Development and testing of the aerial porter exoskeleton.

Back pain is one of the largest drivers of workplace injury and lost productivity in industries around the world. Back injuries were one of the leading reasons in resulting in days away from work at 38.5% across all occupations, increasing for manual laborers to 43%. While the cause of the back pain can vary across occupations, for materiel movers it is often caused from repetitive poor lifting. To reduce the issues, the Aerial Porter Exoskeleton (APEx) was created. The APEx uses a hip-mounted, powered exoskeleton attached to an adjustable vest. An onboard computer calculates the configuration of the user to determine when to activate. Lift form is assisted by using a novel lumbar brace mounted on the sides of the hips. Properly worn, the APEx holds the user upright while providing additional hip torque through a lift. This was tested by having participants complete a lifting test with the exoskeleton worn in the "on" configuration compared with the exoskeleton not worn. The APEx has been shown to deliver 30 Nm of torque in lab testing. The activity recognition algorithm has also been shown to be accurate in 95% of tested conditions. When worn by subjects, testing has shown average peak reductions of 14.9% BPM, 8% in VO2 consumption, and an 8% change in perceived effort favoring the APEx.

Effect of acute myocardial ischemia on inferolateral early repolarization.

BACKGROUND: Inferolateral early repolarization (ER) is associated with an increase in arrhythmic risk, particularly in the presence of myocardial ischemia. OBJECTIVE: The purpose of this study was to determine the effect of myocardial ischemia on ER. METHODS: We retrospectively analyzed procedural electrocardiograms (ECGs) of patients with ER undergoing a controlled, 1-minute coronary balloon occlusion for collateral function testing. ECG leads with ER were analyzed immediately before coronary balloon occlusion (PRE), at 60 seconds of coronary balloon occlusion (OCCL), and >30 seconds after balloon deflation. RESULTS: Seventy-seven patients with ER in the preprocedural ECG (86% inferior, 20% lateral) underwent 135 coronary balloon occlusions during which a J wave was recorded in 224 leads (ER leads). From PRE to OCCL, ST-segment amplitude (ST) in the ER lead increased in 94 cases (44%) from 0.00 ± 0.03 to 0.05 ± 0.06 mV (P < .0001). In this group, J-wave amplitude (JWA) increased from 0.10 ± 0.07 to 0.13 ± 0.09 mV (P < .0001). ST in the ER lead decreased or was unchanged in 121 cases (56%) from PRE to OCCL (from 0.01 ± 0.05 to -0.02 ± 0.04 mV; P < .0001). In this group, JWA decreased from 0.10 ± 0.05 to 0.08 ± 0.07 mV (P < .0001). The change in JWA was related to the change in ST (linear regression analysis; R2 = 0.34; P < .0001), while there was no relation between the change in R-wave amplitude and the change in ST (R2 = 0.0003; P = .83). CONCLUSION: During acute ischemia, JWA mirrors ST-segment changes. This may explain increased arrhythmic vulnerability of patients with ER during myocardial ischemia. It also adds weight to the hypothesis of ER being a phenomenon of repolarization.

Feasibility study of transtibial amputee walking using a powered prosthetic foot.

Passive prosthetic feet are not able to provide non-amputee kinematics and kinetics for the ankle joint. Persons with amputations show reduced interlimb symmetry, slower walking speeds, and increased walking effort. To improve ankle range of motion and push off, various powered prosthetic feet were introduced. This feasibility study analyzed if predefined motor reference trajectories can be used to achieve non-amputee ankle biomechanics during walking with the powered prosthetic foot, Walk-Run Ankle. Trajectories were calculated using the desired ankle angle and ankle moment based spring deflection at a given spring stiffness. Model assumptions of the motor-spring interaction were well reflected in the experiment. The powered foot was able to improve range of motion, peak ankle power, average positive ankle power, peak ankle moment, and positive moment onset compared to a passive usage of the foot. Furthermore, symmetry improvements were identified for step length and duty factor. Further studies with an increased number of subjects are needed to show if the approach is also valid for other amputees. Using this method as a base, trajectories can be further individualized using human in the loop optimization targeting a reduction of user effort, improved stability, or gait symmetry.

A powered prosthetic ankle joint for walking and running.

BACKGROUND: Current prosthetic ankle joints are designed either for walking or for running. In order to mimic the capabilities of an able-bodied, a powered prosthetic ankle for walking and running was designed. A powered system has the potential to reduce the limitations in range of motion and positive work output of passive walking and running feet. METHODS: To perform the experiments a controller capable of transitions between standing, walking, and running with speed adaptations was developed. In the first case study the system was mounted on an ankle bypass in parallel with the foot of a non-amputee subject. By this method the functionality of hardware and controller was proven. RESULTS: The Walk-Run ankle was capable of mimicking desired torque and angle trajectories in walking and running up to 2.6 m/s. At 4 m/s running, ankle angle could be matched while ankle torque could not. Limited ankle output power resulting from a suboptimal spring stiffness value was identified as a main reason. CONCLUSIONS: Further studies have to show to what extent the findings can be transferred to amputees.

Stroke Survivors' Gait Adaptations to a Powered Ankle Foot Orthosis.

BACKGROUND AND PURPOSE: Stroke is the leading cause of long term disability in the United States, and for many it causes loss of gait function. The purpose of this research is to examine stroke survivors' gait adaptations to training on the Powered Ankle Foot Orthosis (PAFO). Of particular interest is the stroke survivors' ability to learn how to store and release energy properly while using the device. The PAFO utilizes robotic tendon technology and supports motion with a single degree of freedom, ankle rotation in the sagittal plane. This actuator comprises a motor and series spring. The user interacts with the output side of the spring while the robot controls the input side of the spring such that typical able body ankle moments would be generated, assuming able body ankle kinematics are seen at the output side of the spring. METHODS: Three individuals post-stroke participated in a three week training protocol. Outcome measures (temporal, kinematic, and kinetic) were derived from robot sensors and recorded for every step. These data are used to evaluate each stroke survivor's adaptations to robotic gait assistance. The robot was worn only on the paretic ankle. For validation of the kinematic results, motion capture data were collected on the third subject. RESULTS: All subjects showed increased cadence, ankle range of motion, and power generation capabilities. Additionally, all subjects were able to achieve a larger power output than power input from the robot. Motion capture data collected from subject three validated the robot sensor kinematic data on the affected side, but also demonstrated an unexpected gait adaptation on the unaffected ankle. CONCLUSIONS: Sensors on the gait assisting robot provide large volumes of valuable information on how gait parameters change over time. We have developed key gait evaluation metrics based on the available robot sensor information that may be useful to future researchers. All subjects adapted their gait to the robotic assistance, and many of their key metrics moved closer to typical able body values. This suggests that each subject learned to utilize the assistive moments generated by the robot, despite having no predefined ankle trajectory input from the robot. The security of being harnessed on the treadmill led to more dramatic and favorable results.