Peak Muscle Forces Research Articles

Non-amputated limb muscle coordination of unilateral transfemoral amputees

Unilateral transfemoral amputees rely heavily on non-amputated limb muscles to regulate the prosthetic gait. In this study, we compared the non-amputated limb muscle coordination of eight unilateral transfemoral amputees to eight able-bodied controls. Inverse dynamics approach was conducted via a musculoskeletal model to obtain lower limb joint moments and muscle forces. In addition to the muscle forces at the instants of peak joint moments and the maximum muscle forces, the peak joint moments of the lower limbs were also investigated. The results showed that there were significant differences of muscle forces between the non-amputated limbs and the controls at the instant of peak hip extension moment, although the peak hip extension moments themselves were not significantly different between the two groups. The non-amputated limbs had significantly smaller peak hip flexion moment and peak knee extension moment, with significant differences between the muscle forces of non-amputated limbs and controls at the two instants. There was no significant difference between the muscle forces of the non-amputated limbs and controls at the peak knee flexion moment instant, despite the fact that the non-amputated limbs had significantly higher peak knee flexion moments. In addition, the non-amputated limbs had significantly smaller maximum muscle forces than the controls. These results demonstrate that amputees modify their muscle coordination to adapt to the specific joint requirements of the prosthetic gait. Our findings suggest the possibility of non-amputated limb muscle atrophy due to the decrease in the peak muscle forces during walking.

Validity and reliability of a flywheel squat test in sport

ABSTRACT The aims of this study were to examine the test-retest reliability and construct validity of the flywheel (FW)-squat test. Twenty male amateur team sports athletes (mean±SD: age 23±3 years) completed one familiarization session and two testing sessions including: FW-squat test with an inertial load of 0.061 kg.m2, standing long jump (SLJ), countermovement jump (CMJ) and 5-m change of direction (COD-5m) tests, and isokinetic strength assessments of the knee extensor and flexor muscles. Test-retest reliability was assessed with intraclass correlation coefficient (ICC) and coefficient of variation (CV) of data collected. Construct validity was determined as the degree of relationships between the FW-squat test outputs and both athletic tests and isokinetic assessments scores computed with Pearson’s correlation coefficients. Excellent relative (ICC=0.94–0.95) and acceptable absolute (CV=5.9%-6.8%) reliability scores were found for both concentric and eccentric power outputs collected during the FW-squat test. The same outputs showed moderate to large positive correlations with concentric and eccentric knee extensor and flexor muscle peak force values (r range: 0.465–0.566) measured during the isokinetic test. The FW-squat test is a valid and reliable test to assess lower limb performance given its correlation with isokinetic test, as well as its excellent relative and acceptable absolute reliability.

Eccentric versus conventional cycle training to improve muscle strength in advanced COPD: A randomized clinical trial

ObjectivesTo compare eccentric (ECC) and conventional concentric (CON) cycle training on quadriceps muscle strength in advanced COPD. Secondary objective was to assess functional capacity. MethodsA parallel-group, assessor-blind, randomized trial was conducted. Severe COPD patients were randomized to either an ECC (n = 13) or CON (n = 11) cycling program for 30-min, 3 times/week for 10 weeks. ECC group trained at ∼4-fold higher power than the CON group at similar relative heart rate intensity. ResultsIsometric and isokinetic quadriceps peak torque improved after ECC but not CON; between group difference was significant for isometric peak muscle force (p < 0.05). Peak cycling power and endurance time increased in both groups (p < 0.05). Dyspnea at peak cycling power improved only after ECC training (p < 0.05). Sensory intensity ratings of dyspnea and leg fatigue were significantly lower (p < 0.05) during ECC compared with CON at equivalent relative heart rate intensities. ConclusionsECC could be an effective alternative and/or adjunct modality to pulmonary rehabilitation in severely ventilatory limited COPD patients.

