Perceptual Strain Research Articles

Evaluating the Physiological and Perceptual Responses of Wearing a Newly Designed Cooling Vest for Construction Workers.

Construction workers are subjected to heat stress because of the hot environment, physically demanding tasks, and/or personal protective equipment. A tailor-made cooling vest that protects construction workers from heat-related injuries was developed. The purpose of the study is to examine a newly designed cooling vest's effectiveness in alleviating physiological and perceptual strain in a hot and humid environment. Twelve male participants performed two trials, i.e., cooling vest (VEST) and control (CON) in a climatic chamber controlled at 37°C temperature, 60% relative humidity, 0.3 m/s air velocity, and 450 W/m2 solar radiation to simulate the summer working environment of construction sites. Two bouts of treadmill exercise intermitted with 30-minute passive recovery were designed to simulate the practical work-rest schedule of the construction industry. The cooling vest was used during the passive recovery period in the VEST condition, and the results were compared with that of no cooling vest in the CON condition. The results revealed that the newly designed cooling vest can significantly alleviate heat strain and improve thermal comfort, based on the decrease in body temperature, heart rate, and subjective perceptions (including perceived exertion, thermal, wetness, and comfort sensation) of the participants. It can also prolong work duration in the subsequent exercise. The cooling countermeasures proposed in this study will be able to provide an effective solution in situations that involve repeated bouts of outdoor construction work.

Sauna exposure immediately prior to short-term heat acclimation accelerates phenotypic adaptation in females

ObjectivesInvestigate whether a sauna exposure prior to short-term heat acclimation (HA) accelerates phenotypic adaptation in females. DesignRandomised, repeated measures, cross-over trial. MethodsNine females performed two 5-d HA interventions (controlled hyperthermia Tre≥38.5°C), separated by 7-wk, during the follicular phase of the menstrual cycle confirmed by plasma concentrations of 17-β estradiol and progesterone. Prior to each 90-min HA session participants sat for 20-min in either a temperate environment (20°C, 40% RH; HAtemp) wearing shorts and sports bra or a hot environment (50°C, 30% RH) wearing a sauna suit to replicate sauna conditions (HAsauna). Participants performed a running heat tolerance test (RHTT) 24-h pre and 24-h post HA. ResultsMean heart rate (HR) (85±4 vs. 68±5 bpm, p≤0.001), sweat rate (0.4±0.2 vs. 0.0±0.0Lh−1, p≤0.001), and thermal sensation (6±0 vs. 5±1, p=0.050) were higher during the sauna compared to temperate exposure. Resting rectal temperature (Tre) (−0.28±0.16°C), peak Tre (−0.42±0.22°C), resting HR (−10±4 bpm), peak HR (−12±7 bpm), Tre at sweating onset (−0.29±0.17°C) (p≤0.001), thermal sensation (−0.5±0.5; p=0.002), and perceived exertion (−3±2; p≤0.001) reduced during the RHTT, following HAsauna; but not HAtemp. Plasma volume expansion was greater following HAsauna (HAsauna, 9±7%; HAtemp, 1±5%; p=0.013). Sweat rate (p≤0.001) increased and sweat NaCl (p=0.006) reduced during the RHTT following HAsauna and HAtemp. ConclusionsThis novel strategy initiated HA with an attenuation of thermoregulatory, cardiovascular, and perceptual strain in females due to a measurably greater strain in the sauna compared to temperate exposure when adopted prior to STHA.

Heat Strain Is Exacerbated on the Second of Consecutive Days of Fire Suppression.

We tested the hypothesis that physiological and perceptual heat strain is exacerbated on the second of back-to-back days of fire suppression work despite evidence of full recovery. Twenty-six career and volunteer firefighters (age = 31 ± 8 yr) completed 20 min of near maximal fire suppression work on consecutive days. Dependent variables were core temperature, heart rate, perceived exertion, and thermal sensation, which were measured before and after fire suppression. Urine specific gravity and body mass were also measured upon arrival at the fire academy as an index of hydration and recovery between days. Urine specific gravity (1.007 ± 0.006 vs 1.005 ± 0.006), body mass (87.7 ± 16.1 vs 87.8 ± 16.0 kg), heart rate (77 ± 14 vs 76 ± 14 bpm), and core temperature (37.2°C ± 0.4°C vs 37.1°C ± 0.7°C) were not different upon arrival on day 1 compared with day 2 (P ≥ 0.26). The increase in core temperature during fire suppression was higher on day 2 (0.7°C ± 0.3°C vs 1.1°C ± 0.5°C, P < 0.01). Heart rate did not differ (after fire suppression: day 1 = 174 ± 19, day 2 = 169 ± 30 bpm, P = 0.60). The magnitude of increase in perceived exertion during fire suppression was greater on day 2 (6.7 ± 1.6 vs 7.4 ± 1.6 a.u., P < 0.01). Absolute thermal sensation at the end of fire suppression was greater on day 2 (3.8 ± 0.8 vs 4.3 ± 0.6 a.u., P < 0.01). Physiological and perceptual heat strain is higher on the second of back-to-back days of fire suppression work.

