The effect of hyperhydration on physiological and perceived strain during treadmill exercise in personal protective equipment

Agreement between measured and self-reported physiological strain in males and females during simulated occupational heat stress

RATIONALE

Monitoring physiological strain is recommended to safeguard workers during heat exposure, but is logistically challenging. The perceptual strain index (PeSI) is a subjective estimate thought to reflect the physiological strain index (PSI) that requires no physiological monitoring. However, sex is known to influence perceptions of heat stress, potentially limiting the utility of the PeSI.

OBJECTIVES

The objective of this study was to assess whether sex modifies the relationship between PeSI and PSI.

METHODS

Thirty-four adults (15 females) walked on a treadmill (moderate intensity; ~200 W/m2) for 180 min or until termination (volitional fatigue, rectal temperature ≥39.5°C) in 16°C, 24°C, 28°C, and 32°C wet-bulb globe temperatures. Rectal temperature and heart rate were recorded to calculate PSI (0-10 scale). Rating of perceived exertion and thermal sensation were recorded to calculate PeSI (0-10 scale). Relationships between PSI and PeSI were evaluated via linear mixed models. Mean bias (95% limits of agreement [LoA]) between PSI and PeSI was assessed via Bland-Altman analysis. Mean absolute error between measures was calculated by summing absolute errors between the PeSI and the PSI and dividing by the sample size.

FINDINGS

PSI increased with PeSI (p < 0.01) but the slope of this relation was not different between males and females (p = 0.83). Mean bias between PSI and PeSI was small (-0.4 points), but the 95% LoA (-3.5 to 2.7 points) and mean absolute error were wide (1.3 points).

IMPACT

Our findings indicate that sex does not appreciably impact the agreement between the PeSI and PSI during simulated occupational heat stress. The PeSI is not a suitable surrogate for the PSI in either male or female workers.

A profile of occupational tasks performed by mounted police officers

BACKGROUND

Within individual policing organisations, there are a wide variety of units and job roles.

OBJECTIVE

To profile the occupational tasks performed by Australian mounted police officers, aiming to offer conditioning insight into this unique job role.

METHODS

Thirteen fully qualified and operational mounted police officers (n = 11 females), who served in the mounted police unit for ∼3.3 (±2.3) years, participated in this observational cohort study. Participants completed a survey outlining common occupational tasks and were monitored throughout four consecutive shifts. Participants' heart rate (HR), respiratory rate (RR), and skin temperature (ST) data were collected via wearable monitoring (Equivital EQ-02, Hidalgo, UK) and body position, physical activity undertaken, task effort, and load carriage were recorded by researchers. A one-way ANOVA was used to assess mean differences in physiological measures between the three most reported tasks.

RESULTS

Survey identified 130 tasks, with 38 listed as most common. The three most reported mounted police tasks were: 'horse riding' (n = 13, 34%), 'mounted patrols' (n = 10, 26%), and 'horse care' (n = 10, 26%). These were also reported as the most physically demanding. HR during 'horse care' and 'horse riding' were significantly higher than when 'mounted patrolling' (27±7bpm, p = 0.001 and 33±8bpm; p = 0.001, respectively). Mean RR was higher when 'horse riding' when compared to 'horse care' (5.3±1.6brpm) and 'mounted patrol' (8.5±1.9brpm).

CONCLUSION

Mounted police officers experience unique physiological challenges throughout their routine occupational tasks. This study highlights the significance of understanding occupation-specific tasks and stressors undertaken by mounted police to develop relevant conditioning, rehabilitation, and monitoring procedures.

Association between physiological and perceptual heat strain while wearing stab-resistant body armor

In this study, we explored the association between physiological and perceptual heat strain while wearing stab-resistant body armor (SRBA). Human trials were performed on ten participants in warm and hot environments. Physiological responses (core temperature, skin temperature, and heart rate), and perceptual responses (thermal sensation vote, thermal comfort vote, restriction of perceived exertion (RPE), wetness of skin, and wetness of clothing) were recorded throughout the trials, and subsequently, the physiological strain index (PSI), and perceptual strain index (PeSI) were calculated. The results indicated that the PeSI showed a significant moderate association with the PSI, and was capable of predicting PSI for low (PSI = 3) and high (PSI = 7) levels of physiological strain with the areas under the curves of 0.80 and 0.64, respectively. Moreover, Bland-Altman analysis indicated that the majority of the PSI ranged within the 95% confidence interval, and the mean difference between PSI and PeSI was 0.14 ± 2.02 with the lower 95% limit and upper 95% limit being -3.82 to 4.10, respectively. Therefore, the subjective responses could be used as an indicator for predicting physiological strain while wearing SRBA. This study could provide fundamental knowledge for the usage of SRBA, and the development of physiological heat strain assessment.

Does the fit of personal protective equipment affect functional performance? A systematic review across occupational domains

OBJECTIVE

To explore the effect of personal protective equipment (PPE) fit on functional performance across a range of occupational domains.

BACKGROUND

PPE introduces an ergonomic, human systems integration, and mass burden to the wearer, and these factors are thought to be amplified if PPE is ill-fitting. However, few studies have considered the role of fit (static, dynamic, and cognitive) when evaluating PPE-related performance detriments in occupational settings.

METHOD

A systematic literature review was conducted to identify relevant studies, which were then critically appraised based on methodological quality and collated to compare key findings and present evidence-based recommendations for future research directions across a range of occupational domains.

RESULTS

16 published studies met the inclusion criteria, 88% of which found that the fit of PPE had a statistically significant effect on occupational performance. Poorly sized PPE resulted in slower or increased reaction time; decreased range of motion or mobility; decreased endurance or tolerance; decreased pulmonary function; and altered muscle activation. Limited research met the inclusion criteria and those that did had risks of bias in methodology quality.

CONCLUSION

Future research evaluating the effect of PPE on performance in occupational settings should aim to recruit a more representative population; consider sex as a covariate; quantify and evaluate PPE fit and performance when integrated with all relevant equipment items; include outcome measures related to all three categories of fit (static, dynamic, cognitive); and assess performance of operationally relevant tasks.

