***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: This study evaluated the effectiveness of a six-pack versus a four-pack cool vest in reducing heat strain in men dressed in firefighting ensemble , while resting and exercising in a warm/humid environment [ 34.4 ° C ( day bulb ) , 28.9 ° C ( wet bulb ) ] . Male volunteers ( n = 12 ) were monitored for rectal temperature ( Tre ) , mean skin temperature ( Tsk ) , heart rate , and energy expenditure during three test trials : control ( no cool vest ) , four-pack vest , and six-pack vest . The cool vests were worn under the firefighting ensemble and over Navy dungarees . The protocol consisted of two cycles of 30 min seated rest and 30 min walking on a motorized treadmill ( 1.12 m · s−1 , 0 % grade ) . Tolerance time for the control trial ( 93 min ) was significantly less than both vest trials ( 120 min ) . Throughout heat exposure , energy expenditure varied during rest and exercise , but no differences existed among all trials ( P > 0.05 ) . During the first 60 min of heat exposure , physiological responses were similar for the four-pack and six-pack vests . However , during the second 60 min of heat exposure the six-pack vest had a greater impact on reducing heat strain than the four-pack  vest . PeakTe and Tsk at the end of heat exposure for 6-pack vest [ mean ( SD ) 38.0(0.3) ° C and 36.8(0.7) ° C ] were significantly lower compared to four-pack [ 38.6 (0.4) ° C and 38.1(0.5) ° C ] and controls [ 38.9(0.5) ° C and 38.4(0.5) ° C ] . Our findings suggest that the six-pack vest is more effective than the four-pack vest at reducing heat strain and improves performance of personnel wearing a firefighting ensemble This study examined whether cooling a fire-fighter  with a high velocity fan , during 10 min rest pauses between , and following , 10 min work periods , decreases heat stress during repetitive fire-fighting activity . Twelve professional fire-fighters ( mean age 31.8 + /- 6.7 years ) completed two , 40 min work/recovery trials in an environmental chamber at 40 degrees C and 70 % relative humidity ( RH ) . One trial was termed an enhanced recovery ( ER ) trial and the other was termed a normal recovery ( NR ) trial . In both conditions subjects wore full protective clothing and breathing apparatus during the work . In the ER trial a subject removed his protective coat and sat in front of a fan during each recovery period . In the NR trial a subject merely unbuckled his coat and was not cooled by a fan during either recovery period . The group mean metabolic cost ( VO2 ) , and the exercise and recovery heart rates were significantly lower ( p < or = 0.05 ) during the ER trial than in the NR condition . Group mean rectal temperature increased by 1.5 degrees C in the NR trial but by only 0.8 degree C during the ER trial . The latter group 's more effective cooling indicates the potential of fan cooling to reduce physiological strain and decrease the risk of heat exhaustion during repetitive fire-fighting activity . The results suggest that a fire-fighter 's short 10 min exposure to heavy work in a hot environment of 40 degrees C and 70 % RH produces minimal heat stress in a healthy fire-fighter . However , a period of fire-fighting exposure greater than 10 min without adequate rest and cooling may lead to a significant accumulation of heat stress and fatigue during further fire-fighting activity , irrespective of physical prowess This study investigated the effects of body cooling using liquid cooling garments ( LCG ) on performance time ( PT ) and recovery in individuals wearing a fully equipped prototype firefighter ensemble ( PFE ) incorporating a self-contained breathing apparatus ( SCBA ) . Six healthy male participants ( three firefighters and three non-firefighters ) completed six experimental sessions in an environmental chamber ( 35 ° C , 50 % relative humidity ) , consisting of three stages of 15 min exercise at 75 % VO2max , and 10 min rest following each exercise stage . During each session , one of the following six conditions was administered in a r and omized order : control ( no cooling , CON ) ; air ventilation of exhaust SCBA gases rerouted into the PFE ( AV ) ; top cooling garment ( TCG ) ; TCG combined with AV ( TCG+AV ) ; a