Prefrontal Cortex and Supplementary Motor Area Activation During Robot-Assisted Weight-Supported Over-Ground Walking in Young Neurological Patients: A Pilot fNIRS Study

Introduction: Rehabilitation therapy devices are designed for practicing intensively task-specific exercises inducing long-term neuroplastic changes underlying improved functional outcome. The Andago enables over-ground walking with bodyweight support requiring relatively high cognitive demands. In this study, we investigated whether we could identify children and adolescents with neurological gait impairments who show increased hemodynamic responses of the supplementary motor area (SMA) or prefrontal cortex (PFC) measured with functional near-infrared spectroscopy (fNIRS) when walking in Andago compared to walking on a treadmill. We further assessed the practicability and acceptability of fNIRS.Methods: Thirteen participants (two girls, 11 boys, age 8.0–15.7 years) with neurological impairments walked in the Andago and on a treadmill under comparable conditions. We measured hemodynamic responses over SMA and PFC during 10 walks (each lasting 20 s.) per condition and analyzed the data according to the latest recommendations. In addition, we listed technical issues, stopped the time needed to don fNIRS, and used a questionnaire to assess acceptability.Results: Hemodynamic responses varied largely between participants. Participants with a typical hemodynamic response (i.e., increased oxygenated hemoglobin concentration) showed large cortical activations during walking in Andago compared to treadmill walking (large effect sizes, i.e., for SMA: r = 0.91, n = 4; for PFC: r = 0.62, n = 3). Other participants showed atypical (SMA: n = 2; PFC: n = 4) or inconclusive hemodynamic responses (SMA: n = 5; PFC: n = 4). The median time for donning fNIRS was 28 min. The questionnaire indicated high acceptance of fNIRS, despite that single participants reported painful sensations.Discussion: Repetitive increased activation of cortical areas like the SMA and PFC might result in long-term neuroplastic changes underlying improved functional outcome. This cross-sectional pilot study provides first numbers on hemodynamic responses in SMA and PFC during walking in Andago in children with neurological impairments, reveals that only a small proportion of the participants shows typical hemodynamic responses, and reports that fNIRS requires considerable time for donning. This information is needed when designing future longitudinal studies to investigate whether increased brain activation of SMA and PFC during walking in Andago could serve as a biomarker to identify potential therapy responders among children and adolescents undergoing neurorehabilitation.

Effects of step length and cadence on hip moment impulse in the frontal plane during the stance phase

Background An excessive daily cumulative hip moment in the frontal plane (determined as the product of hip moment impulse in the frontal plane during the stance phase and mean number of steps per day) is a risk factor for the progression of hip osteoarthritis. Moreover, walking speed and step length decrease, whereas cadence increases in patients with hip osteoarthritis. However, the effects of step length and cadence on hip moment impulse in the frontal plane during the stance phase are not known. Therefore, this study aimed to examine the effects of step length and cadence on hip moment impulse in the frontal plane during the stance phase. Methods We used a public dataset (kinetic and kinematic data) of over-ground walking and selected 31 participants randomly from the full dataset of 57 participants. The selected participants walked at a self-selected speed and repeated the exercise 15 times. We analyzed the data for all 15 trials for each participant. Multiple regression analysis was performed with the hip moment impulse in the frontal plane during the stance phase as the dependent variable and step length and cadence as independent variables. Results The adjusted R2 in this model was 0.71 (p < 0.001). The standardized partial regression coefficients of step length and cadence were 0.63 (t = 5.24; p < 0.001) and −0.60 (t = − 4.58; p < 0.001), respectively. Conclusions Our results suggest that low cadence, not short step length, increases the hip moment impulse in the frontal plane. Our findings help understand the gait pattern with low hip moment impulse in the frontal plane.

