Academic literature on the topic 'Knee – Movements – Sex differences'

Abstract Background and Purpose. Although weight-bearing (WB) exercise and increased hamstring muscle activity may contribute to knee joint stability in knees with an injured anterior cruciate ligament (ACL), the relationship among ACL integrity, muscle activity, and joint surface motion is not fully understood. The purpose of this study was to investigate whether knee joint rolling and gliding movements and electromyographic (EMG) activity differed between subjects with injured ACLs and subjects without knee pathology. Subjects. Fifteen subjects with injured ACLs (9 men and 6 women; mean age=26 years, SD=7, range=18–36) and 15 age- and sex-matched subjects without knee pathology (9 men and 6 women; mean age=25 years, SD=6, range=18–36) participated in the study. Methods. Sagittal-plane knee joint rolling and gliding movements and lower-extremity EMG activity were measured during non-weight-bearing (NWB) and WB movements. Mixed-model analyses of variance were conducted to analyze rolling and gliding and EMG data. Results. During NWB knee extension, greater joint surface gliding occurred in knees with injured ACLs at full knee extension. During WB knee extension, greater gliding occurred in knees with injured ACLs throughout the range of motion tested. No differences in EMG activity occurred between groups. Discussion and Conclusion. The results suggest that, in the absence of increased hamstring muscle activity, anterior tibial displacement is not reduced in knees with injured ACLs during WB movement.

Context:Decelerating movements such as landing from a jump have been proposed to be a common mechanism of injury to the anterior cruciate ligament (ACL).Objective:To compare eccentric hip-abductor strength and kinematics of landing between men and women when performing a hopping task.Setting:Research laboratory.Patients:18 healthy subjects (10 women, 8 men).Main Outcome Measures:Eccentric peak torque of the hip abductors and peak knee-joint angles during a 350-millisecond interval after impact.Results:No significant sex differences were present, but there was a significant inverse relationship between women's eccentric peak torque and peak knee-valgus angle (r= –.61,P= .03).Conclusions:Women with larger eccentric peak torque demonstrated lower peak knee-valgus angles. By not reaching as large of a valgus angle, there is potentially less stress on the ACL. Increasing eccentric hip-abductor strength might improve knee-joint kinematics during landing from a jump.

The aim of this study was to compare biomechanical and perceptual-cognitive variables between sexes during an offensive and defensive agility protocol. Twelve male and female (n = 24) recreational team sport athletes participated in this study, each performing 12 offensive and defensive agility trials (6 left, 6 right) changing direction in response to movements of a human stimulus. Three-dimensional motion, ground reaction force (GRF), and impulse data were recorded across plant phase for dominant leg change of direction (COD) movements, while timing gates and high-speed video captured decision time, total running time, and post COD stride velocity. Subjects also performed a unilateral isometric squat to determine lower body strength and limb dominance. Group (sex) by condition (2 × 2) MANOVAs with follow-up ANOVAs were conducted to examine differences between groups (P ≤ .05). Male athletes demonstrated significantly greater lower body strength, vertical braking force and impulse application, knee and spine flexion, and hip abduction, as well as faster decision time and post COD stride velocity during both agility conditions compared with females. Differences between offensive and defensive movements appear to be attributed to differences in decision time between sexes. This study demonstrates that biomechanical and perceptual-cognitive differences exist between sexes and within offensive and defensive agility movements.

AimsThe use of vitamin E-infused highly crosslinked polyethylene (HXLPE) in total knee prostheses is controversial. In this paper we have compared the clinical and radiological results between conventional polyethylene and vitamin E-infused HXLPE inserts in total knee arthroplasty (TKA).Patients and MethodsThe study included 200 knees (175 patients) that underwent TKA using the same total knee prostheses. In all, 100 knees (77 patients) had a vitamin E-infused HXLPE insert (study group) and 100 knees (98 patients) had a conventional polyethylene insert (control group). There were no significant differences in age, sex, diagnosis, preoperative knee range of movement (ROM), and preoperative Knee Society Score (KSS) between the two groups. Clinical and radiological results were evaluated at two years postoperatively.ResultsDifferences in postoperative ROM and KSS were not statistically significant between the study and control groups. No knee exhibited osteolysis, aseptic loosening, or polyethylene failure. Additionally, there was no significant difference in the incidence of a radiolucent line between the two groups. One patient from the study group required irrigation and debridement, due to deep infection, at six months postoperatively.ConclusionClinical results were comparable between vitamin E-infused HXLPE inserts and conventional polyethylene inserts at two years after TKA, without any significant clinical failure. Cite this article: Bone Joint J 2019;101-B:559–564.