Exploring the comfort of head personal protective equipment for Chinese firefighters: An interview study

Head personal protective equipment (HPPE), such as helmets and masks, are protective equipment worn by firefighters to protect their head, neck, and face when they are performing tasks. As a wearable device, HPPE significantly affects firefighters' occupational safety and health along with job performance. This study aims to explore the influential factors of HPPE comfort and collect corresponding functional requirements. A semi-structured interview was conducted among 5 focus groups comprising 31 Chinese firefighters. Through a qualitative analysis of the interview results, eight dimensions of HPPE comfort were proposed: perceived change, movement, attachment, harm, emotion, anxiety, thermal comfort, and comfort of vision and hearing. The aspects of weight and size matching are the important reasons behind the comfort problems of the current HPPE. Four aspects of functional requirements were summarized: communication tools, goggles, full-face helmets, and lighting. The study findings will provide references for improving HPPE design.

An acute naproxen dose does not affect core temperature or Interleukin-6 during cycling in a hot environment

Non-steroidal anti-inflammatory drugs’ anti-pyretic and anti-inflammatory effects has led some individuals to theorize these medications may blunt core body temperature (Tc) increases during exercise. We utilized a double-blind, randomized, and counterbalanced cross-over design to examine the effects of a 24-h naproxen dose (3–220 ​mg naproxen pills) and placebo (0 ​mg naproxen) on Tc and plasma interleukin-6 (IL-6) concentrations during cycling in a hot or ambient environment. Participants (n ​= ​11; 6 male, 5 female; age ​= ​27.8 ​± ​6.5 years, weight ​= ​79.1 ​± ​17.9 ​kg, height ​= ​177 ​± ​9.5 ​cm) completed 4 conditions: 1) placebo and ambient (Control); 2) placebo and heat (Heat); 3) naproxen and ambient (Npx); and 4) naproxen and heat (NpxHeat). Dependent measures were taken before, during, and immediately after 90 ​min of cycling and then 3 ​h after cycling. Overall, Tc significantly increased pre- (37.1 ​± ​0.4 ​°C) to post-cycling (38.2 ​± ​0.3 ​°C, F_1.7,67.3 ​= ​150.5, p ​< ​0.001) and decreased during rest (37.0 ​± ​0.3 ​°C, F_2.0,81.5 ​= ​201.6, p ​< ​0.001). Rate of change or maximum Tc were not significantly different between conditions. IL-6 increased pre- (0.54 ​± ​0.06 ​pg/ml) to post-exercise (2.46 ​± ​0.28 ​pg/ml, p ​< ​0.001) and remained significantly higher than pre-at 3 ​h post- (1.17 ​± ​0.14 ​pg/ml, 95% CI ​= ​−1.01 to −0.23, p ​= ​0.001). No significant IL-6 differences occurred between conditions. A 24-h, over-the-counter naproxen dose did not significantly affect Tc or IL-6 among males and females cycling in hot or ambient environments.

Perceptual strain in a compensable hot environment: Accuracy and clinical correlates

Heat strain monitoring indexes are important to prevent exertional heat illness (EHI) and uncover risk factors. Two indexes are the Physiological Strain Index (PSI) and a subjective PSI analogue, the Perceptual Strain Index (PeSI). The PeSI is a feasible alternative to PSI in field conditions, although the validity has been variable in previous research. However, the PeSI has been rarely examined at a low heat strain with compensable heat stress, such as during a heat tolerance test (HTT). This study evaluated the discrepancy between the maximal PeSI and maximal PSI achieved during a HTT and determined their association with EHI risk factors, including history of EHI, percent body fat (%BF), relative VO_2max, fatigue and sleep status (n = 121; 47 without prior EHI, 74 with prior EHI). The PSI was calculated using the change in rectal temperature (T_re) and heart rate (HR) and PeSI was calculated based on the formula containing thermal sensation (TS), a T_re analogue, and rate of perceived exertion (RPE), a HR analogue. Significant associations were identified between PSI and PeSI and between PSI_HR and PeSI_HR in the total sample and between PSI and PeSI in the EHI group. Bland-Altman analyses indicated PeSI underestimated PSI in the total sample, PSI_HR was greater than PeSI_HR, and that PSI_core and PeSI_core were not significantly different, but values varied widely at different heat strains. This indicates the use of RPE underestimates HR and that the accuracy of TS to predict T_re may be subpar. This study also demonstrated that participants with higher %BF have a decreased perception of heat strain and that post-fatigue, sleep status and a prior EHI may increase the perception of heat strain. Overall, these results suggest that PeSI is a poor surrogate for PSI in a compensable heat stress environment at low heat strain.

Cardiovascular Effects of Compression Garments During Uncompensable Heat Stress

ABSTRACT

Bautz, J, Hostler, D, Khorana, P, and Suyama, J. Cardiovascular effects of compression garments during uncompensable heat stress. J Strength Cond Res 35(4): 1058-1065, 2021-This study examined the potential hemodynamic benefits of wearing lower extremity compression garments (CGs) beneath thermal protective clothing (TPC) worn by wildland firefighters, while exercising in a heated environment. Using in a counterbalanced design, 10 male subjects ([mean ± SD] age 27 ± 6 years, height 1.78 ± 0.09 m, body mass 74.8 ± 7.0 kg, body fat 10.6 ± 4.2%, and V̇o2max 57.8 ± 9.3 ml·kg-1·min-1) completed control (no CG) and experimental (CG) conditions in randomly assigned order. Protocols were separated by a minimum of 3 days. Subjects exercised for 90 minutes (three, 30-minute segments) on a treadmill while wearing wilderness firefighter TPC and helmet in a heated room. Venous blood was drawn before and after exercise to measure hemoglobin (Hgb), hematocrit (Hct), serum osmolarity (OSM), and serum creatine phosphokinase (CPK). Vital signs and perceptual measures of exertion and thermal comfort were recorded during the protocol. Data were analyzed by the paired t-test. There were no differences in the change in heart rate (84 ± 27 vs. 85 ± 14 b·min-1, p = 0.9), core temperature rise (1.8 ± 0.6 vs. 1.9 ± 0.5° C, p = 0.39), or body mass lost (-1.72 ± 0.78 vs. -1.77 ± 0.58 kg, p = 0.7) between the conditions. There were no differences in the change in Hgb (0.49 ± 0.66 vs. 0.33 ± 1.11 g·dl-1, p = 0.7), Hct (1.22 ± 1.92 vs. 1.11 ± 3.62%, p = 0.9), OSM (1.67 ± 6.34 vs. 6.22 ± 11.39 mOsm·kg-1, p = 0.3), or CPK (22.2 ± 30.2 vs. 29.8 ± 19.4 IU·L-1, p = 0.5). Total distance walked (3.9 ± 0.5 vs. 4.0 ± 0.5 miles, p = 0.2), exercise interval (88.6 ± 3.5 vs. 88.4 ± 3.6 minutes, p = 0.8), and perceptual measures were similar between conditions. Compression garments worn beneath TPC did not acutely alter the physiologic response to exertion in TPC. With greater use in the general public related to endurance activities, the data neither encourage nor discourage CG use during uncompensable heat stress.

