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Uneven ground, slopes, stairs, sidewalks are constraining situations that must be overcome by transfemoral amputees (TFA). However, most of prosthetic systems do not have ankle mobility, the connection between the prosthetic knee and the prosthetic foot being a rigid part. A certain flexibility is allowed by the energy storage restitution feet thanks to their stiffness. But they do not allow a complete adaptation to daily encountered walking situations, like walking on slopes (ascent and descent) or downstairs [1]. Furthermore, TFA have a high risk of falling, with more than 50% of them reporting falling at least once in a year [2]. This risk is increased by the lack of musculature due to the amputation and the lack of mobility of the prosthetic ankle during the swing phase [3]. The aim of this study was to evaluate whether a microprocessor-controlled knee-ankle system (MPK_NEW) can help improve walking in transfemoral amputees. Eleven TFA with an activity level of d4602 (International Classification of Function, Disability and Health) or higher and wearing a microprocessor knee able to control stance and swing phases (MPK_HAB), for at least 3 months, were included in this study. They wore both prostheses (MPK_HAB and MPK_NEW) for 4 weeks, starting randomly with one or the other. At the end of each period, a quantified gait analysis (level ground, 12% slopes ascent and descent, downstairs) was performed using VICON® optoelectronic system (Vicon Motion Systems, Oxford Metrics, UK, sampling at 100 Hz) with 54 full-body markers-set. Flat Foot Time (FFT, where the ankle angle in the sagittal plane was within ± 1.25° of its orientation at 20% of the gait cycle) and Minimum Toe Clearance (MTC, minimum distance between the foot and the ground during the swing phase) were calculated for both prostheses. Student or Wilcoxon test were performed to assess significance at 0.05. Fig. 1 A shows an increase in flat-foot time for all walking situations with the MPK_NEW prosthesis, which was significant (*,p_value < 0.01) for all situations but the slope ascent one. Fig. 1B shows a significant increase in MTC (*, p_value < 0.01) when walking at level ground and ascent slope with the MPK_NEW prosthesis. Fig. 1. Comparison of FFT and MTC for each prosthesis in different walking situations [Display omitted] The knee-ankle synergy allows plantar and dorsal flexion during the stance and swing phases, increasing FFT (stance stability) and MTC (swing phase security) in various daily situations. This was consistent with the literature observed on transtibial amputees and approaching the behavior of asymptomatic subjects [4–6]. Thus, this new prosthetic system may improve stability and security for TFA [4,7], allowing them to better adapt to their daily environment. [ABSTRACT FROM AUTHOR]

During manual wheelchair (MWC) locomotion, the user's upper limbs are subject to heavy stresses and fatigue because the upper body is permanently engaged to propel the MWC. These stresses and fatigue vary according to the environmental barriers encountered outdoors along a given path. This study aimed at conducting a systematic review of the literature assessing the biomechanics of MWC users crossing various situations, which represent physical environmental barriers. Through a systematic search on PubMed, 34 articles were selected and classified according to the investigated environmental barriers: slope; cross-slope; curb; and ground type. For each barrier, biomechanical parameters were divided into four categories: spatiotemporal parameters; kinematics; kinetics; and muscle activity. All results from the different studies were gathered, including numerical data, and assessed with respect to the methodology used in each study. This review sheds light on the fact that certain situations (cross-slopes and curbs) or parameters (kinematics) have scarcely been studied, and that a wider set of situations should be studied. Five recommendations were made at the end of this review process to standardize the procedure when reporting materials, methods, and results for the study of biomechanics of any environmental barrier encountered in MWC locomotion: (i) effectively reporting barriers' lengths, grades, or heights; (ii) striving for standardization or a report of the approach conditions of the barrier, such as velocity, especially on curbs; (iii) reporting the configuration of the used MWC, and if it was fitted to the subject's morphology; (iv) reporting rotation sequences for the expression of moments and kinematics, and when used, the definition of the musculoskeletal model; lastly (v) when possible, reporting measurement uncertainties and model reconstruction errors. [ABSTRACT FROM AUTHOR]