Effects of Ving Tsun sticking-hand training on upper-limb sensorimotor performance in community-dwelling middle-aged and older adults: A randomized controlled trial

ObjectiveTo evaluate the effects of Ving Tsun (VT) sticking-hand training on upper-limb joint position sense and muscular performance in community-dwelling middle-aged and older adults. MethodsThirty-three adults were randomly allocated to either a VT group or a control group. The VT group received VT sticking-hand training twice per week for 3 months. Measurements were taken before and after the intervention period. The primary outcome was elbow-joint repositioning error, which was measured by an elbow-joint passive positioning and active repositioning test using a universal goniometer. Secondary outcomes were upper-limb muscles’ peak force and time taken to reach peak force as measured by a hand-held dynamometer. ResultsNo significant time, group or time-by-group interaction effects were found for elbow-joint repositioning error or upper-limb muscle peak force outcomes. Shoulder flexor time to peak force decreased by 33.8% from pre-test to post-test in the VT group (P = 0.007). Shoulder abductor, internal and external rotator, and elbow extensor times to peak force decreased by 30.0%–35.9% in the VT group (P < 0.05) and by 30.4%–37.1% in the control group (P < 0.05). ConclusionsVT sticking-hand training does not improve elbow-joint position sense or the maximum strength of upper-limb muscles in middle-aged and older adults. However, VT can improve shoulder flexor muscles’ time to reach peak force in these populations. VT had no obvious effect on the time required to reach peak force in other shoulder muscles and elbow extensors.

Computational efficient method for assessing the influence of surgical variability on primary stability of a contemporary femoral stem in a cohort of subjects.

Finite element (FE) modelling can provide detailed information on implant stability; however, its computational cost limits the possibility of completing large numerical analyses into the effect of surgical variability in a cohort of patients. The aim of this study was to develop an efficient surrogate model for a cohort of patients implanted using a common cementless hip stem. FE models of implanted femora were generated from computed tomography images for 20 femora (11 males, 9 females; 50-80years; 52-116kg). An automated pipeline generated FE models for 61 different unique scenarios that span the femur-specific range of implant positions. Peak hip contact and muscle forces for stair climbing were scaled to the donors' body weight and applied to the models. A cohort-specific surrogate for implant micromotion was constructed from Gaussian process models trained using data from FE simulations representing the median and extreme implant positions for each femur. A convergence study confirmed suitability of the sampling method for cohorts with 10+ femora. The final model was trained using data from the 20 femora. Results showed very good agreement between the FE and the surrogate predictions for a total of 1036 alignment scenarios [root mean squared error (RMSE) < 20µm; [Formula: see text] = 0.81]. The total time required for the surrogate model to predict the micromotion range associated with surgical variability was approximately one-eighth of the corresponding full FE analysis. This confirms that the developed model is an accurate yet computationally cheaper alternative to full FE analysis when studying the implant robustness in a cohort of 10+ femora.

EP.95Patient perception of outcome measures for non-ambulant Duchenne muscular dystrophy patients

Many therapeutic clinical trials are ongoing in ambulant Duchenne muscular dystrophy (DMD) patients. However, drugs proven effective in ambulant patients will have to be tested separately in non-ambulant patients. Several outcome measures for non-ambulant patients are under development. Natural history data of these measures is needed, while patients struggle to combine this type of extra visits with their daily life. We assessed patient's perception of several different outcome measures for non-ambulant DMD patients. Non-ambulant DMD patients underwent muscle MRI, peak muscle force tests using a Hand-held dynamometer and Myotools, Functional Workspace, Leap Motion and PUL 2.0 assessments of the right arm, and Active-Seated and PROM assessment of both arms. Using visual analogue scale (VAS) scores (range 0-10), all patients were asked directly after the respective assessment how much fun, annoying and tiresome they perceived it. Highest VAS scores on all three domains were correlated to PUL total score using Spearman correlation coefficients. 20 non-ambulant DMD patients (range 8.6-24.1 yrs) were included. Active-Seated scored highest on fun (median 8), followed by muscle force tests and PUL (median 7). MRI was the most annoying (median 5), while all other tests had a median score of 1 or 2. Active-Seated was the most tiresome (median 6), followed by muscle force tests (median 5), and Functional Workspace (median 4). No significant correlation with PUL total score was found for Active-Seated VAS fun and tiresome scores (ρ=-0.04, p=0.871 and ρ=-0.13, p=0.598), and MRI VAS annoying scores (ρ=-0.46, p=0.053). While Active-Seated and muscle force tests score highest on fun, they are also the most tiresome. MRI has the advantage of no motivation component, but scored highest on annoyment. To improve participation in both therapeutic and natural history studies, patient's perception of outcome measures for non-ambulant DMD patients and their respective burden need to be considered.

