Effect of Protective Clothing and Fatigue on Functional Balance of Firefighters

We investigated the effects of wearing personal protective equipment (PPE), design of PPE (Standard vs.Enhanced), and fatigue during a simulated firefighting activity on the functional balance of firefighters. We defined functional balance as the ability to prevent a loss of balance and maintain body posture while performing functional tasks. A novel Functional Balance Test (FBT) was used to assess functional balance of firefighters while stepping up, stepping down, turning, walking along a beam, and passing under an obstacle. Data are presented from fifty-seven male firefighters, who were randomly divided into two groups: Standard PPE (n=28) and Enhanced PPE (n=29). The specially designed Enhanced PPE was lighter, more breathable, and capable of air circulation, compared to traditional Standard PPE. Each participant performed the FBT at three time periods (baseline with station uniform, pre-activity with PPE, and post-activity with PPE after a live-fire simulated firefighting activity). The firefighting activity involved alternating 2-minute rest- work cycles of four stations: stair climb, forcible entry, room search, and hose advancement. The FBT had four trials each with and without an overhead obstacle. Performance errors (major and minor), performance time, and a composite performance index were recorded. Wearing PPE significantly impaired functional balance, as noted by increases in all performance metrics. Following the firefighting activity, performance time increased by 3% but the number of minor and major errors decreased by 13% and 32%, respectively, suggesting that firefighters may trade-off between speed and accuracy depending on perceived threat to balance safety. There was no significant difference in functional balance between the Enhanced PPE and Standard PPE groups, suggesting that Enhanced PPE with a passive cooling system and an external circulating hose is not effective in improving functional balance of firefighters. A better designed PPE, with an improved cooling system and minimal (or no) protruding attachments may be of benefit in terms of firefighter functional balance.Ope

A pneumatic power harvesting ankle-foot orthosis to prevent foot-drop

<p>Abstract</p> <p>Background</p> <p>A self-contained, self-controlled, pneumatic power harvesting ankle-foot orthosis (PhAFO) to manage foot-drop was developed and tested. Foot-drop is due to a disruption of the motor control pathway and may occur in numerous pathologies such as stroke, spinal cord injury, multiple sclerosis, and cerebral palsy. The objectives for the prototype PhAFO are to provide toe clearance during swing, permit free ankle motion during stance, and harvest the needed power with an underfoot bellow pump pressurized during the stance phase of walking.</p> <p>Methods</p> <p>The PhAFO was constructed from a two-part (tibia and foot) carbon composite structure with an articulating ankle joint. Ankle motion control was accomplished through a cam-follower locking mechanism actuated via a pneumatic circuit connected to the bellow pump and embedded in the foam sole. Biomechanical performance of the prototype orthosis was assessed during multiple trials of treadmill walking of an able-bodied control subject (n = 1). Motion capture and pressure measurements were used to investigate the effect of the PhAFO on lower limb joint behavior and the capacity of the bellow pump to repeatedly generate the required pneumatic pressure for toe clearance.</p> <p>Results</p> <p>Toe clearance during swing was successfully achieved during all trials; average clearance 44 ± 5 mm. Free ankle motion was observed during stance and plantarflexion was blocked during swing. In addition, the bellow component repeatedly generated an average of 169 kPa per step of pressure during ten minutes of walking.</p> <p>Conclusion</p> <p>This study demonstrated that fluid power could be harvested with a pneumatic circuit built into an AFO, and used to operate an actuated cam-lock mechanism that controls ankle-foot motion at specific periods of the gait cycle.</p

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

Effect of SCBA Design and Firefighting Induced Fatigue on Balance, Gait and Safety of Movement

