Modeling, Control, and Clinical Validation of an Upper-Limb Medical Education Task Trainer for Elbow Spasticity and Rigidity Assessment.

The goal of this study was to validate a series elastic actuator (SEA)-based robotic arm that can mimic three abnormal muscle behaviors, namely lead-pipe rigidity, cogwheel rigidity, and spasticity for medical education training purposes. Key characteristics of each muscle behavior were first modeled mathematically based on clinically-observed data across severity levels. A controller that incorporated feedback, feedforward, and disturbance observer schemes was implemented to deliver haptic target muscle resistive torques to the trainee during passive stretch assessments of the robotic arm. A series of benchtop tests across all behaviors and severity levels were conducted to validate the torque estimation accuracy of the custom SEA (RMSE: ~ 0.16 Nm) and the torque tracking performance of the controller (torque error percentage: < 2.8 %). A clinical validation study was performed with seven experienced clinicians to collect feedback on the task trainer's simulation realism via a Classification Test and a Disclosed Test. In the Classification Test, subjects were able to classify different muscle behaviors with a mean accuracy > 87 % and could further distinguish severity level within each behavior satisfactorily. In the Disclosed Test, subjects generally agreed with the simulation realism and provided suggestions on haptic behaviors for future iterations. Overall, subjects scored 4.9 out of 5 for the potential usefulness of this device as a medical education tool for students to learn spasticity and rigidity assessment.

Design and Validation of a Soft Robotic Simulator for Transseptal Puncture Training.

OBJECTIVE: Transseptal puncture (TP) is the technique used to access the left atrium of the heart from the right atrium during cardiac catheterization procedures. Through repetition, electrophysiologists and interventional cardiologists experienced in TP develop manual skills to navigate the transseptal catheter assembly to their target on the fossa ovalis (FO). Cardiology fellows and cardiologists that are new to TP currently train on patients to develop this skill, resulting in increased risk of complications. The goal of this work was to create low-risk training opportunities for new TP operators. METHODS: We developed a Soft Active Transseptal Puncture Simulator (SATPS), designed to match the dynamics, static response, and visualization of the heart during TP. The SATPS includes three subsystems: (i) A soft robotic right atrium with pneumatic actuators mimics the dynamics of a beating heart. (ii) A fossa ovalis insert simulates cardiac tissue properties. (iii) A simulated intracardiac echocardiography environment provides live visual feedback. Subsystem performance was verified with benchtop tests. Face and content validity were evaluated by experienced clinicians. RESULTS: Subsystems accurately represented atrial volume displacement, tenting and puncture force, and FO deformation. Passive and active actuation states were deemed suitable for simulating different cardiac conditions. Participants rated the SATPS as realistic and useful for training cardiology fellows in TP. CONCLUSION: The SATPS can help improve catheterization skills of novice TP operators. SIGNIFICANCE: The SATPS could provide novice TP operators the opportunity to improve their TP skills before operating on a patient for the first time, reducing the likelihood of complications.

Review of assistive devices for the prevention of pressure ulcers: an engineering perspective.