MEASURES OF HIP MUSCLE STRENGTH AND RATE OF FORCE DEVELOPMENT USING A FIXATED HANDHELD DYNAMOMETER: INTRA-TESTER INTRA-DAY RELIABILITY OF A CLINICAL SET-UP

Evaluation of hip muscle function is considered an important part of the examination and treatment of physically active subjects with hip and groin pain. However, methods to reliably measure explosive hip muscle strength are lacking. The purpose was to investigate the reliability of a clinically available set-up using a fixated handheld dynamometer to test isometric peak force and rate of force development of the hip abductors, adductors, flexors, and extensors. Seventeen subjects (males: 9, females: 8, mean aged 25.4 (+/- 4.2) y, with mean body mass of 73.9 (+/- 15.2) kg, and mean height 174.2 (+/- 12.4) cm) were included. One experienced tester performed all measures in a randomized order. Three trials of isometric peak force and early- (0-100 ms) and late-phase (0-200 ms) rate of force development for the hip abductors, adductors, flexors, and extensors were obtained using a fixated handheld dynamometer. The trial with the highest value for each measure was used for analysis. Test-retest sessions were separated by 30 minutes of rest. No systematic between-session bias were observed for any of the measures. The relative intra-tester reliability (ICC2,1) for peak force, 0-100 ms rate of force development, and 0-200 ms rate of force development ranged from 0.93-0.96, 0.82-0.93, and 0.85-0.92, respectively, corresponding to good reliability for all force measures. The present study shows that assessment of isometric hip muscle peak force, including early- (0-100 ms) and late-phase (0-200 ms) rate of force development using a fixated handheld dynamometer have good intra-tester reliability for testing of the hip adductors, abductors, flexors and extensors. Thus, in clinical research settings where an isokinetic dynamometer may not always be readily accessible, the present test procedure can be used as a feasible alternative to reliably provide objective of hip muscle function relevant for rehabilitation of patients with hip and groin pain. Level 3, Reliability study.

Design of the Cooperative Actuation in Hybrid Orthoses: A Theoretical Approach Based on Muscle Models.

Hybrid orthoses or rehabilitation exoskeletons have proven to be a powerful tool for subjects with gait disabilities due to their combined use of electromechanical actuation to provide motion and support, and functional electrical stimulation (FES) to contract muscle tissue so as to improve the rehabilitation process. In these devices, each degree of freedom is governed by two actuators. The main issue arises in the design of the two actuation profiles for there to be natural or normative gait motion in which the two actuators are transparent to each other. Hybrid exoskeleton control solutions proposed in the literature have been based on tracking the desired kinematics and applying FES to maintain the desired motion rather than to attain the values expected for physiological movement. This work proposes a muscle-model approach involving inverse dynamics optimization for the design of combined actuation in hybrid orthoses. The FES profile calculated in this way has the neurophysiological meaningfulness for the device to be able to fulfill its rehabilitative purpose. A general scheme is proposed for a hybrid hip-knee-ankle-foot orthosis. The actuation profiles, when muscle tissue is fatigued due to FES actuation are analyzed, and an integrated approach is presented for estimating the actuation profiles so as to overcome muscle peak force reduction during stimulation. The objective is to provide a stimulation profile for each muscle individually that is compatible with the desired kinematics and actuation of the orthosis. The hope is that the results may contribute to the design of subject-specific rehabilitation routines with hybrid exoskeletons, improving the exoskeleton's actuation while maintaining its rehabilitative function.

