Risk factors predicting exertional heat illness in male Marine Corps recruits

Gardner, John C.; Kark, John A.; Karnei, Karen; Sanborn, Jill S.; Gastaldo, E; Burr, Peggy; Wenger, C. B.

doi:10.1097/00005768-199608000-00001

Cited by 148 publications

(126 citation statements)

References 21 publications

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“…Excess body weight is evidenced by a high body mass index (BMI) and body fat percent (obesity). Gardner et al 24 found that in Marine Corps recruits, a comparatively high BMI Heat acclimatization is one of the more important factors in reducing risk of or the severity of heat-related illness. Heat acclimatization involves a series of biological adjustments to compensate for the adverse physiological effects of heat stress.…”

Section: 11mentioning

confidence: 99%

Development of a perceptual hyperthermia index to evaluate heat strain during treadmill exercise

et al. 2011

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Fire suppression and rescue is a physiologically demanding occupation due to extreme external heat as well as the additional physical and thermal burden of the protective garments. The hot environment challenges body temperature homeostasis inducing heat stress. Accurate field assessment of hyperthermia is complex and unreliable. Purpose: The present investigation developed a perceptually based hyperthermia metric to measure physiologic exertional heat strain during treadmill exercise. Methods:Sixty-five (28.88 ± 6.75 yrs) female (n=11) and male (n=54) firefighters and non-firefighting volunteers participated in four related thermal stress investigations performing treadmill exercise while wearing thermal protective clothing in a heated room. Physiological and perceptual responses (i.e. body core temperature, perceived exertion, and thermal sensation) were assessed at baseline, 20-mins exercise, and at termination. Results: Perceived exertion increased from baseline (0.24 ± 0.42) to termination (7.43 ± 1.86). Thermal sensation increased from baseline (1.78 ± 0.77) to termination (4.50 ± 0.68). Perceived exertion and thermal sensation were measured concurrently with body core temperature to develop a twodimensional graphical representation of three "colored" exertional heat strain zones. Each exertional heat strain zone was representative of a range of mean body core temperature responses such that green incorporated 36.0 to 37.4°C, yellow incorporated 37.5 to 37.9°C, and red incorporated 38.0 to greater than 40.5°C. Conclusions: A perceptual hyperthermia index (PHI) was developed using ratings of iii perceived exertion and thermal sensation. The PHI can provide a quick and easy momentary assessment of the level of risk for exertional heat strain for firefighters engaged in fire suppression and rescue. This metric may be beneficial in high risk environments that threaten the lives of firefighters.

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Section: 11mentioning

confidence: 99%

Development of a perceptual hyperthermia index to evaluate heat strain during treadmill exercise

et al. 2011

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“…Subjects were defined as lean (BMI o25), overweight (BMI [25][26][27][28][29][30] or obese (BMI 430 kg m À2 ) ( Table 1). Data were collected during the first day of this walking march only.…”

Section: Subjectsmentioning

confidence: 99%

“…23 Previous studies showed that body mass index (BMI) was related to the occurrence of heat disorders in highly trained, young soldiers. 24,25 It is, however, unknown whether obesity in the general population is related to the development of fluid and sodium imbalances during prolonged exercise.…”

Section: Introductionmentioning

confidence: 99%

The impact of obesity on physiological responses during prolonged exercise

et al. 2011

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Background: Prolonged, moderate-intensity exercise training is routinely prescribed to subjects with obesity. In the general population, this type of exercise can lead to fluid and sodium imbalance. However, little is known whether obesity alters the risk of fluid and sodium imbalances. Objective: This study examined physiological responses, such as core body temperature, fluid and sodium balance, in lean (BMIo25), overweight (25oBMIo30) and obese (BMI430) subjects during prolonged moderate-intensity exercise. Subjects: A total of 93 volunteers (24-80 years), stratified for BMI, participated in the Nijmegen Marches and walked 30-50 km at a self-selected pace. Heart rate and core body temperature were recorded every 5 km. Subjects reported fluid intake, while urine output was measured and sweat rate was calculated. Baseline and post-exercise plasma sodium levels were determined, and urinary specific gravity levels were assessed before and after exercise. Results: BMI groups did not differ in training status preceding the experiment. Exercise duration (8 h 41 ± 1 h 36 min) and intensity (72 ± 9% HR max ) were comparable across groups, whereas obese subjects tended to have a higher maximum core body temperature than lean controls (P ¼ 0.06). Obese subjects demonstrated a significantly higher fluid intake (Po0.001) and sweat rate (Po0.001), but lower urine output (Po0.05) compared with lean subjects. In addition, higher urine specific gravity levels were observed in obese versus lean subjects after exercise (Po0.05). Furthermore, plasma-sodium concentration did not change in lean subjects after exercise, whereas plasma-sodium levels increased significantly (Po0.001) in overweight and obese subjects. Also, overweight and obese subjects demonstrated a significantly larger decrease in body mass after exercise than lean controls (Po0.05).Conclusion: Obese subjects demonstrate a larger deviation in markers of fluid and sodium balance than their lean counterparts during prolonged moderate-intensity exercise. These findings suggest that overweight and obese subjects, especially under strenuous environmental conditions, have an increased risk to develop fluid and sodium imbalances.

