Work-rest Regimens Research Articles

Effect of cold beverages on whole-body heat exchange in young and older males during intermittent exercise in the heat.

To mitigate health risks associated with occupational heat stress, workers are advised to adhere to a work-rest regimen, and hydrate regularly. However, it remains unclear if beverage temperature influences whole-body heat exchange during work-rest cycles, and if responses differ in older workers who have a blunted heat loss capacity. Ten young (mean [SD]: 22 [3] years) and 10 older (60 [4] years) males performed four 15-min bouts of moderate-intensity cycling at a fixed rate of metabolic heat production (200 W·m-2), each interspersed by 15-min rest in dry heat (40°C, ~12% relative humidity). On separate days, participants consumed either ice-slurry (~0°C), standardized to provide a heat transfer capacity of 75 kJ·m-2, or an identical mass of warm fluid (37.5°C) before the first and third exercise bouts. Evaporative and dry heat exchange (direct calorimetry) and metabolic heat production (indirect calorimetry) were measured continuously to determine cumulative heat storage (summation of heat loss and heat gain) over the entire protocol. Rectal temperature was also measured continuously. Relative to warm fluid, ice-slurry ingestion reduced cumulative heat storage in young (69 [181] vs. 216 [94] kJ) and older males (90 [104] vs. 254 [140] kJ, main effect: p < 0.01), but was unaffected by age (p = 0.49). However, rectal temperature was unaffected by beverage temperature in both groups (all p ≥ 0.15). We show that cold fluid ingestion is an appropriate administrative control for both young and older males as it can mitigate increases in body heat content during moderate-intensity work-rest cycles in dry heat.

Work-rest regimens for work in hot environments: A scoping review.

To limit exposures to occupational heat stress, leading occupational health and safety organizations recommend work-rest regimens to prevent core temperature from exceeding 38°C or increasing by ≥1°C. This scoping review aims to map existing knowledge of the effects of work-rest regimens in hot environments and to propose recommendations for future research based on identified gaps. We performed a search of 10 databases to retrieve studies focused on work-rest regimens under hot conditions. Forty-nine articles were included, of which 35 were experimental studies. Most studies were conducted in laboratory settings, in North America (71%), on healthy young adults, with 94% of the 642 participants being males. Most studies (66%) employed a protocol duration ≤240 min (222 ± 162 min, range: 37-660) and the time-weighted average wet-bulb globe temperature was 27 ± 4°C (range: 18-34). The work-rest regimens implemented were those proposed by theAmerican Conference of Governmental and Industrial Hygiene (20%),National Institute of Occupational Safety and Health (11%), or the Australian Army (3%). The remaining studies (66%) did not mention how the work-rest regimens were derived. Most studies (89%) focused on physical tasks only. Most studies (94%) reported core temperature, whereas only 22% reported physical and/or mental performance outcomes, respectively. Of the 35 experimental studies included, 77% indicated that core temperature exceeded 38°C. Although work-rest regimens are widely used, few studies have investigated their physiological effectiveness. These studies were mainly short in duration, involved mostly healthy young males, and rarely considered the effect of work-rest regimens beyond heat strain during physical exertion.

Climate Warming and Occupational Heat and Hot Environment Standards in Thailand.