PURPOSE: Pressure ulcers (PUs) are prevalent among immobile bed or wheelchair-reliant individuals who experience prolonged sedentary positions. Pressure relief and frequent repositioning of body posture help to mitigate complications associated with PUs. Adherence with regular repositioning is difficult to maintain due to nursing labour shortages or constraints of in-home caregivers. Manual repositioning, transferring, and lifting of immobile patients are physically demanding tasks for caregivers. This review aimed to explore and categorize these devices, discuss the significant technical challenges that need addressing, and identify potential design opportunities. MATERIALS AND METHODS: In this review, a literature search was conducted using PubMED, Science Direct, Google Scholar and IEEE Xplore databases including studies from 1995 until Feb 2023 with keywords such as pressure ulcer, assistive device, pressure relief, repositioning, transfer, etc. Both commercial and research-level devices were included in the search. RESULTS: 142 devices or technologies were identified and classified into four main categories that were further subcategorized. Within each category, the devices were investigated in terms of their mechanical design, actuation methods, control strategies, sensing technologies, and level of autonomy. Limitations of current technologies are design complexity, lack of patient comfort, and a lack of autonomy requiring caregivers frequent intervention. CONCLUSIONS: Several devices have been developed to help with prevention and mitigation of PUs. There remain challenges that hinder the widespread accessibility and use of current technologies. Advancements in assistive technologies for pressure ulcer mitigation could lie at the intersection of robotics, sensors, perception, user-centered design, and autonomous systems.IMPLICATIONS FOR REHABILITATIONFuture advancements in assistive technologies for pressure ulcer mitigation could lie at the intersection of robotics, sensors, perception, user-centered design, and autonomous systems.Most existing technologies for prevention of pressure ulcers are focused on the mechanical advantage rather than user's needs and preferences. Future designers, engineers, and product developers must be educated to conduct user needs studies concurrently with the development of technology to design the devices based on the user's needs to ensure a balanced design outcome.

BIOMECHANICAL EVALUATION OF PNEUMATIC SLEEVE ORTHOSIS FOR LOFSTRAND CRUTCHES.

Crutch walking, especially when using a swing-through gait pattern, is associated with high, repetitive joint forces, hyperextension/ulnar deviation of the wrist, and excessive palmar pressure that compresses the median nerve. To reduce these adverse effects, we designed a pneumatic sleeve orthosis that utilized a soft pneumatic actuator and secured to the crutch cuff for long-term Lofstrand crutch users. Eleven able-bodied young adult participants performed both swing-through and reciprocal crutch gait patterns with and without the custom orthosis for comparison. Wrist kinematics, crutch forces, and palmar pressures were analyzed. Significantly different wrist kinematics, crutch kinetics, and palmar pressure distribution were observed in swing-through gait trials with orthosis use (p<0.001, p=0.01, p=0.03, respectively). Reductions in peak and mean wrist extension (7%, 6%), wrist range of motion (23%), and peak and mean ulnar deviation (26%, 32%) indicate improved wrist posture. Significantly increased peak and mean crutch cuff forces suggest increased load sharing between the forearm and cuff. Reduced peak and mean palmar pressures (8%, 11%) and shifted peak palmar pressure location toward the adductor pollicis denote a redirection of pressure away from the median nerve. In reciprocal gait trials, non-significant but similar trends were observed in wrist kinematics and palmar pressure distribution, whereas a significant effect of load sharing was noticed (p=0.01). These results suggest that Lofstrand crutches modified with orthosis may improve wrist posture, reduce wrist and palmar load, redirect palmar pressure away from the median nerve, and thus may reduce or prevent the onset of wrist injuries.

Exploring the Intersection of Engineering and Medicine Through a Neuroscience Challenge Laboratory.

The medical curriculum is charged with training medical students who can possess both the technical and contextual abilities to adapt to the transformational world of medicine. This new objective would require incorporating engineering principles into the medical curriculum, which was formed by the University of Illinois as the Carle Illinois College of Medicine. As a fully integrated engineering based medical school, students partake in active learning modules that develop their quantitative, innovative, and entrepreneurship skills. An example of the active learning component of the curriculum is the "Neuroscience Engineering Challenge Lab." The purpose of this study was to explore students' perception of the lab and learn how the active-learning curriculum via the design thinking labs can be enhanced. Using a paired samples t test of pre- and post-survey results, we found that the students did not statistically gain a better understanding of the design thinking process (p = 0.052), which is expected due to the majority of students having an engineering background. Contrarily, the lab increased students' understanding of ideation tools (p = 0.003), user-centered design concepts (p = 0.004), preparing a business plan pitch (p = 0.027), and students felt better prepared for their IDEA and Capstone project (p = 0.010). Based on the results, students are becoming more confident with understanding, experience, and applying these specific tools and skills. Therefore, the medical curriculum should provide opportunities for students to develop and apply their innovation skills through active-learning activities such as a Neuroscience Engineering Challenge Lab.

