Instrumented Treadmill Research Articles

The significance of frontal plane static alignment in anticipating dynamic knee moment among transtibial prosthesis users: A cross-sectional study

BackgroundIn the process of transtibial prosthetic fitting, alignment is the process of positioning the prosthetic foot relative to the residual limb. Changes in frontal plane alignment can impact knee moments during walking, which can either cause or, when aligned properly, prevent injuries. However, clinical evaluation of dynamic knee moments is challenging, limiting prosthetists' insights into dynamic joint loading. Typically, knee joint loading is assessed in static stance using the knee moment arm as a proxy for subsequent dynamic alignment. It remains uncertain if static alignment accurately represents actual dynamics during walking. Research questionIs the frontal knee moment arm in stance predictive for the knee moment arm and external knee adduction moment during gait in transtibial bone-anchored prosthesis users? MethodsIn this cross-sectional study, twenty-seven unilateral transtibial bone-anchored prosthesis users underwent data acquisition on the M-Gait instrumented treadmill. Static and dynamic measurements were conducted, and knee moment arm and external knee adduction moment were calculated. Pearson's correlation and linear regression analyses were performed to examine relationships between static and dynamic knee moment arms and external knee adduction moments. ResultsThe static knee moment arm showed significant associations with dynamic knee moment arm at the ground reaction force peaks (First: r=0.60, r2=35%, p<0.001; Second: r=0.62, r2=38%, p=0.001) and knee adduction moment (First: r=0.42, r2=17%, p=0.030; Second: r=0.59, r2=35%, p=0.001). A 1 mm between-subject difference in static knee moment arm corresponded, on average, with a 0.9% difference in knee adduction moment at the first peak and a 1.5% difference at the second peak of the ground reaction force. SignificanceWhile static alignment is important to optimize adduction moments during stance it may only partly mitigate excessive moments during gait. The fair correlation and limited percentage of explained variance underscores the importance of dynamic alignment in optimizing the body's dynamic load during walking.

Long-term solutions of calibrated and generalised Macdonald’s model for pedestrian-induced lateral forces

The inverted pendulum pedestrian model (IPM) for walking on laterally-oscillating structures, originally proposed by Macdonald, has been recently calibrated based on data from pedestrians walking on a laterally-oscillating instrumented treadmill. It was then generalised to be suitable for the application in a predictive manner, i.e. in simulations of lateral structural response for any population of pedestrians. The generalised IPM captures the fundamental pedestrian-structure interaction mechanism and pedestrian-generated lateral forces onto a structure, including the self-excited forces which are critical from the point of view of structural stability. However, since the closed-form solutions of the generalised IPM are currently unavailable, its application requires numerical integration. To address this shortcoming, closed form solutions for the long-term average lateral self-excited forces are derived in this study based on the framework introduced by McRobie. A parametric study is conducted revealing complex interdependencies between pedestrian and bridge behaviour and their influence on the self-excited forces. The presented results are related to the measurements from full-scale bridges and laboratory investigations.

Gait asymmetries after fibular free flap harvest: A cross-sectional observational study

BackgroundThe ability to walk safely after head and neck reconstruction with fibular free flaps in tumor surgery is a high priority for patients. In addition, surgeons and patients require objective knowledge of the functional donor-site morbidity. However, the effects of fibular free flap surgery on gait asymmetries have only been studied for step length and stance duration. This study analyses whether patients who have undergone fibular free flap reconstruction have enduring gait asymmetries compared to age-matched controls. MethodsPatients who underwent head and neck reconstruction with fibular free flaps between 2019 and 2023 were recruited, as well as age-matched controls. Participants walked on an instrumented treadmill at 3 km/h. The primary outcome measures were 22 gait asymmetry metrics. Secondary outcome measures were the associations of gait asymmetry with the length of the harvested fibula, and with the time after surgery. FindingsNine out of 13 recruited patients completed the full assessment without holding on to the handrail on the treadmill. In addition, nine age-matched controls were enrolled. Twenty out of the 22 gait asymmetry parameters of patients were similar to healthy controls, while push-off peak force (p = 0.008) and medial impulse differed (p = 0.003). Gait asymmetry did not correlate with the length of the fibula harvested. Seven gait asymmetry parameters had a strong correlation with the time after surgery. InterpretationOn the long-term, fibular free flap reconstruction has only a limited effect on the asymmetry of force-related and temporal gait parameters while walking on a treadmill.

