nils-herrmann/clean_scirepeval huggingface dataset:
Joint work and ground reaction forces during running with daily-use and running-specific prostheses.
Venue: Journal of biomechanics

Some individuals with a transtibial amputation (TTA) may not have access to running-specific prostheses and therefore choose to run using their daily-use prosthesis. Unlike running-specific prostheses, daily-use prostheses are not designed for running and may result in biomechanical differences that influence injury risk. To investigate these potential differences, we assessed the effect of amputation, prosthesis type, and running speed on joint work and ground reaction forces. 13 people with and without a unilateral TTA ran at speeds ranging from 2.5 m/s to 5.0 m/s. People with TTA ran using their own daily-use and running-specific prostheses. Body kinematics and ground reaction forces were collected and used to compute joint work. People with TTA had smaller peak braking, propulsive and medial/lateral ground reaction forces from the amputated leg compared to people without TTA. People wearing running-specific prostheses had smaller peak amputated leg vertical ground reaction forces compared to daily-use prostheses at speeds above 3.5 m/s. Medial/lateral forces were also smaller in running-specific prostheses, which may present balance challenges when running on varied terrain. Running-specific prostheses stored and returned more energy and provided greater propulsion, resulting in more similar positive hip work between legs compared to daily-use prostheses. Increases in positive hip work, but not device work, highlight the importance of the hip in increasing running speed. Running-specific devices may be beneficial for joint health at running-speeds above 3.5 m/s and provide advantages in propulsion and energy return at all speeds compared to daily-use prostheses, helping people with TTA achieve faster running speeds.
New insights on the proximal femur biomechanics using Digital Image Correlation.
Venue: Journal of biomechanics

Finite element analyses (FEAs) of human femurs are mostly validated by ex-vivo experimental observations. Such validations were largely performed by comparing local strains at a small subset of points to the gold standard strain gauge (SG) measurements. A comprehensive full field validation of femoral FEAs including both strains and displacements using digital image correlation (DIC) full field measurements, especially at medial and lateral surfaces of the neck that experience the highest strains, provide new insights on femurs' mechanical behavior. Five cadaver femurs were loaded in stance position and monitored at the shaft and neck using two DIC systems simultaneously. DIC strains were compared to SG measurements at a limited number of locations so to corroborate DIC measurements by the gold standard technique. These were used to quantitatively assess the validity of FEA strains prediction especially at the neck where fracture usually occurs. Strains measured by DIC correspond well to the SG observations. An excellent agreement was observed between DIC and FEA predicted strains excluding the superior neck surface: FE=1.02×DIC-17,r2=0.977. At the superior neck however, strains were not well predicted by FEA models: Although the FEA predicted high strains at the 'saddle region', these were not observed experimentally. On the other hand, strain concentrations were measured by DIC at numerous vessel holes which were not represented by FE models. Since fractures usually initiate at the subcapital region in stance position ex-vivo experiments, where numerus vessel holes exist, these vessel holes may be required to be accounted for in future FE models so to allow a better estimation of the fracture load. Full field measurements are mandatory to allow a better validation of fracture load and location predictions which are of high clinical importance.
Accuracy of beam theory for estimating bone tissue modulus and yield stress from 3-point bending tests on rat femora.
Venue: Journal of biomechanics

Mechanical analysis of animal long bones often makes use of beam theory to estimate tissue properties from bending tests. An earlier study (van Lenthe et al., 2008) found that beam theory leads to a considerable underestimation of the Young's modulus of mice femora. However, we hypothesized that beam theory might still be an accurate tool for the determination of bone strength from experimental data. The first goal was to test this hypothesis, along with checking if the underestimation of the tissue modulus is also valid for rat femurs. The second goal was to investigate if micro-FE and beam theory would yield similar increases in Young's moduli and yield stress during aging. Twelve rat femurs (12 and 16 weeks old) were scanned using micro-CT and subjected to a three-point bending test from which the bending stiffness and the yield force were obtained. The Young's modulus and yield stress then were calculated by regressing the experimental results with results obtained from beam theory and micro-FE analysis based on the micro-CT scans. It was found that bone strength calculated using beam theory overestimated that calculated from micro-FE by 8.0%. The Young's modulus did not significantly differ. When comparing age groups, similar increases in tissue modulus and yield strength were found for beam theory and micro-FE, with significant differences only for the micro-FE yield stress. We concluded that the use of beam theory to calculate bone yield strength from 3-point bending test results of rat femurs leads to its overprediction.
Effects of vibro-medical insoles with and without vibrations on balance control in diabetic patients with mild-to-moderate peripheral neuropathy.
Venue: Journal of biomechanics