Hand-rim biomechanics during geared manual wheelchair propulsion over different ground conditions in individuals with spinal cord injury.

Geared manual wheelchair wheels, a recently developed alternative propulsion mechanism, have the potential to alleviate the high upper extremity demands required for wheelchair propulsion and help decrease the risk of secondary injuries in manual wheelchair users. The objective of this study was to investigate the effects of using geared manual wheelchairs on hand-rim biomechanics of wheelchair propulsion in individuals with spinal cord injury (SCI). Seven manual wheelchair users with SCI propelled their wheelchairs equipped with geared wheels over tile, carpet, and up a ramp in low gear (gear ratio 1.5:1) and standard gear (gear ratio 1:1) conditions. Hand-rim kinetics and stroke cycle characteristics were measured using a custom instrumented geared wheel. Using the geared wheels in the low gear condition, propulsion speed (P = 0.013), peak resultant force (P = 0.005), peak propulsive moment (P < 0.006), and peak rate of rise of the resultant force (P = 0.035) decreased significantly in comparison with the standard gear condition. The significant increase in the number of stroke cycles when normalized to distance (P = 0.004) and decrease in the normalized integrated moment (P = 0.030) indicated that although a higher number of stroke cycles are required for travelling a given distance in the low gear than the standard gear condition, the low gear condition might be less demanding for the upper extremity. These results suggest that geared wheels could be a useful technology for manual wheelchair users to independently accomplish strenuous propulsion tasks including mobility on carpeted floors and ramp ascension, while reducing the risk factors contributing to the incidence of secondary upper extremity injuries.

Glenohumeral joint dynamics and shoulder muscle activity during geared manual wheelchair propulsion on carpeted floor in individuals with spinal cord injury.

This study investigated the effects of using geared wheels on glenohumeral joint dynamics and shoulder muscle activity during manual wheelchair propulsion. Seven veterans with spinal cord injury propelled their wheelchairs equipped with geared wheels over a carpeted floor in low gear (1.5:1) and standard gear (1:1) conditions. Hand-rim kinetics, glenohumeral joint dynamics, and muscle activity were measured using a custom instrumented geared wheel, motion analysis, and surface electromyography. Findings indicated that the propulsion speed and stroke distance decreased significantly during the low gear condition. The peak hand-rim resultant force and propulsive moment, as well as the peak glenohumeral inferior force and flexion moment, were significantly less during the low gear condition. The peak and integrated muscle activity of the anterior deltoid and pectoralis major decreased significantly, while the normalized integrated muscle activity (muscle activity per stroke distance) was not significantly different between the two conditions. Propulsion on carpeted floor in the low gear condition was accompanied by a reduced perception of effort. The notable decrease in the peak shoulder loading and muscle activity suggests that usage of geared wheels may be beneficial for wheelchair users to enhance independent mobility in their homes and communities while decreasing their shoulder demands.

Can People with Parkinson's Disease Self-Trigger Gait Initiation? A Comparison of Cueing Strategies.

BACKGROUND: An external cue can markedly improve gait initiation in people with Parkinson's disease (PD) and is often used to overcome freezing of gait (FOG). It is unknown if the effects of external cueing are comparable if the imperative stimulus is triggered by the person receiving the cue (self-triggered) or an external source. OBJECTIVE: Two experiments were conducted to compare the effects of self- versus externally triggered cueing on anticipatory postural adjustments (APAs) during gait initiation in people with PD. METHODS: In experiment 1, 10 individuals with PD and FOG initiated gait without a cue or in response to a stimulus triggered by the experimenter or by the participant. Experiment 2 compared self- versus externally triggered cueing across three groups: healthy young adults (n = 16), healthy older adults (n = 11), and a group with PD (n = 10). RESULTS: Experiment 1: Externally triggered cues significantly increased APA magnitudes compared to uncued stepping, but not when the same cue was self-triggered. Experiment 2: APAs were not significantly improved with a self-triggered cue compared to un-cued stepping in both the PD and healthy older adult groups, but the young adults showed a significant facilitation of APA magnitude. CONCLUSION: The effectiveness of an external cue on gait initiation in people with PD and older adults is critically dependent upon whether the source of the trigger is endogenous (self-produced) or exogenous (externally-generated). These results may explain why cueing interventions that rely upon self-triggering of the stimulus are often ineffective in people with PD.