Factors Associated With High-Risk and Low-Risk Bone Stress Injury in Female Runners: Implications for Risk Factor Stratification and Management.

Bone stress injury (BSI) is a common overuse injury in active women. BSIs can be classified as high-risk (pelvis, sacrum, and femoral neck) or low-risk (tibia, fibula, and metatarsals). Risk factors for BSI include low energy availability, menstrual dysfunction, and poor bone health. Higher vertical load rates during running have been observed in women with a history of BSI. The purpose of this study was to characterize factors associated with BSI in a population of premenopausal women, comparing those with a history of high-risk or low-risk BSI with those with no history of BSI. It was hypothesized that women with a history of high-risk BSI would be more likely to exhibit lower bone mineral density (BMD) and related factors and less favorable bone microarchitecture compared with women with a history of low-risk BSI. In contrast, women with a history of low-risk BSI would have higher load rates. Cross-sectional study; Level of evidence, 3. Enrolled were 15 women with a history of high-risk BSI, 15 with a history of low-risk BSI, and 15 with no history of BSI. BMD for the whole body, hip, and spine was standardized using z scores on dual-energy x-ray absorptiometry. High-resolution peripheral quantitative computed tomography was used to quantify bone microarchitecture at the radius and distal tibia. Participants completed surveys characterizing factors that influence bone health-including sleep, menstrual history, and eating behaviors-utilizing the Eating Disorder Examination Questionnaire (EDE-Q). Each participant completed a biomechanical assessment using an instrumented treadmill to measure load rates before and after a run to exertion. Women with a history of high-risk BSI had lower spine z scores than those with low-risk BSI (-1.04 ± 0.76 vs -0.01 ± 1.15; P < .05). Women with a history of high-risk BSI, compared with low-risk BSI and no BSI, had the highest EDE-Q subscores for Shape Concern (1.46 ± 1.28 vs 0.76 ± 0.78 and 0.43 ± 0.43) and Eating Concern (0.55 ± 0.75 vs 0.16 ± 0.38 and 0.11 ± 0.21), as well as the greatest difference between minimum and maximum weight at current height (11.3 ± 5.4 vs 7.7 ± 2.9 and 7.6 ± 3.3 kg) (P < .05 for all). Women with a history of high-risk BSI were more likely than those with no history of BSI to sleep <7 hours on average per night during the week (80% vs 33.3%; P < .05). The mean and instantaneous vertical load rates were not different between groups. Women with a history of high-risk BSI were more likely to exhibit risk factors for poor bone health, including lower BMD, while load rates did not distinguish women with a history of BSI.

A comprehensive dataset on biomechanics and motor control during human walking with discrete mechanical perturbations.

Humans have a remarkable capability to maintain balance while walking. There is, however, a lack of publicly available research data on reactive responses to destabilizing perturbations during gait. Here, we share a comprehensive dataset collected from 10 participants who experienced random perturbations while walking on an instrumented treadmill. Each participant performed six 5-min walking trials at a rate of 1.2 m/s, during which rapid belt speed perturbations could occur during the participant's stance phase. Each gait cycle had a 17% probability of being perturbed. The perturbations consisted of an increase of belt speed by 0.75 m/s, delivered with equal probability at 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% of the stance phase. Data were recorded using motion capture with 25 markers, eight inertial measurement units (IMUs), and electromyography (EMG) from the tibialis anterior (TA), soleus (SOL), lateral gastrocnemius (LG), rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and gluteus maximus (GM). The full protocol is described in detail. We provide marker trajectories, force plate data, EMG data, and belt speed information for all trials and participants. IMU data is provided for most participants. This data can be useful for identifying neural feedback control in human gait, biologically inspired control systems for robots, and the development of clinical applications.

