Effects of air bottle design on postural control of firefighters

Development and evaluation of a novel self-contained breathing apparatus pack to reduce musculoskeletal loads and enhance firefighter comfort

Self‑Contained Breathing Apparatus (SCBA) is an essential piece of personal protective equipment for firefighters, providing essential respiratory support and protection. A major challenge in SCBA research is to reduce musculoskeletal disorders and enhance firefighter comfort while carrying the SCBA. In this study, a novel SCBA pack was designed to reduce SCBA‑related musculoskeletal stress. Ten volunteer firefighters were recruited to participate in the test protocol equipped with a novel SCBA (SCBANovel) and a traditional SCBA (SCBATrad) pack. Surface electromyography and pressure data were collected, and subjective ratings of discomfort using a visual analog scale. The results showed that the SCBANovel significantly reduced trapezius and erector spinae muscle activity. Shoulder and waist pressure were reduced by 19.73%‑32.83% and 18.46%‑41.55%, respectively. In addition, the SCBANovel pack reduced lower back discomfort scores by 59.1%, all compared to the SCBATrad pack. The SCBANovel pack showed a significant reduction in musculoskeletal stress and discomfort in firefighters.Practitioner SummarySCBAs are known to be critical in protecting the health of firefighters, but are often associated with firefighter discomfort and musculoskeletal disorders. We developed the SCBANovel pack and explored the effects on the upper body musculoskeletal system and comfort during walking and running compared to carrying the SCBATrad pack. The SCBANovel pack reduced muscle activity in the trapezius and erector spinae muscles and significantly reduced pressure on the shoulders and lower back.

Multi-sensor fusion for biomechanical analysis: evaluation of dynamic interactions between self-contained breathing apparatus and firefighter using computational methods

Understanding the complex three-dimensional (3D) dynamic interactions between self-contained breathing apparatus (SCBA) and the human torso is critical to assessing potential impacts on firefighter health and informing equipment design. This study employed a multi-inertial sensor fusion technology to quantify these interactions. Six volunteer firefighters performed walking and running experiments on a treadmill while wearing the SCBA. Calculations of interaction forces and moments from the multi-inertial sensor technology were validated against a 3D motion capture system. The predicted interaction forces and moments showed good agreement with the measured data, especially for the forces (normal and lateral) and moments (x- and z-direction components) with relative root mean square errors (RMSEs) below 9.4%, 7.7%, 7.7%, and 7.8%, respectively. Peak pack force reached up to 150 N, significantly exceeding the SCBA's intrinsic weight during SCBA carriage. The proposed multi-inertial sensor fusion technique can effectively evaluate the 3D dynamic interactions and provide a scientific basis for health monitoring and ergonomic optimization of SCBA systems for firefighters.

Evaluation of self-contained breathing apparatus (SCBA) weight on firefighter stamina, comfort, and postural stability

Firefighters wear personal protective equipment to protect them from the thermal and chemical environment in which they operate. The self-contained breathing apparatus (SCBA) provides isolation of the airway from the hazardous fireground. National standards limit SCBA weight, however, integration of additional features could result in an SCBA exceeding the current limit. The purpose of this study was to examine the effects of increased SCBA weight on firefighters' physiological responses, work output, dynamic stability, and comfort. Completion of simulated firefighting activities induced a strong physiological response. Peak oxygen consumption was higher with the lightest SCBA than the heaviest SCBA. Few other physiological differences were noted as SCBA weight increased. Importantly, increased SCBA weight resulted in significantly more negative perceptions by the firefighters and a trend towards significance for the duration of work time prior to reaching volitional fatigue. These results should be considered when assessing changes to existing SCBA weight limits.

