreases in podocyte density and glomerulus hypertrophy are significantly prevented in male arg-ii-/- but not in female mice. However, age-associated glomerulosclerosis is not affected by arg-ii ablation in both sexes. These results demonstrate a role of Arg-II in sex-specific podocyte injury in aging. They may explain the sex-specific differences in the development of renal disease in humans during aging.

Sex differences in musculoskeletal injury epidemiology and subsequent loss of tactical readiness during Marine Corps Officer Candidates School

IntroductionThe US Marine Corps (USMC) Officer Candidates School (OCS) is a 10-week training course for Marine Officer Candidates (MOCs). OCS training is rigorous and demanding, which results in a high...

Identifying sex-specific injury predictors as a key factor in maintaining optimal physical activity levels.

Optimal physical activity is known to reduce cardiovascular, respiratory and endocrine system diseases and, as a consequence, improve quality of life. An important risk factor for reinjuries during normal exercise is the initial connective tissue pathology. The variety of clinical dysplastic manifestations significantly complicate the timely diagnosis of this comorbidity. To establish pathognomonic sex-specific dysplasia phenotypes that indicate a particular sensitivity to physical exertion. The study involved 117 participants with recurrent musculoskeletal injuries that occurred during normal exercise. There were 67 women (57.26%) and 50 men (42.74%), which made it possible to compare the presence of the identified signs between sexes. A validated questionnaire was used to screen their connective tissue status. Ranking the most commonly revealed dysplasia signs depending on their clinical significance made it possible to establish pathognomonic sex-specific phenotypes that indicated a particular susceptibility to injuries. Individualized programs of optimal physical activity are necessary for men with chest deformities, flat-valgus feet, dolichostenomelia, arachnodactylia, hemorrhoids, abdominal muscle diastasis and recurrent hernias. In women, special sensitivity to physical exertion was associated with a combination of signs such as asthenic body, joint hypermobility, overly soft auricles, thin hyperelastic skin, atrophic striae, telangiectasias and varicose veins. Of particular importance were universal signs such as gothic palate, scoliosis, kyphosis, leg deformities, temporomandibular joint crunching, and moderate to high myopia. Participants' connective tissue condition should be considered when designing optimal physical activity programs. Identifying the established sex-specific dysplasia phenotypes will allow timely optimization of training loads, thus reducing the risk of injury.

Sex-specific myoelectric manifestations of localized fatigue during a multi-joint repetitive task

We have previously demonstrated that fatigue at different locations impacts joint angles, angular variability, and coordination variability differently. However, the neuromuscular control aspects underlying these kinematic changes have never been demonstrated. Seventeen young adults (8 males) were recruited. Electromyographic electrodes were placed on: upper trapezius, pectoralis major, anterior and middle deltoid, biceps and triceps brachii, and left and right erector spinae. Subjects performed the repetitive pointing task (RPT) at 1 Hz for 30 s before and after localized fatigue tasks, which consisted of one shoulder, one elbow and one lower back isometric fatiguing protocols until exhaustion in randomized order. Electromyographic amplitude (RMS), variability (SD) and mean power frequency (MnPF) were calculated for each of the pre-fatigue and post-fatigue RPT trials. There were sex × fatigue location interaction effects on upper trapezius RMS (p = 0.038) with males’ values increasing the most after shoulder fatigue. Females’ triceps brachii RMS was greater compared to males after shoulder, elbow, and trunk fatigue (p = 0.003, p = 0.001 and p = 0.007 respectively). There were sex × fatigue location effects on left erector spinae MnPF (p = 0.011) with males and females’ values decreasing the most after trunk fatigue, but more so in males. Results demonstrate that males and females compensate differently during a repetitive pointing task when their elbows, shoulders and trunks are locally fatigued, which could have implications on sex-specific workplace injury risks. See Table 1 for acronyms.

Epidemiology of fractures in indoor patients at a tertiary care centre in India: a study of 3000 cases