Asymmetric gap balancing improves knee kinematic following primary total knee arthroplasty

PurposeThe purpose of this study was to demonstrate closer-to-normal knee kinematics following primary total knee arthroplasty (TKA) performed establishing asymmetric gap balancing intraoperatively.Material and methodTwo age-, sex-, BMI-matched groups of patients underwent medially stabilized TKA because of isolated knee disease. Group A (12 patients) underwent “unrestricted” kinematic alignment (uKA) according to Howell while group B (15 patients) received robot-assisted “simplified” KA (sKA) with an alignment goal (Hip-Knee-Ankle axis-HKA) ± 5° respect to the mechanical axis. Intraoperatively, in group B, the flexion gap at 90° was first set at an average of 1.5 mm (0–5 mm; SD 4.4 mm) tighter in the medial compartment with respect to the lateral; in the same way, the extension gap was then set at an average of 2.0 mm (0–4.5 mm; SD 3.1 mm) tighter in the medial compartment with respect to the lateral. All patients, including a non-arthritic cohort (group C: 5 controls) underwent gait analysis using an instrumented treadmill (WalkerView–WV) equipped with an instrumented belt armed with a 3D video camera. The WV software evaluated multiple spatiotemporal and kinematic parameters, including: (1) contact time (s); (2) knee ROM during gait cycle; (3) step length percentage with respect to total gait (%) and pure step length (cm). Statistical analyses included t-Test and ANOVA and were conducted by using SPSS.ResultsAt the final FU, significant differences were noted during gait between the two TKA groups (uKA-sKA) and the controls. Both TKA groups showed superior mean contact time on the surgical knee (uKA 1 s; sKA 0.97 s) as compared to the controls (0.72 s) (P = 0.002) while no differences were found between them (P = 0.11). TKA groups showed a lower, maximum ROM in the surgical knee (mean uKA 36º; mean sKA 49º) relative to the controls (mean 57º) (P < 0.05) but a statistical difference was found between them (P = 0.003). Both TKA groups showed a higher step length percentage with respect to the total gait and a shorter step length on the surgical side (uKA: mean 8.28% and mean step length 35.5 cm; sKA: mean 8.38% and mean step length 34.6 cm) in comparison to the controls (mean 3.38%; mean step length 71.4 cm) (P < 0.05) while no statistical differences were found between them.ConclusionTo our knowledge, this was the first study to exhibit the kinematic advantages of a slightly asymmetric gap balancing during KA TKA. Combining a medially-stabilized implant design and a surgical technique aiming to obtain a tighter medial compartment represents a promising approach to improve outcomes after TKA.Graphical

IMU-Based Real-Time Estimation of Gait Phase Using Multi-Resolution Neural Networks.

This work presents a real-time gait phase estimator using thigh- and shank-mounted inertial measurement units (IMUs). A multi-rate convolutional neural network (CNN) was trained to estimate gait phase for a dataset of 16 participants walking on an instrumented treadmill with speeds varying between 0.1 to 1.9 m/s, and conditions such as asymmetric walking, stop-start, and sudden speed changes. One-subject-out cross-validation was used to assess the robustness of the estimator to the gait patterns of new individuals. The proposed model had a spatial root mean square error of 5.00±1.65%, and a temporal mean absolute error of 2.78±0.97% evaluated at the heel strike. A second cross-validation was performed to show that leaving out any of the walking conditions from the training dataset did not result in significant performance degradation. A 2-sample Kolmogorov-Smirnov test showed that there was no significant increase in spatial or temporal error when testing on the abnormal walking conditions left out of the training set. The results of the two cross-validations demonstrate that the proposed model generalizes well across new participants, various walking speeds, and gait patterns, showcasing its potential for use in investigating patient populations with pathological gaits and facilitating robot-assisted walking.

Comparison of muscle activity of the lower limbs while running on different treadmill models.

Treadmill running is a common method of exercise and to study human locomotion. Research has examined the kinematics and kinetics of overground and treadmill running, but there has been less focus on the levels of muscle activity during treadmill running. We investigated if muscle activity is different while running overground compared to running on a variety of treadmills. A total of 11 healthy individuals ran at 3 speeds (2.6, 3.6, 4.5 m/s) under 4 different running conditions (3 treadmills, overground). The three treadmills included a typical home exercise treadmill, a midsize commercial research treadmill, and a large, instrumented research treadmill. Surface EMG of the tibialis anterior (TA), gastrocnemius medialis (GM), rectus femoris (RF) and biceps femoris (BF) muscles were measured for each running condition. The integrated EMG was computed for each running condition for the stance and swing phase, as well as 100 ms before and after the heel-strike. Friedman analysis revealed significant effects during the stance phase for GM and RF at all speeds, such that muscle activation was lower on the treadmills relative to overground. During the stance phase at faster speeds, the muscle activity was higher for the TA and lower for the BF while running on the different treadmills compared to overground running. Before heel-strike, the TA was significantly less active during treadmill compared to overground running at 2.6 m/s and the RF showed significantly higher activity at 3.6 m/s and 4.5 m/s while running on the different treadmills. Summarizing, differences were mainly observed between the different treadmill conditions relative to overground running. Muscle activation differences between the different treadmill conditions were observed at faster running speeds for RF during the pre-heel-strike phase only. Different types of treadmills with different mechanical properties affects the muscle activity during stance phase as well as in preparation to heel-strike. Additionally, the muscle activity is greater during overground compared to treadmill running during the stance phase for the GM, BF, and RF.