Quantifying self-contained breathing apparatus on physiology and psychological responses during firefighting: a systematic review and meta-analysis

Objectives. There is no consensus regarding the efficacy of self-contained breathing apparatus (SCBA) on firefighters' physiological and psychological stress responses. This study synthesized and quantified the psycho-physiological demands placed on firefighters wearing SCBA compared to a control group. Methods. Five databases were searched with English-language restrictions from inception to January 2021. As dependent variables, physiological (rectal temperature [T_re], mean skin temperature [T¯sk], heart rate [HR], maximal heart rate [HR_max], maximum oxygen uptake [V_O2max], total sweat rate [TSR]) and psychological (rating of perceived exertion [RPE] and thermal sensation [TS]) responses were continuously collected. This study is registered with PROSPERO (CRD42021228363). Results. Nine eligible studies with 289 participants met the inclusion criteria. The pooled estimates for V_O2max statistically significantly decreased, whereas T¯sk, HR, HR_max, TSR and RPE increased significantly. Additionally, the T_re and TS parameters were elevated but not significant. Subgroup analysis revealed that, except for V_O2max and TSR, the SCBA weight did not differ significantly between groups on any outcome measure. Conclusions. Our meta-analysis indicates that wearing SCBA elicits thermoregulatory, metabolic and psychological stress. However, this is not primarily explained by the weight of SCBA, highlighting the value of ergonomic design and physiological monitoring.

Preventing and Monitoring Work-Related Diseases in Firefighters: A Literature Review on Sensor-Based Systems and Future Perspectives in Robotic Devices

In recent years, the necessity to prevent work-related diseases has led to the use of sensor-based systems to measure important features during working activities. This topic achieved great popularity especially in hazardous and demanding activities such as those required of firefighters. Among feasible sensor systems, wearable sensors revealed their advantages in terms of possibility to conduct measures in real conditions and without influencing the movements of workers. In addition, the advent of robotics can be also exploited in order to reduce work-related disorders. The present literature review aims at providing an overview of sensor-based systems used to monitor physiological and physical parameters in firefighters during real activities, as well as to offer ideas for understanding the potentialities of exoskeletons and assistive devices.

The Effects of Firefighter Equipment and Gear on the Static and Dynamic Postural Stability of Fire Cadets

BACKGROUND

Slips, trips, falls, and jumps were the second leading cause of injuries at the fireground.

RESEARCH QUESTION

The purpose of this study was to explore the effects of firefighter equipment and gear (EQG) on postural stability and determine if load per kg of body mass (L/BM) is associated with postural stability.

METHODS

26 male fire cadets (26.15 ± 4.16 yr., 178.92 ± 6.92 cm, 86.61 ± 9.09 kg) were included in the analyses. Participants performed 3 single-leg landings (SLL) with and without EQG. The first 3 seconds of ground reaction forces following initial ground contact were used to calculate dynamic postural stability index (DPSI). Participants completed 2 static balance tasks (normal stability and limits of stability (LoS)) with and without EQG. Main outcome measures were overall LoS score (LoSS), direction-specific LoSS, and LoS distance (cm) of COP excursion (LoSD) in the anterior, posterior, right, and left directions. Separate paired-samples t-tests were run to determine the differences between load conditions for DPSI, overall LoSS, direction-specific LoSS, and LoSD in all directions. Bivariate correlations were conducted to determine the relationship of L/BM to DPSI, overall LoSS, and LoSS and LoSD in the anterior, posterior, right and left directions.

RESULTS

Due to the use of multiple statistical tests, a Bonferroni correction was used, and the alpha level of .05 was adjusted to .005. DPSI was significantly higher loaded than unloaded, t(25) = -13.965, p < .001, d = 7.032, 95% CI, -0.133 to -0.099. No other comparisons were significant. A significant strong positive correlation (r(24) = .665, p < .001) was observed between L/BM and DPSI. No other correlations were significant.

SIGNIFICANCE

This study demonstrates that firefighter EQG may significantly impact a cadet's ability to maintain postural stability while performing their duties.

Stable and Unstable Load Carriage Effects on the Postural Control of Older Adults

The aim of this study was to investigate the effects of backpack load carriage on quiet standing postural control and limits of stability (LOS) of older adults. Fourteen older adults (65 [6] y) performed quiet standing and a forward, right, and left LOS test in 3 conditions, unloaded, stable, and unstable backpack loads while activity of 4 leg muscles was recorded. Stable and unstable loads decreased postural sway (main effect ηp2=.84, stable P < .001, unstable P < .001), mediolateral (main effect ηp2=.49, stable P = .002, unstable P = .018) and anterior-posterior (main effect ηp2=.64, stable P < .001, unstable P = .001) fractal dimension, and LOS distance (main effect ηp2=.18, stable P = .011, unstable P = .046) compared with unloaded. Rectus femoris (main effect ηp2=.39, stable P = .001, unstable P = .010) and gastrocnemius (main effect ηp2=.30, unstable P = .027) activity increased in loaded conditions during LOS and quiet standing. Gastrocnemius-tibialis anterior coactivation was greater in unstable load than stable loaded quiet standing (main effect ηp2=.24, P = .040). These findings suggest older adults adopt conservative postural control strategies minimizing the need for postural corrections in loaded conditions. Reduced LOS may also increase fall risk when carrying a load. However, there was no difference between unstable and stable loads for postural control variables.

