Hyperoxia improves maximal exercise with the self-contained breathing apparatus (SCBA)

The effects of hyperoxia on maximal exercise while breathing from a self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed three graded exercise tests (GXT) for the assessment of maximal oxygen uptake (Vdot;O _2max): two with 20.95 ± 0.28% O₂ and the third (GXT₄₀) while breathing hyperoxia (40.64 ± 1.29% O₂). No significant differences were found between the two normoxic tests, except for a 16W increase in maximal power output (PO_max) in the second trial (GXT₂₁). Compared to GXT₂₁, hyperoxia significantly increased Vdot;O _2max and PO_max by 10.0 ± 3.8% and 10.2 ± 7.1%, respectively. This was likely due to an increase in O₂ delivery as suggested by the significantly higher oxyhemoglobin saturation. The increase in Vdot;O _2max with hyperoxia was similar to the increase in carbon dioxide production (9.3 ± 6.5%). No other significant differences were found at maximal exercise. However, at the intensity that elicited Vdot;O _2max in GXT₂₁, pulmonary ventilation and SCBA mask pressure were significantly lower during GXT₄₀, suggesting a decrease in the work of breathing. These findings could have significant implications for occupations that involve heavy work with SCBA.     

Physiological responses of firefighters and performance predictors during a simulated rescue of hospital patients

There is incomplete information about how physically demanding rescue work may be. The aim therefore of this paper was to examine the physiological responses of firefighters during a simulated rescue of hospital patients and to relate the firefighters' performance to their endurance, strength and working technique. Fourteen part-time male firefighters with a maximal oxygen uptake (VO_2max) of 4.4 ± 0.3 l/min (mean ± SD) served as subjects in this study. First, each firefighter ascended six floors (a 20.5 m vertical ascent) carrying tools, wearing protective clothing and a breathing apparatus, an extra mass of 37 kg. He thereafter ‘rescued’ six persons by dragging each person on a fire-sheet on a flat floor. The technique used was recorded and the O₂ uptake and the heart rate were measured continuously during the whole operation. The blood lactate concentration and the subjective rating of perceived exertion were measured during and just after the rescue. The VO_2max and the muscle strength were measured in the laboratory. The whole operation was carried out in the course of 5–9 min. The operation was a virtual all-out effort and the peak blood lactate concentration was 13 ± 3 mmol/l. The peak oxygen uptake was 3.7 ± 0.5 l/min (84% of the VO_2max) during the operation. Large and heavy firefighters carried out the task faster than smaller ones. The VO_2max in absolute terms and the dragging technique used were both related to the rescue performance. Rescuing patients at a hospital was physically very demanding and the time needed to complete the task depended on the VO_2max in absolute values and the working technique used. A minimum VO_2max of 4 l/min for firefighters was recommended.     

Effects of the self-contained breathing apparatus and fire protective clothing on maximal oxygen uptake

To examine the effects of firefighting personal protective ensemble (PPE) and self-contained breathing apparatus (SCBA) on exercise performance, 12 males completed two randomly ordered, graded exercise treadmill tests (GXTPPE and GXTPT). Maximal oxygen consumption (VO2max) during GXTPPE was 17.3% lower than the GXTPT in regular exercise clothing (43.0 +/- 5.7 vs. 52.4 +/- 8.5 ml/kg per min, respectively). The lower VO2max during the PPE condition was significantly related (r = 0.81, p < 0.05) to attenuated peak ventilation (142.8 +/- 18.0 vs. 167.1 +/- 15.6 l/min), which was attributed to a significant reduction in tidal volume (2.6 +/- 10.4 vs. 3.2 +/- 0.4 l). Breathing frequency at peak exercise was unchanged (55 +/- 7 vs. 53 +/- 7 breaths/min). The results of this investigation demonstrate that PPE and the SCBA have a negative impact on VO2max. These factors must be considered when evaluating aerobic demands of fire suppression work and the fitness levels of firefighters.     