Feasibility of VR Technology in Eliciting State Anxiety Changes While Walking in Older Women.

Virtual reality (VR) technology offers an exciting way to emulate real-life walking conditions that may better elicit changes in emotional state. We aimed to determine whether VR technology is a feasible way to elicit changes in state anxiety during walking. Electrocardiogram data were collected for 18 older adult women while they navigated a baseline walking task, a dual walking task, and four walking VR environments. Using heart rate variability (HRV) analysis, we found that all four of the VR environments successfully elicited a significantly higher level of state anxiety as compared to the walking baseline, with 84% of participants eliciting a significantly lower HRV in each of the four VR conditions as compared to baseline walking. VR was also found to be a more reliable tool for increasing state anxiety as compared to a dual task, where only 47% of participants demonstrated a significantly lower HRV as compared to baseline walking. VR, therefore, could be promising as a tool to elicit changes in state anxiety and less limited in its ability to elicit changes as compared to a traditional dual task condition.

Scaling of linear anthropometric dimensions in living humans.

OBJECTIVES: Some previous studies suggest that humans do not conform to geometric similarity (isometry) in anthropometric dimensions of the upper and lower limbs. Researchers often rely on a single statistical approach to the study of scaling patterns, and it is unclear whether these methods produce similar results and are equally robust. This study used one bivariate and one multivariate method to examine how linear anthropometric dimensions scale in a sample of adult humans. MATERIALS AND METHODS: Motion capture marker data from 104 adults of varying height and mass were used to calculate anthropometric dimensions. We analyzed scaling patterns in pooled and separate sexes with two methods: (1) bivariate log-log regression and (2) multivariate principal component analysis (PCA). We calculated 95% highest density/confidence intervals for each method and defined positive/negative allometry as estimates lying outside those intervals. RESULTS: Results identified isometric scaling of the upper arm, thigh, and shoulder, positive allometry of the forearm and shank, and negative allometry of the pelvis in the pooled sample using both statistical methods. Patterns of allometry in the pooled sample were similar between methods but differed in magnitude. Sex-specific results differed in both pattern and magnitude between log-log regression and PCA. Only one measurement (shoulder width) departed from isometry in the sex-specific log-log regressions. DISCUSSION: Our findings suggest that especially in sex-specific analyses, the pattern and magnitude of allometry are sensitive to statistical methodology. When body mass was selected as the size variable, most human linear anthropometric dimensions in this sample scaled isometrically and were therefore geometrically similar within sexes.

A comparison of glenohumeral joint kinematics and muscle activation during standard and geared manual wheelchair mobility.

The high prevalence of upper extremity joint injuries among manual wheelchair users is largely attributed to the high repetitive loading during propulsion. The purpose of this study was to evaluate the effects of using geared wheels for manual wheelchair mobility on shoulder joint biomechanics. Fourteen able-bodied participants performed overground propulsion and ramp ascension using standard and geared manual wheelchair wheels. Spatial temporal parameters, glenohumeral joint kinematics, and shoulder muscle activity were quantified. Findings indicated that regardless of the level of slope, the propulsion speed and stroke distance decreased significantly (p ≪ 0.001), and the stroke frequency increased significantly (p ≤ 0.025) during geared manual wheelchair propulsion. The glenohumeral joint ranges of motion in the coronal plane (p ≤ 0.005) and peak joint angles in the coronal (p ≤ 0.023) and transverse (p ≤ 0.012) planes were significantly different between standard and geared wheels usage. Shoulder muscle activity was substantially less using the geared wheels with significant findings in the pectoralis major (level floor, p ≤ 0.008) and infraspinatus (p ≤ 0.014) peak muscle activity, and the anterior deltoid (p ≤ 0.014) and pectoralis major (p ≤ 0.015) integrated muscle activity. However, the shoulder flexor normalized integrated muscle activity (muscle activity per stroke distance) was not different between the wheels.