INTRODUCTION Debate has persisted for many years about whether to sacrifice or replace the posterior cruciate ligament when performing total knee arthroplasty. A paucity of long-term follow-up studies comparing outcomes between cruciate-retaining and posterior-stabilised knees exist. We aimed to compare results at ten-year follow-up. METHODS A matched paired study comparing a cohort of 107 Zimmer Nexgen® Cruciate Retaining (CR) patients with a cohort of 107 Nexgen Posterior-Stabilised (PS) knees matched for age, sex, body mass index and preoperative American Knee Society score was undertaken. All patients underwent independent clinical assessment and knee society scoring preoperatively and at 1, 3, 5, 7 and 10 years postoperatively. RESULTS Fifty-three patients (49.5%) in the CR group and 44 patients (41.1%) in the PS group were alive at 10-year follow-up. There were no significant differences between the CR and PS groups with regards to functional assessment (P = 0.95), overall range of movement (P = 0.46) or patient satisfaction (P = 1.0) at 10 years. However, there was a significantly better score improvement in range of movement in PS knees compared with CR knees (P = 0.027). There were six revisions (5.6%) in the PS group and 1 (0.93%) in the CR group (P = 0.12). Both CR and PS knees showed excellent survivorship with no significant difference at 10 years (P = 0.068). CONCLUSIONS There were no significant differences in functional score, overall range of motion or patient satisfaction between the Nexgen cruciate retaining and posterior stabilised total knee arthroplasty at 10-year follow-up. However, PS knees had a greater score improvement in range of motion compared with CR knees.

To determine sex and race differences in muscle power per unit of muscle contraction, knee-extensor muscle power normalized for knee-extensor muscle volume was measured in 79 middle-aged and older adults (30 men and 49 women, age range 50–85 years). Results revealed that women displayed a 38% faster peak movement velocity than men and African Americans had a 14% lower peak movement velocity than Whites of a similar age when expressed per unit of involved muscle (p< .001). As expected, men exhibited greater knee-extensor strength and peak power per unit of muscle than women, but women had a faster knee-extension movement velocity per unit of muscle than men at the same relative strength level. Moreover, African Americans had greater knee-extensor muscle volume than Whites but exhibited lower knee-extensor strength and lower movement velocity per unit of muscle when tested at the same relative strength levels.

Background Female patients with ACLR are 40% less likely to return to preinjury levels of sport after subsequent ACLR when compared to their male counterparts. Additionally, 24-30% of young female athletes who do return to sport will go on to experience a second ACL injury to the ipsilateral or contralateral knee within 2 years of ACLR. Despite these findings, sex-based differences in clinical outcomes following ACLR are not currently well understood within the adolescent population. Involved limb knee extension weakness, contralateral limb knee extension weakness, and between limb strength asymmetry persist months to years following ACLR among adolescent patients. Improvements in unilateral and symmetry-based measures of knee extension strength during and after the rehabilitation process have been linked to improved patient-reported knee related function, lower extremity functional performance, and decreased risk of subsequent ACL injury among individuals with recent ACLR. Currently, there is a lack of evidence describing the role that sex plays in persistent quadriceps weakness. Therefore, the purpose of this study was to investigate the effects of patient sex on unilateral and symmetry-based measures of knee extension strength, and patient-reported knee function among adolescent individuals with ACL reconstruction (ACLR) within the first year after surgery. Methods: Fifty-two male participants (age = 16.8±1.3 years, BMI = 25.6±5.6 kg/m2, time since surgery = 6.3±1.4 months) and 66 female participants (age = 16.7±1.4 years, BMI = 23.9±3.9kg/m2, time since surgery = 6.8±1.7 months) with unilateral ACLR, 4-12 months prior to enrollment were recruited for this multi-site cross-sectional study. Participants completed bilateral knee extension maximal voluntary isometric contraction (MVIC) torque assessments using a multimodal dynamometer with continuous verbal encouragement from the tester and visual feedback on a nearby monitor. Peak knee extension MVIC torque was identified for each of 3 trials and was normalized to body mass (Nm/kg). Limb symmetry indices were also calculated by dividing the MVIC torque obtained for the involved limb by the MVIC torque obtained for the contralateral limb. Participants also completed the International Knee Documentation Committee (IKDC) Subjective Knee Form to assess patient-reported knee function. Sex-based comparisons of quadriceps strength outcomes and IKDC score were made using separate ANCOVAs where time since surgery was utilized as a covariate. Cohen’s d effect sizes and 95% confidence intervals (CI95) were calculated to assess the magnitude of sex difference for all outcome measures. Odds ratios and CI95 were also calculated to assess the odds of an adolescent female achieving clinical threshold for acceptable involved limb quadriceps strength (MVIC = 3.0 Nm/kg), quadriceps limb symmetry (LSI = 90.0%), and patient-reported knee function (IKDC = 90.0). Results: The involved limb (male = 2.08±0.95 Nm/kg, female = 1.69±0.63 Nm/kg, p = 0.01, d = -0.50, CI95 = -0.13 to -0.87) and contralateral limbs (male = 2.75±0.75 Nm/kg, female = 2.31±0.64 Nm/kg, p = 0.001, d = -0.64, CI95 = -0.26 to -1.01) of male participants were stronger when compared to female participants but limb symmetry (male = 74.7±22.6%, female = 74.7±24.6%, p = 0.95, d = 0.00, CI95 = 0.36 to -0.36) and IKDC score (male = 84.4±16.1, female = 79.4±13.7, p = 0.08, d = -0.34, CI95 = 0.03 to -0.71) was not significantly different between the sexes. Male participants were 5.66 times (CI95 = 1.46 to 21.87) more likely to meet the clinical threshold for acceptable involved limb quadriceps strength and 3.52 times (CI95 = 1.54 to 8.05) more likely to report acceptable knee related function. The likelihood of achieving clinically acceptable limb symmetry was not significantly different between the sexes (OR = 1.17, CI95 = 0.48 to 2.83). Conclusion/Significance: Adolescent female patients may experience significantly worse involved limb and contralateral quadriceps weakness when compared to adolescent male patients despite displaying equally poor limb symmetry and patient-reported knee function during the first 12 month following surgery. Given the importance of involved limb quadriceps strength as a predictor of patient-reported function and movement quality, clinicians should incorporate patient education regarding the importance of quadriceps function and recommend progressive lower extremity loading when implementing patient-centered rehabilitation plans that promote safe return to healthy levels of physical activity following ACLR.