Limb and joint kinetics during walking in individuals with Mild-Moderate Parkinson’s disease

Given the known deficits in spatiotemporal aspects of gait for people with Parkinson’s disease (PD), we sought to determine the underlying gait abnormalities in limb and joint kinetics, and examine how deficits in push-off and leg swing might contribute to the shortened step lengths for people with PD. Ten participants with PD and 11 age-matched control participants walked overground and on an instrumented treadmill. Participants with PD then walked on the treadmill with a posteriorly directed restraining force applied to 1) the pelvis to challenge push-off and 2) the ankles to challenge leg swing. Spatiotemporal, kinematic, and force data were collected and compared between groups and conditions. Despite group differences in spatiotemporal measures during overground walking, we did not observe these differences when the groups walked on a treadmill at comparable speeds. Nevertheless, the hip extension impulse appeared smaller in the PD group during their typical walking. When challenging limb propulsion, participants in the PD group maintained step lengths by increasing the propulsive impulse. Participants with PD were also able to maintain their typical step length against resistance intended to impede swing limb advancement, and even increased step lengths with cuing. The presence of reduced hip extension torque might be an early indicator of gait deterioration in this neurodegenerative disease. Our participants with PD were able to increase hip extension torque in response to needed demands. Additionally, participants with PD were able to increase limb propulsion and leg swing against resistance, suggesting a reserve in limb mechanics.

Comparison of Concurrent and Asynchronous Running Kinematics and Kinetics From Marker-Based and Markerless Motion Capture Under Varying Clothing Conditions.

As markerless motion capture is increasingly used to measure 3-dimensional human pose, it is important to understand how markerless results can be interpreted alongside historical marker-based data and how they are impacted by clothing. We compared concurrent running kinematics and kinetics between marker-based and markerless motion capture, and between 2 markerless clothing conditions. Thirty adults ran on an instrumented treadmill wearing motion capture clothing while concurrent marker-based and markerless data were recorded, and ran a second time wearing athletic clothing (shorts and t-shirt) while markerless data were recorded. Differences calculated between the concurrent signals from both systems, and also between each participant's mean signals from both asynchronous clothing conditions were summarized across all participants using root mean square differences. Most kinematic and kinetic signals were visually consistent between systems and markerless clothing conditions. Between systems, joint center positions differed by 3cm or less, sagittal plane joint angles differed by 5° or less, and frontal and transverse plane angles differed by 5° to 10°. Joint moments differed by 0.3N·m/kg or less between systems. Differences were sensitive to segment coordinate system definitions, highlighting the effects of these definitions when comparing against historical data or other motion capture modalities.

Quadriceps composition and function influence downhill gait biomechanics >1 year following anterior cruciate ligament reconstruction

BackgroundQuadriceps dysfunction is common following anterior cruciate ligament reconstruction and contributes to aberrant gait biomechanics. Changes in quadriceps composition also occur in these patients including greater concentrations of non-contractile tissue. The purpose of this study was to evaluate associations between quadriceps composition, function, and gait biomechanics in individuals with anterior cruciate ligament reconstruction. MethodsForty-eight volunteers with anterior cruciate ligament reconstruction completed gait biomechanics and quadriceps function and composition assessments. Gait biomechanics were sampled during downhill walking (−10° slope) on an instrumented treadmill. Quadriceps function (peak torque and rate of torque development) was assessed via maximal isometric contractions, while composition was evaluated via ultrasound echo intensity. FindingsGreater quadriceps peak torque was associated with a greater peak knee extension moment (r = 0.365, p = 0.015). Greater vastus lateralis echo intensity (i.e. poorer muscle quality) was associated with less knee flexion displacement (r = −0.316, p = 0.032). Greater echo intensity of the vastus lateralis (r = −0.298, p = 0.044) and rectus femoris (r = −0.322, p = 0.029) was associated with a more abducted knee angle at heel strike. Quadriceps peak torque explained 11–16% of the variance in echo intensity. InterpretationBoth quadriceps function and composition influence aberrant gait biomechanics following anterior cruciate ligament reconstruction. Quadriceps composition appears to provide insight into quadriceps dysfunction independent of muscle strength, as they associated with different gait biomechanics outcomes and shared minimal variance. Future research is necessary to determine the influence of changes in quadriceps composition on joint health outcomes.