Free Energy Principle in Human Postural Control System: Skin Stretch Feedback Reduces the Entropy

Human upright standing involves an integration of multiple sensory inputs such as vision, vestibular and somatosensory systems. It has been known that sensory deficits worsen the standing balance. However, how the modulation of sensory information contributes to postural stabilization still remains an open question for researchers. The purpose of this work was to formulate the human standing postural control system in the framework of the free-energy principle, and to investigate the efficacy of the skin stretch feedback in enhancing the human standing balance. Previously, we have shown that sensory augmentation by skin stretch feedback at the fingertip could modulate the standing balance of the people with simulated sensory deficits. In this study, subjects underwent ten 30-second trials of quiet standing balance with and without skin stretch feedback. Visual and vestibular sensory deficits were simulated by having each subject close their eyes and tilt their head back. We found that sensory augmentation by velocity-based skin stretch feedback at the fingertip reduced the entropy of the standing postural sway of the people with simulated sensory deficits. This result aligns with the framework of the free energy principle which states that a self-organizing biological system at its equilibrium state tries to minimize its free energy either by updating the internal state or by correcting body movement with appropriate actions. The velocity-based skin stretch feedback at the fingertip may increase the signal-to-noise ratio of the sensory signals, which in turn enhances the accuracy of the internal states in the central nervous system. With more accurate internal states, the human postural control system can further adjust the standing posture to minimize the entropy, and thus the free energy.

Firefighter protective clothing and self contained breathing apparatus does not alter balance testing using a standard sensory organization test or motor control test in healthy, rested individuals

BACKGROUND

There is a high rate of injury associated with firefighting: in 2016, 21% of all fireground injuries were attributed to falls, jumps and slips. Examining factors related to balance, including experience in wearing firefighter gear, may assist in reducing injury related to falls.

OBJECTIVES

To assess the effects of wearing firefighter gear on postural balance in firefighters and non-firefighters in a rested condition.

METHODS

Each subject attended two sessions. In session 1, informed consent was obtained, a threshold audiogram was collected, and the sensory organization test (SOT) and motor control test (MCT) were administered with the subject dressed in street clothes. The second session was comprised of three different conditions with the order of testing randomized across subjects: street clothing, firefighter protective garments (coat, pants, helmet, hood) with breathing apparatus but no facemask, and firefighter protective garments with breathing apparatus and facemask. Twenty subjects participated: ten firefighters (8 males) and sex and age-matched non-firefighters (8 males) completed the study.

RESULTS

SOT scores were obtained for each sub-condition, including the overall performance score and sensory weightings. For the MCT, latency and amplitude data were obtained for the three forward and three reverse translation conditions. A significant difference was found for large forward surface translations in the MCT in firefighters.

CONCLUSION

In spite of the altered center of balance created by breathing apparatus and the altered visual cues created by the facemask, wearing firefighter gear did not substantively affect anterior-posterior postural stability or motor response to linear translation in rested, healthy individuals. Firefighters and non-firefighters performed similarly across all except one of the experimental conditions.

