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To develop and validate a neural network to estimate hip contact forces (HCF), and lower body kinematics and kinetics during walking in individuals with hip osteoarthritis (OA) using synthesised anatomical key points and electromyography. To assess the capability of the neural network to detect directional changes in HCF resulting from prescribed gait modifications. A calibrated electromyography-informed neuromusculoskeletal model was used to compute lower body joint angles, moments, and HCF for 17 participants with mild-to-moderate hip OA. Anatomical key points (e.g., joint centres) were synthesised from marker trajectories and augmented with bias and noise expected from computer vision-based pose estimation systems. Temporal convolutional and long short-term memory neural networks (NN) were trained using leave-one-subject-out validation to predict neuromusculoskeletal modelling outputs from the synthesised key points and measured electromyography data from 5 hip-spanning muscles. HCF was predicted with an average error of 13.4 ± 7.1% of peak force. Joint angles and moments were predicted with an average root-mean-square-error of 5.3 degrees and 0.10 Nm/kg, respectively. The NN could detect changes in peak HCF that occur due to gait modifications with good agreement with neuromusculoskeletal modelling (r2 = 0.72) and a minimum detectable change of 9.5%. The developed neural network predicted HCF and lower body joint angles and moments in individuals with hip OA using noisy synthesised key point locations with acceptable errors. Changes in HCF magnitude due to gait modifications were predicted with high accuracy. These findings have important implications for implementation of load-modification based gait retraining interventions for people with hip OA in a natural environment (i.e., home, clinic). [ABSTRACT FROM AUTHOR]

Biomechanics plays a significant yet complex role in osteoarthritis (OA) onset and progression. Identifying alterations in biomechanical factors and their complex interactions is critical for gaining new insights into OA pathophysiology and identification of clearly defined and modifiable mechanical treatment targets. This review synthesized biomechanics studies from March 2022 to April 2023, from which three themes relating to human gait emerged: (1) new insights into the pathogenesis of OA using computational modeling and machine learning, (2) technology-enhanced biomechanical interventions for OA, and (3) out-of-lab biomechanical assessments of OA. We further highlighted future-focused areas which may continue to advance the field of biomechanics in OA, with a particular emphasis on exploiting technology to understand and treat biomechanical mechanisms of OA outside the laboratory. The breadth of studies included in this review highlights the complex role of biomechanics in OA and showcase numerous innovative and outstanding contributions to the field. Exciting cross-disciplinary efforts integrating computational modeling, mobile sensors, and machine learning methods show great promise for streamlining in vivo multi-scale biomechanics workflows and are expected to underpin future breakthroughs in the understanding and treatment of biomechanics in OA. [ABSTRACT FROM AUTHOR]

The physical demands of military service place soldiers at risk of musculoskeletal injuries and are major concerns for military capability. This paper outlines the development new training technologies to prevent and manage these injuries. Narrative review. Technologies suitable for integration into next-generation training devices were examined. We considered the capability of technologies to target tissue level mechanics, provide appropriate real-time feedback, and their useability in-the-field. Musculoskeletal tissues' health depends on their functional mechanical environment experienced in military activities, training and rehabilitation. These environments result from the interactions between tissue motion, loading, biology, and morphology. Maintaining health of and/or repairing joint tissues requires targeting the "ideal" in vivo tissue mechanics (i.e., loading and strain), which may be enabled by real-time biofeedback. Recent research has shown that these biofeedback technologies are possible by integrating a patient's personalised digital twin and wireless wearable devices. Personalised digital twins are personalised neuromusculoskeletal rigid body and finite element models that work in real-time by code optimisation and artificial intelligence. Model personalisation is crucial in obtaining physically and physiologically valid predictions. Recent work has shown that laboratory-quality biomechanical measurements and modelling can be performed outside the laboratory with a small number of wearable sensors or computer vision methods. The next stage is to combine these technologies into well-designed easy to use products. [ABSTRACT FROM AUTHOR]