Abstract Context: Lower extremity injury often occurs during abrupt deceleration when attempting to change the body's direction. Although sex-specific biomechanics have been implicated in the greater risk of acute knee injury in women than in men, it is unknown if sex differences in thigh strength affect sex-specific energy absorption and torsional joint stiffness patterns. Objective: To determine sex differences in energy absorption patterns and joint stiffnesses of the lower extremity during a drop jump and to determine if these sex differences were predicted by knee extensor and flexor strength. Design: Cross-sectional study. Setting: Laboratory environment. Patients or Other Participants: Recreationally active, college-aged students (41 women: age = 22.1 ± 2.9 years, height = 1.63 ± 0.07 m, mass = 59.3 ± 8.0 kg; 40 men: age = 22.4 ± 2.8 years, height = 1.77 ± 0.1 m, mass = 80.9 ± 14.1 kg). Intervention(s): Participants performed knee flexor and extensor maximal voluntary isometric contractions followed by double-leg drop-jump landings. Main Outcome Measure(s): Lower extremity joint energetics (J × N−1 × m−1) and torsional joint stiffnesses (Nm × N−1 × m−1 × degrees−1) were calculated for the hip, knee, and ankle during the initial landing phase. Body weight was measured in newtons and height was measured in meters. Sex comparisons were made and sex-specific regressions determined if thigh muscle strength (Nm/kg) predicted sagittal-plane landing energetics and stiffnesses. Results: Women absorbed 69% more knee energy and had 36% less hip torsional stiffness than men. In women, greater knee extensor strength predicted greater knee energy absorption (R2 = 0.11, P = .04), and greater knee flexor strength predicted greater hip torsional stiffness (R2 = 0.12, P = .03). Conclusions: Sex-specific biomechanics during the deceleration phase of a drop jump revealed that women used a strategy to attempt to decrease system stiffness. Additionally, only female strength values were predictive of landing energetics and stiffnesses. These findings collectively demonstrated that the task may have been more difficult for women, resulting in a different movement strategy among those with different levels of thigh strength to safely complete the task. Future researchers should look at other predictive factors of observed sex differences.

