This study aimed to explore novel inertial measurement unit (IMU)-based strategies to estimate respiratory parameters in healthy adults lying on a bed while breathing normally. During the experimental sessions, the kinematics of the chest wall were contemporaneously collected through both a network of 9 IMUs and a set of 45 uniformly distributed reflective markers. All inertial kinematics were analyzed to identify a minimum set of signals and IMUs whose linear combination best matched the tidal volume measured by optoelectronic plethysmography. The resulting models were finally tuned and validated through a leave-one-out cross-validation approach to assess the extent to which they could accurately estimate a set of respiratory parameters related to three trunk compartments. The adopted methodological approach allowed us to identify two different models. The first, referred to as Model 1, relies on the 3D acceleration measured by three IMUs located on the abdominal compartment and on the lower costal margin. The second, referred to as Model 2, relies on only one component of the acceleration measured by two IMUs located on the abdominal compartment. Both models can accurately estimate the respiratory rate (relative error < 1.5%). Conversely, the duration of the respiratory phases and the tidal volume can be more accurately assessed by Model 2 (relative error < 5%) and Model 1 (relative error < 5%), respectively. We further discuss possible approaches to overcome limitations and improve the overall accuracy of the proposed approach.

Reducing energy consumption during walking is a critical goal for transtibial amputees. The study presents the evaluation of a semi-active prosthesis with five transtibial amputees. The prosthesis has a low-power actuator integrated in parallel into an energy-storing-and-releasing foot. The actuator is controlled to compress the foot during the stance phase, supplementing the natural compression due to the user’s dynamic interaction with the ground, particularly during the ankle dorsiflexion phase, and to release the energy stored in the foot during the push-off phase, to enhance propulsion. The control strategy is adaptive to the user’s gait patterns and speed. The clinical protocol to evaluate the system included treadmill and overground walking tasks. The results showed that walking with the semi-active prosthesis reduced the Physiological Cost Index of transtibial amputees by up to 16% compared to walking using the subjects’ proprietary prosthesis. No significant alterations were observed in the spatiotemporal gait parameters of the participants, indicating the module’s compatibility with users’ natural walking patterns. These findings highlight the potential of the mechatronic actuator in effectively reducing energy expenditure during walking for transtibial amputees. The proposed prosthesis may bring a positive impact on the quality of life, mobility, and functional performance of individuals with transtibial amputation.

Robotic lower-limb prostheses have the power to revolutionize mobility by enhancing gait efficiency and facilitating movement. While several design approaches have been explored to create lightweight and energy-efficient devices, the potential of underactuation remains largely untapped in lower-limb prosthetics. Taking inspiration from the natural harmony of walking, we have developed an innovative active transfemoral prosthesis. By incorporating underactuation, our design uses a single power actuator placed near the knee joint and connected to a differential mechanism to drive both the knee and ankle joints. We conducted comprehensive benchtop tests and evaluated the prosthesis with three individuals who have above-knee amputations, assessing its performance in walking, stair climbing, and transitions between sitting and standing. Our evaluation focused on gathering position and torque data recorded from sensors integrated into the prosthesis and comparing these measurements to biomechanical data of able-bodied locomotion. Our findings highlight the promise of underactuation in advancing lower-limb prosthetics and demonstrate the feasibility of our kneeankle underactuated design in various tasks, showcasing its ability to replicate natural movement

Most individuals who experience a stroke exhibit several sensorimotor impairments that limit their independence in everyday activities. Hemiparetic gait is frequently characterized by reduced knee flexion in swing due to knee stiffness or muscle weakness and knee hyperextension or knee buckling in the stance phase. Recently, unilateral-powered orthoses have been designed to overcome the limitations of the passive knee-ankle-foot orthoses. This study presents a unilateral Active Knee Orthosis Exoskeleton, AKO-$\beta$, endowed with a series elastic actuator and designed to assist the knee in flexion and extension movements. The paper describes the system mechatronic design and its characterization on the bench, the control system, and pilot experiments with three post-stroke participants. The device has a weight of 1.78 kg on the user's leg, with a lateral encumbrance of 76 mm. The pilot experiments aimed to verify the effects of the exoskeleton assistance in hemiparetic gait patterns. When walking with the device, participants on average increased the knee flexion on the paretic side by 18.70 deg (+44.9%) during swing and decreased knee hyperextension in stance by 4.50 deg, compared to walking without it. Overall, when walking with the exoskeleton, subjects showed improved Gait Variable Score of the paretic knee profile by 37.5% compared to walking without it. The temporal and spatial gait symmetry indexes did not show clear changes, although an improvement in symmetry was observed in two of the three participants. These preliminary results suggest the potential benefits of the unilateral Active Knee Orthosis exoskeleton to enhance and restore mobility in individuals with hemiparetic gait.

Objectives: To verify the feasibility of the Virtual Eggs Test (VET) and establish the ranges of fragilities of the Virtual Eggs (VEs) for assessing dexterity of stroke subjects and to collect feedback to improve its usability.Methods: An observational non-profit study, with a pre-market medical device. It was conducted at a hospital neurorehabilitation unit. Nine subjects with chronic stroke (5 males; mean age 55.8 ± 18.9) performed the pilot with their paretic arm. Time to complete the test (TT), the number of failures for each VE, the threshold (T), and participants’ self-reported comfort in performing the test were measured.Results: The T varied among participants from 1.70 to 4.88 N/N. The average TT was 20.1 ± 6.5 minutes (range 11-33). Only one subject found the test uncomfortable.Conclusions: The study found that the VET, with minor modifications, is feasible in stroke subjects. It might be useful for assessing sensorimotor impairment in both the affected and the less affected arm. Its metric properties and normative values in the healthy population will be determined in a study currently underway.

Goal: The experimental study of the stumble phenomena is essential to develop novel technological solutions to limit harmful effects in at-risk populations. A versatile platform to deliver realistic and unanticipated tripping perturbations, controllable in their strength and timing, would be beneficial for this field of study. Methods: We built a modular tripping-eliciting system based on multiple compliant trip blocks that deliver unanticipated tripping perturbations. The system was validated with a study with 9 healthy subjects. Results: The system delivered 33 out of 34 perturbations (a minimum of 3 per subject) during the desired gait phase, and 31 effectively induced a tripping event. The recovery strategies adopted after the perturbations were qualitatively consistent with the literature. The analysis of the inertial motion unit signals and the questionnaires suggests a limited adaptation to the perturbation throughout experiments. Conclusions: The platform succeeded in providing realistic trip perturbations, concurrently limiting subjects’ adaptation. The presence of multiple compliant obstacles, tunable regarding position and perturbation strength, represents a novelty in the field, allowing the study of stumbling phenomena caused by obstacles with different levels of sturdiness. The overall system is modular and can be easily adapted for different applications.