BackgroundDuring the period 2001 to 2016, the maximum temperatures in Thailand rose from 38–41oC to 42–44oC. The current occupational heat exposure standard of Thailand issued in 2006 is based on wet bulb globe temperature (WBGT) defined for three workload levels without a work–rest regimen. This study examined whether the present standard still protects most workers.MethodsThe sample comprised 168 heat acclimatized workers (90 in construction sites, 78 in foundries). Heart rate and auditory canal temperature were recorded continuously for 2 hours. Workplace WBGT, relative humidity, and wind velocity were monitored, and the participants' workloads were estimated. Heat-related symptoms and signs were collected by a questionnaire.ResultsOnly 55% of the participants worked in workplaces complying with the heat standard. Of them, 79% had auditory canal temperature ≤ 38.5oC, compared with only 58% in noncompliant workplaces. 18% and 43% of the workers in compliant and noncompliant workplaces, respectively, had symptoms from heat stress, the trend being similar across all workload levels. An increase of one degree (C) in WBGT was associated with a 1.85-fold increase (95% confidence interval: 1.44–2.48) in odds for having symptoms.ConclusionCompliance with the current occupational heat standard protects 4/5 of the workers, whereas noncompliance reduces this proportion to one half. The reasons for noncompliance include the gaps and ambiguities in the law. The law should specify work/rest schedules; outdoor work should be identified as an occupational heat hazard; and the staff should include occupational personnel to manage heat stress in establishments involving heat exposure.

The effect of heat exposure on physical workload and maximum acceptable work duration (MAWD) in a hot and dry climate

This study aimed at determining the effect of heat exposure on physical workload and maximum acceptable work duration in a hot and dry climate. Wet Bulb Globe Temperature, as an environmental index, and heart rate and core body temperature, as physiological indices, were used to assess environmental heat stress. For this purpose, the study was conducted on 86 acclimatized workers of six different sites of an oil industry. The comparison between heart rate at rest and work hours and core body temperature at rest and work hours revealed the existence of a significant different between heart rate and Core Body Temperature (P value<0.001). The results also indicated a significant difference between WBGTTWA and the limit value (P value<0.001). However, the results uncovered that the MAWD should be reduced in some units and, consequently, the work-rest regimens were modified based on this reduction. In addition, the results of this study demonstrated a statistically significant increase in and heart rate after work in excessive heat stress conditions. Heat exposure is perceived as a significant problem by the workers who worked in such workplaces. The results of this study can help managers and workers better plan and control thermal stresses.

INFLUENCE OF MEDICO-SOCIAL RISK FACTORS ON PSYCHOEMOTICAL STATE AND SELF-ESTEEM OF FEMALE PATIENTS OF REPRODUCTIVE AGE WITH TUBERCOLOSIS OF THE RESPIRATORY SYSTEM

Aim - to study the influence of medical and social risk factors on the psychoemotional state and selfesteem of female patients of reproductive age with tuberculosis of the respiratory system. Material and methods. The main group consisted of 93 women aged 18-44 with tuberculosis of the respiratory system who received treatment in one of the anti-tuberculosis institutions of the Nizhny Novgorod region in 2013. The comparison group consisted of 82 almost healthy women of the corresponding age. To assess the psychoemotional state, we carried out a survey using the SAM test method (state of health, activity, mood); to evaluate personality traits - the test «Self-assessment of the personality» by O.I. Motkov. The questionnaire included additional questions of medical and social nature. Results. It was proven that the presence of unfavorable medical and social risk factors in this category of patients causes a decrease in self-evaluation of the positive aspects of the personality, and has a negative impact on the psychoemotional state of patients, causing poor health (lowest evaluated), low activity, bad mood. In the course of long-term treatment, women feel tired and exhausted. Among the medical and social risk factors that have adverse impact on the psychoemotional state and self-esteem of women, the following factors should be highlighted: low level of education, poor financial situation, lack of awareness about prophylaxis of tuberculosis, intense interpersonal relationships in the family, frequent exposure to stress and rueful feelings, irregularity of the prophylactic chest X-ray examinations, violation of the work-rest regime, dietary regimen and quality of nutrition, the history of tubercular contact and incarceration. Conclusion. The results of the research demonstrate the need for developing and implementation of measures of providing psychological assistance to the female patients of reproductive age with active tuberculosis of the respiratory system, as well as new approaches to the prevention of this disease, based on established psychological risk factors for the emergence of tuberculous process and its recurrence.