Objectives: Meniscal injuries are extremely common. Several anatomical features of the knee, including the tibial plateau morphology, have been shown to influence knee biomechanics and the risk of ligamentous injuries. Little is known, however, how these morphological features influence the risk of isolated meniscal injuries in the ACL intact knee. In the current study, we used MRI and 3D image analysis to investigate anatomical variables of knees in patients with and without isolated meniscus tears. We hypothesized that there are differences in slopes and concavity of the tibial plateau between patients with isolated meniscus tears and matched normal controls. Methods: 65 subjects with first-instance isolated medial or lateral meniscal injuries requiring surgical fixation (Age: 15 +/- 2 years, BMI: 23.2 +/- 3.7 Kg/m2; 43% females) were matched to 65 subjects with normal knees and no prior injuries (Age: 15 +/- 2 years, BMI: 23.1 +/- 3.8 Kg/m2; 43% females) based on age, BMI and sex. Sagittal Proton Density SPACE MR images (preoperative for injured group) were used to measure the posterior slope of the medial (MTS) and lateral (LTS) tibial plateau, coronal slope of the tibial plateau (CTS), and the maximum depth of the medial tibia plateau (MTD, as a measure of medial tibial plateau concavity), following established techniques-Figure 1. Two-sample t-test was used to compare the quantified anatomical features between the cases and matched controls. Results: There were no differences in age (p = 0.999), sex distribution (p = 0.999) and BMI (p = 0.963) between the two cohorts. Compared to matched controls, patients with isolated meniscal tears had lower LTS (3.6 +/- 3.2 vs 5.6 +/- 3.0 degrees; p < 0.001), lower MTS (3.4 +/- 2.9 vs 4.9 +/- 2.5 degrees; p = 0.001) and deeper MTD (2.4 +/- 0.8 vs 1.5 +/- 0.8 mm; p < 0.001). There was no difference in CTS between the groups (3.6 +/- 1.6 vs 3.9 +/- 2.2 degrees; p = 0.300). Conclusion: This study suggests that subjects with isolated meniscus tear have a lower posterior tibial slope and a deeper MTD (more concave medial tibial plateau) than matched population who do not have a meniscus tear. This is contrary to what is known for ACL tears, where a higher posterior tibial slope and a shallower MTD have been associated with an increased risk of ACL tear. During load-bearing activities, in particular high impact movements such as jumping, increased tibial slope and decreased MTD have shown to result in greater anterior shear forces across the knee. In contrast, the less sloped and more concave plateau will experience lower shear forces but more compression, which could be detrimental to the meniscus. This study provides preliminary evidence suggesting a link between tibial plateau morphology and risk of isolated meniscal injuries. Further mechanistic studies are required to better understand the interaction between knee morphology, meniscal loading and subsequent risk of injury. [Figure: see text]

Context: After anterior cruciate ligament reconstruction (ACLR), women have a greater risk of incurring a second anterior cruciate ligament injury and they display different landing movement patterns than men. It remains unclear if clinical movement-assessment tools, such as the Landing Error Scoring System (LESS), can detect sex differences in movement patterns after ACLR. Objective: To compare total LESS scores and individual LESS errors between men and women with a history of ACLR. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: A total of 168 individuals (41 men and 127 women; mean age: men = 20 years [range, 19–25 years], women = 19 years [range, 18–20 years]; mean time since surgery: men = 21 months [range, 12–36 months], women = 27.5 months [range, 17–39 months]) with a history of primary, unilateral ACLR. Main Outcome Measure(s): Participants completed a minimum of 3 trials of a drop vertical-jump task scored using the LESS. The between-sexes difference in LESS score was assessed using analysis of covariance, whereas the associations between participant sex and errors on each LESS item were assessed using logistic or multinomial regression. Results: Women displayed a greater number of total landing errors (men = 4.6 ± 2.3, women = 6.1 ± 2.3; P < .001) and were more likely to commit errors in trunk flexion at initial contact (men = 4.9%, women = 23.6%; odds ratio [OR] = 4.94), medial knee position at initial contact (men = 17.1%, women = 42.5%; OR = 6.01), medial knee displacement (men = 24.4%, women = 73.2%; OR = 7.88), total joint displacement (1 error: men = 58.5%, women = 71.7%, OR = 2.10; 2 errors: men = 7.3%, women = 14.2%, OR = 3.71), and overall impression (1 error: men = 75.6%, women = 84.3%, OR = 3.24; 2 errors: men = 2.4%, women = 10.2%, OR = 12.89) compared with men. Conclusions: Women with ACLR displayed worse LESS scores and were more likely to commit errors related to medial knee displacement and overall landing quality than men with ACLR.

Muscular stabilisation strategies during activities of daily living alter in the presence of knee osteoarthritis (OA). By examining neuromuscular adaptations using our weight-bearing target match protocol, the main objective of this research is to establish sex differences in adaptations of neuromuscular control that are associated with older males and females with and without OA. 66 participants completed the protocol while EMG, ground reaction forces (GRF), and kinematics were recorded. Muscle activation patterns were presented in polar plots with an EMG vector representing normalised muscle activation in twelve directions, each representing a GRF vector scaled to 30% maximal effort. Asymmetry about the polar plot (activation occurring in one direction more than another) was determined and specificity index (SI) and mean direction of activation were calculated when appropriate. Healthy females demonstrated greater rectus femoris (RF) mean muscle magnitude (XEMG) (p=0.067) and less biceps femoris (BF) XEMG than healthy males (p=0.084) and females with OA (p=0.041), and males and females with OA demonstrated greater RF XEMG than healthy controls of the same sex (p=0.016, 0.072, respectively). Females with OA had significantly greater medial gastrocnemius XEMG than healthy females (p=0.031) and males with OA (p=0.020). Females with OA have less specificity in all muscles compared to males with OA and OA participants generally had less specificity compared to healthy controls of the same sex. Healthy males had the largest SI for lateral gastrocnemius with an asymmetrical activation pattern contrasting the more symmetrical activation pattern of all other groups. In conclusion, we suggest OA-affected adults and healthy females use a quadriceps dominant strategy to stabilise the joint, and that this strategy may be a compensatory mechanism for reduced quadriceps function. We suggest RF, BF, MG, and LG should be targeted for prophylactic intervention as they displayed altered activation strategies in participants with OA and healthy females.