Non-steroidal anti-inflammatory drugs on core body temperature during exercise: A systematic review

BACKGROUND

Because of their anti-pyretic effects, some individuals prophylactically use non-steroidal anti-inflammatory drugs (NSAIDs) to blunt core temperature (Tc) increases during exercise, thus, potentially improving performance by preventing hyperthermia and/or exertional heat illness. However, NSAIDs induce gastrointestinal damage, alter renal function, and decrease cardiovascular function, which could compromise thermoregulation and increase Tc. The aim of this systematic review was to evaluate the effects of NSAIDs on Tc in exercising, adult humans.

METHODS

We conducted searches in MEDLINE, PubMed, Cochrane Reviews, and Google Scholar for literature published up to November 2020. We conducted a quality assessment review using the Physiotherapy Evidence Database scale. Nine articles achieved a score ≥ seven to be included in the review.

RESULTS

Seven studies found aspirin, ibuprofen, and naproxen had no effect (p > .05) on Tc during walking, running, or cycling for ≤ 90 min in moderate to hot environments. Two studies found significant Tc changes. In one investigation, 81 mg of aspirin for 7-10 days prior to exercise significantly increased Tc during cycling (p < .001); final Tc at the end of exercise = 38.3 ± 0.1 °C vs. control = 38.1 ± 0.1 °C. In contrast, participants administered 50 mg rofecoxib for 6 days experienced significantly lower Tc during 45 min of cycling compared to placebo (NSAID Tc range ≈ 36.7-37.2 °C vs control ≈ 37.3-37.8 °C, p < 0.05).

CONCLUSIONS

There are limited quality studies examining NSAID effects on Tc during exercise in humans. The majority suggest taking non-selective NSAIDs (e.g., aspirin) 1-14 days before exercise does not significantly affect Tc during exercise. However, it remains unclear whether Tc increases, decreases, or does not change during exercise with other NSAID drug types (e.g., naproxen), higher dosages, chronic use, greater exercise intensity, and/or greater environmental temperatures.

Breathability and Safety Testing of Personal Protective Equipment: "Human-comfort" Factor Remains Undefined

Healthcare systems all over the world have been enormously affected by the COVID-19 pandemic. Healthcare workers (HCWs) taking care of these patients need personal protective equipments (PPEs) standardized for full protection from droplets and aerosols carrying viral load to variable distances. There has been a surge of manufacturers supplying these protective gears in India and regulatory agencies have issued technical specifications pertaining to PPEs focusing solely on synthetic blood penetration tests (SBPTs) and keeping the upper limit of non-woven fabric to 95 g/m² (GSM). These PPE specifications are silent on air permeability (AP) and water/moisture vapor transmission rate (WVTR/MVTR) of the fabric. As a result, most of the PPE kits, despite having appropriate SBPT certifications from regulatory agencies, have extremely poor permeability and breathability. The acceptability of PPEs by HCWs can be vastly improved when the end-users are proactively invited to participate in “comfort testing” of PPEs before getting issuance of certification for marketing. “Field testing” or “end-user trials” in which HCWs don the PPE and assess it for comfort while performing different types of clinical work, e.g., in intensive care units (ICUs), operation theaters, cath labs, etc., also takes into account a hitherto often ignored “human-comfort-factor” that not only enhances the understanding of HCWs about the need for the PPEs but can also motivate them to use it without worrying about discomfort. We hereby propose that comfort fit testing (COmfort and Material Fit is an Obviously Required Test) should be a part of the mandatory testing and certification process for PPE, so that the industry invests wisely in manufacturing PPE kits that are not only certified for fabric but are also tested for comfort factors.

How to cite this article: Kapoor A, Baronia AK, Azim A, Agarwal G, Prasad N, Mishra R, et al. Breathability and Safety Testing of Personal Protective Equipment: “Human-comfort” Factor Remains Undefined. Indian J Crit Care Med 2021;25(1):12–15.

Heat stress and physiological and perceptual strains of date harvesting workers in palm groves in Jiroft

BACKGROUND

Outdoor workers are exposed to heat caused by atmospheric conditions and solar radiation. More specifically, those working in palm groves are more in danger of heat stresses since they harvest their crops in hot seasons.

OBJECTIVE

This study was aimed at investigating heat stresses and strains in date harvesting workers in groves around Jiroft, Southeastern Iran.

METHODS

This study was a descriptive-analytical one of cross-sectional type. In this study, three environmental indices including Wet Bulb Globe Temperature index (WBGT), Environmental Stress Index (ESI) and Discomfort Index (DI), the physiological strain index (PSI) as well as perceptual strain index (PeSI) were analyzed to investigate stresses and strains in workers. For this purpose, 59 date harvesting workers (36 men and 23 women) in palm groves in Jiroft were analyzed. With accordance to date harvesting season, data collection was carried out from August to September, 2017.

RESULTS

In this research, the means of environmental indices including WBGT, ESI and DI were 32.77°C, 30.39°C and 33.22°C, respectively and they all revealed direct and significant correlation. Moreover, Time-Weighted Average for Wet Bulb Globe Temperature index (WBGT.TWA) was significantly different from Threshold Limit Values for Wet Bulb Globe Temperature index (WBGT.TLV). The scores of the PSI and PeSI were 2.28 and 6.61, respectively.