shortened whole body cooling garment ( SCG ) , and SCG combined with AV ( SCG+AV ) . Results showed that total PT completed was longer under SCG and SCG+AV compared with CON , AV , TCG , and TCG+AV ( p < 0.01 ) . Magnitude of core temperature ( Tc ) elevation was significantly decreased when SCG was utilized ( p < 0.01 ) , and heart rate recovery rate ( 10 min ) was enhanced under SCG , SCG+AV , TCG , and TCG+AV compared with CON ( p < 0.05 ) . Estimated Esw rate ( kg·h−1 ) was the greatest in CON , 1.62 ( 0.37 ) , and the least in SCG+AV 0.98 ( 0.44 ) : ( descending order : CON > AV > TCG = TCG+AV > SCG > SCG+AV ) without a statistical difference between the conditions ( p < 0.05 ) . Results of the present study suggest that the application of LCG underneath the PFE significantly improves the recovery during a short period of rest and prolongs performance time in subsequent bouts of exercise . LCG also appears to be an effective method for body cooling that promotes heat dissipation during uncompensable heat stress Heart rate ( HR ) , rectal temperature ( Tre ) , blood pressure , temperature and relative humidity changes inside clothing were measured on 18 professional firemen ( mean age 29.4 + /- 7.4 yr , VO2 max 41.4 + 8.8 ml kg-1 min-1 ) wearing fire fighter 's uniforms ( SU ) or aluminized , fire resistant , impermeable clothing with self contained breathing apparatus ( FE ) .  The subjects exercised on a cycle ergometer with a work load of 1.5 W kg-1 , at 39 + /- 1 degree C and at 70 + /- 5 % relative humidity . They stopped exercising at a point of subjective fatigue and overheating which -- according to their judgement -- would cause them to stop working during real fire fighting . The working time until fatigue for subjects wearing FE was considerably lower than the corresponding value for SU . The HR and Tre values rose progressively throughout the exercise with no tendency to reach a plateau . In some cases the HR reached near maximal level . The Tre continued to rise even during 10 min of recovery and in many subjects exceeded 39 degrees C. These data showed that despite spontaneous termination of exercise , the limit of tolerance was reached by most of the subjects BACKGROUND Studies , to date , have not revealed the extent to which the heat strain of continuous heavy exercise while wearing NBC protective clothing can be reduced by providing liquid- or air-cooling and whether one system is more effective than the other in aiding heat transfer from the body and the clothing . It was of interest to know to what extent present-day cooling technologies can reduce the heat strain of light and heavy exercise in NBC clothing and to compare these reductions to other strategies that have employed changes in clothing design . HYPOTHESIS It was hypothesized that there would be no difference between the liquid and air cooling systems and that sufficient cooling power would be delivered to the body to reduce the heat strain of heavy exercise to a level similar to that experienced with light exercise when no cooling was provided . METHODS Eight males performed 6 r and omized exposures for a maximum of 3 h at 40 degrees C and 30 % relative humidity that involved either light ( L ) ( walking at 3.5 km x h(-1 ) or heavy ( H ) ( walking at 4.8 km x h(-1 ) and a 5 % grade ) exercise while wearing the NBC protective clothing ensemble with no cooling ( N ) , liquid ( L ) or air ( A ) cooling . RESULTS For L exercise , tolerance time was significantly increased from 100 min with N to the maximum of 3 h with either cooling system . There was no difference between L and A cooling in the extent of the changes in rectal temperature , heart rate and heat flow . For H exercise , tolerance time was significantly increased 150 % from 57 min with N to 149 min with L and 140 min with A. These latter values for HL and HA were not different from each other but both were significantly greater than L exercise with N. Rectal temperature increased more quickly during HL compared with HA during the first 60 min of exposure but there were no differences between cooling trials for the remainder of the heat exposure . CONCLUSIONS It was concluded that sufficient cooling power could be delivered to the body to effectively reduce the heat