Perception or reality: Can thermal perceptions inform management of firefighters in the heat?

ABSTRACTAccurately assessing the physiological status of firefighters during work in the heat is critical to ensuring their safety. Evaluating core temperatures (Tc) in the field is problematic due to cost and limitations in technology and accuracy. As such, fire services rely on individual perceptions of wellbeing. The present study aimed to establish whether perceptual responses measured using the perceptual strain index (PeSI), calculated from rate of perceived exertion (RPE) and thermal sensation (TS), could reliably predict the physiological strain (PSI) encountered by experienced firefighters working in a hot environment. We conducted two firefighting simulations (set-pace and self-paced) in a purposefully built heat chamber (100 ± 5°C) comprised of two 20-min periods separated by a 10-min recovery outside the chamber. Physiological strain was measured via heart rate (HR) and gastrointestinal temperature (Tgi) and compared with PeSI at 5-min intervals. To evaluate the predictive ability of the PeSI for PSI, mean differences and the 95% limits of agreement (LOA) were established, along with correlation coefficients at each 5-min interval. Moderately significant correlations occurred in the second work bout of the self-paced trial only (10 min: r = 0.335, 15 min: r = 0.498, 20 min r = 0.439) with no other correlations observed at any other time during either trial or during the rest periods. Bland-Altman analysis revealed mean differences of −0.74 ± 2.70 (self-paced) and +0.04 ± 2.04 (set-paced) between PeSI and PSI with the 95% LOA being −4.77 to 3.28 (self-paced) and −4.01 to 2.01 (set-paced). The wide LOA and lack of correlations observed between perceptual and physiological strain in both self-paced and set-paced work trials indicate that PeSI is not sufficiently reliable as a sole measure of wellbeing for firefighters working in the heat. Hence, we recommend that fire services prioritise the development of reliable and effective monitoring tools for use in the field.

The Influence of Mid-Event Deception on Psychophysiological Status and Pacing Can Persist across Consecutive Disciplines and Enhance Self-paced Multi-modal Endurance Performance.

Purpose: To examine the effects of deceptively aggressive bike pacing on performance, pacing, and associated physiological and perceptual responses during simulated sprint-distance triathlon.Methods: Ten non-elite, competitive male triathletes completed three simulated sprint-distance triathlons (0.75 km swim, 500 kJ bike, 5 km run), the first of which established personal best “baseline” performance (BL). During the remaining two trials athletes maintained a cycling power output 5% greater than BL, before completing the run as quickly as possible. However, participants were informed of this aggressive cycling strategy before and during only one of the two trials (HON). Prior to the alternate trial (DEC), participants were misinformed that cycling power output would equal that of BL, with on-screen feedback manipulated to reinforce this deception.Results: Compared to BL, a significantly faster run performance was observed following DEC cycling (p < 0.05) but not following HON cycling (1348 ± 140 vs. 1333 ± 129 s and 1350 ± 135 s, for BL, DEC, and HON, respectively). As such, magnitude-based inferences suggest HON running was more likely to be slower, than faster, compared to BL, and that DEC running was probably faster than both BL and HON. Despite a trend for overall triathlon performance to be quicker during DEC (4339 ± 395 s) compared to HON (4356 ± 384 s), the only significant and almost certainly meaningful differences were between each of these trials and BL (4465 ± 420 s; p < 0.05). Generally, physiological and perceptual strain increased with higher cycling intensities, with little, if any, substantial difference in physiological and perceptual response during each triathlon run.Conclusions: The present study is the first to show that mid-event pace deception can have a practically meaningful effect on multi-modal endurance performance, though the relative importance of different psychophysiological and emotional responses remains unclear. Whilst our findings support the view that some form of anticipatory “template” may be used by athletes to interpret levels of psychophysiological and emotional strain, and regulate exercise intensity accordingly, they would also suggest that individual constructs such as RPE and affect may be more loosely tied with pacing than previously suggested.