Metabolic demands of law enforcement personal protective equipment during exercise tasks

Many occupations require the use of personal protective equipment (PPE) but the added metabolic demands are unknown for certain professions. The purpose of this study was to quantify metabolic and perceptual differences between activity with and without the PPE ensemble required for police officers. Twelve participants were asked to complete experimental and control exercise sessions consisting of three modes of exercise (walking, jogging and stepping). A significant main effect (p < 0.01) for gear was found for heart rate (beats per minute) and VO₂ (L/min) between conditions. Dependent t-tests revealed significant differences for perceived effort, discomfort and session rating of perceived exertion between trials. Medium to large effect sizes for all variables with significant main effects between modes (p < 0.01, η² = 0.51–0.96, 1–β = 0.98–1.0, d = 0.42–2.7) were observed. These findings help to increase awareness of how PPE affects metabolic demands and perception of discomfort during exercise.     

Physiological response of beach lifeguards in a rescue simulation with surf

The objective of this study was to examine the physiological response of 14 lifeguards in a swimming pool simulation with 1.7 m waves and to study the efficiency of the torpedo buoy. The rescue time was determined with and without material, as were lactate levels, heart rate and VO_2max. The results obtained showed a VO_{2 max} rate of 3.4 ± 0.8 l/min without equipment and 3.3 ± 0.8 l/min with equipment. Moreover, the time taken to swim towards the victim without equipment decreased by 7.7 s, while towing time was reduced by 10.8 s if said equipment was used. These results show that aquatic rescue makes considerable physiological demands on the swimmer and they also provide important data on the type of training and aptitude levels required by individuals wishing to join these rescue groups. The equipment currently used has a negative affect on the swim.

Statement of Relevance: The study shows that beach rescues make very high physiological demands on rescuers, thus underlining the need to perform entry tests for these highly demanding rescue teams. The auxiliary equipment is a help in the return time of rescue. However, it causes delays in the approach to the victim.     

The accuracy of the critical power test for predicting time to exhaustion during cycle ergometry

The purpose of this study was to determine the relationship between actual time to exhaustion or time limit (AT_LIM) during bicycle ergometry and predicted time to exhaustion (PT_LIM from the Critical Power (CP) test Fourteen males (x¯ ± SD = 22·36 ± 2·13 years) volunteered as subjects for this investigation. The subjects visited the laboratory on seven occasions separated by at least 24 h. The first two visits were used for the determination of CP; during the remaining sessions the subjects rode a Monarch bicycle ergometer at power loadings of CP — 20%, CP, CP + 20%, CP + 40% and CP + 60% for the determination of AT_LIM. Theoretically, power loadings les;CP can be maintained indefinitely without exhaustion and the PT_LIM for power loadings > CP can be estimated from the results of the CP test. The accuracy of the CP test for estimating the time to exhasution during bicycle ergometry was determined by comparing AT_LIM to PT_LIM using correlation coefficients, standard error of estimates and related t-tests. The results of this study indicated that there were no significant (p > 0·05) differences between AT_LIM and PT_LIM for power loadings > CP (AT_LIM vs PT_LIM at CP + 20% = 8·19 ± 3·90 vs 7·13 ± 2·69min, t = 2·106, r =0·893, SEE = l·21min; CP + 40% = 3·60 ± 1·37 vs 3·46 ± 1·18min, t = 0·842, r = 0·882, SEE = 0·556min; CP + 60% = 2·36 ± 0·95 vs 2·32 ± 0·79min; t = 0·328 r = 0·841, SEE = 0·428min). Power curve analyses however, indicated that the CP test overestimated the power loading which could be maintained for 60 min by a mean of approximately 17%.     

A comparison of two physical ability tests for firefighters

Smoke diving is physically demanding, and firefighters must therefore meet certain minimum physical requirements. The aim of this study was to compare the physiological demands of two fire fitness tests: a test of 8-min treadmill walking approved by the Norwegian Labour Inspection Authority (NLIA) (a laboratory test) and a Canadian test consisting of 10 firefighting specific tasks carried out in sequence (an applied field test). If the Canadian field test is as physically demanding as the NLIA-approved laboratory test, it may be suitable for testing Norwegian firefighters. Twenty-two male professional firefighters were tested on separate days. In both tests, the subjects wore a complete firefighting outfit including a breathing apparatus. The test durations were 8 min (NLIA test) versus approximately 6 min (Canadian test). Neither the peak O₂ uptake (VO₂) of approximately 45 ml kg ^? 1 min ^? 1 nor the blood lactate concentration (BLC) at test termination ( ≈ 9 mmol L ^? 1) differed between the two tests. Rating of perceived exertion (RPE_CR-10) was lower for the Canadian test than for the Norwegian test (5.2 ± 1.5 vs. 7.0 ± 2.0, respectively), and the exercise time at a high VO₂ was also shorter. In conclusion, the Canadian test appeared to be almost as physically demanding as the NLIA-approved test, having equal peak VO₂ and BLC, but shorter time at a high VO₂ and shorter duration. It might thus be a suitable alternative to the NLIA test with some modifications. The advantage of the Canadian field test is the inclusion of specific firefighting-like tasks that are not part of the NLIA test.     