Muscle compensation strategies to maintain glenohumeral joint stability with increased rotator cuff tear severity: A simulation study

Rotator cuff tear (RCT) in older adults may cause decreased muscle forces and disrupt the force balance at the glenohumeral joint, compromising joint stability. Our objective was to identify how increased RCT severity affects glenohumeral joint loading and muscle activation patterns using a computational model. Muscle volume measurements were used to scale a nominal upper limb model’s peak isometric muscle forces to represent force-generating characteristics of an average older adult male. Increased RCT severity was represented by systematically decreasing peak isometric muscle forces of supraspinatus, infraspinatus, and subscapularis. Five static postures in both scapular and frontal planes were evaluated. Results revealed that in both scapular and frontal planes, the peak glenohumeral joint contact force magnitude remained relatively consistent across increased RCT severity (average 1.5% and −4.2% change, respectively), and a relative balance of the transverse force couple is maintained even in massive RCT models. Predicted muscle activations of intact muscles, like teres minor, increased (average 5–30% and 4–17% in scapular and frontal planes, respectively) with greater RCT severity. This suggests that the system is prioritizing glenohumeral joint stability, even with severe RCT, and that unaffected muscles play a compensatory role to help stabilize the joint.

Is muscle mechanical function altered in polycystic ovary syndrome?

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of women of reproductive age. The aim of the current study was to assess muscle mechanical function in PCOS and its relationship with hormonal and metabolic features of the syndrome. The study included 44 women with PCOS, all having clinical or biochemical hyperandrogenism, chronic oligo-anovulation and PCOM, and 32 age- and BMI-matched healthy women. Anthropometric, hormonal and biochemical measurements were performed. Muscle mechanical function including lower limb explosive strength and average power (AvP) was measured using isokinetic dynamometry, a valid and reliable instrument for measuring muscle strength. The mean age and BMI of the women with PCOS and controls were 21.8 ± 3.2 versus 22.8 ± 3years and 26.1 ± 5.4 versus 25.5 ± 5.7kg/m2, respectively (p = NS for both). PCOS patients had higher androgen levels, whereas total and regional fat and lean body mass and insulin resistance parameters were similar between the groups. The peak muscle force output defined as the peak torque of knee extensor and flexor muscles was higher in normal weight women compared to overweight and obese (p < 0.05 for both) but did not differ in patients and controls. AvP determined by the time-averaged integrated area under the curve at 60°/s angular velocity was higher in the PCOS group for extension and flexion (50.3 ± 21.2 vs 42.1 ± 11.6 and 35.3 ± 27 vs 22.2 ± 11.1, respectively, p < 0.05 for both). These measurements were correlated with bioavailable testosterone (r = 0.29, p = 0.012, r = 0.36, p = 0.001, respectively). Muscle mechanical function is altered in PCOS. Women with PCOS have increased average lower limb power that is associated with hyperandrogenism.

Muscle force adaptation to changes in upper body position during seated sprint cycling

ABSTRACTSprint cycling performance depends upon the balance between muscle and drag forces. This study assessed the influence of upper body position on muscle forces and aerodynamics during seated sprint cycling. Thirteen competitive cyclists attended two sessions. The first session was used to determine handlebar positions to achieve pre-determined hip flexion angles (70–110° in 10° increments) using dynamic bicycle fitting. In the second session, full body kinematics and pedal forces were recorded throughout 2x6-s seated sprints at the pre-determined handlebar positions, and frontal plane images were used to determine the projected frontal area. Leg work, joint work, muscle forces and frontal area were compared at three upper body positions, being optimum (maximum leg work), optimal+10° and optimal-10° of hip flexion. Larger hip (p = 0.01–0.02) and reduced knee (p = 0.02–0.03) contribution to leg work were observed at the optimal+10° position without changes at the ankle joint (p = 0.39). No differences were observed in peak muscle forces across the three body positions (p = 0.06–0.48). Frontal area was reduced at optimum+10° of hip flexion when compared to optimum (p = 0.02) and optimum-10° (p < 0.01). These findings suggest that large changes in upper body position can influence aerodynamics and alter contributions from the knee and hip joints, without influencing peak muscle forces.