A Field Study on Thermal Comfort of Traditional Metal Processing Factories

A traditional metal processing factory is a hot workplace. Previously, the rationality of the work-rest time regimen and the hazard of workload on employee health have been evaluated; however, thermal comfort of workers in such a hot workplace has not been discussed. This paper uses the standard new effective temperature as the thermal environment index to investigate the neutral temperature, preferred temperature, and comfortable temperature range. The doors and windows in traditional metal processing factories are always open; therefore, the neutral temperature is almost the same as the neutral temperature in semi-outdoor and outdoor environments. In addition, the preferred temperature is slightly higher than the neutral temperature. We also discovered that the comfortable temperature range in traditional metal processing factories is larger than that in office environments, but smaller than that in semi-outdoor and outdoor environments.

Application of the Predicted Heat Strain Model in Development of Localized, Threshold-based Heat Stress Management Guidelines for the Construction Industry

Existing heat stress risk management guidelines recommended by international standards are not practical for the construction industry which needs site supervision staff to make instant managerial decisions to mitigate heat risks. The ability of the predicted heat strain (PHS) model [ISO 7933 (2004). Ergonomics of the thermal environment analytical determination and interpretation of heat stress using calculation of the predicted heat strain. Geneva: International Standard Organisation] to predict maximum allowable exposure time (D lim) has now enabled development of localized, action-triggering and threshold-based guidelines for implementation by lay frontline staff on construction sites. This article presents a protocol for development of two heat stress management tools by applying the PHS model to its full potential. One of the tools is developed to facilitate managerial decisions on an optimized work-rest regimen for paced work. The other tool is developed to enable workers' self-regulation during self-paced work.

Management of climatic heat stress risk in construction: A review of practices, methodologies, and future research

Climatic heat stress leads to accidents on construction sites brought about by a range of human factors emanating from heat induced illness, and fatigue leading to impaired capability, physical and mental. It is an occupational characteristic of construction work in many climates and the authors take the approach of re-engineering the whole safety management system rather than focusing on incremental improvement, which is current management practice in the construction industry. From a scientific viewpoint, climatic heat stress is determined by six key factors: (1) air temperature, (2) humidity, (3) radiant heat, and (4) wind speed indicating the environment, (5) metabolic heat generated by physical activities, and (6) “clothing effect” that moderates the heat exchange between the body and the environment. By making use of existing heat stress indices and heat stress management processes, heat stress risk on construction sites can be managed in three ways: (1) control of environmental heat stress exposure through use of an action-triggering threshold system, (2) control of continuous work time (CWT, referred by maximum allowable exposure duration) with mandatory work-rest regimens, and (3) enabling self-paced working through empowerment of employees. Existing heat stress practices and methodologies are critically reviewed and the authors propose a three-level methodology for an action-triggering, localized, simplified threshold system to facilitate effective decisions by frontline supervisors. The authors point out the need for “regional based” heat stress management practices that reflect unique climatic conditions, working practices and acclimatization propensity by local workers indifferent geographic regions. The authors set out the case for regional, rather than international, standards that account for this uniqueness and which are derived from site-based rather than laboratory-based research.

Comparison of rest allowance models for static muscular work

Static muscular work associated with awkward postures with or without the application of force to an external object results in fatigue, discomfort, and musculoskeletal disorders. To prevent the effects of fatigue, sufficient and well-spaced rest periods are recommended. This paper presents an approach to determining rest periods for static muscular work in manufacturing workstations and compares the recommendations from four rest allowances models. The approach was applied to seven workstations in three industrial sectors: four workstations in the printing industry, one in the automotive industry and two in plant nurseries. The rest allowances proposed by the four models were compared with an estimation of rest allowances using the EN1005-3 standard. Results showed substantial differences in the recommendations from the different rest allowances models. Shoulder fatigue was the determining factor in the rest allowance for most workstations assessed. Caution should be exercised when using EN1005-3 to estimate rest allowances. Relevance to industry Static and intermittent static muscular work are known risk factors for work-related musculoskeletal disorders (WMSD). Determining appropriate work-rest regimens for static muscular work in industrial settings may be an efficient way to reduce this risk, but information to guide the selection of the most appropriate rest allowance model is lacking.