To compare lower limb strength and countermovement jump (CMJ) kinetics between elite female footballers with and without a history of anterior cruciate ligament reconstruction (ACLR), hamstring strain, or hip/groin injury. Cross-sectional. Field-based. 369 elite female Australian football, soccer and rugby league players aged 15–35. Isometric hip adductor and abductor strength, eccentric knee flexor strength, and CMJ vertical ground reaction forces, including between-leg asymmetry. Players reported their lifetime history of ACLR, and whether they had sustained a hamstring strain, or hip/groin injury in the previous 12-months. Players with a unilateral history of ACLR (n = 24) had significant between-leg asymmetry in eccentric knee flexor strength (mean = −6.3%, 95%CI = −8.7 to −3.9%, P <.001), isometric hip abductor strength (mean = −2.5%, 95%CI = −4.3 to −0.7%, P =.008), and CMJ peak landing force (mean = −5.5%, 95%CI = −10.9 to −0.1%, P =.046). Together, between-leg asymmetry in eccentric knee flexor strength, isometric hip abductor strength, and CMJ peak landing force distinguished between players with and without prior ACLR with 93% accuracy. Elite female footballers with a history of ACLR, but not hamstring or hip/groin injury, exhibit persistent between-leg asymmetries in lower limb strength and jump kinetics following a return to sport. • Elite female footballers with prior ACLR display chronic between-leg asymmetries in knee flexor strength, hip abductor strength, and jump-landing force. • Lower limb strength and jump kinetics are not impaired after hamstring or hip/groin injury. • These data may have implications for ACLR rehabilitation and return to sport criteria. [ABSTRACT FROM AUTHOR]

Objectives: To quantify the changes in work done by lower limb joint moments during maximal speed running following a sports-specific repeated running protocol.Design: Observational with repeated-measures.Methods: Recreational athletes (n = 18 (9 females), aged = 26.2 ± 6.2 years) performed 12 maximal 30-m sprints on a non-motorised treadmill. Three-dimensional kinematics and ground reaction forces were subsequently recorded during a 10-m maximal overground sprint before and immediately after the repeated running protocol, from which we calculated work done by sagittal plane hip, knee, and ankle moments. Relative work (J/kg) was reported as a percentage of positive and negative work done by the sum of joint moments.Results: Following the repeated running protocol, maximal sprint speed decreased by 19% and was accompanied by reductions in total positive (-1.47 J/kg) and negative (-0.92 J/kg) work, in addition to work done by hip (-0.43 to -0.82 J/kg) and knee (-0.28 J/kg) moments during swing. Compared to before the repeated running protocol, less relative work was done by hip (-9%) and knee (-3%) extension moments during swing. Reductions in work done by hip and knee joint moments during swing were significantly correlated with reductions in maximum running speed (r = 0.61-0.89, p < 0.05).Conclusions: A sports-specific repeated running protocol resulted in reductions in mechanical work done by sagittal plane hip and knee joint moments during maximal overground sprinting. Interventions focused on maintaining positive work done by the hip flexors/extensors and negative work done by knee flexors/extensors during the swing phase of running may help prevent reductions in speed following repeated sprinting. [ABSTRACT FROM AUTHOR]

Deep hip muscle retraining is a common objective of non-operative management for femoroacetabular impingement (FAI) syndrome. These muscles are considered to have an important role in hip joint stabilization, however, it is unclear whether their function is altered in the presence of hip pathology. This exploratory study aimed to investigate activation patterns of the hip muscles during two squatting tasks in individuals with and without FAI syndrome. Fifteen individuals with FAI syndrome (symptoms, clinical examination and imaging) and 14 age- and sex-comparable healthy controls underwent testing. Intramuscular fine-wire and surface electrodes recorded electromyographic activity of selected deep and superficial hip muscles during the squatting tasks. Activation patterns from individual muscles were compared between-groups using a wavelet-based linear mixed effects model (P < 0.05). There were no between-group differences for squat depth or speed during descent or ascent for either task. Participants with FAI syndrome exhibited patterns of activation that differed significantly to controls across all muscles (P < 0.05) when squatting using their preferred strategy. Unlike controls, participants with FAI syndrome exhibited a pattern of activation for obturator internus during descent that was similar in amplitude to ascent, despite the contrasting contraction type (i.e. eccentric vs concentric). Individuals with FAI syndrome appear to implement a protective strategy as the hip descends towards the impingement position. Future studies should examine patients prospectively to establish whether these strategies are counterproductive for pathology and warrant rehabilitation. • Hip muscle activation is altered during squatting in FAI syndrome. • Activation of external rotators is similar in descent and ascent in FAI syndrome. • Neuromuscular strategy appears protective as hip approaches impingement. • Unclear whether these strategies are counterproductive and warrant rehabilitation. [ABSTRACT FROM AUTHOR]