Poincaré analysis detects pathological limb loading rate variability in post-anterior cruciate ligament reconstruction individuals

BackgroundPost-ACLR individuals can experience repeated exposure to variable limb loading, which contributes to development of knee osteoarthritis. Variable limb loading can present as loading rate variability (LRV) and is magnified during tasks like fast walking when the system is stressed. Nonlinear measures that evaluate temporal variability have successfully detected changes in gait variability associated with altered motor control, however, appropriately describing and uncovering the nature of gait variability has been challenging. Here, Poincaré analysis, a nonlinear method unique in its ability to capture different aspects of variability, served to uncover and quantify changes in limb LRV. It was hypothesized that post-ACLR individuals’ overloaded limbs would quantitatively and graphically demonstrate greater short-term stride-to-stride and long-term limb LRV during fast walking compared to the underloaded and healthy control limbs. MethodsFourteen post-ACLR individuals and fourteen healthy controls completed a walking protocol on an instrumented treadmill where they walked at 1.0 m/s and 1.5 m/s for 5-minutes each. A Welch’s test was performed to compare differences in short-term and long-term LRV metrics for the post-ACLR individuals’ overloaded and underloaded limbs and the healthy controls’ right limbs. ResultsAnalyses revealed that the post-ACLR individuals’ overloaded limb exhibited significantly greater short-term and long-term values compared to the underloaded and healthy control limbs at 1.5 m/s (p<0.05). Additionally, the loading rate data was widely scattered across the plots for the overloaded limb, indicating greater LRV. SignificancePoincaré analysis successfully identified that post-ACLR overloaded limbs exhibited impaired motor control during fast walking based on quantitative and graphical changes in variability. This highlights the clinical applications of Poincaré analysis, with the plots potentially serving as an easy-to-interpret diagnostic tool for pathological limb LRV.

Transfemoral prosthetic simulators versus amputees: ground reaction forces and spatio-temporal parameters in gait.

This study aimed to compare the ground reaction forces (GRFs) and spatio-temporal parameters as well as their asymmetry ratios in gait between individuals wearing a transfemoral prosthetic simulator (TFSim) and individuals with unilateral transfemoral amputation (TFAmp) across a range of walking speeds (2.0-5.5 km h-1). The study recruited 10 non-disabled individuals using TFSim and 10 individuals with unilateral TFAmp using a transfemoral prosthesis. Data were collected using an instrumented treadmill with built-in force plates, and subsequently, the GRFs and spatio-temporal parameters, as well as their asymmetry ratios, were analysed. When comparing the TFSim and TFAmp groups, no significant differences were found among the gait parameters and asymmetry ratios of all tested metrics except the vertical GRFs. The TFSim may not realistically reproduce the vertical GRFs during the weight acceptance and push-off phases. The structural and functional variations in prosthetic limbs and components between the TFSim and TFAmp groups may be primary contributors to the difference in the vertical GRFs. These results suggest that TFSim might be able to emulate the gait of individuals with TFAmp regarding the majority of spatio-temporal and GRF parameters. However, the vertical GRFs of TFSim should be interpreted with caution.