Transient Thermal Analysis of a Magnetorheological Knee for Prostheses and Exoskeletons during Over-Ground Walking

Proper knee movement is essential for accomplishing the mobility daily tasks such as walking, get up from a chair and going up and down stairs. Although the technological advances in active knee actuators for prostheses and exoskeletons to help impaired people in the last decade, they still present several usage limitations such as overweight or limited mechanical power and torque. To address such limitations, we developed the Active Magnetorheological Knee (AMRK) that comprises a Motor Unit (MU), which is a motor-reducer (EC motor and Harmonic Drive) and a MR clutch, that works in parallel to a magnetorheological (MR) brake. Magnetorheological fluids, employed in the MR clutch and brake, are smart materials that have their rheological properties controlled by an induced magnetic field and have been used for different purposes. With this configuration the actuator can work as a motor, clutch or brake and can perform similar movements than a healthy knee. However, the stability, control, and life of magnetorheological fluids critically depend on the working temperature. By reaching a certain temperature limit, the fluid additives quickly deteriorate, leading to irreversible changes of the MR fluid. In this study, we perform a transient thermal analysis of the AMRK, when it is used for walking over-ground, to access possible fluid degradation and user’s discomfort due overheating. The resulting shear stress in the MR clutch and brake generates heat, increasing the fluid temperature during the operation. However, to avoid overheating, we proposed a mode of operation for over-ground walking aiming to minimize the heat generation on the MR clutch and brake. Other heat sources inside the actuator are the coils, which generate the magnetic fields for the MR fluid, bearings, EC motor and harmonic drive. Results show that the MR fluid of the brake can reach up to 31°C after a 6.0 km walk, so the AMRK can be used for the proposed function without risks of fluid degradation or discomfort for the user.

Effects of Obesity on Adaptation Transfer from Treadmill to Over-Ground Walking

Discerning whether individuals with obesity transfer walking adaptation from treadmill to over-ground walking is critical to advancing our understanding of walking adaptation and its usefulness in rehabilitating obese populations. We examined whether the aftereffects following split-belt treadmill adaptation transferred to over-ground walking in adults with normal-weight body mass index (BMI) and obese BMI. Nineteen young adults with obesity and 19 age-matched adults with normal weight walked on flat ground at their preferred speed before and after walking on a treadmill with tied belts (preferred speed) and with the split-belt at their preferred speed and at a speed 50% slower than their preferred speed. The adaptation and aftereffects in step length and double-limb support time symmetry were calculated. We found that the amount of temporal adaptation was similar for adults with obesity and with normal weight (p > 0.05). However, adults with obesity showed greater asymmetry for double-limb support time following split-belt treadmill walking compared to adults with normal weight (p < 0.05). Furthermore, the transfer of asymmetry for double-limb support time from the treadmill to over-ground walking was less in adults with obesity than in adults with normal weight (p < 0.05). The transfer of adapted gait following split-belt treadmill walking provides insight into how atypical walking patterns in individuals with obesity could be remediated using long-term gait training.

Novel active magnetorheological knee prosthesis presents low energy consumption during ground walking

This study analyses the energy consumption of an active magnetorheological knee (AMRK) actuator that was designed for transfemoral prostheses. The system was developed as an operational motor unit (MU), which consists of an EC motor, a harmonic drive and a magnetorheological (MR) clutch, that operates in parallel with an MR brake. The dynamic models of the MR brake and MU were used to simulate the system’s energetic expenditure during over-ground walking under three different working conditions: using the complete AMRK; using just its motor-reducer, to operate as a common active knee prosthesis (CAKP), and using just the MR brake, to operate as a common semi-active knee prosthesis (CSAKP). The results are used to compare the MR devices power consumptions with that of the motor-reducer. As previously hypothesized, to use the MR brake in the swing phase is more energetically efficient than using the motor-reducer to drive the joint. Even if using the motor-reducer in regenerative braking mode during the stance phase, the differences in power consumption among the systems are remarkable. The AMRK expended 16.3 J during a gait cycle, which was 1.6 times less than the energy expenditure of the CAKP (26.6 J), whereas the CSAKP required just 6.0 J.