Females suffer anterior cruciate ligament (ACL) injuries at a 2 to 10-fold greater rate compared to male athletes participating in similar sports. Altered movement patterns and inadequate knee stiffness are two interrelated factors that may increase ACL injury risk. Onset of these neuromuscular risk factors may coincide with the rapid adolescent growth that results in the divergence of a multitude of neuromuscular parameters between sexes. The overall purpose of this dissertation was to determine if neuromuscular ACL injury risk factors in female athletes increase following rapid growth and development compared to males. Male and female athletes were tested with three-dimensional motion analysis techniques during a drop vertical jump over two consecutive years to determine if ACL injury risk factors increased. Pubertal females showed a significant longitudinal increase in knee abduction angle compared to post-pubertal females and both male groups. The increase in knee abduction angle appeared to remain consistent, as the post pubertal female cohort had greater overall knee abduction compared to post-pubertal males. Similar results were found with a greater magnitude of knee abduction moment in post-pubertal females compared to males. Males and females increased ankle, knee and hip active stiffness from the first to second year of testing. Ankle and hip stiffness were increased significantly more in the pubertal group compared to post-pubertal. Sex and maturational group differences were found in hip and ankle joint stiffness. Post-pubertal males had significantly greater hip stiffness than the other groups (even when normalized to body mass). This indicates that post-pubertal males utilized a different neuromuscular strategy during landing. Males had a significantly greater increase from year to year in vertical jump height compared to females. Vertical jump height is often related to a measure of whole body power and indicates that males had a significant neuromuscular spurt compared to females. Early puberty appears to be a critical phase related to the divergence of increased ACL injury risk factors. Injury prevention programs that focus on neuromuscular training may be beneficial to help address the development of ACL injury risk factors that occur in female athletes during maturation.

Female intercollegiate basketball players experience a three times greater rate of ACL injuries than their male counterparts. This investigation hypothesized that women and men perform the cutting maneuver differently with respect to ground reaction forces and knee range of motion.The subjects performed a ninety degree cut on a force platform while being video taped. The male subjects exhibited a 23.1 percent greater (p=.0167) knee flexion angle than did the female subjects. The female subjects exhibited a 25.5 percent greater (p=.0022) braking force than did the male subjects. The impact maximum was not statistically significant (p=.3290).The performance characteristics exhibited by the female subjects in this study would suggest that the cutting maneuver is more dangerous for female basketball player. Female athletes should be taught correct performance of the cutting maneuver. I addition to technique, strength training should be encouraged to develop a stronger secondary stabilization mechanism for the knee.<br>School of Physical Education

The role of sex in the organization of movement is not commonly addressed in the literature. The objective of this thesis was to determine whether differences exist between males and females in the way they organize their movements during dodging to protect a food item. Detailed kinematic analysis of these movements in adult rats shows that females move their snout through a greater spatial curvature, relative to the pelvis, than males. The sex of the robbing animal did not alter the sex-typical movement paterns exhibited. Manipulation of neonatal androgens altered the sex-typical dodge patterns of both males and females. Removal of androgens at weaning however, did not affect the male-typical pattern. The existence of sex differences in the organization of movement provides a new level of analysis for the study of sexual dimorphism in behavior.<br>x, 228 leaves : ill. ; 28 cm.