CONCLUSION

The results of this study indicated that date picking workers were exposed to heat stress more than the reference value of WBGT recommended by American Conference of Governmental Industrial Hygienists (ACGIH). In addition, workers suffered a low degree of physiological strain and a moderate degree of perceptual strain caused by heat stress in palm groves in Jiroft.

Impacts of cooling intervention on the heat strain attenuation of construction workers

This study aimed to evaluate the effectiveness and practicality of a cooling intervention with a newly designed cooling vest on heat strain attenuation in the construction industry. Fourteen construction workers volunteered to participate in the field study. Each participant took part in two trials, i.e., cooling and control. Construction work included morning and afternoon sessions. Cooling intervention was implemented for 15 and 30 min during the morning and afternoon rest periods, respectively, between repeated bouts of work. Micrometeorological (wet-bulb globe temperature [WBGT]), physiological (tympanic temperature and heart rate), and perceptual (ratings of perceived exertion [RPE] and thermal sensation) measurements were taken during the test. Heat strain indices, including physiological strain index (PSI_HR) and perceptual strain index (PeSI), were estimated accordingly. During the study, construction workers were exposed to a hot environment with a mean WBGT of 31.56 ± 1.87 °C. Compared with the control, physiological and perceptual strain were significantly reduced in the cooling condition during rest and subsequent work periods (p < 0.05; d = 0.24-1.07, small to large cooling effect). Cooling intervention significantly alleviates heat strain in the construction industry. The effectiveness and practicality of a proposed cooling intervention were tested in a field study. Results provide a reference for setting guidelines and promoting application on a range of construction sites.

Identifying and characterising the physical demands for an Australian specialist policing unit

Many police organisations incorporate specialist policing roles where incumbents are tasked with providing operational response capabilities above and beyond the general duties policing role. The current research utilised subjective job task analysis methods to identify and characterise the physically demanding, frequently occurring, and operationally important tasks, as well as the dominant fitness component for each task, inherent to specialist policing roles in an Australian policing organisation. This was achieved through engagement with subject matter experts and online survey responses from specialist police incumbents. In total, 11 criterion tasks were identified, which covered a range of physical capacities including muscular strength, muscular endurance, and aerobic power. The most physically demanding tasks included those with an arrest component, requiring high muscular strength and power capacities. Having identified the criterion tasks, three operational scenarios were constructed, which incorporated each of the 11 tasks in different operational contexts. The criterion tasks and composite scenarios will allow practitioners within specialised police units to develop evidence-based strategies, including physical selection procedures and physical training programs, specific to the demands of their work.

Comparison of heat strain recovery in different anti-heat stress clothing ensembles after work to exhaustion

A hot environment combined with physically demanding tasks can subject workers to a higher risk of heat stress. A series of regulations and guidelines have been proposed to design appropriate anti-heat stress work uniform to reduce body heat strain. The present study aimed to examine heat strain recovery in different anti-heat stress clothing ensembles after work to exhaustion in the heat. 10 healthy males performed intermittent treadmill running/walking to exhaustion, followed by 30min passive recovery sitting in a climatic chamber, which simulated the hot and humid outdoor environment (34°C temperature, 60% relative humidity, 0.3m/s air velocity, and 450W/m² solar radiation). The participants took part in five wear trials in counter-balanced order, including Sportswear, CIC Uniform, NEW Uniform, ICEBANK Cooling Vest, and NEW Cooling Vest, which have different levels of cooling capacity. Core temperature, skin temperature, heart rate, sweat loss, ratings of perceived exertion, and thermal sensations were measured throughout the entire heat exposure period. Physiological heat strain indices, including the physiological strain index (PhSI) and the perceptual strain index (PeSI), were used as a yardstick to quantify and compare the rate of recovery. Significantly lower physiological strain was observed in the newly developed NEW Uniform and NEW Cooling Vest groups compared with the commonly worn CIC Uniform group during recovery. At the end of the recovery period, participants in NEW Cooling Vest achieved the highest recovery (42.18% in PhSI and 81.08% in PeSI), followed by ICEBANK Cooling Vest, Sportswear, NEW Uniform, and CIC Uniform. The cooling capacity of anti-heat stress clothing ensembles and the recovery time significantly affect the rate of recovery in PhSI and PeSI, which may benefit the industry by formulating the appropriate work-rest schedule by considering the clothing effect.

Physiological and perceptual strain of firefighters during graded exercise to exhaustion at 40 and 10 °C

Purpose. To study whether perceptual identification should be included as a measure to evaluate physiological stress. Methods. Physiological variables oxygen uptake (V_O2), ventilation, heart rate, blood lactate concentration, rectal temperature (T_rec) and mean skin temperature, and perceptual variables rate of perceived exertion, thermal sensation and time to exhaustion, were measured at submaximal and maximal intensities during graded exercise on a treadmill to exhaustion in 12 firefighters wearing protective clothing and extra mass at 40 and 10 °C. Physiological strain index (PhSI) and perceptual strain index (PeSI) were calculated. Results. Apart from T_rec, all physiological and perceptual variables were higher at submaximal intensities of 40 °C. Time to exhaustion was 16% shorter and the corresponding V_O2 was reduced by 7% in the heat. A high correlation (r = 89) between PhSI and PeSI was found at both temperatures. PeSI scores were equal to PhSI at both ambient temperatures, except at the two highest intensities in the heat, where PeSI was higher. Conclusions. These findings support use of perceptual identification to evaluate physiological stress. However, at very high intensities under hot conditions the perceptual strain was estimated higher than the physiological strain. More precise indexes are needed to include perceptual measures in safety standard.