Abstract Abnormal hip joint contact forces (HJCF) are considered a primary mechanical contributor to the progression of hip osteoarthritis (OA). Compared to healthy controls, people with hip OA often present with altered muscle activation patterns and greater muscle co-contraction, both of which can influence HJCF. Neuromusculoskeletal (NMS) modelling is non-invasive approach to estimating HJCF, whereby different neural control solutions can be used to estimate muscle forces. Static optimisation, available within the popular NMS modelling software OpenSim, is a commonly used neural control solution, but may not account for an individual's unique muscle activation patterns and/or co-contraction that are often evident in pathological population. Alternatively, electromyography (EMG)-assisted neural control solutions, available within CEINMS software, have been shown to account for individual activation patterns in healthy people. Nonetheless, their application in people with hip OA, with conceivably greater levels of co-contraction, is yet to be explored. The aim of this study was to compare HJCF estimations using static optimisation (in OpenSim) and EMG-assisted (in CEINMS) neural control solutions during walking in people with hip OA. EMG-assisted neural control solution was more consistent with both EMG and joint moment data than static optimisation, and also predicted significantly higher HJCF peaks (p < 0.001). The EMG-assisted neural control solution also accounted for more muscle co-contraction than static optimisation (p = 0.03), which probably contributed to these higher HJCF peaks. Findings suggest that the EMG-assisted neural control solution may estimate more physiologically plausible HJCF than static optimisation in a population with high levels of co-contraction, such as hip OA. [ABSTRACT FROM AUTHOR]

Objectives: This study investigated isometric and isokinetic hip strength in individuals with and without symptomatic femoroacetabular impingement (FAI). The specific aims were to: (i) determine whether differences exist in isometric and isokinetic hip strength measures between groups; (ii) compare hip strength agonist/antagonist ratios between groups; and (iii) examine relationships between hip strength and self-reported measures of either hip pain or function in those with FAI.Design: Cross-sectional.Methods: Fifteen individuals (11 males; 25±5 years) with symptomatic FAI (clinical examination and imaging (alpha angle >55° (cam FAI), and lateral centre edge angle >39° and/or positive crossover sign (combined FAI))) and 14 age- and sex-matched disease-free controls (no morphological FAI on magnetic resonance imaging) underwent strength testing. Maximal voluntary isometric contraction strength of hip muscle groups and isokinetic hip internal (IR) and external rotation (ER) strength (20°/s) were measured. Groups were compared with independent t-tests and Mann-Whitney U tests.Results: Participants with FAI had 20% lower isometric abduction strength than controls (p=0.04). There were no significant differences in isometric strength for other muscle groups or peak isokinetic ER or IR strength. The ratio of isometric, but not isokinetic, ER/IR strength was significantly higher in the FAI group (p=0.01). There were no differences in ratios for other muscle groups. Angle of peak IR torque was the only feature correlated with symptoms.Conclusions: Individuals with symptomatic FAI demonstrate isometric hip abductor muscle weakness and strength imbalance in the hip rotators. Strength measurement, including agonist/antagonist ratios, may be relevant for clinical management of FAI. [ABSTRACT FROM AUTHOR]

Abstract In-vivo hip joint contact forces (HJCF) can be estimated using computational neuromusculoskeletal (NMS) modelling. However, different neural solutions can result in different HJCF estimations. NMS model predictions are also influenced by the selection of neuromuscular parameters, which are either based on cadaveric data or calibrated to the individual. To date, the best combination of neural solution and parameter calibration to obtain plausible estimations of HJCF have not been identified. The aim of this study was to determine the effect of three electromyography (EMG)-informed neural solution modes (EMG-driven, EMG-hybrid, and EMG-assisted) and static optimisation, each using three different parameter calibrations (uncalibrated, minimise joint moments error, and minimise joint moments error and peak HJCF), on the estimation of HJCF in a healthy population (n = 23) during walking. When compared to existing in-vivo data, the EMG-assisted mode and static optimisation produced the most physiologically plausible HJCF when using a NMS model calibrated to minimise joint moments error and peak HJCF. EMG-assisted mode produced first and second peaks of 3.55 times body weight (BW) and 3.97 BW during walking; static optimisation produced 3.75 BW and 4.19 BW, respectively. However, compared to static optimisation, EMG-assisted mode generated muscle excitations closer to recorded EMG signals (average across hip muscles R2 = 0.60 ± 0.37 versus R2 = 0.12 ± 0.14). Findings suggest that the EMG-assisted mode combined with minimise joint moments error and peak HJCF calibration is preferable for the estimation of HJCF and generation of realistic load distribution across muscles. [ABSTRACT FROM AUTHOR]