A new simple dynamic muscle fatigue model and its validation

Musculoskeletal disorder (MSD) is one of the major health problems that are related to physical labor especially in jobs requiring manual work. In some literature, muscle fatigue is considered to be closely related to MSD, especially for muscle related disorders. In addition to many existing analysis techniques for muscle fatigue assessment and MSD risk analysis, this paper proposes a new muscle fatigue model. The new proposed model reflects the influence of external load, workload history, and individual differences. This model is simple in mathematics and can be easily applied in real time calculation, such as the application in real time virtual work simulation and evaluation. The new model was mathematically validated with 24 existing static models by comparing the calculated METs (Maximum Endurance Times), and qualitatively or quantitatively validated with three existing dynamic models. The proposed model shows high or moderate similarities in predicting the METs with all the 24 static models. Validation results with the three dynamic models were also promising. The main limitation of the model is that it still lacks experimental validation for more dynamic situations. Relevance to industry Muscle fatigue is one of the main reasons causing MSDs in industry, especially for physical work. Correct evaluation of muscle fatigue is necessary to determine work–rest regimens and reduce the risk of MSD.

Percentile values for determining maximum endurance times for static muscular work

The maximum endurance time (MET) is a key parameter for the ergonomic evaluation of static work. The aim of this study is to offer practitioners MET values in relation to the %MVC (percentage of maximum voluntary contraction) that take into account the results of several studies published on MET. Twenty four published MET models were combined to extract MET percentile values that reflect the interindividual variability and differences among the experimental methods used to develop the models. The MET differences by muscle group are also verified. The results of this study show that, (1) there is a significant difference between the MET values for the back/hip and the MET values for the upper limbs, for a same %MVC value; (2) the model-generated MET values follow a lognormal distribution. A summary table is presented showing the most frequently used percentile values (5th, 10th and 15th percentiles) of the MET corresponding to a range of %MVC values. The data from this paper allow engineers and ergonomics practitioners to design workstations that can accommodate a desired proportion of the worker population, i.e., designs that are not restricted only to the 50th percentile. Relevance to industry Static and intermittent static muscular work is a known risk factor for musculoskeletal disorders (MSD). Estimation of MET to accommodate a percentage of the worker population is a necessary step in determining appropriate work-rest regimens for static muscular work in industrial settings.

LD-PACE II: a new cardiomyostimulator for cardiac bioassist.

The LD-PACE II was designed for use in cardiomyoplasty, aortomyoplasty, and skeletal muscle ventricles. All parameters specified as programmable can be changed in a noninvasive manner (using a programming interface wand connected to a computer using the Windows 95/98 environment). Two new functions may be very useful clinically, based on experimental research. 1. Work-rest regimen. The LD-PACE II is able to deliver alternating periods of muscle contractions and rest. Work and rest periods may be programmed independently between 1 and 120 minutes in increments of 1 minute. The work-rest regimen may be useful clinically if muscle contractions are needed for cardiac assist postoperatively. 2. Night/day regimen. This feature allows for a change in the ratio of muscle contractions according to a patient's activity level. During the day the cardiosynchronization ratio may be set from 1:1 to 1:4, and during the night it may be set for 1:8 to 1:16. This allows the muscle to have a long rest period, prevents overuse, and prolongs battery life. These two new features make this cardiomyostimulator very attractive for cardiomyoplasty in particular. The addition of the work-rest and night-day regimens allow the muscle to rest for periods during the day to prevent overuse, subsequent damage, and potential atrophy.

Multistep approach to electrical stimulation after cardiomyoplasty.