Perceived exertion is as effective as the perceptual strain index in predicting physiological strain when wearing personal protective clothing

ObjectiveThe perceptual strain index (PeSI) has been shown to overcome the limitations associated with the assessment of the physiological strain index (PSI), primarily the need to obtain a core body temperature measurement. The PeSI uses the subjective scales of thermal sensation and perceived exertion (RPE) to provide surrogate measures of core temperature and heart rate, respectively. Unfortunately, thermal sensation has shown large variability in providing an estimation of core body temperature. Therefore, the primary aim of this study was to determine if thermal comfort improved the ability of the PeSI to predict the PSI during exertional-heat stress. MethodsEighteen healthy males (age: 23.5years; body mass: 79.4kg; maximal aerobic capacity: 57.2ml·kg−1·min−1) wore four different chemical/biological protective garments while walking on treadmill at a low (<325W) or moderate (326–499W) metabolic workload in environmental conditions equivalent to wet bulb globe temperatures 21, 30 or 37°C. Trials were terminated when heart rate exceeded 90% of maximum, when core body temperature reached 39°C, at 120min or due to volitional fatigue. Core body temperature, heart rate, thermal sensation, thermal comfort and RPE were recorded at 15min intervals and at termination. Multiple statistical methods were used to determine the most accurate perceptual predictor. ResultsSignificant moderate relationships were observed between the PeSI (r=0.74; p<0.001), the modified PeSI (r=0.73; p<0.001) and unexpectedly RPE (r=0.71; p<0.001) with the PSI, respectively. The PeSI (mean bias: −0.8±1.5 based on a 0–10 scale; area under the curve: 0.887), modified PeSI (mean bias: −0.5±1.4 based on 0–10 scale; area under the curve: 0.886) and RPE (mean bias: −0.7±1.4 based on a 0–10 scale; area under the curve: 0.883) displayed similar predictive performance when participants experienced high-to-very high levels of physiological strain. ConclusionsModifying the PeSI did not improve the subjective prediction of physiological strain. However, RPE provided an equally accurate prediction of physiological strain, particularly when high-to-very high levels of strain were observed. Therefore, given its predictive performance and user-friendliness, the evidence suggests that RPE in isolation is a practical and cost-effective tool able to estimate physiological strain during exertional-heat stress under these work conditions.

Influence of Chronic Heat Acclimatization on Occupational Thermal Strain in Tropical Field Conditions.

Objective:To examine whether non-heat acclimatized (NHA) emergency responders endure greater physiological and perceptual strain than heat acclimatized (HA) counterparts in tropical field settings.Methods:Eight HA and eight NHA men urban search and rescue personnel had physiological and perceptual responses compared during the initial 4 hours shift of a simulated disaster in tropical conditions (ambient temperature 34.0 °C, 48% relative humidity, wet bulb globe temperature [WBGT] 31.4 °C).Results:From the 90th minute through to end of shift, HA (38.5 °C) sustained a significantly higher gastrointestinal temperature than NHA (38.1 °C) (mean difference 0.4 ± 0.2 °C, 95% confidence interval [CI] 0.2 to 0.7 °C, P = 0.005) despite comparable heart rate (P = 0.30), respiratory rate (P = 0.88), and axilla skin temperature (P = 0.47). Overall, perception of body temperature was similar between cohorts (P = 0.87).Conclusions:The apparent tolerance of greater physiological strain by HA responders occurred in the absence of perceptual differences.