HSP90 Inhibitor, NVP-AUY922, Improves Myelination in Vitro and Supports the Maintenance of Myelinated Axons in Neuropathic Mice.

Hereditary demyelinating neuropathies linked to peripheral myelin protein 22 (PMP22) involve the disruption of normal protein trafficking and are therefore relevant targets for chaperone therapy. Using a small molecule HSP90 inhibitor, EC137, in cell culture models, we previously validated the chaperone pathway as a viable target for therapy development. Here, we tested five commercially available inhibitors of HSP90 and identified BIIB021 and AUY922 to support Schwann cell viability and enhance chaperone expression. AUY922 showed higher efficacy, compared to BIIB021, in enhancing myelin synthesis in dorsal root ganglion explant cultures from neuropathic mice. For in vivo testing, we randomly assigned 2–3 month old C22 and 6 week old Trembler J (TrJ) mice to receive two weekly injections of either vehicle or AUY922 (2 mg/kg). By the intraperitoneal (i.p.) route, the drug was well-tolerated by all mice over the 5 month long study, without influence on body weight or general grooming behavior. AUY922 improved the maintenance of myelinated nerves of both neuropathic models and attenuated the decline in rotarod performance and peak muscle force production in C22 mice. These studies highlight the significance of proteostasis in neuromuscular function and further validate the HSP90 pathway as a therapeutic target for hereditary neuropathies.

MON-205 Is Muscle Mechanical Function Altered In Polycystic Ovary Syndrome?

Context: Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of women of reproductive age, characterized by androgen excess, ovulatory dysfunction and polycystic ovaries (PCOM). Limited and conflicting data are available regarding musculoskeletal system and muscle strength in PCOS. Objective: The aim of the current study was to assess muscle mechanical function in PCOS and its relation with hormonal and metabolic features of the syndrome. Design: The study included 44 women with PCOS, all having clinical or biochemical hyperandrogenism, chronic oligo-anovulation and PCOM (2003 Rotterdam criteria – phenotype A), and 32 age- and BMI-matched healthy women. Anthropometric, hormonal and biochemical measurements were performed in all participants. Muscle mechanical function including lower limb explosive strength and average power was measured by using isokinetic dynamometry, a valid and reliable instrument for measuring muscle strength. Results: The mean age and BMI of the women with PCOS and healthy controls were 21.8+3.2 versus 22.8+3 years and 26.1+5.4 versus 25.5+5.7 kg/m2 respectively (p=NS for both). PCOS patients had higher modified Ferriman-Gallwey (mFG) scores and higher levels of bioavailable testosterone (bT) than controls (p<0.05 for both), whereas fasting glucose and fasting insulin levels were similar between the groups. Isokinetic measurement of quadriceps and hamstring strength were performed by Biodex 3 dynamometer at an angular velocity of 60°/s. The peak muscle force output during the assessment was defined as the peak torque (PTQ) and was reported as body weight-normalized (Nm/kg) PTQ. Average power (AvP) was determined by the time-averaged integrated area under the curve at 60°/s angular velocity. The normalized values of knee extensor and flexor PTQ at 60°/s were similar between patients and controls whereas these values were higher in normal weight individuals compared to overweight-obese individuals (p<0.05 for both). The AvP at 60°/s with extension and flexion was significantly higher in PCOS group (50.3+21.2 vs 42.1+11.6 and 35.3+27 vs 22.2+11.1 respectively, p <0.05 for both). These measurements were correlated with bT (r=0.29, p=0.012, r=0.36, p=0.001 respectively). Conclusion: Muscle mechanical function is altered in PCOS. Women with PCOS have increased average lower limb power that is associated with hyperandrogenism.