A field study of the effectiveness and practicality of a novel hybrid personal cooling vest worn during rest in Hong Kong construction industry

A novel hybrid cooling vest (HCV) incorporated with phase change materials (PCMs) and ventilation fans has been developed for construction workers in Hong Kong to attenuate heat stress and prevent heat-related illnesses, and its effectiveness and practicality have been validated in this study. A total of 140 wear trials involving of 140 workers were conducted in Hong Kong construction sites during the summer time. Each wear trial involves a two-day wear test, of which one day workers wore the HCV (denoted as VEST) during resting, and another day they wore traditional workwear (denoted as CON). Subjects were asked to rate their perceived exertion (RPE), thermal sensations (TS) and 7 other subjective attributes. There were significant differences in the effectiveness on reducing workers' heat strain between VEST and CON in terms of alleviations of heart rate (ΔHR), ΔTS, ΔRPE as well as ΔPeSI (p < 0.001). The practicality of HCV is evidenced by a significant improvement by 0.93-1.34 on the rating scores of perceived cooling effect, sensations of comfort and skin dryness during rest and fatigue recovery in VEST at the level of 0.05, and high ratings of 4.85-5 (rating scale from 1 to 7, and the higher the better) by subjects on the preference, fitness as well as effectiveness to combat heat stress. In addition, a remarkable proportion of 91 per cent of subjects prefer to use this newly designed HCV as a cooling measure during rest. The power to alleviate perceptual heat stain (PeSA) in VEST is about twice of that by rest, which means HCV can notably improve the workers' perceptual heat strain in a limited resting duration. However, the strain alleviation power of HCV nearly remains unchanged with the prolonged rest duration. Thus, the optimal work-rest schedule needs to be investigated in a further study.

Exercise in personal protective equipment in a hot, humid environment does not affect risk propensity

We tested the hypothesis that heat stress created by light exertion in encapsulating personal protective equipment (PPE) in a hot, humid environment increases risk propensity. Ten healthy subjects (29 ± 7 y) completed 2 trials presented in a counter-balanced manner. Subjects donned encapsulating PPE, and in one trial they wore a tube-lined shirt underneath that was perfused with 5°C water. Subjects completed 2 15 min bouts of walking exercise on a treadmill at ˜50% maximal heart rate in a 32°C, 81% RH environment. Subjects completed the Balloon Analog Risk Task (BART), an objective measure of risk-taking, before, between the 2 exercise bouts, and following the final exercise bout. Personal cooling lowered (P < 0.01) mean skin temperature by 8.0 ± 1.6°C. Intestinal temperature rose (P < 0.01) in both trials, but was lower (P < 0.01) at the end of exercise in the cooling trial (38.0 ± 0.3°C vs. 37.6 ± 0.3°C). BART derived indices of risk propensity were not affected by trial or time (trial × time interaction: P ≥ 0.33). These data indicate that 60 min of exposure to mild heat stress created by light exertion in encapsulating PPE does not affect risk-taking behavior.

Emergency Incident Rehabilitation: Resource Document to the Position Statement of the National Association of EMS Physicians

Position Statement: Emergency Incident Rehabilitation The National Association of EMS Physicians® believes that: Emergency operations and training conducted while wearing protective clothing and respirators is physiologically and cognitively demanding. The heat stress and fatigue created by working in protective clothing and respirators creates additional risk of illness/injury for the public safety provider. Emergency incident rehabilitation provides a structured rest period for rehydration and correction of abnormal body core temperature following work in protective clothing and respirators. Emergency incident rehab should be conducted at incidents (e.g. fireground, hazardous materials, and heavy rescue emergencies) and trainings involving activities that may lead to exceeding safe levels of physical and mental exertion. Emergency incident rehabilitation is incident care, not fitness for duty, and meant to reduce physiologic strain and prepare the responder to return to duty at the current incident and for the remainder of the shift. EMS should play a role in emergency incident rehabilitation with providers trained to understand the physiologic response of healthy individuals to environmental, exertional, and cognitive stress and implement appropriate mitigation strategies. An appropriately qualified physician should have oversight over the creation and implementation of emergency incident rehabilitation protocols and may be separate from the roles and responsibilities of the occupational medicine physician. There are no peer-reviewed data related to cold weather rehabilitation. Future studies should address this limitation to the literature.

Pilot Study Examining the Effects of Atropine on Performance during Uncompensable Heat Stress

In many operational scenarios, hypohydration can be corrected with oral rehydration following the work interval. Although rare, there are potential situations that require extended intervals of uncompensable heat stress exposure while working in personal protective equipment (PPE). Under these conditions, retention of body water may be valuable to preserve work capacity and reduce cardiovascular strain. We conducted a pilot study comparing intramuscular atropine sulfate versus saline placebo to establish the safety profile of the protocol and to provide pilot data for future investigations. Five, healthy, heat-acclimated subjects completed this crossover design laboratory study. Each subject performed up to one hour of exertion in a hot environment while wearing a chemical resistant coverall. Atropine sulfate (0.02 mg/kg) or an equivalent volume of sterile saline was administered by intramuscular injection. Core temperature, heart rate, perceptual measures, and changes in body mass were measured. All five subjects completed the acclimation period and both protocols. No adverse events occurred, and no pharmacologically induced delirium was identified. Change in body mass was less following exercise influenced by atropine sulfate (p = 0.002). Exertion time tended to be longer in the atropine sulfate arm (p = 0.08). Other measures appeared similar between groups. Intramuscular atropine sulfate reduced sweating and tended to increase the work interval under uncompensable heat stress when compared to saline placebo. Heart rate and temperature changes during exertion were similar in both conditions suggesting that the influence of an anticholinergic agent on thermoregulation may be minimal during uncompensable heat stress.

KEY WORDS

thermoregulation; cholinolytic; anticholinergic; reaction time.

Validation of Perceptual Strain Index to Evaluate the Thermal Strain in Experimental Hot Conditions

Background:

The incidence of heat stress is one of the most common problems in workplaces and industries. Many heat stress indices have been developed, and these indices have some disadvantages. The purpose of this study is to validate the perceptual strain index (PeSI) in experimental hot conditions.

Methods:

This study is of cross-sectional carried out on 15 men at five different thermal conditions (35°C, 30°C, 27°C, 24°C, and 21°C) in a climate chamber and on a treadmill at three levels of light (2.4 kph), medium (4.8 kph) and heavy activity (6.3 kph). Heart rate and oral temperature were respectively measured to calculate the physiological strain index. Also, thermal sensation and rate perceive exertion were respectively measured to calculate the PeSI. Finally, the correlation between the indices was analyzed using Pearson correlation test and regression analysis.