People with degenerative cervical myelopathy have impaired reactive balance during walking

BackgroundPeople with degenerative cervical myelopathy are known to have impaired standing balance and walking abilities, but less is known about balance responses during walking. Research questionThe aim of this project was to assess reactive balance impairments during walking in people with degenerative cervical myelopathy (PwDCM). We hypothesized that center of mass motion following perturbations would be larger in PwDCM and gluteus medius electromyographic amplitude responses would be decreased in PwDCM. MethodsReactive balance responses were quantified during unanticipated lateral pulls to the waist while treadmill walking. Walking biomechanics data were collected from 10 PwDCM (F=6) and 10 non-myelopathic controls (F=7) using an 8 camera Vicon System (Vicon MX T-Series). Electromyography was collected from lower limb muscles. Participants walked on an instrumented treadmill and received lateral pulls at random intervals and in randomized direction at 5% and 2.5% body mass. Participants walked at 3 prescribed foot placements to control for effects of the size of base of support. ResultsAs compared with controls, the perturbation-related positional change of the center of mass motion (ΔCOM) was increased in PwDCM (p=0.001) with similar changes in foot placement (p>0.05). Change in gluteus medius electromyography, however, was less in PwDCM than in controls (p<0.001). SignificanceAfter experimentally controlling step width, people with mild-to-moderate degenerative cervical myelopathy at least 3 months following cervical spine surgery have impaired reactive balance during walking likely coupled with reduced gluteus medius electromyographic responses. Rehabilitation programs focusing on reactive balance and power are likely necessary for this population.

Accuracy of unilateral and bilateral gait assessment using a mobile gait analysis system at different walking speeds

BackgroundPrevious research on the accuracy of mobile measurement systems has focused on parameters related to the whole gait cycle. Specifically, bilateral gait characteristics were primarily used as outcome measures. Research question:How accurate are unilateral gait characteristics detected using a mobile system at various fixed walking speeds? Methods:Gait analysis during treadmill walking at velocities (VEL) of 2.5 (v1), 4.5 (v2) and 6.5 km/h (v3) was performed in a population of 47 healthy young adults, consisting of 27 females (age: 23 ± 2 years, BMI: 21.4 ± 2.2 kg/m²) and 20 males (age: 22 ± 1 years, BMI: 23.3 ± 3.4 kg/m²). Spatiotemporal gait data were simultaneously determined using an instrumented treadmill (gaitway 3D) and a mobile gait analysis system (RehaGait). Besides VEL, bilateral (stride length [SL], cadence [CAD]) and unilateral (contact duration [CON], single [SS] and double support duration [DS]) outcomes were validated. ResultsAcross the three VEL investigated, the correlations between both measurement systems were almost perfect in SL and CAD (r > 0.97). In addition, SL significantly differed (p < 0.01) with moderate to large effects, whereby the root mean squared error (RMSE) did not exceed 1.8 cm. RMSE in CAD was not higher than 0.33 spm and statistically significant differences were only present at v1 (d = 0.63). DS was the most erroneous unilateral parameter with values for %RMSE ranging from 9% at v1 to 14% at v3. In CON and SS %RMSE was in a magnitude of 2–4% across all VEL.Furthermore, VEL affected measurement accuracy in unilateral outcomes with moderate to large effects (F (2, 45) > 6.0, p < 0.01, ηp2 > 0.11) with consistently higher differences at lower velocities. Significance:Based on the results presented the validity of the mobile gait analysis system investigated to detect gait asymmetries must be questioned.

Cues to land softly and quietly result in acute reductions in ground reaction force loading rates in runners

BackgroundA common gait retraining goal for runners is reducing vertical ground reaction force (GRF) loading rates (LRs), which have been associated with injury. Many gait retraining programs prioritize an internal focus of attention, despite evidence supporting an external focus of attention when a specific outcome is desired (e.g., LR reduction). Research QuestionDoes an external focus of attention (using cues for quiet, soft landings) result in comparable reductions in LRs to those achieved using a common internal focus (forefoot striking while barefoot)? MethodsThis observational study included 37 injured runners (18 male; mean age 36 (14) years) at the OMITTED Running Center. Runners wore inertial measurement units over the distal-medial tibia while running on an instrumented treadmill at a self-selected speed. Data were collected for three conditions: 1) Shod-Control (wearing shoes, without cues); 2) Shod-Quiet (wearing shoes, cues for quiet, soft landings); and 3) Barefoot-FFS (barefoot, cues for forefoot strike (FFS)). Within-subject variables were compared across conditions: vertical instantaneous loading rate (LR, primary outcome); vertical stiffness during initial loading; peak vertical GRF; peak vertical tibial acceleration (TA); and cadence. ResultsVertical LR, stiffness, and TA were lower in the Shod-Quiet compared to Shod-Control p < 0.001). Peak vertical GRF and cadence were not different between Shod-Quiet and Shod-Control. Reductions in stiffness and LR were similar between Shod-Quiet and Barefoot-FFS, and GRF in Barefoot-FFS remained similar to both shod conditions. However, runners demonstrated additional reductions in TA and increased cadence when transitioning from Shod-Quiet to the Barefoot-FFS condition (p < 0.05). SignificanceThese results suggests that a focus on quiet, soft landings may be an effective gait retraining method for future research.