Hip joint muscle forces during gait in patients with femoroacetabular impingement syndrome are associated with patient reported outcomes and cartilage composition

Femoroacetabular impingement syndrome (FAIS) consists of abnormal hip joint morphology and pain during activities of daily living. Abnormal gait mechanics and potentially abnormal muscle forces within FAI patients leads to articular cartilage damage. Therefore, there is a necessity to understand the effects of FAI on hip joint muscle forces during gait and the link between muscle forces, patient reported outcomes (PRO) and articular cartilage health. The purposes of this study were to assess: (1) hip muscle forces between FAI patients and healthy controls and (2) the associations between hip muscle forces with PRO and cartilage composition (T1ρ/T2 mapping) within FAI patients. Musculoskeletal simulations were used to estimate peak muscle forces during the stance phase of gait in 24 FAI patients and 24 healthy controls. Compared to controls, FAI patients ambulated with lower vasti (30% body-weight, p = 0.01) and higher sartorius (4.0% body-weight, p < 0.01) forces. Within FAI patients, lower peak gluteus medius, gluteus minimus, sartorius and iliopsoas forces were associated with worse hip joint pain and function (R = 0.43–0.70, p = 0–0.04), while lower muscle forces were associated with increased T1ρ and T2 values (i.e. altered cartilage composition) within the hip joint cartilage (R = −0.44 to −0.58, p = 0.006–0.05). Although FAI patients demonstrate abnormal muscle forces, it is unknown whether or not these altered muscle force patterns are associated with pain avoidance or weak musculature. Further investigation is required in order to better understand the effects of FAI on hip joint muscle forces and the associations with hip joint cartilage degeneration.

Lean mass and lower limb muscle function in relation to hip strength, geometry and fracture risk indices in community-dwelling older women.

SummaryIn a population-based sample of British women aged over 70 years old, lean mass and peak lower limb muscle force were both independently associated with hip strength and fracture risk indices, thereby suggesting a potential benefit of promoting leg muscle strengthening exercise for the prevention of hip fractures in postmenopausal women.IntroductionTo investigate cross-sectional associations of lean mass and physical performance, including lower limb muscle function, with hip strength, geometry and fracture risk indices (FRIs) in postmenopausal women.MethodsData were from the Cohort of Skeletal Health in Bristol and Avon. Total hip (TH) and femoral neck (FN) bone mineral density (BMD), hip geometry and total body lean mass (TBLM) were assessed by dual x-ray absorptiometry (DXA). Finite element analysis of hip DXA was used to derive FN, intertrochanteric and subtrochanteric FRIs. Grip strength, gait speed and chair rise time were measured objectively. Lower limb peak muscle force and muscle power were assessed by jumping mechanography.ResultsIn total, 241 women were included (age = 76.4; SD = 2.6 years). After adjustment for age, height, weight/fat mass and comorbidities, TBLM was positively associated with hip BMD (βTH BMD = 0.36, P ≤ 0.001; βFN BMD = 0.26, P = 0.01) and cross-section moment of inertia (0.24, P ≤ 0.001) and inversely associated with FN FRI (− 0.21, P = 0.03) and intertrochanteric FRI (− 0.11, P = 0.05) (estimates represent SD difference in bone measures per SD difference in TBLM). Lower limb peak muscle force was positively associated with hip BMD (βTH BMD = 0.28, P ≤ 0.001; βFN BMD = 0.23, P = 0.008) and inversely associated with FN FRI (− 0.17, P = 0.04) and subtrochanteric FRI (− 0.18, P = 0.04). Associations of grip strength, gait speed, chair rise time and peak muscle power with hip parameters were close to the null.ConclusionsLean mass and lower limb peak muscle force were associated with hip BMD and geometrical FRIs in postmenopausal women. Leg muscle strengthening exercises may therefore help prevent hip fractures in older women.

Loading of the hip and knee joints during whole body vibration training.