Results:

Pearson correlation test showed a high correlation (r = 0.94) between the PeSI and physiological strain index (P = 0/001). It was also observed a high correlation between the PeSI and the oral temperature (r = 0.78, P = 0/001) and the heart rate (r = 0.90, P = 0/001). In addition, there was found a moderate correlation (r = 0.71) between the PeSI and the wet bulb glob temperature (P = 0/001). However, there was no correlation between the PeSI and the body mass index (r = 0.0009, P = 0.79).

Conclusions:

The research findings showed when there is no access to other forms of methods to evaluate the heat stress, it can be used the PeSI in evaluating the strain because of its favorable correlation with the thermal strain.

Practical on-site measurement of heat strain with the use of a perceptual strain index

OBJECTIVES

There have been increased interests in research on quantifying heat strain of construction workers and formulating corresponding guidelines for working in hot weather. The aim of this study was to validate a subjective measurement tool, the perceptual strain index (PeSI), for measuring heat strain in real-work settings.

METHODS

A total of sixteen construction workers were invited to participate in the field surveys. Empiric-based human monitoring was carried out with simultaneous micrometeorological (wet-bulb globe temperature, WBGT), physiological (heart rate, HR), and perceptual (perceived exertion, RPE; thermal sensation, TS) measurements throughout the test. The relative heart rate (RHR), the physiological strain index (PSIHR), and the PeSI were then calculated accordingly.

RESULTS

The PeSI exhibited moderate correlations with WBGT and RHR (r = 0.42 and 0.40, respectively), which indicated the PeSI was sensitive to the variants of WBGT and RHR. The results of regression analysis indicated that the PeSI changed in the same general manner as the PSIHR, with a relatively large determination coefficient (R(2) = 0.67). The established perceptual strain zone illustrated that the PeSI ranging from 7 to 8 would be the exposure limit of construction workers in hot weather.

CONCLUSION

The PeSI is a simple, robust, reliable, and user-friendly tool for heat strain assessment in occupational settings. The perceptual strain zone will provide practical guidelines for on-site heat strain monitoring for construction workers.

The use of pregame hyperhydration with intravenous fluids in National Collegiate Athletic Association Football Bowl Subdivision teams

OBJECTIVE

To determine the frequency of pregame intravenous fluid hyperhydration (PIVFH) usage, administration protocols, indications, complications, and perceived efficacy by National Collegiate Athletic Association Football Bowl Subdivision (NCAA-FBS) teams.

DESIGN

Cross-sectional survey study.

SETTING

National Collegiate Athletic Association Football Bowl Subdivision.

PARTICIPANTS

Head athletic trainers from NCAA-FBS institutions.

INTERVENTION

Voluntary, anonymous 15-item validated online survey instrument.

MAIN OUTCOME MEASURES

Number of teams reporting use of PIVFH.

RESULTS

The survey response rate was 64% (77 of 120). Thirty percent of respondents reported the utilization of PIVFH, administered to an average of 2 to 3 players. The most common reasons cited for using PIVFH were to prevent muscle cramps (95%), heat illness (79%), and dehydration (68%). Additionally, 47% of programs used PIVFH to improve player exercise tolerance and 47% per player request. Twenty-four percent of programs that used PIVFH reported the occurrence of associated complications. Only 15% of respondents believed that PIVFH improved their teams' overall performance.

CONCLUSIONS

PIVFH is a common practice among NCAA-FBS teams. PIVFH is used most often to prevent muscle cramps, dehydration, and heat illness. The relatively few numbers of players per team who receive PIVFH suggest that higher risk individuals were targeted for administration.

Core temperature and heart rate response to repeated bouts of firefighting activities

During live-fire firefighting operations and training evolutions, firefighters often consume multiple cylinders of air and continue to wear their personal protective equipment even after fire suppression activities have ceased. However, most studies have only reported core temperature changes during short-term firefighting activities and have shown a very modest increase in core temperature. Therefore, the purpose of this study is to evaluate core temperature and heart rate (HR) during repeated bouts of firefighting activity over ∼3 h. The results of this study show that core temperatures increase by an average of 1.9°C--to a larger magnitude than previously reported--and continue to increase during subsequent work cycles (38.4 vs. 38.7) even after long breaks of more than 30 min. The rate of core temperature increase during work continues to increase later in the training exercise (from 0.036 to 0.048°C/min), increasing the risk for exertional heat stress particularly if long-duration firefighting activity is required at these later times.

PRACTITIONER SUMMARY

To date, core temperature and HR changes during firefighting have been reported for short-term studies, which may significantly underestimate the physiological burden of typical firefighting activities. Firefighter core temperatures are shown to increase to a larger magnitude than previously observed and the rate of rise in core temperature increases during subsequent firefighting activities.

Performance benefits of rehydration with intravenous fluid and oral glycerol

PURPOSE

Intravenous (IV) saline has been used by athletes attempting to accelerate rehydration procedures. The diuresis from IV rehydration may be circumvented through the concomitant use of oral glycerol. We aimed to examine the effects of rehydrating with four different regimens of IV fluid and oral glycerol on subsequent 40-km cycling time trial performance.

METHODS

Nine endurance-trained men were dehydrated by 4% bodyweight via exercise in the heat. They then rehydrated with 150% of the fluid lost via four protocols using a randomized crossover design: 1) oral = sports drink and water; 2) oral glycerol = sports drink, water, and glycerol; 3) IV = half as normal saline, half of sports drink, and water; and 4) IV with oral glycerol = half as normal saline, half as sports drink, water, and glycerol. After this, they completed a 40-km cycling performance test in the heat.

RESULTS

Compared with oral rehydration, there were significant performance benefits (P < 0.05) when rehydrating with oral glycerol (improved time to complete 40 km by 3.7%), IV (3.5%), and IV with oral glycerol (4.1%). Plasma volume restoration was highest in IV with oral glycerol, then IV, then oral glycerol, then oral (P < 0.01 for all of these comparisons). There were no differences in HR, tympanic/skin temperatures, sweat rate, blood lactate concentration, thermal stress, or RPE between groups.

CONCLUSIONS

Combining IV fluid with oral glycerol resulted in the greatest fluid retention; however, it did not improve exercise performance compared with either modality alone.