Here we presented a report for the Fire Service documenting an examination of the effect of SCBA and firefighting induced fatigue on firefighters’ gait, balance, and safety of movement. More detailed, peer-reviewed scientific reports can be found in academic literature and are available at the Illinois Fire Service Institute. Fireground operations are inherently dangerous, with overexertion/ strain and slips, trips, and falls being the two leading causes of injury. 26.5% of fireground injuries are a result of overexertion or strain, conditions which may be accelerated by the fact that firefighting activities can induce near maximal heart rates and elevated core temperatures. The high levels of effort and exertion needed to complete such activities may be made worse by the firefighter’s turnout gear and self-contained breathing apparatus (SCBA). Anecdotal evidence suggests a trend in the Fire Service toward extended duration SCBA (greater than 30-min), which may further increase the physical demand on the firefighter. Further, nearly 23% of fireground injuries are the result of a slip, trip, and/or fall. These injuries often occur while or following firefighting activities, and may often be a result of the fatigue those activities have induced in the firefighter. Extended duration SCBA are typically heavier and may reduce the time before the firefighter becomes fatigued. Thirty firefighters were recruited to take part in repeated-measures study to examine the effects of SCBAs and duration of work cycle have on physiological strain, balance, gait, and safety of movement. Firefighters completed seven different conditions with various SCBA (30, 45, and 60-minute standard cylindrical SCBA and a low-profile 45-min prototype) and durations of simulated firefighting (one or two bouts) in a heated environmental chamber (117°F (47°C)). Four activities were performed (stair climb, hose advance, secondary search, and overhaul) on two-minute work-rest cycles. Subjects also completed an obstacle course designed to test their gait and functional balance prior to, and immediately after the simulated firefighting activities. Following firefighting activity firefighters had elevated heart rates and core temperatures. The firefighters also generally performed worse in the obstacle course. The size of the SCBA had a minimal impact on the firefighters, though it did decrease the performance on a Functional Balance Test. The low-profile prototype SCBA impacted the firefighters in a similar manner as the traditional cylindrical SCBA, though firefighters generally took longer to pass through a 16-inch on-center stud space. When firefighters completed multiple bouts of simulated firefighting activity heart rates and core temperatures were elevated relative to a single bout while the number of repetitions performed during each activity decreased. Performance during the obstacle course was also more negatively impacted following a second bout of activity than after a single bout.U.S. Department of Homeland Security through the Assistance to Firefighters Grant Program (Research and Development grant: EMW-2010-FP-01606)Ope

Egress Efficacy of Persons with Multiple Sclerosis During Simulated Evacuations

Expedited evacuation of commercial and residential structures in the event of an emergency may be more difficult for persons with physical movement disorders. There is a need to better characterize the impact of such disorders and provide movement data to improve evacuee and responder safety. We undertook a pilot, feasibility study that investigated the ability of persons with multiple sclerosis (MS) and controls without MS to walk along a 48 m long path that included five different door configurations with various opening hardware and closure mechanisms, both before and after a six-minute walk, simulating a long evacuation path. Persons with MS took longer to complete the evacuation circuit (102 vs. 31 s) and to pass through each door (average 4.8 vs. 1.4 s) compared to controls. During the six-minute walk, persons with MS had decreased walking speed (0.7 vs. 1.9 m/s). The MS population demonstrated more conservative gait biomechanics throughout the simulation, i.e., wider, shorter and slower steps. Timing and biomechanical differences between populations and the potential fatigue induced through an extended evacuation can be used to improve understanding of movement in populations with disabilities, and incorporate these data into estimation of flow rates during evacuation.Funding support for MB was provided by the National Science Foundation Engineering Research Center for Compact and Efficient Fluid Power (0540834), with additional support from the Foundation of the Consortium of Multiple Sclerosis Centers’ Multiple Sclerosis Workforce of the Future program.Ope

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.This work was supported by the Department of Homeland Security Fire Prevention and Safety, Federal Emergency Management Agency [grant number EMW-2010-FP-01606].Ope

Improving joint torque calculations: Optimization-based inverse dynamics to reduce the effect of motion errors

Abstract The accuracy of joint torques calculated from inverse dynamics methods is strongly dependent upon errors in body segment motion profiles, which arise from two sources of noise: the motion capture system and movement artifacts of skin-mounted markers. The current study presents a method to increase the accuracy of estimated joint torques through the optimization of the angular position data used to describe these segment motions. To compute these angular data, we formulated a constrained nonlinear optimization problem with a cost function that minimizes the difference between the known ground reaction forces (GRFs) and the GRF calculated via a top-down inverse dynamics solution. To evaluate this approach, we constructed idealized error-free reference movements (of squatting and lifting) that produced a set of known &apos;&apos;true&apos;&apos; motions and associated true joint torques and GRF. To simulate real-world inaccuracies in motion data, these true motions were perturbed by artificial noise. We then applied our approach to these noise-induced data to determine optimized motions and related joint torques. To evaluate the efficacy of the optimization approach compared to traditional (bottom-up or top-down) inverse dynamics approaches, we computed the root mean square error (RMSE) values of joint torques derived from each approach relative to the expected true joint torques. Compared to traditional approaches, the optimization approach reduced the RMSE by 54% to 79%. Average reduction due to our method was 65%; previous methods only achieved an overall reduction of 30%. These results suggest that significant improvement in the accuracy of joint torque calculations can be achieved using this approach.