The Influence of "Super-Shoes" and Foot Strike Pattern on Metabolic Cost and Joint Mechanics in Competitive Female Runners.

The objective of this study is to assess the influence of "super-shoes" on metabolic cost and joint mechanics in competitive female runners and to understand how foot strike pattern may influence the footwear effects. Eighteen competitive female runners ran four 5-min bouts on a force instrumented treadmill at 12.9 km·h -1 in 1) Nike Vaporfly Next% 2™ (SUPER) and 2) Nike Pegasus 38™ (CON) in a randomized and mirrored order. Metabolic power was improved by 4.2% ( P < 0.001; d = 0.43) and metatarsophalangeal (MTP) negative work ( P < 0.001; d = 1.22), ankle negative work ( P = 0.001; d = 0.67), and ankle positive work ( P < 0.001; d = 0.97) were all smaller when running in SUPER compared with CON. There was no correlation between foot strike pattern and the between-shoe (CON to SUPER) percentage change for metabolic power ( r = 0.093, P = 0.715). Metabolic power improved by 4.2% in "super-shoes" (but only by ~3.2% if controlling for shoe mass differences) in this cohort of competitive female runners, which is a smaller improvement than previously observed in men. The reduced mechanical demand at the MTP and ankle in "super-shoes" are consistent with previous literature and may explain or contribute to the metabolic improvements observed in "super-shoes"; however, foot strike pattern was not a moderating factor for the metabolic improvements of "super-shoes." Future studies should directly compare the metabolic response among different types of "super-shoes" between men and women.

Optimizing wearable motion tracking by assessing sagittal joint angle accuracy with minimal sensor use

Introduction&#x0D; Wearable motion tracking technology often focuses on reducing the number of sensors to simplify design and lower costs. Research has shown that single IMUs can reconstruct leg kinematics (Gholami et al., 2020; Hossain et al., 2022; Lim et al., 2020) and ground reaction forces (Jiang et al., 2020) effectively. Additionally, model-based methods have demonstrated the feasibility of using fewer gyroscopes to estimate stride length and motion range in healthy individuals and patients with coxarthritis (Salarian et al., 2013). In this study, we aim to assess the precision of sagittal joint angle estimations using strain sensors while minimizing sensor count.&#x0D; Methods&#x0D; We conducted a study with ten participants based on our previous work that involved collecting single-leg treadmill running data to monitor lower limb joint angles with piezoresistive strain sensors. Subjects ran on an instrumented treadmill at 8-10 km/h, wearing athletic pants embedded with nine strain sensors located on the hip, knee, and ankle. Optical motion capture provided reference kinematics. Our prior research achieved less than 1.5° error in the sagittal plane using a machine-learning approach. The current study explores the extent to which sensor reduction is possible without meaningful loss of accuracy. Three evaluation measures were used for assessment: Pearson correlation, dynamic time warping, and root-mean-squared error.&#x0D; Results&#x0D; The results from our correlation analysis will be used to develop a model that optimally balances between accuracy and minimizing the number of sensors. This has practical implications in sports science, where athletes could benefit from less intrusive and more comfortable performance monitoring, and in healthcare, for remote monitoring of patients with mobility issues.&#x0D; References&#x0D; Gholami, M., Napier, C., &amp; Menon, C. (2020). Estimating lower extremity running gait kinematics with a single accelerometer: A deep learning approach. Sensors, 20(10), Article 2939. https://doi.org/10.3390/s20102939&#x0D; Hossain, M. S., Bin, Dranetz, J., Choi, H., &amp; Guo, Z. (2022). DeepBBWAE-Net: A CNN-RNN based deep superlearner for estimating lower extremity sagittal plane joint kinematics using shoe-mounted IMU sensors in daily living. IEEE Journal of Biomedical and Health Informatics, 26(8), 3906-3917. https://doi.org/10.1109/jbhi.2022.3165383&#x0D; Jiang, X., Napier, C., Hannigan, B., Eng, J. J., &amp; Menon, C. (2020). Estimating vertical ground reaction force during walking using a single inertial sensor. Sensors, 20(15), Article 4345. https://doi.org/10.3390/s20154345&#x0D; Lim, H., Kim, B., &amp; Park, S. (2020). Prediction of lower limb kinetics and kinematics during walking by a single IMU on the lower back using machine learning. Sensors, 20(1), Article 130. https://doi.org/10.3390/s20010130&#x0D; Salarian, A., Burkhard, P. R., Vingerhoets, F. J. G., Jolles, B. M., &amp; Aminian, K. (2013). A novel approach to reducing number of sensing units for wearable gait analysis systems. IEEE Transactions on Biomedical Engineering, 60(1), 72–77. https://doi.org/10.1109/TBME.2012.2223465