Fire service instructor's undergarment choice to reduce Interleukin-6 and minimise physiological and perceptual strain

Fire Service Instructors frequently experience high levels of physiological and perceptual strain during live fire exposures. Instructors are also at risk of cardiovascular illnesses, with cardiac death being the greatest cause of fire fighter death. Current practice for UK instructors is to select undergarment type based on personal preference, between a boiler suit (BOILER) and a wicking base layer (WBL). Research suggests that shorts and t-shirt (SHORTS) may also be a beneficial alternative undergarment choice. The UK South East Fire Service requested an investigation to identify if undergarment selection can lessen the strain experienced by instructors, and reduce the acute inflammatory response to fire exposures. Eight males completed three 45min sessions in a heat chamber (49.5±1.4°C and 16.9±4.3% RH) whilst performing intermittent walking. At the end of heat exposure change in heart rate was not effected by garment type (p=0.061, ηp2=0.373). Change in rectal temperature was different between garments (p=0.009, ηp2=0.271), with trends suggesting that BOILER resulted in a greater change (1.03±0.60°C) than SHORTS (0.76±0.37°C, p=0.589, d=0.21) and WBL (0.72±0.33°C, p=0.545, d=0.25). Interleukin-6 post exposure was greater for BOILER (6.96±0.28pgmL−1) than both SHORTS (6.59±0.30pgmL−1, p=0.043, d=0.42) and WBL (6.45±0.43pgmL−1, p=0.031, d=0.51). Overall, undergarment type had little impact on physiological or perceptual strain. However, wearing WBL or SHORTS may reduce the inflammatory response, and consequently decrease the risk of cardiovascular events.

Physiological and perceptual effects of a cooling garment during simulated industrial work in the heat

ObjectiveEvaluate physiological and perceptual responses using a phase change cooling (PCC) garment during simulated work in the heat. MethodsTwenty males wearing compression undergarments, coverall suit, gloves, and hard-hat, completed two randomly assigned trials (with PCC inserts or control, CON) of simulated industrial tasks in the heat (34.2 ± 0.05 °C, 54.7 ± 0.3%RH). Trials consisted of two 20 min work bouts, a maximum performance bout, and 10 min of recovery. ResultsPhysiological strain index (PSI) was lower during PCC after the second work bout and during recovery (all P < 0.05). PCC reduced heat storage (27.0 ± 7.6 W m−2) compared to CON (42.7 ± 9.9 W m−2, P < 0.001). Perceptual strain index (PeSI) was reduced with PCC compared to CON (P < 0.001), however performance outcomes were not different between trials (P = 0.10). ConclusionsPCC during work in the heat attenuated thermal, physiological, and perceptual strain. This PCC garment could increase safety and reduce occupational heat illness risk.

Role of work uniform in alleviating perceptual strain among construction workers.

This study aims to examine the benefits of wearing a new construction work uniform in real-work settings. A field experiment with a randomized assignment of an intervention group to a newly designed uniform and a control group to a commercially available trade uniform was executed. A total of 568 sets of physical, physiological, perceptual, and microclimatological data were obtained. A linear mixed-effects model (LMM) was built to examine the cause-effect relationship between the Perceptual Strain Index (PeSI) and heat stressors including wet bulb globe temperature (WBGT), estimated workload (relative heart rate), exposure time, trade, workplace, and clothing type. An interaction effect between clothing and trade revealed that perceptual strain of workers across four trades was significantly alleviated by 1.6–6.3 units in the intervention group. Additionally, the results of a questionnaire survey on assessing the subjective sensations on the two uniforms indicated that wearing comfort was improved by 1.6–1.8 units when wearing the intervention type. This study not only provides convincing evidences on the benefits of wearing the newly designed work uniform in reducing perceptual strain but also heightens the value of the field experiment in heat stress intervention studies.

Psychophysiological Responses to Repeated-Sprint Training in Normobaric Hypoxia and Normoxia.

To compare psychophysiological responses to 6 repeated-sprint sessions in normobaric hypoxia (RSH) and normoxia (RSN) in team-sport athletes during a 2-wk "live high-train low" training camp. While residing under normobaric hypoxia (≥14 h/d, FiO2 14.5-14.2%), 23 lowland elite field hockey players performed, in addition to their usual training, 6 sessions (4 × 5 × 5-s maximal sprints, 25-s passive recovery, 5 min rest) under either RSH (FiO2 ~14.5%) or RSN (FiO2 21%). Sprint 1 and 5 times, physiological strain (heart rate [HR], arterial oxyhemoglobin saturation [SpO2]), and perceptual responses (overall peripheral discomfort, difficulty breathing, and lower-limb discomfort) were monitored. During the 1st session, HR increased across sets (P < .001) independently of the conditions, while SpO2 was globally lower (P < .001) for RSH (averaged value: 91.9% ± 1.2%) vs RSN (96.9% ± 0.6%). Thereafter, SpO2 and HR remained similar across sessions for each condition. While 1st-sprint time remained similar, last-sprint time and fatigue index significantly decreased across sets (P < .01) and sessions (P < .05) but not between conditions. Ratings of overall perceived discomfort, difficulty breathing, and lower-limb discomfort were higher (P < .05) in RSH vs RSN at the 1st session. During subsequent sessions, values for overall perceived discomfort (time [P < .001] and condition [P < .05] effects), difficulty breathing (time effect; P < .001), and lower-limb discomfort (condition [P < .001] and interaction [P < .05] effects) decreased to a larger extent in RSH vs RSN. Despite higher hypoxia-induced physiological and perceptual strain during the 1st session, perceptual responses improved thereafter in RSH so as not to differ from RSN. This indicates an effective acclimation and tolerance to this innovative training.

