Anterior cruciate ligament (ACL) injuries most commonly occur following a perturbation. Perturbations make the athlete unbalanced or at loss of control, which ultimately can lead to injury. The purpose of this study was to identify differences in ACL agonist and antagonist muscle forces, between sexes, during unexpected perturbations. Twenty recreational athletes were perturbed during walking at a speed of 1.1 m/s. Motion analysis data were used to create subject-specific musculoskeletal models and static optimization was performed to calculate muscle forces in OpenSim. Statistical parametric mapping (SPM) was used to compare muscle forces between males and females during the stance phase of the perturbed cycle. selleckchem Females illustrated higher ACL antagonist muscle forces (p less then 0.05) and lower ACL agonist muscle forces, compared to their male counterparts. The quadriceps (QUADs) muscle group peak was about 1.4 times higher in females (35.50 ± 8.71 N/kg) than males (22.81 ± 5.83 N/kg during 57%-62% of the stance phase (p less then 0.05). Females presented a larger peak of gastrocnemius (GAS) at two instances 12.42 ± 4.5 N/kg vs. 8.10 ± 2.83 N/kg between 70% and 75% at p less then 0.05 and 2.26 ± 0.55 N/kg vs. 0.52 ± 0.09 N/kg between 95% and 100% at p less then 0.05. Conversely, males illustrated higher initial hamstrings (HAMS) peak of 10.67 ± 4.15 N/kg vs. 5.38 ± 1.1 N/kg between 8% and 11%. Finally, males showed almost double the soleus (SOL) peak at 30.63 ± 8.64 N/kg vs. 17.52 ± 3.62 N/kg between 83% and 92% of the stance phase at p less then 0.001. These findings suggest that females may exhibit riskier neuromuscular control in unanticipated situations, like sports.Root resorption is closely related to orthodontic force and affects orthodontic treatment with high incidence; however, the mechanism governing this effect is unclear. Microcracks are associated with bone resorption and may also play an important role in root resorption. This study aimed to assess the occurrence of microcracks on the root surface induced by orthodontic force, analyze the association between force and microcrack development, and propose potential measures to reduce microcracks. Different loads (0.5, 1, or 2 N) were applied between the left first molar and anterior teeth for different durations (1, 3, 7, or 14 days) in a rabbit model. The first molar was dissected and its surface was examined using scanning electron microscopy (SEM), which revealed the presence of microcracks on the compressed side of the root apices. The number, width, and length of microcracks were all positively correlated with the load magnitude and duration. The breaking strength of the root apex was tested by using a digital force tester. In addition, a finite element (FE) model was used to analyze the stress at the root apices and the crack propagation on the root surfaces. link2 FE analysis calculated that the regions of maximum stress at the root apices were consistent with the microcrack regions observed via SEM. These results imply that orthodontic force can directly induce the occurrence and development of microcrack, and may contribute to further root resorption. Therefore, an appropriate interval and direction of orthodontic force may help reduce microcracks and prevent root resorption.Accurate assessment of 3D tibio-femoral kinematics is essential for understanding knee joint functionality, but also provides a basis for assessing joint pathologies and the efficacy of musculoskeletal interventions. Until now, however, the assessment of functional kinematics in healthy knees has been mostly restricted to the loaded stance phase of gait, and level walking only, but the most critical conditions for the surrounding soft tissues are known to occur during high-flexion activities. This study aimed to determine the ranges of tibio-femoral rotation and condylar translation as well as provide evidence on the location of the centre of rotation during multiple complete cycles of different gait activities. Based on radiographic images captured using moving fluoroscopy in ten healthy subjects during multiple cycles of level walking, downhill walking and stair descent, 3D femoral and tibial poses were reconstructed to provide a comprehensive description of tibio-femoral kinematics. Despite a significant increase in joint flexion, the condylar antero-posterior range of motion remained comparable across all activities, with mean translations of 6.3-8.3 mm and 7.3-9.3 mm for the medial and lateral condyles respectively. Only the swing phase of level walking and stair descent exhibited a significantly greater range of motion for the lateral over the medial compartment. Although intra-subject variability was low, considerable differences in joint kinematics were observed between subjects. The observed subject-specific movement patterns indicate that accurate assessment of individual pre-operative kinematics together with individual implant selection and/or surgical implantation decisions might be necessary before further improvement to joint replacement outcome can be achieved.Rapid force generation across submaximal levels has been evaluated with the rate of force development scaling factor (RFD-SF) in different isometric tasks, while such measurement was still not verified in dynamic tasks. Our study was designed to evaluate the feasibility of the RFD-SF in dynamic drop jump (DJ) task (RFD-SFDJ). A total of 55 young athletes performed isometric plantarflexion at different submaximal intensities and 60 DJs (6 different drop heights). For each participant we calculated linearity (r2) and slope in isometric task (RFD-SFPF), eccentric part of DJ (RFD-SFDJ-ECC) and concentric part of DJ (RFD-SFDJ-CON), as well as average jump height (DJH) from each drop height. Our results revealed strong linear force-RFD relationship for isometric plantarflexion (r2 = 0.90 ± 0.06), eccentric (r2 = 0.87 ± 0.09) and concentric phase of DJ (r2 = 0.80 ± 0.18). Significant moderate positive correlations were calculated between RFD-SFPF and RFD-SFDJ-ECC (r = 0.311, p less then 0.05) and small negative correlations between RFD-SFDJ-CON and RFD-SF (r = -0.276, p less then 0.05). Significant positive moderate correlations were seen only between RFD-SFDJ-ECC and DJH from 10 cm (r = 0.459, p less then 0.001) and 15 cm (r = 0.423, p less then 0.01). This is the first study to introduce and confirm that RFD-SFDJ can be obtained from the multi-joint tasks (60 jumps) and still provide acceptable reliability and linear relationship. Furthermore, RFD-SFDJ may have greater practical application than RFD-SF assessed under the isometric conditions. This verification of RFD-SFDJ opens opportunities for further research regarding its practical application.Mechanical properties of cancellous bone is of increasing interest due to its involvement in aging pathologies and oncology. Characterization of fragile bone tissue is challenging and available methodologies include quasi-static compressive tests of small size specimens, ultrasound and indentation techniques. We hypothesized that modal analysis of flexure beams could be a complementary methodology to obtain Young modulus. The sampling methodology was adapted such that the uniqueness of the linear dynamic response was available to determine the elastic modulus from natural frequencies and mode shapes. In a first step, the methodology was validated using a synthetic bone model as control. Then, water-jet cutting allowed collecting fourteen small beam-like specimens in canine distal femurs. X-ray microtomography confirmed the microarchitecture preservation, the homogeneity and the isotropy at the specimen scale to derive effective properties. The first natural frequency in clamped-free boundary conditions was used to obtain mean values of Young modulus, which ranged from 210 MPa to 280 MPa depending on the specimen collection site. Experimental tests were rapid and reproducible and our preliminary results were in good agreement with literature data. In conclusion, beam modal analysis could be considered for exploring mechanical properties of fragile and scarce biological tissues.Kinematic characteristics of the double-leg stance (DLS) to a single-leg stance (SLS) transition were analyzed in a group of young adolescent girls to assess their postural stability control. Twenty volunteers participated in a single experimental session during which their postural stability was assessed based upon the center of pressure (COP) trajectories during the transitions in two typical sensory conditions with eyes open (EO) and with eyes closed (EC). To quantify the postural control we applied Fitts’ model treating the postural sway as the noise at the initial and the target setpoint control. Results showed that in young healthy subjects characteristics of the transition to either left or right single-leg stance were quite symmetrical. The postural sway at the target posture was characterized by the double increase of postural sway when tested with EO and by the almost quadrupled amount of sway in EC trials. The sway at the target resulted in the decline of the COP mean and peak velocity proportionally to the movement index of difficulty (ID). The estimated ID value increased by 74% in EC trials while the probability of instability increased to 70%. The DLS-SLS test can be recommended for clinical and laboratory assessment of postural stability.Muscle strength and force production are important measures of patient progress during physical rehabilitation. Reliable and objective measurements are important to ascertain throughout rehabilitation. Current methods-manual muscle testing, electromechanical dynamometer, and hand-held dynamometer-are accurate and reliable, but have limitations that prevent wide implementation. link3 As healthcare systems adapt to more patient-centered outcome models, changes to the delivery of rehabilitation, whether at-home or in the clinic, must also change to become more cost effective and accessible and provide quantifiable information regarding patient progress. We developed a novel Force Sensing (FoSe) device to quantify either tensile or compressive isometric muscle strength. The device was tested in a laboratory setting with healthy participants (n = 32) and compared to the commonly used hand-held dynamometer (HHD). Participants used both devices to perform several common isometric muscle tests including hip abduction, knee extension, knee flexion, shoulder external rotation, and shoulder internal rotation. Compared to the HHD, FoSe was found to be an accurate and reliable measurement of force production. Intraclass Correlation Coefficients ranged from 0.58 to 0.89 without a magnitude dependent variation in force measurement. A second round of clinical testing with a patient population is warranted to determine FoSe’s ability to measure clinically relevant asymmetry and progress over time. Further usability testing also needs to be conducted to determine the adequacy of FoSe for at-home use by both patients and clinicians.Developmental dysplasia of the hip (DDH) is characterized by abnormal bony anatomy, which causes detrimental hip joint loading and leads to secondary osteoarthritis. Hip joint loading depends, in part, on muscle-induced joint reaction forces (JRFs), and therefore, is influenced by hip muscle moment arm lengths (MALs) and lines of action (LoAs). The current study used subject-specific musculoskeletal models and in-vivo motion analysis to quantify the effects of DDH bony anatomy on dynamic muscle MALs, LoAs, and their contributions to JRF peaks during early (~17%) and late-stance (~52%) of gait. Compared to healthy hips (N = 15, 16-39 y/o), the abductor muscles in patients with untreated DDH (N = 15, 16-39 y/o) had smaller abduction MALs (e.g. anterior gluteus medius, 35.3 vs. 41.6 mm in early stance, 45.4 vs. 52.6 mm late stance, p ≤ 0.01) and more medially-directed LoAs. Abduction-adduction and rotation MALs also differed for major hip flexors such as rectus femoris and iliacus. The altered MALs in DDH corresponded to higher hip abductor forces, medial JRFs (1.