Still a controversial procedure, cardiomyoplasty (CMP) improves the failing heart's ability to contract by using a latissimus dorsi muscle (LDM), but to date, hemodynamic results correlate poorly with clinical improvement. The following two causes for apprehension bar attempting to change the conventional electrical stimulation (ES) protocol to improve CMP results: (1) fear of beginning ES for LDM-assisted contraction immediately postmobilization and CMP and (2) fear of stopping or slowing ES during sleep periods. In ten different experimental series, I used animal models of CMP to determine how to apply ES to newly mobilized LDM, how to begin partial cardiac assist immediately post-CMP, and how to suspend ES for 12 hours daily. From my experimental series I noted the following three results. (1) Different ES regimens applied 1 hour postmobilization changed the contractile force (CF). After a 30-minute fatigue test, CF decreased by 34% +/- 3% with continuous ES at 30 contractions per minute (cpm), by 23% +/- 2% with continuous ES at 15 cpm, by 25% +/- 5% with ES in a work-rest regimen at 30 cpm, and by 8% +/- 3% with ES in a work-rest regimen at 15 cpm. (2) Imitation of partial cardiac assist immediately postmobilization slightly decreased CF. Sixteen days postmobilization, during a 30-minute fatigue test in animals in which ES had been started immediately after mobilization, CF decreased by only 6% +/- 3% and did not change when ES was combined with imitation of cardiac assist for 30 minutes twice daily (work-rest regimen). (3) ES cessation for 24 hours daily or 12 hours daily in CMP model created no difference in ejection fraction (EF) with ES (54% +/- 4% vs 53% +/- 5%, respectively (or in left ventricular end-diastolic volume (LVEDV, 234.3 ml +/- 1.0 ml vs 24.8 mL +/- 0.6 mL, respectively) or in LV end-systolic volume (LVESV; 12.1 mL +/- 0.7 mL vs 12.8 mL +/- 0.7 mL, respectively). For improving angiographic potential in the LDM, ES can be started safely immediately post-CMP at 15 cpm (a 1:4 or 1:5 regimen) and single impulses per burst. For partial cardiac assist and for improving LDM performance, cardiac assist can be used for 30 minutes twice daily immediately post-CMP. To rest the muscle and save it from overuse, muscle contraction can be either stopped or slowed down during hours of sleep.

WORK-REST REGIMEN AND NIGHT/DAY REGIMEN - TWO NEW FUNCTIONS IN A NEW CARDIOMYOSTIMULATOR (LD-PACE II) DESIGNED FOR CARDIAC BIOASSIST

LD-PACE II, a new cardiomyostimulator was manufactured by CCC del Uruguay with the support of the Illini Group, Chicago, Illinois. The LD-PACE II was designed for use in cardiomyoplasty, aorto myoplasty, and skeletal muscle ventricle. All parameters specified as programmable can be changed in a noninvasive manner (using a programming interface wand connected to a computer using the Windows 95/98 environment). Most of the functions of the new stimulator are similar to functions of previously used devices (Transform, Medtronic; EKS 445, Russia), however new two functions could be extremely important fo clinical use based on experimental research. 1. Work-rest regimen. In the conventional stimulation regimen, the latissimus dorsi muscle (LDM) works 24 hours daily with no rest except for short periods between contractions. The LD-PACE II is able to deliver alternating periods of muscle contractions and rest. Work and rest periods may be programmed independently between 1 and 120 minutes in increments of one minute. The work-rest regimen may be useful clinically if muscle contractions are needed for cardiac assist postoperatively. Morphological (light microscopy, transmission electron microscopy) and electrophysiological data show that a short period of work followed by a long period of rest does not damage the ischemic muscle. 2. Night/day regimen. This feature is also brand new. It allows for a change in the ratio of muscle contractions according to a patient's activity level. During the day the cardiosynchronization ratio may be set from 1:1 to 1:4 and during the night it may be set for 1:8 to 1:16. This allows the LDM to have a long rest period, prevents overuse, and prolongs battery life. Data confirmed that there is no depression in hemodynamics when the ratio is slowed or turned off during the night. The first tests of the LD-PACE II in Milwaukee, WI, Detroit, MI and Paris (France) showed good functional ability of a high caliber.