Physiological responses of Police Officers during job simulations wearing chemical, biological, radiological and nuclear personal protective equipment

The aim of this study was to quantify the physiological responses of Police Officers wearing chemical, biological, radiological and nuclear personal protective equipment (CBRN PPE) during firearms house entry (FE) unarmed house entry (UE) and crowd control (CC) simulations. Participants volunteered from the UK Police Force [FE (n = 6, age 33 ± 4 years, body mass 85.3 ± 7.9 kg, (·)VO₂max 53 ± 5 ml · kg⁻¹ · min⁻¹), UE and CC (n = 11, age 34 ± 5 years, body mass 88.5 ± 13.8 kg, (·)VO₂max 51 ± 5 ml · kg⁻¹ · min⁻¹)]. Heart rate reserve (HRR) during FE was greater than UE (74 ± 7 vs. 62 ± 6%HRR, p = 0.01) but lower in CC (39 ± 7%HRR, p < 0.01). Peak core body temperature was greater during FE (39.2 ± 0.3°C) than UE (38.9 ± 0.4°C, p < 0.01) and CC (37.5 ± 0.3°C, p < 0.01), with similar trends in skin temperature. There were no differences in the volume of water consumed (1.13 ± 0.44 l, p = 0.51) or change in body mass (-1.68 ± 0.65 kg, p = 0.74) between simulations. The increase in body temperature was a primary physiological limitation to performance. Cooling strategies and revised operating procedures may improve Police Officers' physical performance while wearing CBRN PPE.

PRACTITIONER SUMMARY

In recent years, the likelihood of Police Officers having to respond to a chemical, biological, nuclear or radiological (CBRN) incident wearing personal protective equipment (PPE) has increased. Such apparel is likely to increase physiological strain and impair job performance; understanding these limitations may help improve Officer safety and operational effectiveness.

Intravenous fluid use in athletes

CONTEXT

Time allowing, euhydration can be achieved in the vast majority of individuals by drinking and eating normal beverages and meals. Important to the competitive athlete is prevention and treatment of dehydration and exercise-associated muscle cramps, as they are linked to a decline in athletic performance. Intravenous (IV) prehydration and rehydration has been proposed as an ergogenic aid to achieve euhydration more effectively and efficiently.

EVIDENCE ACQUISITION

PubMed database was searched in November 2011 for all English-language articles related to IV utilization in sport using the keywords intravenous, fluid requirements, rehydration, hydration, athlete, sport, exercise, volume expansion, and performance.

RESULTS

Limited evidence exists for prehydration with IV fluids. Although anecdotal evidence does exist, at this time there are no high-level studies confirming that IV prehydration prevents dehydration or the onset of exercise-associated muscle cramps. Currently, there are no published studies describing IV fluid use during the course of an event, at intermission, or after the event as an ergogenic aid.

CONCLUSION

The use of IV fluid may be beneficial for a subset of fluid-sensitive athletes; this should be reserved for high-level athletes with strong histories of symptoms in well-monitored settings. Volume expanders may also be beneficial for some athletes. IV fluids and plasma binders are not allowed in World Anti-Doping Agency-governed competitions. Routine IV therapy cannot be recommended as best practice for the majority of athletes.

Physical and thermal strain of firefighters according to the firefighting tactics used to suppress wildfires

The aim of this study was to analyse the physiological strain of firefighters, using heart rate (HR) and core temperature, during real wildfire suppression according to the type of attack performed (direct, indirect or mixed). Three intensity zones were established according to the HR corresponding to the ventilatory threshold (VT) and respiratory compensation threshold (RCT): zone 1, <VT; zone 2 (Z2), between VT and RCT; zone 3 (Z3), >RCT. The exercise workload (training impulse (TRIMP)), the physiological strain index (PSI) and the cumulative heat strain index(CHSI) were calculated using the time spent in each zone, and the HR and core temperature, respectively. Significantly higher mean HR, time spent in Z2 and Z3 and TRIMP h(-1) were found in direct and mixed versus indirect attacks. The highest PSI and CHSI were observed in the direct attack. In conclusion, exercise strain and combined thermal strain, but not core temperature during wildfire suppression, are related to the type of attack performed. STATEMENT OF RELEVANCE: Our findings demonstrated that wildfire firefighting is associated with high physiological demands, which vary significantly depending on the tactics chosen for performing the task. These results should be kept in mind when planning programmes to improve wildland firefighters' physical fitness, which will allow improvement in their performance.

Physiological recovery from firefighting activities in rehabilitation and beyond

OBJECTIVES

The primary objective of this study was to document the timeline of physiologic recovery from firefighting activities in order to inform emergency medical services (EMS) of vital sign values that might be expected during incident rehabilitation and in developing rehabilitation protocols to make decisions about when to return personnel to the fireground. Secondarily, we compared two different incident rehabilitation strategies to determine effectiveness in reducing physiologic strain following firefighting.

METHODS

A repeated-measures randomized crossover design was utilized in which firefighters conducted a controlled set of firefighting activities, after which they completed incident rehabilitation in one of two conditions: 1) similar to currently used rehabilitation protocols and 2) with active cooling and nutritional intervention. Following 15 minutes of rehabilitation, each firefighter was asked to perform a simulated rescue "dummy drag" and then recover for 120 minutes in a quiet area. Core temperature and heart rate were recorded throughout the study. Blood pressures and subendocardial viability ratios were obtained before firefighting, after firefighting, and at standardized times during rehabilitation and recovery.

RESULTS

Heart rate and core temperature increased during firefighting, and core temperature continued to increase for 7 minutes after completion of firefighting activities. These values did not return to baseline until at least 50 minutes after firefighting activity. Systolic blood pressures were significantly reduced during rehabilitation (15.2%), and recovered 7.7% during the first 30 minutes of recovery, but remained significantly lower than before firefighting for at least 120 minutes. An index of subendocardial perfusion was also significantly depressed for up to 110 minutes after firefighters. Differences between rehabilitation protocols were minimal.