Oxygen uptake and muscle activity limitations during stepping on a stair machine at three different climbing speeds

Abstract

This laboratory study examined human stair ascending capacity and constraining factors including legs’ local muscle fatigue (LMF) and cardiorespiratory capacity. Twenty-five healthy volunteers, with mean age 35.3 years, maximal oxygen uptake (VO_2max) of 46.7?mL·min^?1·kg^?1 and maximal heart rate (HR) of 190 bpm, ascended on a stair machine at 60 and 75% (3?min each) and 90% of VO_2max (5?min or until exhaustion). The VO₂, maximal heart rate (HR_max) and electromyography (EMG) of the leg muscles were measured. The average VO_2highest reached 43.9?mL·min^?1·kg^?1, and HR_highest peaked at 185 bpm at 90% of VO_2max step rate (SR). EMG amplitudes significantly increased at all three levels, p?<?.05, and median frequencies decreased mostly at 90% of VO_2max SR evidencing leg LMF. Muscle activity interpretation squares were developed and effectively used to observe changes over time, confirming LMF. The combined effects of LMF and cardiorespiratory constraints reduced ascending tolerance and constrained the duration to 4.32?min.

Practitioner Summary: To expedite ascending evacuation from high-rise buildings and deep underground structures, it is necessary to consider human physical load. This study investigated the limiting physiological factors and muscle activity rate changes (MARC) used in the muscle activity interpretation squares (MAIS) to evaluate leg local muscle fatigue (LMF). LMF and cardiorespiratory capacity significantly constrain human stair ascending capacities at high, constant step rates.     

Effect of wearing personal protective clothing and self-contained breathing apparatus on heart rate,temperature and oxygen consumption during stepping exercise and live fire training exercises

Fire fighter breathing apparatus instructors (BAIs) must possess the ability to respond to both the extrinsic stress of a high temperature environment and the intrinsic stress from wearing personal protective equipment (PPE) and self-contained breathing apparatus (SCBA), repeatedly and regularly, whilst training recruits in live fire training exercises (LFTEs). There are few previous investigations on BAIs in hot environments such as LFTEs, since the main research focus has been on regular fire fighters undertaking exercises in temperate or fire conditions at a moderate to high exercise intensity. In this study, the intrinsic cardiovascular stress effects of wearing PPE + SCBA were first investigated using a step test whilst wearing gym kit (control), weighted gym kit (a rucksack weighted to the equivalent of PPE + SCBA) and full PPE + SCBA (weight plus the effects of protective clothing). The extrinsic effects of the very hot environment were investigated in BIAs in LFTEs compared to mock fire training exercises (MFTEs), where the fire was not ignited. There was an increase in heart rate due to the modest workload imposed on the BAIs through carrying out the MFTEs (25.0 (18.7)%) compared to resting. However, when exposed to fire during the LFTEs, heat storage appears to be significant as the heart rate increased by up to 39.8 (±20.1)% over that of the mock LFTEs at temperate conditions. Thus, being able to dissipate heat from the PPE is particularly important in reducing the cardiovascular responses for BAIs during LFTEs.     