Problematic Issues in Prevention of Injuries and Illnesses Resulting from Exposure to Heat and Cold Stress

Abstract In the threshold limit values (TLVs) for heat and cold stress published by the American Conference of Governmental Industrial Hygienists, the main approach for prevention is similar: the frequency and length of required rest periods depend on the climatic conditions of the working area and the work metabolism. Whereas methods and instruments for measuring the climatic conditions are fairly well established for practical application, the methods available for assessing the effects of clothing and work metabolism at the job site are cumbersome and/or inaccurate. Both TLVs stipulate that the recommended work-rest regimens are valid only if the Workers' clothing is adapted to the climatic conditions of the working area. Yet there is no standard method to measure the insulation, vapor permeability, and ventilation of working uniforms and different protective garments. Some new methods are described which hold promise to solve these problems. Recommendations on methods to assess metabolism include qual...

Is it possible to perform immediate cardiac assist using untrained latissimus dorsi muscle in a work-rest regimen?

The authors investigated what contractile force (CF) could be obtained from unconditioned latissimus dorsi muscle immediately after mobilization and for the 2 week vascular period of recovery. Latissimus dorsi muscle mobilization was performed on seven adult (4 experimental and 3 control) sheep leaving only the pedicle and the peripheral muscle intact. Telectronics stimulators (Myostim 7220; Teletronics Pacing Systems, Inc, Englewood, CO) were implanted. Immediately after mobilization 11-35% of the initial CF was lost. A 30 min fatigue test was performed 1 hr after mobilization (20 g/kg preload, 10 V, 10 Hz, 15 BPM, 6 impulses per burst) using a 1 min work-1 min rest regimen. Two sheep lost 2-12% of initial CF; two increased CF by 14-24%. At the end of the fatigue test, CF consisted of 74-89% of immobilized CF. Electrical stimulation training of the muscle was then initiated with the following regimen in the experimental animals only: 15 BPM, single impulses, 5 V, 10 Hz. Every day the muscle was exercised using a work-rest regimen to mimic cardiac assist, starting with 20 min on day 2, and increasing by 2 min per day until a total of 50 min was reached on day 16. All animals were retested for CF using a 42 min fatigue test on days 6, 11, and 16. On day 6, there was no fatigue evident in the experimental group during the 42 min test. CF after testing was 59-81% (mean 67%) of initial data. In the control group (animals with no electrical stimulation training protocol), CF decreased by 11% (from 64 to 53%). On day 11, there was no fatigue evident in the experimental group; CF in all animals increased by 2-8%. On day 16, there was also no fatigue evident in the experimental group; CF increased by 0-9%. An additional 20 min of continuous contraction (15 BPM) fatigue testing was performed on the muscle without rest between the tests. No fatigue was evident at the end of testing. Light microscopic analysis of latissimus dorsi muscle biopsy specimens taken on the days of testing showed no evidence of necrotic damage. Our investigations suggest that it may be possible to start muscle transformation immediately after mobilization and use the untrained latissimus dorsi muscle for cardiac assist immediately after surgery for short periods.

Differences in cardiorespiratory responses during and after arm crank and cycle exercise