CONCLUSIONS

The timeline for recovery from firefighting activities is significantly longer than the typical 10-20-minute rehabilitation period that often is provided on the fireground. Modifications from the current rehabilitation protocol do not appear to improve the recovery timeline when rehabilitation is conducted in a cool room. While firefighters often are concerned about elevated blood pressures, this study suggests that firefighters and EMS personnel should also be cognizant of the potential dangers of hypotension.

Seventy-five percent of National Football League teams use pregame hyperhydration with intravenous fluid

OBJECTIVE

To determine the number of National Football League (NFL) teams using pregame hyperhydration with intravenous fluid (IVF), the most common protocols for using the IVF, the complications from this routine, and the perceived efficacy of this treatment.

DESIGN

Cross-sectional survey study.

SETTING

National Football League.

PARTICIPANTS

The head athletic trainer from all 32 NFL teams received and completed the survey.

INTERVENTION

A survey designed to answer the aforementioned topics.

MAIN OUTCOME MEASURES

Number of teams using IVF to hyperhydrate euvolemic players before NFL games.

RESULTS

All teams (100%, 32 of 32) responded. Seventy-five percent (24 of 32) of NFL teams used pregame hyperhydration with IVF. On average, 5 to 7 players per team per game received IVF. Players received an average of 1.5 L of fluid, an average of 2.5 hours before the game. When the athletic trainers were asked to mark all the reasons why they use pregame hyperhydration with IVF, the most commonly cited reason was muscle cramps (23 of 24). However, player request was the number one answer (10 of 24) when the athletic trainers were asked to mark only the primary reason for giving IVF. Of the 27 head athletic trainers who had used pregame hyperhydration with IVF in the past, 13 (48%) reported complications.

CONCLUSIONS

Pregame hyperhydration is a common practice in the NFL. Because pregame hyperhydration with IVF is often a player- driven routine and has potential complications, more scientific studies are needed to determine its true efficacy.

Comparison of active cooling devices with passive cooling for rehabilitation of firefighters performing exercise in thermal protective clothing: a report from the Fireground Rehab Evaluation (FIRE) trial

BACKGROUND

Thermal protective clothing (TPC) worn by firefighters provides considerable protection from the external environment during structural fire suppression. However, TPC is associated with physiologic derangements that may have adverse cardiovascular consequences. These derangements should be treated during on-scene rehabilitation periods.

OBJECTIVE

To examine heart rate and core temperature responses during the application of four active cooling devices, currently being marketed to the fire service for on-scene rehabilitation, and compare them with passive cooling in a moderate temperature (approximately 24 degrees C) and with an infusion of cold (4 degrees C) saline.

METHODS

Subjects exercised while they were wearing TPC in a heated room. Following an initial exercise period (bout 1), the subjects exited the room, removed the TPC, and for 20 minutes cooled passively at room temperature, received an infusion of cold normal saline, or were cooled by one of four devices (fan, forearm immersion in water, hand cooling, or water-perfused cooling vest). After cooling, the subjects donned the TPC and entered the heated room for another 50-minute exercise period (bout 2).

RESULTS

The subjects were not able to fully recover core temperature during a 20-minute rehabilitation period when provided rehydration and the opportunity to completely remove the TPC. Exercise durations were shorter during bout 2 when compared with bout 1 but did not differ by cooling intervention. The overall magnitudes and rates of cooling and heart rate recovery did not differ by intervention.

CONCLUSIONS

No clear advantage was identified when active cooling devices and cold intravenous saline were compared with passive cooling in a moderate temperature after treadmill exercise in TPC.

Comparison of rehydration regimens for rehabilitation of firefighters performing heavy exercise in thermal protective clothing: a report from the fireground rehab evaluation (FIRE) trial

BACKGROUND

Performing fire suppression activities results in cardiovascular stress, hyperthermia, and hypohydration. Fireground rehabilitation (rehab) is recommended to blunt the deleterious effects of these conditions.

OBJECTIVE

We tested the hypothesis that three rehydration fluids provided after exercise while wearing thermal protective clothing (TPC) would produce different heart rate or core temperature responses during a second bout of exercise in TPC.

METHODS

On three occasions, 18 euhydrated firefighters (16 men, two women) wearing TPC completed a standardized, 50-minute bout of upper and lower body exercise in a hot room that mimicked the National Fire Protection Association (NFPA) rehabilitation guidelines of "two cylinders before rehab" (20 minutes of work, 10 minutes of recovery, 20 minutes of work). After an initial bout of exercise (bout 1), subjects were randomly assigned water, sport drink, or an intravenous (IV) infusion of normal saline equal to the amount of body mass lost during exercise. After rehydration, the subject performed a second bout of exercise (bout 2). Heart rates, core and skin temperatures, and exercise durations were compared with a two-way analysis of variance (ANOVA).

RESULTS

Subjects were firefighters with a mean (+/- standard deviation [SD]) age of 28.2 +/- 11.3 years and a mean peak oxygen consumption (VO(2peak)) of 37.4 +/- 3.4 mL/kg/min. The mean amount of fluid provided during the rehabilitation period was 527 +/- 302 mL. No subject could complete either the pre- or postrehydration 50-minute bout of exercise. The mean (+/-SD) times to exhaustion were longer (p < 0.001) in bout 1 (25.9 +/- 12.9 min, water; 28.0 +/- 14.1 min, sport drink; 27.4 +/- 13.8 min, IV) compared with bout 2 (15.6 +/- 9.6 min, water; 14.7 +/- 8.6 min, sport drink; 15.7 +/- 8.0 min, IV) for all groups but did not differ by intervention. All subjects approached their age-predicted maximum heart rate at the end of bout 1 (180 +/- 11 bpm) and bout 2 (176 +/- 13 bpm). Core temperature rose 1.1 degrees C +/- 0.7 degrees C during bout 1 and 0.5 degrees C +/- 0.4 degrees C during bout 2. Core temperatures, heart rates, and exercise times during bout 2 did not differ between the rehydration fluids.

CONCLUSIONS

Performances during a second bout of exercise in TPC did not differ when firefighters were rehydrated with water, sport drink, or IV normal saline when full rehydration was provided. Of concern was the inability of all subjects to complete two consecutive periods of heavy exercise in TPC, suggesting that the NFPA's "two cylinders before rehab" guideline may not be appropriate in continuous heavy work scenarios.