Ergonomics diary

Physiological, perceptual and physical responses to a typical circuit weight-training (CWT) regimen were recorded in two studies. The aims were to assess the intensity of exercise during CWT; and to determine whether physical responses as evaluated by spinal shrinkage were related to physiological and perceptual responses to CWT. In the first study (n = 10) heart rate (HR), oxygen consumption (VO), ventilation (VE), blood lactate (La) and perceived exertion (RPE) were measured in response to CWT. Mean ( ± SD) time to complete three circuits of CWT was 17.8 (± 1-4) min. The HR max, VO₂max and peak La, measured first during an incremental treadmill test, were 195 (±13) beats.min ^?159-7 (±4-8) ml.kg^?1.min^?1 and 14-3 (±3-5) mM respectively. Mean HR and vO₂ during CWT were 69% and 50% of the respective maximal values. The HR-VO₂ ratio observed on the treadmill was elevated during CWT, with VO₂ being lowered relative to HR. Mean VE and La values were 52-7 (± 14-5) l.min^?1 and 6-9 ( ± 3-6) mM. The effect of the same CWT regimen on spinal loading as indicated by change in stature (shrinkage) was investigated in a second study (n = 8). The mean ( ± SD) time taken to complete the circuit was 17-4 ( ± 1-3) min. Mean shrinkage due to CWT (2-5 ± 1 -5?mm) was unrelated to the time taken to complete the circuits, to HR, RPE or to low back pain ratings (p > 0-05). Observations suggest that CWT as represented in these studies engages anaerobic as well as aerobic mechanisms but the exercise intensity may not provide sufficient stimulation for aerobic training. The physical load on the spine indicated by spinal shrinkage was not related to the physiological or perceptual strain.     

The effects of caffeine during exercise in fire protective ensemble

To examine the effects of caffeine during exercise in fire protective ensemble (FPE), 10 healthy males completed 3 × 10 min bouts of treadmill exercise on two separate days. Sixty minutes prior to exercise either 6 mg/kg of caffeine (CAFF) or dextrose placebo (PLA) capsules were ingested (randomly assigned, double blind). End-exercise gastrointestinal temperature (T_gi) was higher in CAFF compared to PLA (38.80 ± 0.08°C vs. 38.43 ± 0.11°C, p ≤ 0.01). Ventilation ([Vdot] _E) and tidal volume (V_t) were also significantly higher in CAFF, which resulted in higher consumption of air from the self-contained breathing apparatus. While perceived exertion in the caffeine condition was decreased (p ≤ 0.05) compared to placebo, the higher T_gi values increased calculated physiological strain index in CAFF (p ≤ 0.01). Caffeine appears to alter the physiological and psycho-physical responses to exercise in FPE and may influence factors related to work tolerance in firefighting. These findings are relevant to occupations such as firefighting where workers are encapsulated during exposure to heavy physical work and/or environmental heat. The results indicate that workers may be more susceptible to heat-related fatigue, illness or injury with ingestion of significant amounts of caffeine. To the authors' knowledge this is the first study involving humans and exercise to detect an increase in body temperature with caffeine ingestion.     

Effect of load position on physiological and perceptual responses during load carriage with an internal frame backpack

The purpose of this study was to determine the effect of load position in an internal frame backpack on physiological and perceptual variables. Ten female participants walked on a level treadmill for 10?min carrying 25% of their body weight in a high, central, or low position. The variables measured included oxygen consumption (VO₂), heart rate (HR), respiratory exchange ratio (R), respiratory rate (RR), minute ventilation (VE), and rating of perceived exertion (RPE). VO₂, VE, and RPE were significantly lower in the high position (18.6?±?2.3?ml/kg/min, 31.7?±?5.0?l/min, 2.8?±?0.8, respectively) compared to the low position (22.2?±?3.0?ml/kg/min, 38.6?±?7.5?l/min, 3.7?±?1.0, respectively). HR, R, and RR did not change significantly as the load was moved from the high (129.8?±?16.8, 0.89?±?0.06, 30.3?±?4.2, respectively) to the low position (136.0?±?25.3, 0.92?±?0.04, 33.8?±?5.2, respectively). The results of this study suggest that load placement is an important factor in the physiological and perceptual responses to load carriage, and that packing heavy items high in the backpack may be the most energy efficient method of carrying a load on the back.     

Real-time core body temperature estimation from heart rate for first responders wearing different levels of personal protective equipment

First responders often wear personal protective equipment (PPE) for protection from on-the-job hazards. While PPE ensembles offer individuals protection, they limit one's ability to thermoregulate, and can place the wearer in danger of heat exhaustion and higher cardiac stress. Automatically monitoring thermal–work strain is one means to manage these risks, but measuring core body temperature (T_c) has proved problematic. An algorithm that estimates T_c from sequential measures of heart rate (HR) was compared to the observed T_c from 27 US soldiers participating in three different chemical/biological training events (45–90 min duration) while wearing PPE. Hotter participants (higher T_c) averaged (HRs) of 140 bpm and reached T_c around 39°C. Overall the algorithm had a small bias (0.02°C) and root mean square error (0.21°C). Limits of agreement (LoA ± 0.48°C) were similar to comparisons of T_c measured by oesophageal and rectal probes. The algorithm shows promise for use in real-time monitoring of encapsulated first responders.     