Modulation of anticipatory postural adjustments using a powered ankle orthosis in people with Parkinson's disease and freezing of gait.

BACKGROUND: Freezing of gait (FOG) during gait initiation in people with Parkinson's disease (PD) may be related to a diminished ability to generate anticipatory postural adjustments (APAs). Externally applied perturbations that mimic the desired motion of the body during an APA have been demonstrated to shorten and amplify APAs; however, no portable device has been tested. In this study, a portable powered ankle-foot orthosis (PPAFO) testbed was utilized to investigate the effect of mechanical assistance, provided at the ankle joint, on the APAs during gait initiation. RESEARCH QUESTION: Does mechanical assistance provided at the ankle joint improve APAs during gait initiation in people with PD and FOG? METHODS: Thirteen participants with PD and FOG initiated gait across five test conditions: two self-initiated (uncued) conditions in walking shoes [Baseline-Shoes], and the PPAFO in unpowered passive mode [Baseline-PPAFOPassive]; three "go" cued conditions that included an acoustic tone with the PPAFO in unpowered passive mode [Acoustic + PPAFOPassive], the mechanical assistance from the PPAFO [PPAFOActive], and the acoustic tone paired with mechanical assistance [Acoustic + PPAFOActive]. A warning-cue preceded the imperative "go" cue for all the cued trials. Peak amplitudes and timings of the vertical ground reaction forces (GRFs) and center of pressure (COP) shifts from onset to toe-off were compared across conditions. RESULTS: Mechanical assistance significantly increased the peak amplitudes of the GRFs and COP shifts, reduced APA variability, and decreased the time to toe-off relative to the passive conditions. SIGNIFICANCE: These findings demonstrate the potential utility of mechanical assistance at the ankle joint (with or without an acoustic cue) as a method to generate more consistent, shortened, and amplified APAs in people with PD and FOG.

A Neuromechanical Model of Reduced Dorsiflexor Torque During the Anticipatory Postural Adjustments of Gait Initiation.

Anticipatory postural adjustments (APAs) precede gait initiation and function to accelerate the center of mass forward and towards the initial stance leg. Impairments in APA generation, such as those seen in people with Parkinson's disease (PD), can impact the quality of the first step. An initial burst of activity in the dorsiflexor muscle (tibialis anterior) of the stepping leg is an important contributor to the posterior excursion of the center of pressure that accelerates the center of mass forward during an APA. Tibialis anterior activation can be diminished or absent in people with PD; however, the neuromechanical consequence of this diminished dorsiflexor torque on APA generation is not fully understood. Computational models of gait initiation that include components of the neuromuscular system may provide additional insight. In this paper, an inverted pendulum model of the body generated from healthy young adult data was used to simulate reduced dorsiflexor torque during an APA for gait initiation. Forward body lean angle and center of pressure were assessed over various settings of decreased dorsiflexor torque and compared to experimental data from a person with PD. Results from the model demonstrate that reducing the peak dorsiflexor torque by as little as 8-Nm may alter forward body lean and the center of pressure excursion from their nominal trajectories. These results can help inform how much torque is needed from an external device to effectively modulate APAs for gait initiation, as well as provide insight into compensation strategies for reduced dorsiflexor torque in pathology.

Assessing gait changes in firefighters after firefighting activities and while carrying asymmetric loads.