&lt;p class="abstract"&gt;&lt;strong&gt;Background: &lt;/strong&gt;Implementing appropriate fracture control measures and treatment protocols is crucial to maximizing health and development gains. This requires an in depth understanding of age-specific, sex-specific and cause-specific injury patterns at the national and subnational levels. No such study on fracture epidemiology has been undertaken in the Indian population.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods: &lt;/strong&gt;Study was conducted in a tertiary care centre (KEM hospital, Mumbai) which is one of the highest volume trauma centres in the country. Data of 3000 patients was obtained from the medical records department for the year 2016-2019. Patients were segregated with respect to their genders and into three age groups. Etiology of fracture was noted, and fractures classified according to the anatomical area. Whether the patient received conservative or operative management was also recorded.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results: &lt;/strong&gt;43.83% of the fractures occurred in 18-50 years age group. 41.33% in the above 50 group and only 14.73% in the below 18 age group. Overall male to female ratio was 1.4: 1. Vehicular accident was the most common mode of injury (47.07%) followed by fall from height (21.03%). Proximal femur fractures were the most common accounting for 19.57% of all fractures followed by forearm (10.53%), tibia diaphysis (8.10%). Talus was the least common. 81.07% cases were managed operatively and 18.93% conserved.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions: &lt;/strong&gt;Our study highlights that Indian epidemiology is unique from our Western counterparts. Population affected is much younger, old age males are affected more than females. Lower limb fractures are more prevalent and road traffic accidents are responsible for almost half the fractures.&lt;/p&gt;

Sex-Specific Regulation of Interferon-γ Cytotoxicity in Mouse Liver by Autophagy.

Interferon-γ (IFNγ) is a central activator of immune responses in the liver and other organs. IFNγ triggers tissue injury and inflammation in immune diseases, which occur predominantly in females for unknown reasons. Recent findings that autophagy regulates hepatotoxicity from proinflammatory cytokines led to an examination of whether defective hepatocyte autophagy underlies sex-specific liver injury and inflammation induced by IFNγ. A lentiviral autophagy-related 5 (Atg5) knockdown was performed to decrease autophagy-sensitized alpha mouse liver (AML 12) hepatocytes to death from IFNγ in combination with IL-1β or TNF. Death was necrosis attributable to impaired energy homeostasis and adenosine triphosphate depletion. Male mice with decreased autophagy from a tamoxifen-inducible, hepatocyte-specific Atg5 knockout were resistant to IFNγ hepatotoxicity whereas female knockout mice developed liver injury and inflammation. Female mice had increased IFNγ-induced signal transducer and activator of transcription 1 (STAT1) levels compared to males. Blocking STAT1, but not interferon regulatory factor 1, signaling prevented IFNγ-induced hepatocyte death in autophagy-deficient AML12 cells and female mice. The mechanism of death is STAT1-induced overexpression of nitric oxide synthase 2 (NOS2) as in vitro hepatocyte death and in vivo liver injury were blocked by NOS2 inhibition. Decreased hepatocyte autophagy sensitizes mice to IFNγ-induced liver injury and inflammation through overactivation of STAT1 signaling that causes NOS2 overexpression. Hepatotoxicity is restricted to female mice, suggesting that sex-specific effects of defective autophagy may underlie the increased susceptibility of females to IFNγ-mediated immune diseases.

Functional organization of the insula in men and women with obstructive sleep apnea during Valsalva.

Obstructive sleep apnea (OSA) patients show impaired autonomic regulation, perhaps related to functional reorganization of the insula, which in healthy individuals shows sex-specific anterior and right dominance during sympathetic activation. We examined insular organization of responses to a Valsalva maneuver in OSA with functional magnetic resonance imaging (fMRI). We studied 43 newly diagnosed OSA (age mean ± SD: 46.8 ± 8.7 years; apnea-hypopnea index (AHI) ± SD: 32.1 ± 20.1 events/hour; 34 males) and 63 healthy (47.2 ± 8.8 years; 40 males) participants. Participants performed four 18-second Valsalva maneuvers (1-minute intervals, pressure ≥ 30 mmHg) during scanning. fMRI time trends from five insular gyri-anterior short (ASG); mid short (MSG); posterior short (PSG); anterior long (ALG); and posterior long (PLG)-were assessed for within-group responses and between-group differences with repeated measures ANOVA (p < 0.05); age and resting heart rate (HR) influences were also assessed. Right and anterior fMRI signal dominance appeared in OSA and controls, with no between-group differences. Separation by sex revealed group differences. Left ASG anterior signal dominance was lower in OSA versus control males. Left ASG and ALG anterior dominance was higher in OSA versus control females. In all right gyri, only OSA females showed greater anterior dominance than controls. Right dominance was apparent in PSG and ALG in all groups; females showed right dominance in MSG and PLG. OSA males did not show PLG right dominance. Responses were influenced substantially by HR but modestly by age. Anterior and right insular fMRI dominance appears similar in OSA versus control participants during the sympathetic phase of the Valsalva maneuver. OSA and control similarities were present in just males, but not necessarily females, which may reflect sex-specific neural injury.

Sex-Specific Intubation Biomechanics: Intubation Forces Are Greater in Male Than in Female Patients, Independent of Body Weight.