Purpose: During manual wheelchair (MWC) skill acquisition, users adapt their propulsion technique through changes in biomechanical parameters. This evolution is assumed to be driven towards a more efficient behavior. However, when no specific training protocol is provided to users, little is known about how they spontaneously adapt during overground MWC locomotion. For that purpose, we investigated this biomechanical spontaneous adaptation within the initial phase of low-intensity uninstructed training. Materials and methods: Eighteen novice able-bodied subjects were enrolled to perform 120 min of uninstructed practice with a field MWC, distributed over 4 weeks. Subjects were tested during the very first minutes of the program, and after completion of the entire training protocol. Spatiotemporal parameters, handrim forces, motor force, rolling resistance and fore-aft stability were investigated using an instrumented field wheelchair. Results: Participants rapidly increased linear velocity of the MWC, thanks to a higher propulsive force. This was achieved thanks to higher handrim forces, combined with an improved fraction of effective force for startup but not for propulsion. Despite changes in mechanical actions exerted by the user on the MWC, rolling resistance remained constant but the stability index was noticeably altered. Conclusion: Even if no indication is given, novice MWC users rapidly change their propulsion technique and increase their linear speed. Such improvements in MWC mobility are allowed by a mastering of the whole range of stability offered by the MWC, which raises the issue of safety on the MWC. The learning process of manual wheelchair locomotion induces adaptations for novice users, who change their propulsion technique to improve their mobility. Several wheelchair biomechanical parameters change during the learning process, especially wheelchair speed, handrim forces, motor force, rolling resistance and fore-aft stability. Fore-aft stability on the wheelchair rapidly reached the tipping limits for users. Technical solutions that preserve stability but do not hinder mobility have to beimplemented, for instance by adding anti-tipping wheels rather than moving the seat forwards with respect to the rear wheels axle. [ABSTRACT FROM AUTHOR]

Purpose:Wheelchair locomotion is constraining for the upper limbs and involves a set of motor tasks that need to be learnt by a novice user. To understand this integration process, we investigated the evolution of shoulder kinetics during start-up and propulsion within the initial phase of low-intensity uninstructed training. Materials and methods:Seventeen novice able-bodied subjects performed a 120-min uninstructed practice distributed over 4 weeks. During the initial and final sessions, upper limbs kinematics and hand-rim kinetics were continuously collected. Inverse kinematics and dynamics coupled to a three-dimensional linked-segment model were used to compute shoulder net moments. Results:Participants increased the speed of the wheelchair with practice. In average, an increase of shoulder net moments and mechanical work during the push phase was observed. Conversely, during the recovery phase, participants slightly increased shoulder power but maintained a similar level of shoulder loading. However, individual evolutions allowed the definition of two groups defined as: “increasers”, who increased shoulder loading and mechanical work versus “decreasers”, who managed to limit shoulder loading while improving the wheelchair speed. Conclusion:These findings underline that individual adaptation strategies are essential to take into account when designing a rehabilitation protocol for wheelchair users. Implications for RehabilitationThe learning process of manual wheelchair locomotion is essential for the assimilation of motor tasks leading individuals to select their propulsion technique.Novice users display different learning strategies: some people increase shoulder loading very early but others spontaneously manage to increase the wheelchair speed while maintaining a constant level of shoulder loading.Wheelchair rehabilitation programs should be individualized to take into account the subject-specific learning strategy. [ABSTRACT FROM PUBLISHER]