The differences in cardiorespiratory responses were examined during and after intermittent progressive maximal arm-crank and cycle exercise. Arm-crank exercise was performed in a standing position using no torso restraints to maximize the amount of active skeletal muscle mass. Recovery was followed for 16 min. In the tests a variety of ventilatory gas exchange variables, heart rate, the blood pressure, and the arm venous blood lactate concentration were measured in 21 untrained healthy men aged 24-45 years. At equal submaximal external workloads for arm cranking and cycling (50 and 100 W) the respiratory frequency, tidal volume, pulmonary ventilation, oxygen uptake, carbon dioxide output, the respiratory exchange ratio, heart rate, the arm venous blood lactate concentration, and the ventilatory equivalent for oxygen were higher (P less than 0.001) during arm cranking than cycling. The maximal workload for arm cranking was 44% lower than that for cycling (155 +/- 37 vs 277 +/- 39 W, P less than 0.001) associated with significantly (P less than 0.001) lower maximal tidal volume (-20%), oxygen uptake (-22%), carbon dioxide output (-28%), systolic blood pressure (-17%) and oxygen pulse (-22%) but a higher ventilatory equivalent for carbon dioxide (+22%) and arm venous blood lactate concentration (+37%). However, these responses after arm-crank and cycle exercises behaved almost similarly during recovery. The high cardiorespiratory stress induced by arm work should be taken into account when the work stress and work-rest regimens in actual manual tasks are assessed, and when arm work is used for clinical testing, and in physiotherapy particularly for patients with heart or pulmonary diseases.

Workers self-pacing in hot conditions: A case study

It is not always possible in hot environments, to determine safe work-rest regimens based upon heat stress criteria. Is it then a good health policy to rely upon the self-pacing of the workers? To address this question, we observed the spontaneous work-rest cycles of seven masonry workers allocated to the maintenance of a float-glass furnace and the workers' heart rate and rectal temperature were continuously monitored. Results showed that the regimens adopted by the workers were poorly related to physiological parameters. The duration of each heat exposure was significantly related to the worker aerobic capacity, but not to the heart rate level reached at the end of the working period. Due to self-pacing of the task, heart rates and rectal temperatures remained within acceptable limits for all workers but one, even though these workers were rather old and had a rather low physical capacity. These favourable results may be ascribed to a spontaneous limitation of the effective working time to about 25% of the shift duration and to the fact that subjects worked, in pairs alternately, to perform the task. It is concluded that self-regulation of the work-rest cycles can be an effective means to protect the workers exposed to hot conditions from an excessive physiological strain, providing that the task has no urgent character and does not involve productivity incentives, and that the workers are well trained to their job.

Cardiorespiratory and thermal effects of wearing gas protective clothing.

Six healthy men aged 25 to 37 walked on a treadmill at work levels of 21 and 41% of their VO2max for 25 to 30 min wearing gas protective clothing (GPC) consisting of an impermeable suit with a self-contained breathing apparatus (total weight 25 kg) or shorts (control tests, CT) in a temperate environment (ta 24.3 degrees C +/- 1.0 degrees C, rh 30-50%). When the GPC was worn at 21 and 41% VO2max, the most prominent increases, compared with the CT, were noted in the heart rate (means +/- SE, 120 +/- 5 vs 76 +/- 3 beats min-1 and 171 +/- 5 vs 103 +/- 3 beats min-1), mean skin temperature (36.1 +/- 0.2 vs 31.3 degrees C +/- 0.1 degree C and 36.9 +/- 0.3 vs 30.9 degrees C +/- 0.4 degrees C) and sweat rate (473 +/- 51 vs 70 +/- 23 g m-2 h-1 and 766 +/- 81 vs 135 +/- 18 g m-2 h-1) indicating a high cardiovascular and thermoregulatory strain, which was not decreased by ventilating the suit with an air flow of 281 min-1 at 41% VO2max. The ventilation, oxygen consumption and production of carbon dioxide increased in relation to the extra weight of the GPC, partly dependent on the dynamic work level. It was concluded that the increase in the physiological load caused by the GPC was so high that the work-rest regimens, workers' level of physical fitness, cardiovascular health and heat tolerance should be considered whenever gas protective clothing is used.

The TLV work-rest regimens for occupational exposure to heat: A review of their development : Annals of Occupational Hygiene 1979, 22.1, 55–62.

The TLV work-rest regimens for occupational exposure to heat: A review of their development : Annals of Occupational Hygiene 1979, 22.1, 55–62.