BackgroundStudies of head, neck, and cervical spine morphology and tissue material properties indicate that cervical spine biomechanics differ between adult males and females. These differences result in sex-specific cervical spine kinematics and injury patterns in response to standardized loading conditions. Because direct laryngoscopy and endotracheal intubation require the application of a load to the cervical spine, intubation biomechanics should be sex-specific. The aim of this study was to determine if intubation forces during direct laryngoscopy differ between male and female patients and, if so, is the difference independent of body weight.MethodsWe pooled original data from three previously published adult clinical intubation studies that used methodologically reliable intubation force measurements (measured total laryngoscope force applied to the tongue, and force values were insensitive to or accounted for other laryngoscope blade forces). All patients had undergone direct laryngoscopy and orotracheal intubation with a Macintosh 3 blade under general anesthesia. Patient data included sex, age, height, weight, and maximum intubation force. Least squares multivariable linear regression was performed between the dependent variable (maximum intubation force) and two independent variables (patient sex and patient weight). A third term was added for the interaction between patient sex and weight.ResultsAmong all patients (males n=42, females n=59), the median intubation force was 42.2 N (25th to 75th percentiles: 31.5 to 57.4 N). While controlling for patient body weight, intubation force differed between the sexes; P=0.011, with greater intubation force in male patients. While controlling for patient sex, there was a positive association between patient body weight and intubation force; P=0.009. In addition, there was a significant interaction between patient sex and weight; P=0.002, with intubation force in male patients having greater dependence on body weight. The difference in intubation force between male and female patients who had the same body weight exceeded 5 N when body weight exceeded 75 kg, and intubation force differences between male and female patients increased as patient body weight increased. Additional analyses using robust regression and using body mass index instead of weight provided comparable results.ConclusionIn adult patients, the biomechanics of direct laryngoscopy and intubation are sex-specific. Our findings support the need to control for patient sex and weight in future clinical and laboratory studies of the human cervical spine and head and neck biomechanics.

Injury risks among elite competitive alpine skiers are underestimated if not registered prospectively, over the entire season and regardless of whether requiring medical attention.

Prospective studies assessing the injuries occurring in elite competitive alpine skiers are lacking, and a full picture of all injuries, including those not requiring medical attention, is absent. Likewise, little is known about the sex-specific injury risks and patterns of elite skiers throughout an entire season (i.e. an off-season preparation period and a competition period). Accordingly, this study investigated the injuries of a national team cohort with respect to season period and sex. Over an entire season, all injuries occurring in 44 SwissNational Ski Team members (25 females and 19 males) were registered, regardless of whether they required medical attention. Skiers were prospectively monitored by the Oslo Sports Trauma Research Centre (OSTRC) questionnaire and by continuously updated team medical records. Finally, these data were used as a reference for supplemental interviews, in which the correctness and completeness of the prospective data were verified. The risk of suffering at least one injury during an entire season was 75.0% with a 95% confidence interval (73.1%, 76.9%) for traumatic injuries, and 52.3% (50.0%, 54.5%) for overuse injuries. Traumatic injuries concerned the head, lower leg and knee, while overuse injuries affected the lumbar spine, knee and hip. During the competition period, skiers were more prone to traumatic injuries, while during the off-season preparation period, skiers' risk was higher for overuse injuries. Over an entire season, there were no sex differences. However, females were more vulnerable to traumatic injuries during the preparation period and overuse injuries during the competition period, while males had a higher risk for overuse injuries during the preparation period. When prospectively registering injuries among elite competitive alpine skiers over an entire season, regardless of whether the injuries required medical attention, the injury risks were alarmingly high and substantially larger than those previously reported. Moreover, since injury risks and patterns are season period and sex dependent, it is strongly recommended that (1) injury registration focuses on both the off-season preparation period and the competition period and (2) prevention efforts are specifically tailored to the sex of the athletes. II.

Sex-Specific Analysis at Two Time Points in Three High-Impact Orthopaedic Sports Medicine Journals