The purpose of this study was to investigate the effects of a total-contact insole with and without subthreshold mechanical random noise on the balance control in diabetic patients with mild-to-moderate peripheral neuropathy. Twenty diabetic patients with mild-to-moderate neuropathy was recruited to this study. A total-contact insole was prototyped and vibratory motors were embedded into it. The parameters of the center of pressure (amplitude, velocity, and phase plane portrait) were analyzed after 30-minute walks with the shoe only, the shoe with vibro-medical insole with and without vibrations in eyes open and closed condition. The center of pressure amplitude, velocity, and phase plane portrait in the anterior-posterior and medio-lateral directions were significantly decreased using a vibro-medical insole without vibration in the eyes open condition (p < 0.05), as compared to the shoe, and with vibro- medical insole with vibration in both eyes open and closed conditions (p < 0.05) compared to the shoe. A significant drop was observed in the center of pressure amplitude, velocity and phase plane portrait parameters when the vibro-medical insole with vibration was used compared to vibro- medical insole without vibration in eyes closed condition (p < 0.05). The use of vibro-medical insoles was found to improve the patient's balance control, as compared to the shoe. In the eyes closed condition, an improvement in the balance control was observed only with vibro-medical insole with vibration rather than vibro-medical insole without vibration or the shoe. Current finding suggest that a combination of the total-contact insole with vibration may improve the balance control remarkably in diabetic patients with mild-to-moderate neuropathy.
Joint laxity varies in response to partial and complete anterior cruciate ligament injuries throughout skeletal growth.
Venue: Journal of biomechanics

Anterior cruciate ligament (ACL) injuries are increasingly common in the skeletally immature population. As such there is a need to increase our understanding of the biomechanical function of the joint following partial and complete ACL injury during skeletal growth. In this work, we aimed to assess changes in knee kinematics and loading of the remaining soft tissues following both partial and complete ACL injury in a porcine model. To do so, we applied anterior-posterior tibial loads and varus-valgus moments to stifle joints of female pigs ranging from early juvenile to late adolescent ages and assessed both kinematics and in-situ loads carried in the bundles of the ACL and other soft tissues including the collateral ligaments and the menisci. Partial ACL injury led to increased anterior tibial translation only in late adolescence and small increases in varus-valgus rotation at all ages. Complete ACL injury led to substantial increases in translation and rotation at all ages. At all ages, the medial collateral ligament and the medial meniscus combined to resist the majority of applied anterior tibial load following complete ACL transection. Across all ages and flexion angles, the contribution of the MCL ranged from 45 to 90% of the anterior load and the contribution of the medial meniscus ranged from 14 to 35% of the anterior load. These findings add to our current understanding of age-specific functional properties of both healthy and injured knees during skeletal growth.
Selecting the appropriate input variables in a regression approach to estimate actively generated muscle moments around L5/S1 for exoskeleton control.
Venue: Journal of biomechanics

Back support exoskeletons are designed to prevent work-related low-back pain by reducing mechanical loading. For actuated exoskeletons, support based on moments actively produced by the trunk muscles appears a viable approach. The moment can be estimated by a biomechanical model. However, one of the main challenges here is the feasibility of recording the required input variables (kinematics, EMG data, ground reaction forces) to run the model. The aim of this study was to evaluate how accurate different selections of input variables can estimate actively generated moments around L5/S1. Different multivariate regression analyses were performed using a dataset consisting of spinal load, body kinematics and trunk muscle activation levels during different lifting conditions with and without an exoskeleton. The accuracy of the resulting models depended on the number and type of input variables and the regression model order. The current study suggests that third-order polynomial regression of EMG signals of one or two bilateral back muscle pairs together with exoskeleton trunk and hip angle suffices to accurately estimate the actively generated muscle moment around L5/S1, and thereby design a proper control system for back support exoskeletons.
3rd International workshop on spinal loading and deformation.
Venue: Journal of biomechanics

s 10 Session 1: Intervertebral Disc – Tissue Mechanics 11 Session 2: Debate on Mechanical Load – Injury/Degeneration/Pain 25 Session 3: Motion Segments: Load Sharing 29 Session 4: Lumbar Spine I: Shape and Kinematics 40 Session 5: Lumbar Spine II: Loads and Kinematics – Injury/Degeneration/Pain 52 Session 6: Spinal Loads – In-Vivo Measurements and Modeling 64 Session 7: Spinal Loads – Computational Models 76 Session 8: Trunk Stabilization and Control 86
Current perspectives on the role of biomechanical loading and genetics in development of disc degeneration and low back pain; a narrative review.
Venue: Journal of biomechanics