Reducing heat stress under thermal insulation in protective clothing: microclimate cooling by a ‘physiological’ method

Heat stress caused by protective clothing limits work time. Performance improvement of a microclimate cooling method that enhances evaporative and to a minor extent convective heat loss was tested. Ten male volunteers in protective overalls completed a work-rest schedule (130 min; treadmill: 3 × 30 min, 3 km/h, 5% incline) with or without an additional air-diffusing garment (climatic chamber: 25°C, 50% RH, 0.2 m/s wind). Heat loss was supported by ventilating the garment with dry air (600 l/min, ?5% RH, 25°C). Ventilation leads (M ± SD, n = 10, ventilated vs. non-ventilated) to substantial strain reduction (max. HR: 123 ± 12 b/min vs. 149 ± 24 b/min) by thermal relief (max. core temperature: 37.8 ± 0.3°C vs. 38.4 ± 0.4°C, max. mean skin temperature: 34.7 ± 0.8°C vs. 37.1 ± 0.3°C) and offers essential extensions in performance and work time under thermal insulation.     

The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus

The e^ffects of hyperoxia on submaximal exercise with the self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed a graded exercise test for the determination of ventilatory threshold (VT) and then a submaximal practice trial with a normoxic gas mixture. The normoxic (20.93 ± 0.22% O₂ ; SUB₂₁) and hyperoxic (40.18 ± 0.73% O₂; SUB₄₀) submaximal trials were then administered in a random order. All exercise tests were completed on separate days while wearing firefighting gear and the SCBA. Compared with SUB₂₁, hyperoxia significantly reduced minute ventilation ([Vdot]_E ), mask pressure (P_mask), heart rate, blood lactate concentration, perceived exertion, and perceived breathing distress. As expected, hemoglobin saturation remained higher (p<0.05) during SUB₄₀. The reductions in both [Vdot]_E and P_mask with hyperoxia imply a reduction in the work of breathing during exercise. Total gas consumption was 10.3 ± 8.1% lower during SUB₄₀ when compared to SUB₂₁, another finding that has significant practical implications for occupational safety.     

A new kayak ergometer based on wind resistance

Abstract

An ergometer for kayak paddlers has been developed and used for winter training, measurements of work capacity and maximal oxygen uptake ([Vdot]O₂ max). Force is transmitted from the paddle by means of a wire connected to a flywheel mounted with six 9 × 9cm blades. Resistance, therefore, is based on wind turbulence generated by the flywheel. The mechanical efficiency of the ergometer at 63% (range 48-77) of [Vdot]O₂ max was 17% (range 16-18) (n= 13). The [Vdot]O₂ max was similar during bicycling (median 4·9; range 4·4-5·4l/min), arm cranking (median 4·8; range 4·3-5·11/min), on-water rowing in a kayak (median 4·7; range 4·0-4·91/min) and during rowing the kayak ergometer (median 4·8; range 4·3-5·21/min), (n = 6, p> 0·05). Work capacity during a 5 min ‘all-out’ test was 272 W (range 253–304 W) on the kayak ergometer (n = 17). The use of the ergometer for training helped to increase the aerobic power during arm exercise of Danish paddlers. Before introduction of the ergometer (February 1986), their VO₂ max was 4·6 (range 3·8-5·2) 1/min while 12 months later, it was 50 (range 4·2–5·7) 1/min (n = 14, p < 0·01). The ergometer has thus been found.useful for training and evaluation of work capacity in kayak paddlers.     

Air management and physiological responses during simulated firefighting tasks in a high-rise structure

Air consumption, oxygen uptake (VO₂), carbon dioxide output (VCO₂) and respiratory exchange ratio (RER = VCO₂/VO₂) were measured directly from the self-contained breathing apparatus (SCBA) as 36 professional firefighters (three women) completed scenarios of high-rise stair climbing and fifth floor search and rescue. During stair climbing VO₂ was 75 ± 8% VO_2max (mean ± SD), RER = 1.10 ± 0.10, and heart rate = 91 ± 3% maximum (based on maximum treadmill data). Firefighters stopped climbing on consuming 55% of the air cylinder then descended. In the fifth floor search and rescue VO₂ was slightly lower than stair climbing but RER remained elevated (1.13 ± 0.12) reflecting high anaerobic metabolism. The first low air alarm sounded, indicating 25% of the air remaining in a “30-min cylinder”, during the stair climb at 8 min with 19 of 36 sounding before 12 min. Aggressive air management strategies are required for safety in high-rise firefighting.     