PurposeTo determine how well the orthopaedic sports medicine literature reported sex-specific analysis (SSA) in 2011 and 2016.MethodsThe 3 highest-impact orthopaedic sports medicine subspecialty journals (American Journal of Sports Medicine; Arthroscopy; and Knee Surgery, Sports Traumatology, Arthroscopy) were selected for review. Two independent investigators reviewed all journal issues published during 2 different calendar years (2011 and 2016). All randomized controlled, prospective and retrospective group, and case–control studies were included. Studies were stratified into those that involved SSA, where sex was a variable in a multifactorial statistical model, and those that only reported sex as a demographic characteristic or used sex-matched groups without further analysis.ResultsA total of 960 studies evaluating 3,400,569 patients met criteria and were included in this review. Although 44.4% of the overall study population was female, only 293 (30.5%) studies included patient sex as variable in a multifactorial statistical model. The proportion of studies that performed SSA did not differ between 2011 (29.6%) and 2016 (31.1%; P = .607), although publications from American Journal of Sports Medicine were likely to report SSA (P < .05). Of the 293 studies that reported SSA, 91 (31%) demonstrated a significant difference in outcomes. The most commonly reported differences were in outcomes following anterior cruciate ligament, medial patellofemoral ligament, and posterior cruciate ligament reconstruction; autograft preparation; postoperative use of opiates following arthroscopy; and recovery after sports-related concussions.ConclusionsAlthough most sports medicine studies include approximately 50% female and 50% male patients, statistical analysis differentiating the 2 subsets is not routinely performed. Only 30.5% of all studies performed SSA, 31% of which reported a statistically significant difference in the data when comparing outcomes between male and female patients with the same treatment modalities.Clinical RelevanceThe current study demonstrates that the orthopaedic sports medicine subspecialty literature is lacking in reporting SSA, and that there has been minimal improvement over a 5-year time period. In addition, this study highlights the high percentage of significant findings within the studies that performed SSA and underscores the differences in sex-specific injury patterns and treatment outcomes.

PEAK LOWER EXTREMITY SOCCER INJURIES OCCUR IMMEDIATELY FOLLOWING GROWTH IN ADOLESCENTS: AN EPIDEMIOLOGIC REVIEW OF EMERGENCY DEPARTMENT VISITS

BACKGROUND:Soccer has become the most popular youth sport in the world. Within the last decade, there has been limited epidemiologic research on pediatric soccer-related injuries based on sex and age.PURPOSE:To examine trends associated with soccer injuries presenting to emergency departments and to describe differences in injury pattern and location based on sex and age during periods of growth.METHODS:An epidemiologic study was conducted utilizing publicly accessible data from the National Electronic Injury Surveillance System (NEISS). The NEISS compiles Emergency Department (ED) data on all injuries presenting to the approximately 100 participating network hospitals in the United States. Information on all soccer-related injuries occurring in ages 7-19 from January 2009 – December 2018 was extracted and summary statistics were calculated.RESULTS:Approximately 54,287 pediatric soccer-related injuries were identified. The average age for all injuries was 13.3 years, and males (60.50%) presented more often than females (39.50%).Concussions and head injuries (15.57%) were most commonly reported overall, with a greater percentage occurring in females than males (17.44% vs. 14.35%). The ankle (15.3%) was the second most common injury location with females also presenting more commonly than males (18.71% vs. 13.62%).Age and sex-based evaluation noted peaks in lower extremity injuries in females younger than in males. Both ankle (F=13-15 years, M=15-17 years) and knee (F=14 years, M=16 years) injuries peaked at ages coinciding with recognized sex-based lower extremity skeletal maturity (Figure 1).CONCLUSION:Peak pediatric soccer-related ankle and knee injuries presenting to emergency departments occur at different ages in females and males and appear to, on average, coincide with maturation (age 14 in females and 16 in males). Lower extremity injuries significantly increase nearing the completion of lower extremity growth, and may indicate appropriate timing for differential sex-specific injury prevention programs within soccer.Figure 1.Number of ankle and knee injuries compared between age and sex.

Relationship between mechanical properties (shear modulus and viscosity), age, and sex in uninjured Achilles tendons.

Tendon mechanical properties have been proposed as a biomarker of tendon health to track response to injury and treatment. Prior to utilizing these properties in an injured population, it is critical to understand how these are influenced by age and sex in an uninjured population. A retrospective analysis was conducted of 118 uninjured Achilles tendons to evaluate the relationship between tendon mechanical properties, age and sex. Mechanical properties (shear modulus and viscosity) were assessed using continuous shear wave elastography. A moderator regression analysis was completed to examine the relationship between tendon mechanical properties, age and sex, after adjusting for body mass index and physical activity level. There was an interaction between age and sex for shear modulus (p=0.049, R2 change=0.034). Females had a negative relationship between age and shear modulus (p=0.030, β=-0.350) but no relationship was observed for males (p=0.78, β=0.031). A positive relationship was found between age and viscosity (p=0.034, β=0.214). Increased viscosity was related to increased age with no difference between sexes. The effect of aging on shear modulus differed between men and women and may help explain sex specific injury risks and their differing response to mechanical load.