During whole body vibrations, the total contact force in knee and hip joints consists of a static component plus the vibration-induced dynamic component. In two different cohorts, these forces were measured with instrumented joint implants at different vibration frequencies and amplitudes. For three standing positions on two platforms, the dynamic forces were compared to the static forces, and the total forces were related to the peak forces during walking. A biomechanical model served for estimating muscle force increases from contact force increases. The median static forces were 122% to 168% (knee), resp. 93% to 141% (hip), of the body weight. The same accelerations produced higher dynamic forces for alternating than for parallel foot movements. The dynamic forces individually differed much between 5.3% to 27.5% of the static forces in the same positions. On the Powerplate, they were even close to zero in some subjects. The total forces were always below 79% of the forces during walking. The dynamic forces did not rise proportionally to platform accelerations. During stance (Galileo, 25 Hz, 2 mm), the damping of dynamic forces was only 8% between foot and knee but 54% between knee and hip. The estimated rises in muscle forces due to the vibrations were in the same ranges as the contact force increases. These rises were much smaller than the vibration-induced EMG increases, reported for the same platform accelerations. These small muscle force increases, along with the observation that the peak contact and muscle forces during vibrations remained far below those during walking, indicate that dynamic muscle force amplitudes cannot be the reason for positive effects of whole body vibrations on muscles, bone remodelling or arthritic joints. Positive effects of vibrations must be caused by factors other than raised forces amplitudes.

Body Composition and Strength Parameters in Elite Judo Athletes 5 Years after Anterior Cruciate Ligament Reconstruction.

The purpose of this study was to investigate if there are still deficits in muscle mass or strength capabilities in elite judo athletes with a history of anterior cruciate ligament reconstruction (ACLR) after their return to the sport. Therefore, bioimpedance analysis, 3D-laser thigh circumference measurement and isokinetic dynamometry in a closed kinetic chain were used. The side-to-side differences were investigated in a group of judo athletes 5 years after ACLR (n=17) and compared with a group of healthy judo athletes (n=27). Neither thigh circumferences, nor muscle masses of the lower extremities differed in formerly injured judo athletes compared to healthy judo athletes. In contrast, isokinetic strength testing showed a significantly larger side-to-side difference of peak muscle force in formerly injured judo athletes (p=0.021). They provided significantly lower peak forces with the formerly injured leg than with the non-injured leg (p<0.001). The authors conclude that strength capabilities, but not body composition, remains altered in recovered judo athletes in mean 5 years after ACLR and definitely after their return to sports. This indicates that the focus of rehabilitation protocols and return to sports assessments should focus more on maximum strength capabilities.

Virtual trial to evaluate the robustness of cementless femoral stems to patient and surgical variation

Primary stability is essential for the success of cementless femoral stems. In this study, patient specific finite element (FE) models were used to assess changes in primary stability due to variability in patient anatomy, bone properties and stem alignment for two commonly used cementless femoral stems, Corail® and Summit® (DePuy Synthes, Warsaw, USA). Computed-tomography images of the femur were obtained for 8 males and 8 females. An automated algorithm was used to determine the stem position and size which minimized the endo-cortical space, and then span the plausible surgical envelope of implant positions constrained by the endo-cortical boundary. A total of 1952 models were generated and ran, each with a unique alignment scenario. Peak hip contact and muscle forces for stair climbing were scaled to the donor’s body weight and applied to the model. The primary stability was assessed by comparing the implant micromotion and peri-prosthetic strains to thresholds (150 μm and 7000 µε, respectively) above which fibrous tissue differentiation and bone damage are expected to prevail. Despite the wide range of implant positions included, FE prediction were mostly below the thresholds (medians: Corail®: 20–74 µm and 1150–2884 µε, Summit®: 25–111 µm and 860–3010 µε), but sensitivity of micromotion and interfacial strains varied across femora, with the majority being sensitive (p < 0.0029) to average bone mineral density, cranio-caudal angle, post-implantation anteversion angle and lateral offset of the femur. The results confirm the relationship between implant position and primary stability was highly dependent on the patient and the stem design used.