Physiological and Perceptual Effects of a Cooling Garment During Simulated Industrial Work in the Heat

Work in the heat increases physiological strain, especially when clothing limits heat dissipation. Using phase change cooling garments (CG) to mitigate core temperature rise may reduce physiological strain and prevent heat illness. PURPOSE: Evaluate the physiological and perceptual effects of using a phase change CG while conducting simulated industrial work in the heat. METHODS: Male participants (n=20, age 25 ± 4 y, ht 1.79 ± 0.08 m, body mass 75.0 ± 10.7 kg, body fat 13.6 ± 5.2%) wearing compression undergarments, coverall suit, gloves, and hard-hat to mimic industry clothing, completed two randomly assigned trials in an environmental chamber (34.2 ± 0.05°C, 54.7 ± 0.3%RH). Trials consisted of two 20 min work bouts (W1 and W2; separated by five min seated rest) and involved treadmill walking, lifting and moving boxes, tests of dexterity, and carrying dumbbells over steps. A final performance (PER) bout (maximum number of repetitions in 15 min of box moving, dexterity tests, and carrying dumbbells over steps) was followed by 10 min of recovery (REC). Phase change inserts (10°C) were added to the compression undergarment during the CG trial after baseline measures and replaced pre-PER, while the control (CON) trial included no inserts. Physiological and perceptual measures were recorded post W1, W2, and PER, and at three and 10 min of REC. Heat storage (HS) was also calculated. RESULTS: Rectal temperature was different at 3 min (CON 38.78 ± 0.38°C, CG 38.52 ± 0.39°C, P=0.003) and 10 min (CON 38.72 ± 0.37°C, CG 38.36 ± 0.40°C, P<0.001) of REC. Heart rate was lower in the CG trial (P<0.05) post-W2, pre-PER, and at 3 min and 10 min REC (CON 118 ± 13, CG 100 ± 12 bpm, P<0.001). Skin temperature was reduced with CG from post W1 (P<0.001) through 10 min REC (CON 36.9 ± 0.6°C, CG 32.9 ± 1.2°C, P<0.001). HS was reduced with CG (27.0 ± 7.6W·m-2) compared to CON (42.7 ± 9.9W·m-2, P<0.001). Rating of perceived exertion was decreased with CG from W2 (P=0.04) through 10 min REC (P=0.004). PER repetitions were not different between trials (CON 5.6 ± 1.1, CG 5.8 ± 1.1, P=0.10). CONCLUSION: The data indicated that the cooling intervention attenuated thermal, physiological, and perceptual strain during work in the heat. This CG could increase safety, facilitate performance, and reduce heat illness risk in occupational settings. Funded by PreventaMed, Inc.

Fire Service Instructor's undergarment choice can minimise physiological and perceptual strain

The South East Regional Fire Service requested an investigation into the effect of different undergarments worn by fire service instructors, to help improve thermoregulation and reduce the strain experienced. Literature suggests that wearing shorts and t-shirt may reduce heat strain [1], whilst no research has yet established the effect of wearing compression undergarments in fire environments. The study aimed to identify which type of undergarment [boiler suit (BOILER), whole body compression garments (COMPRESSION) or shorts and t-shirt (SHORTS)] produced the least physiological and perceptual strain.

16th International Conference on Environmental Ergonomics (ICEE XV).

We performed a firefighting simulation of repeated work-rest bouts while wearing fire-fighting ensemble (FFE) and self-contained breathing apparatus (SCBA) in the heat, removing the helmet and SCBA during recovery and comparing cranial cooling (CC) versus passive (CON) exposure. We hypothesized that CC would better counteract heat storage compared to passive cooling.