Background: The analysis of biomechanical parameters derived from the body center of mass (BCoM) 3D motion allows for the characterization of gait impairments in people with lower-limb amputation, assisting in their rehabilitation. In this context, magneto-inertial measurement units are promising as they allow to measure the motion of body segments, and therefore potentially of the BCoM, directly in the field. Finding a compromise between the accuracy of computed parameters and the number of required sensors is paramount to transfer this technology in clinical routine.Research Question: Is there a reduced subset of instrumented segments (BSN) allowing a reliable and accurate estimation of the 3D BCoM acceleration transfemoral amputees?Methods: The contribution of each body segment to the BCoM acceleration was quantified in terms of weight and similarity in ten people with transfemoral amputation. First, body segments and BCoM accelerations were obtained using an optoelectronic system and a full-body inertial model. Based on these findings, different scenarios were explored where the use of one sensor at pelvis/trunk level and of different networks of segment-mounted sensors for the BCoM acceleration estimation was simulated and assessed against force plate-based reference acceleration.Results: Trunk, pelvis and lower-limb segments are the main contributors to the BCoM acceleration in transfemoral amputees. The trunk and shanks BSN allows for an accurate estimation of the sagittal BCoM acceleration (Normalized RMSE ≤ 13.1 %, Pearson's correlations r ≥ 0.86), while five segments are necessary when the 3D BCoM acceleration is targeted (Normalized RMSE ≤ 13.2 %, Pearson's correlations r ≥ 0.91).Significance: A network of three-to-five segments (trunk and lower limbs) allows for an accurate estimation of 2D and 3D BCoM accelerations. The use of a single pelvis- or trunk-mounted sensor does not seem advisable. Future studies should be performed to confirm these results where inertial sensor measured accelerations are considered. [ABSTRACT FROM AUTHOR]

Manual wheelchair (MWC) locomotion exposes the user's upper-body to large and repetitive loads, which can lead to upper limbs pain and injuries. A thinner understanding of the influence of MWC settings on propulsion biomechanics could allow for a better adaptation of MWC configuration to the user, thus limiting the risk of developing such injuries. Advantageously compared to experimental studies, simulation methods allow numerous configurations to be tested. Recent studies have developed predictive locomotion simulation using optimal control methods. However, those models do not consider MWC anteroposterior stability, potentially resulting in unreasonable propulsion strategies. To this extent, this study aimed at confirming if constraining MWC anteroposterior stability in the optimal control formulation could lead to a different simulated movement. For this purpose, a four-link rigid-body system was used in a forward dynamics optimization paired with an anteroposterior stability constraint to predict MWC locomotion dynamics of the upper limbs during both startup and steady-state propulsion. Simulation results indicated the occurrence of MWC tipping when stability was not constrained, and that the constrained optimal control algorithm predicted different propulsion strategies. Hence, further proceedings of MWC locomotion simulation and optimal control investigations should take the anteroposterior stability into account to achieve more realistic simulations. Additionally, the implementation of the anteroposterior stability constrains unexpectedly resulted in a reduction of the computational time. [ABSTRACT FROM AUTHOR]

Objective Manual wheelchair (MWC) is a constraining form of locomotion for the musculoskeletal system and many MWC users are concerned by musculoskeletal disorders (MSD). Detecting and quantifying MWC related activities are of high interest for the day-to-day follow-up of patients using a MWC as a primary mode of locomotion. Indeed, it could assist clinician in early identification of MSD occurrence or optimizing the user environment (furnishing arrangements, etc). Since few years, several tools combining sensors and data processing algorithms were developed. However, the validation of these tools is difficult, in particular because video analysis used as a reference is both highly time consuming and sometimes inaccurate due to the cameras field of view. Hence, there is a need of an alternative reference method to facilitate the validation of such tools. As an alternative to video analysis, we propose to use an instrumented MWC, initially dedicated for investigating MWC biomechanics, as a new reference method for tasks identifications. Material/patients and methods This MWC was equipped with handrim dynamometers to measure handrim forces and two angular potentiometers fixed on rear wheels to determine the MWC trajectory. Data processing included data aggregation followed by multichannel symbolic representation based on force and velocity thresholds. Currently, the method was implemented for flat horizontal displacement and allowed distinguishing resting: start-up, propulsion, braking and turning motion various curvature radii. The method was tested on 18 able-bodied subjects during actual displacements. Results Results show that for most subjects, the method allowed identifying start-up, propulsion, braking and turning motion tasks. However, a specific adaptation of some thresholds was required for 2 subjects. Since the first subject kept his hands on the handrims during the recovery phase, making difficult the separation of the different tasks and the other subject used a desynchronized propulsion pattern between right and left upper-limbs (close to an alternative push strategy), which resulted in a failure of the identification of propulsion cycle. Discussion, conclusion Even if a real validation of this method against video analysis is still required, the results of the method are encouraging. Some works are still needed to include displacements on more various inclined surfaces and uneven terrain. [ABSTRACT FROM AUTHOR]