One of the most common causes of injuries among firefighters is slips, trips, and falls on the fireground. Acute fatigue from firefighting activities and/or carrying asymmetric loads might impact gait characteristics increasing slip, trip, and fall risk. The purpose of this study was to examine the effects of fatigue from simulated firefighting activities and carrying asymmetric loads (fire hose over one shoulder) on firefighters' gait behavior. Both firefighting activities and asymmetric hoseload carriage led to shorter step lengths, stride lengths, single leg support time, and longer double leg support time, suggesting firefighters adopted cautious gait strategies. Simulated firefighting activities performed in either a live-fire training tower or laboratory-based environmental chamber using a firefighting activity simulator resulted in nearly identical effects on gait kinematics. This result suggests that gait assessment in a laboratory-based environmental chamber can be used as effective simulations in place of specialized burn facilities.

Effects of simulated firefighting and asymmetric load carriage on firefighter obstacle crossing performance.

Slips, trips, and falls (STF) of firefighters may occur while traversing stationary obstacles. STF risk may be amplified by fatigue from firefighting and carrying an asymmetric load. Vertical and horizontal clearances of the lead (VCL, HCL) and trailing (VCT, HCT) foot and contact with a 30 cm obstacle were examined in 24 firefighters. We examined the impact on obstacle crossing performance due to three exercise protocols (treadmill walking or simulated firefighting in an environmental chamber, and simulated firefighting in a live-fire burn building) and carrying a hose load on the right shoulder. Post-activity fatigue resulted in significant decreases in HCL and VCT. Adding a hose load did not affect choice of lead/trailing foot, but did significantly decreased HCL and increased VCL. The hose load amplified acute fatigue effects by causing a sharper decrease in both VCL and VCT. Clearances were significantly impacted by interaction effects of exercise protocol type and acute fatigue. HCL decreased and VCL remained consistent following both simulated firefighting tasks, but HCL remained unchanged and VCL increased following the treadmill protocol. Contact errors increased with fatigue and load, and more errors occurred following simulated firefighting task protocols compared to treadmill walking. Our findings suggest that both acute fatigue and carrying an additional load can cause decrements in firefighter movement, which may place a firefighter at greater STF risk. Simulated firefighting testing protocols may have greater impact on movement performance than treadmill walking. Knowledge of these results may assist in the development of a reliable, laboratory based, and standardizable simulated firefighting exercise protocol.

Impact of SCBA size and fatigue from different firefighting work cycles on firefighter gait.

Risk of slips, trips and falls in firefighters maybe influenced by the firefighter's equipment and duration of firefighting. This study examined the impact of a four self-contained breathing apparatus (SCBA) three SCBA of increasing size and a prototype design and three work cycles one bout (1B), two bouts with a five-minute break (2B) and two bouts back-to-back (BB) on gait in 30 firefighters. Five gait parameters (double support time, single support time, stride length, step width and stride velocity) were examined pre- and post-firefighting activity. The two largest SCBA resulted in longer double support times relative to the smallest SCBA. Multiple bouts of firefighting activity resulted in increased single and double support time and decreased stride length, step width and stride velocity. These results suggest that with larger SCBA or longer durations of activity, firefighters may adopt more conservative gait patterns to minimise fall risk. Practitioner Summary: The effects of four self-contained breathing apparatus (SCBA) and three work cycles on five gait parameters were examined pre- and post-firefighting activity. Both SCBA size and work cycle affected gait. The two largest SCBA resulted in longer double support times. Multiple bouts of activity resulted in more conservative gait patterns.

Design and analysis of coiled fiber reinforced soft pneumatic actuator.

Fiber reinforced elastomeric enclosures (FREEs) are soft pneumatic actuators that can contract and generate forces upon pressurization. Typical engineering applications utilize FREEs in their straight cylindrical configuration and derive actuation displacement and forces from their ends. However, there are several instances in nature, such as an elephant trunk, snakes and grapevine tendrils, where a spiral configuration of muscle systems is used for gripping, thereby establishing a mechanical connection with uniform force distribution. Inspired by these examples, this paper investigates the constricting behavior of a contracting FREE actuator deployed in a spiral or coiled configuration around a cylindrical object. Force balance is used to model the blocked force of the FREE, which is then related to the constriction force using a string model. The modeling and experimental findings reveal an attenuation in the blocked force, and thus the constriction force caused by the coupling of peripheral contact forces acting in the spiral configuration. The usefulness of the coiled FREE configuration is demonstrated in a soft arm orthosis for crutch users that provides a constriction force around the forearm. This design minimizes injury risk by reducing wrist load and improving wrist posture.