Can perceptual indices estimate physiological strain when wearing personal protective clothing in the heat?

Explosive ordnance disposal (EOD) often requires technicians to wear multiple protective garments in challenging environmental conditions. The accumulative effect of increased metabolic cost coupled with decreased heat dissipation associated with these garments predisposes technicians to high levels of physiological strain. It has been proposed [1] that a perceptual strain index (PeSI) using subjective ratings of thermal sensation and perceived exertion as surrogate measures of core body temperature and heart rate, may provide an accurate estimation of physiological strain. Therefore, this study aimed to assess if the PeSI could estmate the physiological strain index (PSI) across a range [2] of metabolic workloads and environments while wearing heavy EOD and chemical protective clothing.

Influence of Dehydration on Intermittent Sprint Performance.

This study examined the effects of dehydration on intermittent sprint performance and perceptual responses. Eight male collegiate baseball players completed intermittent sprints either dehydrated (DEHY) by 3% body mass or euhydrated (EU). Body mass was reduced through exercise in the heat with controlled fluid restriction occurring 1 day before the trial. Participants completed twenty-four 30-m sprints divided into 3 bouts of 8 sprints with 45 seconds of rest between each sprint and 3 minutes between each bout. Perceived recovery status (PRS) scale was recorded before the start of each trial. Heart rate (HR), ratings of perceived exertion (RPE) (0-10 OMNI scale), and perceived readiness (PR) scale were recorded after every sprint, and session RPE (SRPE) was recorded 20 minutes after completing the entire session. A 2 (condition) × 3 (bout of sprints) repeated-measures ANOVA revealed a significant main effect of condition on mean sprint time (p = 0.03), HR (p < 0.01), RPE (p = 0.01), and PR (p = 0.02). Post hoc tests showed significantly faster mean sprint times for EU vs. DEHY during the second (4.87 ± 0.29 vs. 5.03 ± 0.33 seconds; p = 0.01) and third bouts of sprints (4.91 ± 0.29 vs. 5.12 ± 0.44 seconds; p = 0.02). Heart rate was also significantly lower (p ≤ 0.05) for EU during the second and third bouts. Post hoc measures also showed significantly impaired (p ≤ 0.05) feelings of recovery (PRS) before exercise and increased (p ≤ 0.05) perceptual strain before each bout (PR) during the second and third bouts of repeated sprint work (i.e., RPE and PR) and after the total session (SRPE) in the DEHY condition. Dehydration impaired sprint performance, negatively altered perception of recovery status before exercise, and increased RPE and HR response.

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

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. 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. 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. 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.

Evaluating the physiological and perceptual responses of wearing a newly designed construction work uniform

Properly selected fabrics and smartly designed uniform are essential to improve thermal and moisture performance of summer clothes. As compared to a commercial uniform (CON) that was commonly worn by construction workers, a newly designed work uniform (NEW) consists of a smartly designed short-sleeved shirt with superior air permeability and a pair of full-length pants with excellent overall moisture management capacity. The aim of this study was to examine the effectiveness of NEW on combating body physiological and perceptual strain through conducting human wear trials in the laboratory experiment. Twelve participants took part in two trials (one with wearing NEW and another with wearing CON) on two experimental days. Each trial included a rest–intermittent running–recovery cycle inside a climatic chamber controlled at 34.5℃ and 75% relative humidity. The major findings manifested that the mean skin temperature ([Formula: see text]) of participants with NEW was significantly lower than that with CON toward a high running speed (8.5 km/h, 4% slope). During passive recovery, thermo-physiological strain (intestinal temperature ( Tin), [Formula: see text], and mean body temperature [Formula: see text]) of participants with NEW was significantly lower than that with CON. The perceptual strain of participants with NEW was significantly alleviated during exercise and post-exercise recovery periods as the participants felt cooler, drier, and more comfortable than those with CON. It was concluded that the newly designed work uniform is effective in alleviating thermo-physiological and perceptual strain during intermittent exercise and post-exercise recovery in hot and humid environment.