Dynamic knee joint stiffness and contralateral knee joint loading during prolonged walking in patients with unilateral knee osteoarthritis

BackgroundLong duration walking, a commonly recommended treatment option for knee osteoarthritis (OA), may lead to increased knee joint loading. Research questionTo evaluate the effects of prolonged walking on dynamic knee joint stiffness and contralateral knee joint contact forces (KCFs) in individuals with unilateral symptomatic knee OA. MethodsTwenty-six older adults with knee OA completed a 45-minute bout of walking on a treadmill. Dynamic knee joint stiffness, estimated KCFs, measured ground reaction forces (GRFs), and simulated muscle forces were evaluated for both the symptomatic and asymptomatic limbs at 15-minute intervals using repeated measures, analysis of variance (ANOVA). ResultsDynamic knee joint stiffness during the early weight-acceptance phase of gait was significantly higher for the symptomatic limb throughout the 45-minute bout of walking. A significant increase in peak KCFs and simulated muscle forces were also observed during the weight-acceptance phase of gait for both limbs after 30 and 45 min of walking. Additionally, significantly elevated peak KCFs and muscle forces were observed during the late-stance phase of gait for the contralateral asymptomatic limb throughout the 45-minute bout of walking. SignificanceWalking durations of 30 min or greater lead to increased knee joint loading. Additionally, the elevated dynamic knee joint stiffness observed for the symptomatic knee during the weight acceptance phase of gait appears to be unrelated to the knee joint loading profile. Finally, the greater KCFs during the late-stance phase of gait observed for the asymptomatic limb are consistent with previously demonstrated risk factors for OA development and progression.

Recovery of respiratory function in mdx mice co-treated with neutralizing interleukin-6 receptor antibodies and urocortin-2.

Impaired ventilatory capacity and diaphragm muscle weakness are prominent features of Duchenne muscular dystrophy, with strong evidence of attendant systemic and muscle inflammation. We performed a 2-week intervention in young wild-type and mdx mice, consisting of either injection of saline or co-administration of a neutralizing interleukin-6 receptor antibody (xIL-6R) and urocortin-2 (Ucn2), a corticotrophin releasing factor receptor 2 agonist. We examined breathing and diaphragm muscle form and function. Breathing and diaphragm muscle functional deficits are improved following xIL-6R and Ucn2 co-treatment in mdx mice. The functional improvements were associated with a preservation of mdx diaphragm muscle myosin heavy chain IIx fibre complement. The concentration of the pro-inflammatory cytokine interleukin-1β was reduced and the concentration of the anti-inflammatory cytokine interleukin-10 was increased in mdx diaphragm following drug co-treatment. Our novel findings may have implications for the development of pharmacotherapies for the dystrophinopathies with relevance for respiratory muscle performance and breathing. The mdx mouse model of Duchenne muscular dystrophy shows evidence of hypoventilation and pronounced diaphragm dysfunction. Six-week-old male mdx (n= 32) and wild-type (WT; n= 32) mice received either saline (0.9% w/v) or a co-administration of neutralizing interleukin-6 receptor antibodies (xIL-6R; 0.2mgkg-1 ) and corticotrophin-releasing factor receptor 2 agonist (urocortin-2; 30μgkg-1 ) subcutaneously over 2weeks. Breathing and diaphragm muscle contractile function (ex vivo) were examined. Diaphragm structure was assessed using histology and immunofluorescence. Muscle cytokine concentration was determined using a multiplex assay. Minute ventilation and diaphragm muscle peak force at 100Hz were significantly depressed in mdx compared with WT. Drug treatment completely restored ventilation in mdx mice during normoxia and significantly increased mdx diaphragm force- and power-generating capacity. The number of centrally nucleated muscle fibres and the areal density of infiltrates and collagen content were significantly increased in mdx diaphragm; all indices were unaffected by drug co-treatment. The abundance of myosin heavy chain (MyHC) typeIIx fibres was significantly decreased in mdx diaphragm; drug co-treatment preserved MyHC typeIIx complement in mdx muscle. Drug co-treatment increased the cross-sectional area of MyHC typeI and IIx fibres in mdx diaphragm. The cytokines IL-1β, IL-6, KC/GRO and TNF-α were significantly increased in mdx diaphragm compared with WT. Drug co-treatment significantly decreased IL-1β and increased IL-10 in mdx diaphragm. Drug co-treatment had no significant effect on WT diaphragm muscle structure, cytokine concentrations or function. Recovery of breathing and diaphragm force in mdx mice was impressive in our studies, with implication for human dystrophinopathies.