The effect of firefighter personal protective equipment on static and dynamic balance

Firefighters work in unpredictable conditions, necessitating the use of personal protective equipment (PPE). However, the additional weight from the PPE and self-contained breathing apparatus (SCBA) alters their centre of mass (COM), restricts movement and limits vision (face mask) contributing to a firefighters' challenge of maintaining balance. Thus, the purpose of this study was to quantify the effects of firefighter PPE on static and dynamic balance. Participants performed two sets of three functional balance tests: (1) Static Single Leg (SSL); (2) Dynamic Single Leg (DSL); (3) Limits of Stability (LOS). The balance tests were performed under one control and three randomised PPE conditions: (1) athletic clothing; (2) turnouts; (3) turnouts + SCBA; (4) turnouts + SCBA + face mask. Our study found turnouts + SCBA both with and without the face mask negatively affected dynamic balance. These findings identify factors in fall-related injuries and strategies to reduce occupational risk. Practitioner summary: Slips, trips and falls are the most common cause of injury in firefighters. Our study investigated the effects of firefighter personal protective equipment (PPE) on static and dynamic balance utilising a computerised balance instrument. We found that turnouts with a self-contained breathing apparatus (SCBA) with or without face mask negatively affected balance.

Postural stability pattern as an important safety factor of firefighters

BACKGROUND

Firefighting is a hazardous profession that involves high fall risk and is crucial component for the safety of people.

OBJECTIVE

The aim of this study was to identify factors that impact on postural stability patterns of firefighters.

METHODS

The study examined 177 Polish firefighters from the National Firefighting and Rescue System (NFRS) aged 31.9±10.1 years, with body height of 179.6±5.93, body mass of 83.9±11.0 and BMI of 26.0±3.03. Postural stability was evaluated by means of the Balance System SD (Biodex USA) set at the level 12 of instability, in a sportswear, bunker gear, with and without visual input. The fall risk test (FRI) was also performed. Four indices were analysed: overall stability index (OSI), anterior-posterior stability index (APSI), medial-lateral stability index (MLSI), and fall risk index (FRI).

RESULTS

Mean results for fall risk index (FRI) were in the normal range for all age groups regardless of the type of clothing the firefighters were wearing. Individual results obtained in the fall risk test, 128 firefighters were in the normal range for their age, furthermore, 10 firefighters obtained better results than the normal range, 34 firefighters had worse results and 5 people failed to complete the test. Postural stability with eyes closed was found to decline with age. Wearing bunker gear did not have an effect on postural stability.

CONCLUSIONS

Balance tests should be integrated into the firefighting training routines in order to improve balance and support fall prevention. Exercises with reduced visual input should also be incorporated into the training methodology.

Using trunk posture to monitor heat strain at work

This study aimed to determine if trunk posture during walking is related to increases in rectal temperature (T_re). 24 males treadmill walked in one of four conditions (1): 30 min at 3.0 mph and 0% grade, 20 °C and 50% relative humidity (RH), wearing healthcare worker (HCW) PPE; (2): 30 min at 3.0 mph and 0% grade, 27.5 °C and 60% RH, HCW PPE; (3): 30 min at 3.0 mph and 0% grade, 32.5 °C and 70% RH, HCW PPE; and (4): 40 min at 40% VO₂max, 30 °C and 70% RH, wearing firefighter PPE. Trunk posture (Zephyr BioHarness 3) and T_re were measured continuously. T_re was positively related to trunk posture, controlling for covariates (B = 3.49, p < .001). BMI and age moderated this relationship (T_re×age, B = 0.76, p < .001; T_re*BMI, B = -1.85, p < .001). Trunk posture measurement may be useful in monitoring fall potential and magnitude of heat stress of workers in hot environments. Practitioner Summary: Occupational hyperthermia increases worker risk for heat illness and injury but is difficult to monitor in the field. This investigation shows that trunk posture is independently and positively related to core temperature. Non-invasive measurement or visual inspection of trunk posture could provide novel insight on individual heat strain level.

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.

Ankle restrictive firefighting boots alter the lumbar biomechanics during landing tasks

Firefighters incur high incidences of lower back and body injuries. Firefighting boots, with specific design requirements, have been shown to reduce ankle range of motion. This reduction has been associated with impaired force dissipation and lower body kinematic alterations. Thus, the aim of this study was to determine the relationship between firefighting boots, lumbar biomechanics and load carriage during landing. Our data indicates that when wearing firefighting boots, lumbar forces increased and kinematics changed in frontal and transverse planes. These changes may be occurring due to the restrictive shaft of the firefighting boot reducing ankle range of motion. Comparisons between unloaded and loaded conditions also showed increased changes in lumbar biomechanics, independent of footwear worn. Therefore, wearing firefighting boots, in addition to operational loading, may be placing firefighters at greater risk of lumbar injuries. Future research investigating firefighting boots and additional load carriage on lower body biomechanics during landing is recommended.