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“…Exertional heat illness (EHI) is comprised of a number of acute heat illness disorders (25). These acute disorders of heat illness include heatstroke (ICD-9 code 9920), heat exhaustion (ICD-9 code 9923-9925), and heat cramps (ICD-9 code 9922).…”

Section: Physiology Of Heat Illness and Sequelaementioning

confidence: 99%

“…On the continuum, heatstroke is defined either clinically or on the basis of a rectal temperature of > 104.9°F (40.5°C) with an outcome of death if 106°F (41 .rC) is reached (54). Environmental and clothing variables are the most common factors that affect heat stress, but other important factors include hydration, acclimatization, age, physical fitness, body fat, gender, body size, diet, previous heat illness, dmgs and alcohol (25), (49).…”

Section: Physiology Of Heat Illness and Sequelaementioning

confidence: 99%

Risk Factors and Mortality in Relation to Heat Illness Severity

Wallace¹

2003

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Public reporting burden for (his coliectbn of Information is estimated to average 1 hour per response, Including the time for reviewing instructions, searcliing existing data sources, galfieting and maintaining ttie data needed, and completing and reviewing ttie collection of information. Send comments regarding this burden estimate or any other aspect of this collection of Information, Including suggestions for reducing Uiis burden, to Washington Headquarters Services, Cireclotate for infomialion Operations and Reports, t215 Jefferson Davis Highway, Suite 1204, Artinglon, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. AGENCY USE ONLY (Leave blank). REPORT DATE JUNE 2003 3. REPORT TYPE AND DATES COVERED TECHNICAL REPORT TITLE AND SUBTITLE RISK FACTORS AND MORTALITY IN RELATION TO HEAT ILLNESS SEVERITY AUTHOR(S)ROBERT F. WALLACE, Sc.D, M.P.H. Study 1. A case-crossover study was conducted in male and female Marine Corps recruits in basic tiaining at Marine Corps Recruit Depot (MCRD), Parris Island, SC to investigate the effects of alternative indices of heat exposure on exertional heat illness (EHI) risk. Weather measurements were obtained for 2,069 cases of EHI identified in this population during 1979-1997. As expected, the risk for developing EHI increased with increasing wet bulb globe temperature (WBGT), which is the standard heat index used by the Marine Corps. EHI risk was found to be associated not only with the WBGT at the time of the event, but by the previous day's average WBGT as well. This result suggests evidence of a cumulative effect of previous day's heat exposure in these Marine recruits at MCRD. Study 2. A matched case control study was conducted to investigate the effects of fitness and conditioning on EHI risk, as well as to compare the risk factors for mild and severe cases of EHI, as distinguished by core body temperature shortly after the event. Physical fitness, anthropomefric and physiological measurements were acquired for 660 EHI cases identified in this population for the period 1988-1996 and matched to 1,723 controls by initial training platoon. For severe cases, BMI and initial run-time did not have independent effects, but instead showed a less-than-additive effect at high levels of each. In contrast, BMI and run-time appeared to have independent effects on risk of mild EHI. FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)UStudy 3. A cohort mortality study was carried out among male and female U.S. Army personnel hospitalized for heat illness (HI) at U.S. Army hospitals during 1971-2000. Hospitalization records were obtained for 3,971 cases of HI and 17,233 referent cases of appendicitis (APX). Male and female HI cases had a 40% increased rate of all-cause mortality compared to APX cases. Further examining cause-specific deaths, male cases of HI were at increased risk of death from cardiovascular disease (CVD), ischemic heart disease (IHD), and heat related sites (CVD, liver [non-alcoho...

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Risk factors predicting exertional heat illness in male Marine Corps recruits

Cited by 148 publications

References 21 publications

Development of a perceptual hyperthermia index to evaluate heat strain during treadmill exercise

Development of a perceptual hyperthermia index to evaluate heat strain during treadmill exercise

The impact of obesity on physiological responses during prolonged exercise

Risk Factors and Mortality in Relation to Heat Illness Severity

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