Gait biomechanics do not differ between adolescents with and without patellofemoral pain.

To determine if adolescents with patellofemoral pain exhibit different biomechanical characteristics to asymptomatic adolescents during walking and running. Twenty-eight adolescents with patellofemoral pain (16 male, 12 female, mean [SD] age: 14.3 [1.7] years) and 24 asymptomatic adolescents (13 male, 11 female, mean [SD] age: 14.1 [1.6] years) participated. Participants walked and ran on an instrumented treadmill in a standardized athletic shoe. Continuous hip, knee, and ankle joint angles and moments, and frontal plane pelvic motion were compared between groups using one-dimensional statistical parametric mapping independent t-tests (alpha <0.05). Cadence and stride length were compared between groups using independent t-tests. During walking, adolescents with patellofemoral pain had a higher hip extension moment at 7%-8% of the gait cycle (p = 0.04) and walked with a shorter stride length (mean difference [95% confidence interval] = -0.07 [-0.1, -0.01] m). There were no other differences between groups during walking. During running, adolescents with patellofemoral pain had greater knee flexion than asymptomatic adolescents at 35%-40% of the gait cycle (p = 0.04) and ran with a higher cadence (mean difference [95% confidence interval] = 5.8 [2.0, 9.5] steps/min). There were no other statistically significant differences between groups during running. Adolescents with patellofemoral pain demonstrate few biomechanical differences to asymptomatic adolescents during walking and running. The identified differences are likely of limited clinical importance. Biomechanical alterations which have been previously associated with patellofemoral pain in adults, may not need to be the target of management of adolescent patellofemoral pain.

Achilles Tendon Loading during Running Estimated Via Shear Wave Tensiometry: A Step Toward Wearable Kinetic Analysis.

Understanding muscle-tendon forces (e.g., triceps surae and Achilles tendon) during locomotion may aid in the assessment of human performance, injury risk, and rehabilitation progress. Shear wave tensiometry is a noninvasive technique for assessing in vivo tendon forces that has been recently adapted to a wearable technology. However, previous laboratory-based and outdoor tensiometry studies have not evaluated running. This study was undertaken to assess the capacity for shear wave tensiometry to produce valid measures of Achilles tendon loading during running at a range of speeds. Participants walked (1.34 m·s -1 ) and ran (2.68, 3.35, and 4.47 m·s -1 ) on an instrumented treadmill while shear wave tensiometers recorded Achilles tendon wave speeds simultaneously with whole-body kinematic and ground reaction force data. A simple isometric task allowed for the participant-specific conversion of Achilles tendon wave speeds to forces. Achilles tendon forces were compared with ankle torque measures obtained independently via inverse dynamics analyses. Differences in Achilles tendon wave speed, Achilles tendon force, and ankle torque across walking and running speeds were analyzed with linear mixed-effects models. Achilles tendon wave speed, Achilles tendon force, and ankle torque exhibited similar temporal patterns across the stance phase of walking and running. Significant monotonic increases in peak Achilles tendon wave speed (56.0-83.8 m·s -1 ), Achilles tendon force (44.0-98.7 N·kg -1 ), and ankle torque (1.72-3.68 N·m·(kg -1 )) were observed with increasing locomotion speed (1.34-4.47 m·s -1 ). Tensiometry estimates of peak Achilles tendon force during running (8.2-10.1 body weights) were within the range of those estimated previously via indirect methods. These results set the stage for using tensiometry to evaluate Achilles tendon loading during unobstructed athletic movements, such as running, performed in the field.