Degenerative changes in the disc have long been of interest; they are thought to be strongly associated with low back pain and caused by inappropriate loading or through injury. However, independent of the magnitude of occupational spinal loading, twin studies find that the heritability of lumbar disc degeneration is 34-74%. This finding has led to intensive searches for susceptibility genes; some genes associated with disc degeneration have been identified, though all with small effects on the degenerative process. The complex nature of degenerative changes suggests that many different genes are involved, and that interactions with environmental factors are influential in progression of degeneration. Low back pain itself also appears heritable (30-46%). The most important clinical question though, is not how discs degenerate but is disc degeneration related to low back pain. Imaging studies find many people with degenerate discs or even with discs showing pathological features such as herniations, are asymptomatic. However results are obscured by the lack of consistent definitions of the phenotypes of disc degeneration and of low back pain. Epidemiological studies could help disentangle these complex relationships, but they will only be successful once consistent classifications and phenotypes of both disc degeneration and low back pain are developed.
Piezoelectricity in the Intervertebral disc.
Venue: Journal of biomechanics

Lower back pain is a major global health challenge that can often be caused by degeneration of the Intervertebral Disc (IVD). While IVD biomechanics are a key factor in the degenerative cycle, many mechanotransduction pathways remain unknown, in particular the electro-mechanical coupling in the loaded tissue. However, despite evidence for a role in the mechanically-induced remodelling of similar tissue, piezoelectricity has been overlooked in the IVD. In this study, we investigate the piezoelectric properties of the Annulus Fibrosus (AF) and the Nucleus Pulposus (NP) by measuring the direct piezoelectric effect of mechanically-induced electrical potential change. To verify these findings, we conducted Piezoresponse Force Microscopy (PFM) to measure the inverse effect of electrically-induced deformation. We demonstrate that, for the first time, piezoelectricity is generated throughout the IVD. Piezoelectric effects were greater in the AF than the NP, owing to the organised collagen networks present. However, the piezoresponse found in the NP indicates piezoelectric properties of non-collagenous proteins that have not yet been studied. The voltage generated by longitudinal piezoelectricity in-vivo has been calculated to be ~1 nV locally, indicating that piezoelectric effects may directly affect cell alignment in the AF and may work in conjunction with streaming potentials throughout the IVD. In summary, we have highlighted an intricate electro-mechanical coupling that appears to have distinct physiological roles in the AF and NP. Further study is required to elucidate the cell response and determine the potential role of piezoelectric effects in regeneration and preventative measures from degeneration.
Joint moments and power in the acceleration phase of bend sprinting.
Venue: Journal of biomechanics

Joint kinetics of the lower limb (hip, knee, ankle, midfoot and metatarsophalangeal joints) were investigated during the acceleration phase of bend sprinting and straight-line sprinting. Within the bend sprinting literature, it is generally accepted that sprint performance on the bend is restricted by moments in the non-sagittal plane preventing the production of force in the sagittal plane. However, there is limited evidence in conditions representative of elite athletics performance that supports this hypothesis. Three-dimensional kinematic and ground reaction force data were collected from seven participants during sprinting on the bend (36.5 m radius) and straight, allowing calculation of joint moment, power and energy. No changes in extensor moment were observed at the hip and knee joints. Large effect sizes (g = 1.07) suggest a trend towards an increase in left step peak ankle plantarflexion moment. This could be due to a greater need for stabilisation of the ankle joint as a consequence of non-sagittal plane adaptations of the lower limb. In addition, the observed increase in peak MTP joint plantar-flexor moment might have implications for injury risk of the fifth metatarsal. Energy generation, indicated by positive power, in the sagittal plane at the MTP and ankle joints was moderately lower on the bend than straight, whilst increases in non-sagittal plane energy absorption were observed at the ankle joint. Therefore, energy absorption at the foot and ankle may be a key consideration in improving bend sprinting performance.
Commonly reported isokinetic parameters do not reveal long-term strength deficits of the Triceps surae complex following operative treatment of Achilles tendon rupture.
Venue: Journal of biomechanics

Isokinetic strength assessments are common outcome measures following operatively treated Achilles tendon (AT) ruptures. However, there is a lack of clarity on whether commonly reported outcome measures (such as peak joint moment) are sufficient to describe the extent of long-term functional deficits following AT rupture and repair. The present study conducted a comprehensive isokinetic evaluation of the Triceps surae complex in 12 participants who previously underwent AT rupture and repair. Testing occurred 4.4 (±2.6) years following surgery, and consisted of maximal isokinetic strength assessments of the plantarflexors at two angular velocities (30 and 60°∙s-1) with the knee in flexed and straight positions. Differences between injured and non-injured limbs were tested through discrete and statistical parametric mapping analysis. Average joint moment showed significant main effects between injured and non-injured limbs, but common isokinetic parameters such as peak moment and angle of peak moment did not. The normalised moment curves showed a significant main effect of limb, angular velocity and knee joint position on joint moment throughout different portions of the range of motion. Temporal analysis revealed a significantly greater ability of the non-injured limb to sustain plantarflexor moments across a range of testing conditions. Participants who had undergone operative treatment of AT ruptures did not display inter-limb differences in discrete isokinetic strength outcomes that are often used in the literature. Instead, temporal analyses were required to highlight the reduced capacity of the injured limb to generate end-range joint moments and to sustain higher levels of joint moment for longer periods.
Sudden gait perturbations elicit sex-specific neuromuscular trunk responses in persons with low back pain.
Venue: Journal of biomechanics