The effect of firefighter protective garments, self-contained breathing apparatus and exertion in the heat on postural sway

Fire suppression wearing thermal protective clothing (TPC) and self-contained breathing apparatus (SCBA) challenges a firefighter's balance and may explain firefighter falls. Postural control based on force plate centre of pressure (COP) was compared for healthy subjects wearing TPC and SCBA before and after 20 min of heavy physical exertion in hot conditions. Baseline measures with and without TPC and SCBA (two different SCBA cylinder masses) were compared before and after exertion that included elements of fire suppression activities in an environmental chamber. COP excursion and variability increased with exertion for TPC and SCBA conditions compared to non-stressed conditions. The two different cylinder masses had no significant effect. Wearing TPC and SCBA when physically stressed in a hot environment increases postural sway and exacerbates postural control. Subjects compensated for the extra mass and adjusted to control postural sway with the addition of TPC and SCBA, but the stress protocol amplified these adjustments. Practitioner Summary: Firefighters wear thermal protective clothing (TPC) and self-contained breathing apparatus (SCBA) when heat-stressed and fatigued. Wearing TPC and SCBA was found to negatively impact balance when stressed, but not for non-stressed or two different sized SCBA tanks. Simulating fire-ground conditions wearing TPC and SCBA should be considered for improving balance.

Ergonomics and Beyond: Understanding How Chemical and Heat Exposures and Physical Exertions at Work Affect Functional Ability, Injury, and Long-Term Health

OBJECTIVE

To honor Tom Waters's work on emerging occupational health issues, we review the literature on physical along with chemical exposures and their impact on functional outcomes.

BACKGROUND

Many occupations present the opportunity for exposure to multiple hazardous exposures, including both physical and chemical factors. However, little is known about how these different factors affect functional ability and injury. The goal of this review is to examine the relationships between these exposures, impairment of the neuromuscular and musculoskeletal systems, functional outcomes, and health problems with a focus on acute injury.

METHOD

Literature was identified using online databases, including PubMed, Ovid Medline, and Google Scholar. References from included articles were searched for additional relevant articles.

RESULTS

This review documented the limited existing literature that discussed cognitive impairment and functional disorders via neurotoxicity for physical exposures (heat and repetitive loading) and chemical exposures (pesticides, volatile organic compounds [VOCs], and heavy metals).

CONCLUSION

This review supports that workers are exposed to physical and chemical exposures that are associated with negative health effects, including functional impairment and injury. Innovation in exposure assessment with respect to quantifying the joint exposure to these different exposures is especially needed for developing risk assessment models and, ultimately, preventive measures.

APPLICATION

Along with physical exposures, chemical exposures need to be considered, alone and in combination, in assessing functional ability and occupationally related injuries.

A Portable Sensory Augmentation Device for Balance Rehabilitation Using Fingertip Skin Stretch Feedback

Neurological disorders are the leading causes of poor balance. Previous studies have shown that biofeedback can compensate for weak or missing sensory information in people with sensory deficits. These biofeedback inputs can be easily recognized and converted into proper information by the central nervous system (CNS), which integrates the appropriate sensorimotor information and stabilizes the human posture. In this study, we proposed a form of cutaneous feedback which stretches the fingertip pad with a rotational contactor, so-called skin stretch. Skin stretch at a fingertip pad can be simply perceived and its small contact area makes it favored for small wearable devices. Taking advantage of skin stretch feedback, we developed a portable sensory augmentation device (SAD) for rehabilitation of balance. SAD was designed to provide postural sway information through additional skin stretch feedback. To demonstrate the feasibility of the SAD, quiet standing on a force plate was evaluated while sensory deficits were simulated. Fifteen healthy young adults were asked to stand quietly under six sensory conditions: three levels of sensory deficits (normal, visual deficit, and visual + vestibular deficits) combined with and without augmented sensation provided by SAD. The results showed that augmented sensation via skin stretch feedback helped subjects correct their posture and balance, especially as the deficit level of sensory feedback increased. These findings demonstrate the potential use of skin stretch feedback in balance rehabilitation.