Kinematic Gait Adjustments to Virtual Environments on Different Surface Conditions: Do Treadmill and Over-Ground Walking Exhibit Different Adaptations to Passive Virtual Immersion?

Background. The aim of this study was to examine the kinematic gait adjustments performed in response to passive and photorealistic virtual reality environment (VRE) demands during over-ground and treadmill walking conditions and determine whether the surface presentation order affects the gait adjustments in response to different VREs. Methods. Twenty young participants divided into two groups performed two virtual reality (VR) walking protocols which included two different VREs (snowy and crowded conditions). Group A performed the VR over-ground protocol (four natural walking (NW), seven VR snowy, and seven VR crowded trials) followed by the VR treadmill protocol (four NW, one VR snowy, and one VR crowded trials); Group B performed the VR treadmill protocol (four NW, seven VR snowy, and seven VR crowded trials) followed by the VR over-ground protocol (four NW, one VR snowy, and one VR crowded trials). Center of mass (COM) excursion angles and mediolateral (ML) COM excursions were analyzed and used as outcome measures. Results. Group A showed higher COM excursion angles and ML-COM excursion on over-ground VR trials compared to NW trials ( p < 0.05 ), while Group B only showed kinematic changes for the crowded VRE compared to NW trials during the treadmill walking protocol ( p < 0.05 ). Post over-ground exposure, Group A showed greater COM excursion angle and ML-COM excursions on VR trials compared to NW trials during the treadmill walking protocol ( p < 0.05 ). Post treadmill exposure, Group B only showed higher COM excursion angles for the snowy VRE compared to NW trials during the over-ground walking protocol ( p < 0.01 ). Conclusion. Results showed that higher kinematic gait adjustments in response to VRE demands were observed during over-ground walking. Additionally, higher sensorimotor responses to VRE demands were observed when the VR protocol was first performed on the over-ground surface and followed by the treadmill walking condition (Group A) compared to the opposite (Group B).

Cerebellar Transcranial Direct Current Stimulation for Motor Learning in People with Chronic Stroke: A Pilot Randomized Controlled Trial

Cerebellar transcranial direct current stimulation (ctDCS) is a non-invasive brain stimulation technique that alters neural plasticity through weak, continuous, direct currents delivered to the cerebellum. This study aimed to evaluate the feasibility of conducting a randomized controlled trial (RCT) delivering three consecutive days of ctDCS during split-belt treadmill training (SBTT) in people with chronic stroke. Using a double-blinded, parallel-group RCT design, eligible participants were randomly allocated to receive either active anodal ctDCS or sham ctDCS combined with SBTT on three consecutive days. Outcomes were assessed at one-week follow-up, using step length symmetry as a measure of motor learning and comfortable over-ground walking speed as a measure of walking capacity. The feasibility of the RCT protocol was evaluated based on recruitment, retention, protocol deviations and data completeness. The feasibility of the intervention was assessed based on safety, adherence and intervention fidelity. Of the 26 potential participants identified over four months, only four were enrolled in the study (active anodal ctDCS n = 1, sham ctDCS n = 3). Both the inclusion criteria and the fidelity of the SBTT relied upon the accurate estimation of step length asymmetry. The method used to determine the side of the step length asymmetry was unreliable and led to deviations in the protocol. The ctDCS intervention was well adhered to, safe, and delivered as per the planned protocol. Motor learning outcomes for individual participants revealed that treadmill step length symmetry remained unchanged for three participants but improved for one participant (sham ctDCS). Comfortable over-ground walking speed improved for two participants (sham ctDCS). The feasibility of the planned protocol and intervention was limited by intra-individual variability in the magnitude and side of the step length asymmetry. This limited the sample and compromised the fidelity of the SBTT intervention. To feasibly conduct a full RCT investigating the effect of ctDCS on locomotor adaptation, a reliable method of identifying and defining step length asymmetry in people with stroke is required. Future ctDCS research should either optimize the methods for SBTT delivery or utilize an alternative motor adaptation task.