Accepted and presented at The Design of Medical Devices Conference (DMD2016)

The development of powered orthoses and exoskeletons for robotic gait assistance has led to new issues related to their control. Limited work has been published regarding when to provide plantarflexor torque to the ankle [2]). Optimizing timing using metabolic data can be timeconsuming (10 s of minutes of walking). In addition to functional energetics, the effect of these devices on joint biomechanics should also be considered. The portable powered ankle foot orthosis (PPAFO) is capable of providing both plantarflexor and dorsiflexor torques by using a pneumatic rotary actuator at the ankle Joint biomechanics have been observed to vary considerably when the plantarflexor torque actuation timing was varied when using the PPAFO By estimation of a walker&apos;s instantaneous state of the limb during a single stride, as represented by a specific % GC, it is possible to detect and control for various gait events. Properly timed control of powered assistance during walking is a crucial task to prevent tripping or fall risk. Early state estimation-controlled PPAFO studies used dorsiflexor and plantarflexor actuation timings based on the normative event timings for healthy able-bodied adult gait In this study, we took a biomechanics approach and used replication of ankle angle kinematics as the optimization criteria. We proposed a multistep, supervised learning classification algorithm to identify the plantarflexor actuation as early or late using the ankle angle collected during walking. 2 Methods 2.1 Experimental Protocol. Five healthy adult males (age 26.40 6 5.0 yr, height 1.79 6 4.7 m, and weight 80.70 6 5.8 kg), without any neurological, gait, or postural disorders, participated in the study. All the subjects gave informed consent, and this study was approved by the university&apos;s Institutional Review Board. Each subject participated in two sessions of experiments in the same day with a break of up to 10 min. There were two test conditions per session (shoes only and PPAFO on right leg). In session 1, data were collected to create training data for the classifier. In session 2, the trained classifier was combined with a bisection search technique to quickly identify the appropriate actuation timing for a specific user. To assess the accuracy of the classifier, cross-correlation analysis was used to compare the shoe-only and PPAFO data. The shoe-only data were considered to be the true reference data, being generated during normal walking conditions; thus indicating normal plantarflexion timing. Training of the classification algorithm was done in between sessions 1 and 2. More detailed explanations of session 1, training, and session 2 are described below. 2.1.1 Data Collection (Session 1). First, to record normative ankle angle using motion capture (Vicon), each subject walked on a treadmill for 30 s while wearing their own shoes (trial 1). Three markers were placed on the ankle-foot to determine the ankle angle. While wearing, on the right leg, the PPAFO each subject walked on the treadmill for 30 s trials. The plantarflexor actuation timing started at 30%, 35%, 40%, 45%, 50%, 55%, or 60% GC, for a total of seven sequential trials. After completing these trials, the PPAFO ankle data were visually inspected by comparing with normative shoe ankle data and the 5% interval which contained the transition point between early and late actuation was identified. Then, four additional trials at 1% increments were collected to fill this interval. The expectation was to find within this interval the appropriate torque timing at a resolution of 1% GC. 2.1.2 Training of Classification Algorithm. Data from session 1 were considered as training data for the classification algorithm and were analyzed to find the parameters that identified actuation timing as either early or late actuation. First, the ankle angle data (last 20 strides for each trial) were separated by individual strides and denoted as a vector consisting of ankle angle data for a full GC. Fourier coefficients for each vector were then calculated by using a discrete Fourier transformation. Using vectors of Fourier coefficients for early and late actuations, a full training matrix was developed. Using principal component analysis, a feature map was derived from this Fourier coefficient training matrix. The dimension of the feature map d was further reduced by including only the top principal components or features. Real-time data were collected and classified for d ¼ 20. Using this feature map