Impact of SCBA size and firefighting work cycle on firefighter functional balance.

Slips, trips and falls are leading causes of fireground injuries. A functional balance test (FBT) was used to investigate the effects of self-contained breathing apparatus (SCBA) size and design, plus firefighting work cycle. During the FBT, subjects walked along a narrow platform and turned in defined spaces, with and without an overhead obstacle. Thirty firefighters wore three varying-sized standard SCBAs and a low-profile prototype SCBA during three simulated firefighting work/rest cycles. Firefighters were tested pre- and post-firefighting activity (one bout, two bouts with a 5-min break, or back-to-back bouts with no break). Subjects committed more errors and required longer completion times with larger SCBAs. Use of the prototype SCBA lead to lower times and fewer errors. Performing a second bout of firefighting increased completion time. Firefighters need to consider how SCBA and amount of physical activity on the fireground may influence balance in order to reduce the risk of injury.

Physiological response to firefighting activities of various work cycles using extended duration and prototype SCBA.

Firefighters' self-contained breathing apparatus (SCBA) protects the respiratory system during firefighting but increases the physiological burden. Extended duration SCBA (>30 min) have increased air supply, potentially increasing the duration of firefighting work cycles. To examine the effects of SCBA configuration and work cycle (length and rest), 30 firefighters completed seven trials using different SCBA and one or two bouts of simulated firefighting following work cycles common in the United States. Heart rate, core temperature, oxygen consumption, work output and self-reported perceptions were recorded during all activities. Varying SCBA resulted in few differences in these parameters. However, during a second bout, work output significantly declined while heart rates and core temperatures were elevated relative to a single bout. Thirty seven per cent of the subjects were unable to complete the second bout in at least one of the two-bout conditions. These firefighters had lower fitness and higher body mass than those who completed all assigned tasks. Practitioner Summary: The effects of extended duration SCBA and work/rest cycles on physiological parameters and work output have not been examined. Cylinder size had minimal effects, but extended work cycles with no rest resulted in increased physiological strain and decreased work output. This effect was more pronounced in firefighters with lower fitness.

Six-Minute Walk Test Performance in Persons With Multiple Sclerosis While Using Passive or Powered Ankle-Foot Orthoses.

OBJECTIVE: To determine whether a powered ankle-foot orthosis (AFO) that provides dorsiflexor and plantar flexor assistance at the ankle can improve walking endurance of persons with multiple sclerosis (MS). DESIGN: Short-term intervention. SETTING: University research laboratory. PARTICIPANTS: Participants (N=16) with a neurologist-confirmed diagnosis of MS and daily use of a prescribed custom unilateral passive AFO. INTERVENTIONS: Three 6-minute walk tests (6MWTs), 1 per footwear condition: shoes (no AFO), prescribed passive AFO, and portable powered AFO (PPAFO). Assistive devices were worn on the impaired limb. MAIN OUTCOME MEASURES: Distance walked and metabolic cost of transport were recorded during each 6MWT and compared between footwear conditions. RESULTS: Each participant completed all three 6MWTs within the experimental design. PPAFO use resulted in a shorter 6MWT distance than did a passive AFO or shoe use. No differences were observed in metabolic cost of transport between footwear conditions. CONCLUSIONS: The current embodiment of this PPAFO did not improve endurance walking performance during the 6MWT in a sample of participants with gait impairment due to MS. Further research is required to determine whether expanded training or modified design of this powered orthosis can be effective in improving endurance walking performance in persons with gait impairment due to MS.