Hand and Forearm, But Not Neck Cooling, Reduces Thermophysiological and Perceptual Strain Following Passive Hyperthermia

Combined hand and forearm cooling effectively attenuates hyperthermia during exercise, and improves recovery between bouts of exercise in an uncompensable heat stress environment. Neck cooling can also be effective in reducing thermoregulatory strain during exercise in high ambient temperatures, or when magnitude of cooling is sufficient. PURPOSE: To determine the effect of active cooling on temperature, heart rate and thermal sensation following passive hyperthermia. METHODS: Eleven healthy participants (22±5 y; 173±10 cm; 71.8±15.1 kg) were passively heated to 39°C rectal temperature (Tre) by 40°C whole-body immersion. They were then removed from the water and sat quietly in a room (24.6±0.8°C and 49.8±6.3% rh) and used either a 2.6 m2 commercially available cooling towel wrapped against the surface of their neck (NT), hand and forearm immersion in 10.5±1.3°C water (H) or cooled passively (C) until Tre reached 38°C. Heart rate, Tre, mean skin temperature (Tsk), and thermal sensation (TS) were measured pre and post whole-body immersion, and every 5 min during cooling. Nude body mass was measured before and after each trial. One and two way repeated measures ANOVA were used to determine differences across time and between groups. RESULTS: Time to cool was faster (p<0.01) with H (24±7 min) compared to C and NT (C: 37±13 min; NT: 38±9 min). There were Tre interaction effects (time and condition, p<0.01) at 10 min cooling with H (38.7±0.3°C) compared to NT (39.0±0.2°C) and C (38.9±0.2°C), and at 15 min cooling with H (38.4±0.4°C) when compared to NT (38.7±0.2°C) and C (38.7±0.3°C). There was also a lower Tsk (p<0.05) when using H (34.5±2.7°C) compared to NT (34.9±2.9°C) and C (34.7±2.8°C). Mean heart rate during recovery was lower (p<0.01) when using hand cooling (96±19 beats·min-1) compared to both neck towel cooling (107±20 beats·min-1) and control (105±22 beats·min-1). Perceived TS was found to be lower (p<0.01) with H (4.1±1.7) compared to NT and C (NT 4.7±1.4; C 4.6±1.5). Across the duration of each of the trials, there was no significant difference in body mass change. CONCLUSION: Neck towel cooling was found to be an ineffective hyperthermia recovery strategy. However, hand and forearm cooling effectively reduced thermal strain and recovery time, along with decreasing heart rate and improving perceptual responses.

Can perceptual indices estimate physiological strain across a range of environments and metabolic workloads when wearing explosive ordnance disposal and chemical protective clothing?

ObjectiveExplosive ordnance disposal (EOD) often requires technicians to wear multiple protective garments in challenging environmental conditions. The accumulative effect of increased metabolic cost coupled with decreased heat dissipation associated with these garments predisposes technicians to high levels of physiological strain. It has been proposed that a perceptual strain index (PeSI) using subjective ratings of thermal sensation and perceived exertion as surrogate measures of core body temperature and heart rate, may provide an accurate estimation of physiological strain. Therefore, this study aimed to determine if the PeSI could estimate the physiological strain index (PSI) across a range of metabolic workloads and environments while wearing heavy EOD and chemical protective clothing. MethodsEleven healthy males wore an EOD and chemical protective ensemble while walking on a treadmill at 2.5, 4 and 5.5km·h−1 at 1% grade in environmental conditions equivalent to wet bulb globe temperature (WBGT) 21, 30 and 37°C. WBGT conditions were randomly presented and a maximum of three randomised treadmill walking trials were completed in a single testing day. Trials were ceased at a maximum of 60-min or until the attainment of termination criteria. A Pearson's correlation coefficient, mixed linear model, absolute agreement and receiver operating characteristic (ROC) curves were used to determine the relationship between the PeSI and PSI. ResultsA significant moderate relationship between the PeSI and the PSI was observed [r=0.77; p<0.001; mean difference=0.8±1.1a.u. (modified 95% limits of agreement −1.3 to 3.0)]. The ROC curves indicated that the PeSI had a good predictive power when used with two, single-threshold cut-offs to differentiate between low and high levels of physiological strain (area under curve: PSI three cut-off=0.936 and seven cut-off=0.841). ConclusionsThese findings support the use of the PeSI for monitoring physiological strain while wearing EOD and chemical protective clothing. However, future research is needed to confirm the validity of the PeSI for active EOD technicians operating in the field.