Persons with low back pain (LBP) exhibit delayed trunk muscle onset and increased co-contractions as a response to quasi-static and dynamic sudden trunk loading in comparison to back-healthy controls. Although LBP is more prevalent in females, sex-specific responses have not been well documented. Therefore, the purpose was to explore sex-specific neuromuscular differences, to gait perturbation, in LBP patients. Twenty-nine LBP patients (12m/17f;31 ± 10yrs; 174 ± 12 cm; 71 ± 16 kg) walked on a split-belt treadmill at 1 m/s, while 15 right-sided random perturbations (treadmill-belt decelerating, 40 m/s2, 50 ms duration; 200 ms after heel contact) were applied. Muscle activity was assessed using a 12-lead surface EMG (6 back/6 abdominal muscles; 4000 Hz). EMG-RMS [%] (0-200 ms after perturbation) was calculated and normalized to RMS of unperturbed gait for each muscle. Furthermore, muscle onsets (ms) were determined. Two-way ANOVA (factors: sex/muscle) was applied to account for sex differences in main outcomes. EMG-RMS (amplitudes; mean) ranged from 356% to 901% in males and 349% to 694% in females representing a significant interaction effect (sex * muscle: p = 0.017). Post-hoc analysis revealed significant differences for EMG-RMS analysis of rectus abdominis left (p = 0.043; f > m) as well as obliques externus right/left (p = 0.018/p = 0.005; f < m). In the time domain, females showed overall, shorter (mean: 90 ± 16 ms) response times compared to males (mean: 98 ± 22 ms, sex effect: p < 0.0001). In this LBP population, abdominal muscle activation discriminated females from males. Specifically, females had higher activity of the rectus abdominis muscles and lower activation of the externus oblique muscles. These different activation strategies might be relevant to the development of sex-specific intervention strategies.
Non-uniformity of displacement and strain within the Achilles tendon is affected by joint angle configuration and differential muscle loading.
Venue: Journal of biomechanics

Although the Achilles tendon (AT) has been studied for more than a century, a complete understanding of the mechanical and functional consequences of AT structural organization is currently lacking. The aim of this study was to assess how joint angle configuration affects subtendon displacement and strain of soleus (SOL) and lateral gastrocnemius (LG) muscles. Knots sutured onto SOL and LG subtendons of 12 Wistar rats, were videotaped to quantify displacements and the ankle torque was assessed for different isometric activation conditions (i.e., individual and simultaneous) of the triceps surae muscles. Changing ankle and knee joint angle affected the magnitude of displacement, relative displacement and strain of both SOL and LG subtendons. SOL subtendon behavior was not only affected by changes in ankle angle, but also by changes in knee angle. Displacement of SOL subtendon decreased (28-49%), but strain increased in response to knee extension. Independent of joint angle configuration, stimulation of any combination of the muscles typically resulted in displacements and strains of LG and SOL subtendons. Typically SOL displaced more but LG displaced more when stimulated at longer muscle lengths. Our results demonstrate that the distinct subtendons of the Achilles tendon can move and deform differently, but are not fully independent. Within the AT, there appears to be a precarious balance between sliding allowance and mechanical connectivity between subtendons.
Improved accuracy of biomechanical motion data obtained during impacts using a time-frequency low-pass filter.
Venue: Journal of biomechanics

Biomechanical motion data involving impacts are not adequately represented using conventional low-pass filters (CF). Time-frequency filters (TFF) are a viable alternative, but have been largely overlooked by movement scientists. We modified Georgakis and Subramaniam's (2009) fractional Fourier filter (MFrFF) and demonstrated it performed better than CFs for obtaining lower leg accelerations during football instep kicking. The MFrFF displayed peak marker accelerations comparable to a reference accelerometer during foot-to-ball impact (peak % error = -5.0 ± 11.4%), whereas CFs severely underestimated these peaks (30-70% error). During the non-impact phases, the MFrFF performed comparably to CFs using an appropriate (12-20 Hz) cut-off frequency (RMSE = 37.3 ± 7.6 m/s2 vs. 42.1 ± 11.4 m/s2, respectively). Since accuracy of segmental kinematics is fundamental for understanding human movement, the MFrFF should be applied to a range of biomechanical impact scenarios (e.g. locomotion, landing and striking motions) to enhance the efficacy of study in these areas.