Cluster analysis successfully identifies clinically meaningful knee valgus moment patterns: frequency of early peaks reflects sex-specific ACL injury incidence

BackgroundBiomechanical studies of ACL injury risk factors frequently analyze only a fraction of the relevant data, and typically not in accordance with the injury mechanism. Extracting a peak value within a time series of relevance to ACL injuries is challenging due to differences in the relative timing and size of the peak value of interest.Aims/hypothesesThe aim was to cluster analyze the knee valgus moment time series curve shape in the early stance phase. We hypothesized that 1a) There would be few discrete curve shapes, 1b) there would be a shape reflecting an early peak of the knee valgus moment, 2a) youth athletes of both sexes would show similar frequencies of early peaks, 2b) adolescent girls would have greater early peak frequencies.MethodsN = 213 (39% boys) youth soccer and team handball athletes (phase 1) and N = 35 (45% boys) with 5 year follow-up data (phase 2) were recorded performing a change of direction task with 3D motion analysis and a force plate. The time series of the first 30% of stance phase were cluster analyzed based on Euclidean distances in two steps; shape-based main clusters with a transformed time series, and magnitude based sub-clusters with body weight normalized time series. Group differences (sex, phase) in curve shape frequencies, and shape-magnitude frequencies were tested with chi-squared tests.ResultsSix discrete shape-clusters and 14 magnitude based sub-clusters were formed. Phase 1 boys had greater frequency of early peaks than phase 1 girls (38% vs 25% respectively, P < 0.001 for full test). Phase 2 girls had greater frequency of early peaks than phase 2 boys (42% vs 21% respectively, P < 0.001 for full test).ConclusionsCluster analysis can reveal different patterns of curve shapes in biomechanical data, which likely reflect different movement strategies. The early peak shape is relatable to the ACL injury mechanism as the timing of its peak moment is consistent with the timing of injury. Greater frequency of early peaks demonstrated by Phase 2 girls is consistent with their higher risk of ACL injury in sports.

Classification of gait muscle activation patterns according to knee injury history using a support vector machine approach

Abnormal muscle activation patterns during gait following knee injury that persist past the acute injury and rehabilitation phase (>three years) are not well characterized but may be related to post-traumatic knee osteoarthritis. The aim was to characterize the abnormal muscle activity from electromyograms of five leg muscles that were recorded during treadmill walking for young adults with and without a previous knee injury 3–12 years prior. The wavelet transformed and amplitude normalized electromyograms yielded intensity patterns that reflect the muscle activity of these muscles resolved in time and frequency. Patterns belonging to the affected or unaffected leg in previously injured participants and patterns belonging to a previously injured vs. uninjured participant were grouped and then classified using a principal component analysis followed by a support vector machine. A leave-one-out cross-validation was used to test the model significance and generalization. The results showed that trained classifiers could successfully recognize whether muscle activation patterns belonged to the affected or unaffected leg of previously injured individuals. Classification rates of 83% were obtained for all subjects, 100% for females only, indicating sex-specific knee injury effects. In contrast, it was not possible to discriminate between patterns belonging to the previously injured legs or dominant legs of control subjects. For females, the injured leg showed a stronger muscle activity for hamstring muscles and a lower activity for the vastus lateralis. In conclusion, systematic knee injury effects on the neuromuscular control of the knee during gait were present 3–12 years later.

Epidemiology of physical activity-related injuries in Chinese university students.

Knowledge gaps of the physical activity-related injury (PARI) problem among general undergraduates exist. We conducted a study in four universities, where 1421 students graded 1-3 were interviewed face-to-face during April and May after their completion of the baseline survey in March and April 2017, aiming to describe the incidence and characteristics of PARI. PARI experience and physical activity (PA) participation in the past 12months were collected. Injury incidence density (IID) and risk, and injury characteristics were evaluated for the overall sample and by gender. Pearson chi-square or Fisher's exact tests and independent-sample t tests were used to test between-group differences. We found that 486 PARIs were reported totally by 289 participants, with an overall IID of 0.57 per 1000hours of exposure (males: 1.07, females: 0.45) and an injury risk of 0.34 injuries/student/y (males: 0.52; females: 0.28). Higher IIDs were found in roller skating, football, and basketball. The majority of injuries occurred outdoors and involved the lower extremities, with sprain and strain being the primary injury types. Moreover, most injuries were new, acute, and happened in non-contact situations. Of all injuries, 52.1% required medical attention and 64.6% resulted in inactivity of one or more days. Some significant differences were observed between males and females. Our study indicates that PARI is a public health concern among Chinese university students, which can provide direction for targeted prophylactic interventions to underpin the sex-specific injury mechanism to reduce PARI.