The anterior cruciate ligament (ACL) plays an important role in knee joint stability, and unfortunately is one of the most commonly injured knee joint structures. The muscles surrounding the knee are also critical for stabilising the knee joint and their activations are altered following ACL injury. Despite the fact that ACL injuries are up to 8 times more likely to occur in females compared to males, there is limited research evaluating the effects of sex on how ACL-deficient individuals adjust neuromuscular control strategies during varying loading conditions. In order to have clinicians implement optimal rehabilitation strategies for ACL-deficient males and females, it is crucial to understand the adaptive functional strategies that are taking place once an ACL injury has occurred. The purpose of this thesis was therefore to provide objective and quantitative measurements describing the functional roles of muscles surrounding the knee. This was accomplished and outlined in this thesis through two chapters in manuscript format and summarised below. i) Sex and ACL-deficiency influence functional muscle roles during an isometric, weight-bearing, force-generation task First, the functional roles of muscles were quantified through the assessment of muscle activations during a series of multi-directional force-production tasks in ACL-deficient males and females while weight bearing. A highly controlled, isometric, force-matching task, whereby participants modulated ground reaction forces in various combinations of sagittal and frontal plane loads was used to quantify force-generation strategies (muscle activations and functional role) of the knee joint. Mean activation magnitudes and profile patterns from 10 muscles in the lower extremity (rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, lateral gastrocnemius, medial gastrocnemius, tensor fascia latae, adductor muscle group, and gluteus medius) were recorded using wireless electromyography (EMG) sensors. Their activations were quantified with an orientation analysis to determine if differences in functional muscle roles existed between four groups; healthy female controls, healthy male controls, ACL-deficient females, and ACL-deficient males. Overall, different functional muscle roles were found between groups. Healthy male controls activated their muscles the most specifically; females with ACL-deficiency activated their muscles the least specifically, while healthy female controls and males with ACL-deficiency shared similar functional muscle roles. This suggests that there was a specificity hierarchy in the ability, or efficiency, to modulate the activation of muscles about the knee joint when exposed to various directional loading conditions. ii) Associations between subjective measures of knee dysfunction and measures of ground reaction forces in ACL-deficient males and females Correlational relationships were evaluated between perceived knee joint function and functional capacity of the knee joint. These relationships were calculated between patient reported outcome measures (PROM) from commonly used knee assessment scoring scales maximal generated forces in the sagittal and frontal planes. Both ACL-deficient groups had significantly lower perceived knee joint function compared to healthy controls. A trend towards significance was observed in the ability to generate maximum forces in the sagittal and frontal planes, with ACL-deficient females generating smaller maximal posterior GRFs compared to healthy females. Only two statistically significant correlations (both for ACL-deficient females) were found between maximal medial GRFs and patient reported outcome measures from the Lysholm and Tegner scoring scales. This indicates that there may be a discrepancy in the sensitivity of subjective outcome measures between sexes and their corresponding ability to generate maximum GRFs. In conclusion, sex differences exist in subjective outcome measures and the functional strategy of neuromuscular control of the knee joint both before and after ACL-injury. The results of this thesis indicate the need for sex-specific tailoring of rehabilitation programs, thus providing an opportunity to improve the success rate of rehabilitation following ACL-injury. Moreover, sensitivity of subjective outcome measures and their relation to simple, practical, functional tasks between sexes warrants further investigations.

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

The rapid growth of an older demographic is an increasing concern around the world. Older people have been reported to suffer from physiological and neuromuscular declines in several systems including skeletal muscles, central nervous system, cardiovascular processes and respiratory function. These age-related changes are often reflected through impairments in functional performance of occupational tasks as well as activities of daily living. This may make an older population more prone to musculoskeletal disorders and injuries. In addition, health problems and injury risks are likely amplified by factors such as obesity. Obesity has emerged as a serious health concern in the United States in recent decades. However, obesity-related changes in performance and motor control as well as how they will be modified by gender, specifically among older adults, are still largely unexplored. As motor variability has recently been reported to be associated with fatigue development and may have the potential to reveal underlying mechanisms of neuromuscular control, the main goals of this study were to investigate the influence of gender and obesity on motor performance, neuromuscular control and endurance in the elderly, by examining differences in motor variability during intermittent submaximal isometric exertions of the knee and hand. Fifty-two older participants with age over 65 were recruited into four groups: obese male (9), obese female (13), non-obese male (15) and non-obese female (15). The obese groups consisted of those whose BMI was greater than 30 kg/m2. Participants were asked to perform intermittent (15s on and 15s off) isometric handgrip and knee extensions at 30% MVC until exhaustion. Force and muscle activations of the Vastus Lateralis, Rectus Femoris, Extensor Carpi Radialis and Flexor Carpi Radialis muscles were collected through the endurance task. Motor variability was quantified using the coefficient of variation (CV) and sample entropy (SaEn) of the surface electromyography (EMG) and force signals. Motor variability during exercise differed both between males and females, and between obese and non-obese people, reflecting different motor strategies employed in order to prolong endurance. Overall, across all individuals, we observed a significant positive correlation between cycle-to-cycle variability of knee extensor muscle activation during the baseline period of the task and endurance time. As for gender differences, males exhibited longer endurance times than females, and seemed to achieve that through utilizing a motor strategy involving a more variable (higher CV) and less complex (lower SaEn) agonistic muscle activity. Since this was accompanied by a lower fluctuation in the force signal (lower CV) and a higher complexity of force (SaEn), we interpreted this to be a motor strategy involving more variable recruitment of synergistic and antagonistic motor units during the knee extension task to prolong endurance time, among males compared to females. As for obesity differences, there were no obesity-related changes in endurance time. However, obese individuals exhibited a greater cycle-to-cycle variability that was positively correlated with endurance time during the knee extension task, indicating a larger alteration in the recruitment of motor units across successive contractions, which contributed to comparable endurance time and performance with their non-obese counterparts. During the hand-grip tasks, variabilities in force and muscle activity followed similar trends as the knee extension task. However, there were no significant gender or obesity differences in endurance time, and there also weren't any significant correlations between any of the dependent variables with endurance time. Thus, this study was a basic investigation into changes in motor variability and how it was associated with the development of fatigue among older adults; and the potential influences of gender and obesity on the relationships. Two tasks of high relevance to both occupational life and activities of daily living, i.e. knee extension and hand-grip were considered. Our findings enhance the theoretical understanding of the underlying neuromuscular control patterns and their relationship with fatigue for different individuals. Given that both aging and obesity rates are rising continuously and becoming a substantial health and safety problem especially in the occupational environment, the results from this study are both timely and critical for practical design applications, especially by recognizing the importance of having a variable motor pattern in task performance, even among older adults.<br>MS