Cardiorespiratory and thermoregulatory response of working in fire-fighter protective clothing in a temperate environment

The cardiorespiratory and thermal responses of two intensities of treadmill exercise were compared for brief periods (12 min) in fire ensemble (FE) but without self contained breathing apparatus, and sports ensemble (SE), in a temperature environment. A further experiment explored the responses of subjects exercising in FE over a prolonged period (60 min). Eighteen male firefighters wearing either FE or SE walked on a level treadmill for 6 min at 5 km.h^-1 increasing to 7 km.h^-1 for 6 min. Following a recovery interval of 1 h, the exercise protocol was repeated in the second ensemble; the order of ensemble was balanced. Heart rate (HR), rectal temperature (T_re ), VO _2max and rating of perceived exertion (RPE) were monitored continuously under both ensembles. At 7 km.h^-1, VO ₂ was significantly higher (p<0.05) in FE (36.1 and 39.9 ml.kg^-1.min^-1) than in SE and represented 74% V _{O2 max}. There were no changes T _re. In experiment 2, following a rest interval of at least 36 h, eight subjects in FE walked on the treadmill at 6 km.h ^-1 (gradient 10%) for 60 min also in temperate conditions, where HR, T _re and R PE were recorded at 10-min intervals. During the 60-min exercise in FE, HR reached 161 beats.min ^-1 and T _re increased to 38.38°C. Despite considerable subject discomfort, T _re remained below dangerous levels (38.48°C). When R PE were compared with a physiological strain index (PSI) calculated from T _re and HR data over 60 min, there was no significant difference (p <0.05) with a correlation coefficient (r) of 0.98. The results suggest that R PE and PSI are closely related when exercise is sufficiently prolonged or intense to elevate T _re and HR in fire-fighters wearing FE in temperate conditions. If further investigation confirms this relationship for hot humid conditions in which fire-fighters operate, then with training, it may provide individuals with a valid measure of dangerous levels of perceived heat strain.     

The physical and physiological workload of refuse collectors

In order to secure a safer and healthy work situation, the heavy physical loads imposed on 23 refuse collectors (aged 26-54) working in the city of Haarlem, in The Netherlands, were studied in a series of three experiments between 1984 and 1987. The aims were respectively (1) to study the load for workers collecting dustbins or polythene bags; (2) to introduce changes to reduce the load to avoid exceeding the overload criteria by individual refuse collectors; and (3) to investigate the effects of interventions to improve the efficiency of refuse collecting. The maximal isometric lifting force (F_max) and the maximal aerobic power( [Vdot]O_2max of 23 refuse collectors were measured in the laboratory. F_max was measured with an isometric dynamometer pulling with one arm from the floor; the mean value was 912 (± 127)N. VO_2max was measured running on a treadmill; the mean value was 43-3 (±0-8) ml O₂ per kg body mass per min. The physical load on the oxygen transport system was measured through work analysis and by a continuous registration of the heart rate over three working days. Criteria for overload were set at a mean external load of 20% Fm? and a mean energy expenditure of 30% VO_2max and an energy expenditure of 50% VO_2max or more for a maximum of 60 min per day. Replacement of dustbins by polythene bags resulted in a 70% increase in the total amount of refuse collected, an increase in throwing frequency, but a lower mean load per throw, and no significant differences in the mean heart rate over the working day. When polythene bags were used the mean values did not exceed the overload criteria, but 39% of the individual collectors did have a workload that was too high with respect to one of the criteria. In the last experiment the collectors were advised to reduce their work load by (a) lifting no more than two bags at a time; (b) reducing their walking pace; and (c) taking more breaks. Although compliance with the recommendations was good, and the weight lifted and the walking speed decreased, the physiological load remained the same. This may have been caused by a 15% increase in the total amount of refuse that had to be collected at that time.     

Using trunk posture to monitor heat strain at work

Abstract

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.