The gender gap in STEM (Science, Technology, Engineering, and Mathematics) is among the widest across education and professional fields, with an underrepresentation of girls and women, particularly in engineering and biomechanics. This issue begins early in education and worsens as females progress into more senior roles. To address this gap, we designed and implemented the Biomechanics Research and Innovation Challenge (BRInC), a 100-day STEM program focused on mentoring and role modelling to engage high school girls and early-career biomechanists at key phases where they most commonly disengage in STEM. We evaluated the influence of the program on (i) identity and perceptions towards science, engineering, and biomechanics; (ii) attitudes towards biomechanics, maths and science; and (iii) attitudes towards gender bias, education and career aspirations in STEM, within high school girls following participation in the BRInC program. We observed significant and positive shifts in girls' perceptions of both biomechanics and engineering. Participation in the program appeared to lead to favourable shifts in attitudes towards biomechanics, maths, and science and fostered a positive influence on girls' education and career aspirations, igniting an interest in future research opportunities. Innovative STEM engagement programs, such as BRInC, highlight the promising potential of targeted and bespoke approaches to address the underrepresentation of females in biomechanics and STEM-related education and careers. Future programs should strive to enhance socioeconomic and cultural diversity, employ whole of life-cycle approaches by offering programs for girls and women at various phases of the STEM pathway, and prioritize impact assessments to effectively monitor progress. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the reliability and validity of ultrasonography for measurement of hamstring muscle and semitendinosus (ST) tendon cross-sectional area (CSA). On two consecutive days, muscle anatomical CSA (ACSA) and ST tendon CSA were measured at standardized positions (30%-80% of thigh length; half the distance from the distal muscle-tendon junction to the popliteal crease) on 12 legs using ultrasonography and compared with corresponding magnetic resonance imaging measures. Inter-day intraclass correlation coefficients were good-to-excellent (0.882-0.996) for all assessed muscle and tendon sites. The limits of agreement widths were narrowest (range: 17%-52%) when muscle ACSA was large but were wide at sites with relatively small ACSA (≤184%) and for ST tendon CSA (range: 72%). Results suggest ultrasound-based measures of individual hamstring muscle maximal ACSA are reliable and valid and ST tendon CSA measures are reliable but require comparison with cadaveric or intra-operative measurements to verify validity. [ABSTRACT FROM AUTHOR]

The deep hip muscles are often omitted in studies investigating hip contact forces using neuromusculoskeletal modelling methods. However, recent evidence indicates the deep hip muscles have potential to change the direction of hip contact force and could have relevance for hip contact loading estimates. Further, it is not known whether deep hip muscle excitation patterns can be accurately estimated using neuromusculoskeletal modelling or require measurement (through invasive and time-consuming methods) to inform models used to estimate hip contact forces. We calculated hip contact forces during walking, squatting, and squat-jumping for 17 participants using electromyography (EMG)-informed neuromusculoskeletal modelling with (informed) and without (synthesized) intramuscular EMG for the deep hip muscles (piriformis, obturator internus, quadratus femoris). Hip contact force magnitude and direction, calculated as the angle between hip contact force and vector from femoral head to acetabular center, were compared between configurations using a paired t -test deployed through statistical parametric mapping (P < 0.05). Additionally, root mean square error, correlation coefficients (R2), and timing accuracy between measured and modelled deep hip muscle excitation patterns were computed. No significant between-configuration differences in hip contact force magnitude or direction were found for any task. However, the synthesized method poorly predicted (R2-range 0.02–0.3) deep hip muscle excitation patterns for all tasks. Consequently, intramuscular EMG of the deep hip muscles may be unnecessary when estimating hip contact force magnitude or direction using EMG-informed neuromusculoskeletal modelling, though is likely essential for investigations of deep hip muscle function. [ABSTRACT FROM AUTHOR]

A better understanding of deep hip muscle function is needed to establish whether retraining and strengthening these muscles is a worthwhile target for rehabilitation. This study aimed to determine the contribution of the deep hip muscles to the direction of hip loading in the acetabulum. Hip contact forces were calculated during walking and squatting for 12 participants (age: 24 ± 4 yrs, 4 females) using electromyography-informed neuromusculoskeletal modelling. Models were configured with different deep hip muscle activation levels: deep hip muscles (piriformis, obturator internus and externus, gemellus superior and inferior, and quadratus femoris) informed by intramuscular electromyography measurements (i.e., normal activation; assisted activation) and simulated with zero (no activation) or maximal (maximal activation) activation. The angle between the hip contact force and the vector from the femoral head to the acetabular center (hip contact force angle) was calculated for all configurations, where lower angles equated to hip loading directed towards the acetabular center. The position and spread of acetabular loading during both tasks were calculated for all configurations and compared using a within-participant analysis of variance via statistical parametric mapping (P < 0.05). Maximal activation resulted in lower hip contact force angles and more anterior-inferior oriented, albeit a slightly reduced, spread of acetabular loading compared to assisted activation and no activation. Results suggest that, if activated maximally, the deep hip muscles can change the direction of hip loading away from commonly damaged areas of acetabular cartilage. Targeted training of these muscles may be relevant for individuals with hip pathology who present with unfavorable regional loading and/or cartilage lesions. [ABSTRACT FROM AUTHOR]