Despite years of research, females continue to have a higher incidence of non-contact ACL injuries. One of the major findings of this research is that males and females perform certain tasks, such as, cutting, landing, and single-leg squatting, differently. In particular, females tend to move the knee into a more valgus position; a motion putting the ACL at risk for injury. Yet the underlying spinal control mechanisms modulating this motion are unknown. Additionally, the mechanisms regulating the ability to rapidly initiate and produce maximal torque are also unknown. Therefore, the purpose was to: 1) determine if the sexes modulate spinal control differently, 2) examine the contributions of spinal control mechanisms to valgus knee motion, and 3) identify contributions of spinal control to the ability to rapidly produce force. The spinal control variables were the first derivative of the Hoffmann (H)-reflex, the first derivative of extrinsic pre-synaptic inhibition (EPI), the first derivative of intrinsic pre-synaptic inhibition (IPI), recurrent inhibition (RI), and V-waves. To assess the neuromuscular system’s ability to rapidly activate, rate of torque development (RTD) and electromechanical delay (EMD) were measured. Lastly, valgus motion was determined by the frontal plane projection angle (FPPA). The results reveal males and females do modulate spinal control differently; specifically males had an increased RTD, which is the slope of the torque-time curve, and increased RI, which is a post-synaptic regulator of torque output. However, the spinal control mechanisms did not significantly contribute to FPPA at the knee. EMD which is the time lag from muscle activity to torque production was significantly predicted by the spinal control mechanisms. Specifically, EPI, a modulator of afferent inflow from peripheral and descending sources, IPI, a regulator of Ia afferent inflow, and sex significantly contributed to EMD. Lastly, the spinal control mechanisms significantly contributed to RTD. Specifically, IPI, sex, and V-waves, a measure of supraspinal drive, all significantly contributed to RTD.<br>Graduation date: 2009

Moving home is an event that most people experience at some stage in their lives. Previous research has shown that while men and women tend to have similar rates of migration overall, significant variations occur according to age. In this chapter, the authors examine these demographic influences on migration for internal migration in Britain using data from the 2001 Census Special Migration Statistics at district scale. The analysis of migrations rates reveals some subtle differences between males and females by age but spatial patterns of net migration for both sexes emphasise that losses for London and provincial urban centres and gains in rural Britain vary significantly by age. The chapter uses a national area classification framework to summarise the patterns of net migration taking place in the year before the 2001 Census at district scale and the latter part of the chapter explores indices of population stability – turnover and churn – that provide alternative insights into migration patterns across the country, particularly when disaggregated by age. These measures of migration are important because it is apparent that some areas that exhibit relatively low net rates of movement, actually have large numbers of migrants moving within their boundaries as well as inflows from and outflows to other areas – movements which clearly impact on the stability of their populations and have policy implications.

To establish the age- and sex-related normative values of sagittal alignment in asymptomatic Chinese adults, and to investigate the changes and possible associated compensation mechanisms across age groups. 584 asymptomatic Chinese adults aged 20–89 years were recruited. Subjects were grouped according to age and gender. Whole-body standing radiographs were acquired for evaluating sagittal alignment from spine to lower limb. Sagittal parameters between gender in different age groups were compared via independent t test. Pearson correlation analysis was used to demonstrate relationships between parameters. Thoracic kyphosis (TK) increased steadily while lumbar lordosis decreased gradually in both genders. Pelvic tilt (PT) in male is greater than in female across all age groups with age related gradual increase. There were significant differences between male and female from 20s to 60s in terms of knee flexion angle (KA) and ankle dorsiflexion angle (AA), but the differences were not significant after 60s. T1 pelvic angle (TPA) was significantly correlated with spinal, pelvic and lower-limb alignment. The older group (≥50 years) had a stronger correlation of TPA with PT and KA, whereas the younger (&lt;50 years) had stronger correlation with TK. This study comprehensively presented the normative sagittal alignment based on a large asymptomatic population, which could serve as an age- and gender-specific reference value for spine surgeons when planning for correction surgery. Age can influence the recruitment of compensation mechanism that involve more pelvic and lower limb mechanisms for elderly people.

Equilibrium represents the motor capability responsible for the performance of virtually all functional movements. Thus, the importance of early diagnosis of equilibrium levels in boys and girls was recognized as the key factor for the prevention of motor deficits and muscles misbalances later in life. Purpose: The purpose of this paper was to show the difference between boys and girls aged 7‒10 years in the level of unilateral static balance of the take-off leg. Methods: Research was conducted at the Kvarner Athletics Club Rijeka, and it involved 80 children aged 7‒10 years (38 boys and 42 girls). Measurement of static unilateral equilibrium was obtained using Gyko Inertial System (Microgate, Bolzano, Italy). Three attempts were made in 20 seconds and two motor variables were observed: medio-lateral and antero-posterior trajectories of the body. For both variables, the arithmetic mean, the minimum and maximum score and standard deviation were calculated. Moreover, a non-parametric method of the Mann-Whitney U test was used to determine statistical significance between boys and girls. Statistical significance was set at p &lt; 0.05. Results: Statistically, girls have significantly better results compared to boys, both in the medio-lateral trajectory variable (M_Sumg = 335.1, M_Sumb = 479.34) and the antero-posterior trajectory variable (M_Sumg = 291.14, M_Sumb = 411.71). Conclusion: The results of this study showed that girls aged 7‒10 years achieved significantly better results compared to boys in observed motor variables (medio-lateral and antero-posterior trajectory of the body), when performing a static unilateral take-off leg balance test. These results are consistent with previous research. Indications for such results stem from different perspectives, among which the most common one refers to the earlier maturation of the systems responsible for postural control in female bodies. Recommendation for further research is to conduct examination on a larger sample of subjects, in younger children (pre-school age) and with both legs.

Advanced prostheses are currently being sold in consumer markets. The development of these advanced prostheses is largely a result of a better understanding of the biomechanics of human locomotion [1]. Powered and microprocessor controlled prostheses are offering better performance in a variety of movements and in the gait cycle. However the focus in lower limb prosthetics has been largely on locomotion (e.g. walking, stair gait and running). This study focuses on the sit and stand cycles of an individual with an Otto Bock C-leg and an Ossur Power Knee prosthesis, comparing his ability to utilize each prosthesis and comparing his cycle to that of a healthy (non-amputee) control subject. This study is part of a larger ongoing study of the sit and stand cycles seen in a large population of unilateral transfemoral prosthetic users of various kinds. The purpose of this study is to compare the difference in method of standing, and assistance provided by the prosthesis. With the knowledge gained from this study we hope to better understand the biomechanics of the sit and stand cycles, leading to better prostheses in the future.

During neural activity in the brain, humans transmit and process information and decide upon actions or responses. When neural activity occurs, blood flow and blood quantity increase in the tissue near the active neurons, and the ratio of oxygenated to deoxygenated hemoglobin in the blood changes. In this paper, we used near-infrared spectroscopy (NIRS) to determine the state of hemoglobin oxygenation at the cerebral surface and on that basis performed real-time color mapping of brain activity (the brain activation response) in the target regions. In this paper, we describe measurements of brain activation using NIRS so as to clarify any differences between conscious and unconscious movement. Bio-locomotion is divided into voluntary movements, which are made voluntarily and consciously, and passive movements, which are made passively and unconsciously. Accordingly, in this paper we investigate the brain activation associated with these two types of movements. The subject successively moves his/her lower legs through knee bends. We measure the brain activities while the subject, who is sitting on a chair moves back and forth. In addition, we carry out an experiment on the effects of the existence or nonexistence of movement caused by vibration on brain activities to consider the results.

Abstract Human’s motion and its mechanisms had become interesting in the last years, where the medecine’s field search for rehabilitation methods for handicapped persons. Other fields, like sport sciences, professional or military world, search to distinguish profiles and ways to train them with specific purposes. Besides, recent findings in neuroscience try to describe these mechanisms from an organic point of view. Until now, different researchs had given a model about control motor that describes how the union between the senses’s information allows adaptable movements. One of this sense is the proprioception, the sense which has a quite big factor in the orientation and position of the body, its members and joints. For this reason, research for new strategies to explore proprioception and improve the theories of human motion could be done by three different vias. At first, the sense is analysed in a case-study where three groups of persons are compared in a controlled enviroment with three experimental tasks. The subjects belong to each group by the kind of sport they do: sedentary, normal sportsmen (e.g. athletics, swimming) and martial sportmen (e.g. karate, judo). They are compared thinking about the following hypothesis: “Martial Sportmen have a better proprioception than of the other groups’s subjects: It could be due to the type of exercises they do in their sports as empirically, a contact sportsman shows significantly superior motor skills to the members of the other two groups. The second via are records from encephalogram (EEG) while the experimental tasks are doing. These records are analised a posteriori with a set of processing algorithms to extract characteristics about brain’s activity of the proprioception and motion control. 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