strain of wearing NBC protective clothing during heavy exercise in a hot environment to a level comparable to or slightly lower than that experienced with light exercise and no cooling Abstract Objectives . The primary objective of this study was to document the timeline of physiologic recovery from  firefighting activities  in order to inform emergency medical services ( EMS ) of vital sign values that might be expected during incident rehabilitation and in developing rehabilitation protocol s to make decisions about when to return personnel to the fireground . Secondarily , we compared two different incident rehabilitation strategies to determine effectiveness in reducing physiologic strain following firefighting . Methods . A repeated- measures r and omized crossover design was utilized in which firefighters conducted a controlled set of firefighting activities , after which they completed incident rehabilitation in one of two conditions : 1 ) similar to currently used rehabilitation protocol s and 2 ) with active cooling and nutritional intervention . Following 15 minutes of rehabilitation , each firefighter was asked to perform a simulated rescue “ dummy drag ” and then recover for 120 minutes in a quiet area . Core temperature and heart rate were recorded throughout the study . Blood pressures and subendocardial viability ratios were obtained before firefighting , after firefighting , and at st and ardized times during rehabilitation and recovery . Results . Heart rate and core temperature increased during firefighting , and core temperature continued to increase for 7 minutes after completion of firefighting activities . These values did not return to baseline until at least 50 minutes after firefighting activity . Systolic blood pressures were significantly reduced during rehabilitation ( 15.2 % ) , and recovered 7.7 % during the first 30 minutes of recovery , but remained significantly lower than before firefighting for at least 120 minutes . An index of subendocardial perfusion was also significantly depressed for up to 110 minutes after firefighters . Differences between rehabilitation protocol s were minimal . Conclusions . The timeline for recovery from firefighting activities is significantly longer than the typical 10–20-minute rehabilitation period that often is provided on the fireground . Modifications from the current rehabilitation protocol do not appear to improve the recovery timeline when rehabilitation is conducted in a cool room . While firefighters often are concerned about elevated blood pressures , this study suggests that firefighters and EMS personnel should also be cognizant of the potential dangers of hypotension BACKGROUND The purpose of this study was to compare a vapor compression microclimate cooling system ( MCC ) and a personal ice cooling system ( PIC ) for their effectiveness in reducing physiological strain when used with cooling garments worn under the impermeable self-contained toxic environment protective outfit ( STEPO ) . A second comparison was done between the use of total body ( TOTAL ) and hooded shirt-only ( SHIRT ) cooling garments with both the MCC and PIC systems . It was hypothesized that the cooling systems would be equally effective , and total body cooling would allow 4 h of physical work in the heat while wearing STEPO . METHODS Eight subjects ( six men , two women ) attempted four experiments at 38 degrees C ( 100 degrees F ) , 30 % rh , 0.9 m x sec(-1 ) wind , while wearing the STEPO .  Subjects attempted 4 h of treadmill walking ( rest/exercise cycles of 10/20 min ) at a time-weighted metabolic rate of 303 + /- 50 W. RESULTS Exposure time was not different between MCC and PIC , but exposure time was greater with TOTAL ( 131 + /- 66 min ) than with SHIRT ( 83 + /- 27 min ) for both cooling systems ( p < 0.05 ) . Cooling rate was not different between MCC and PIC , but cooling rate while wearing TOTAL ( 362 + /- 52 W ) was greater than with SHIRT ( 281 + /- 48 W ) ( p < 0.05 ) . Average heat storage was lower with MCC ( 39 + /- 20 W x m(-2 ) ) than with PIC ( 50 + /- 17 W x m(-2 ) ) in both TOTAL and SHIRT ( p < 0.05 ) . Also , average heat storage while wearing TOTAL ( 34 + /- 19 W x m(-2 ) ) was less than with SHIRT ( 55 + /- 13 W x m(-2 ) ) for both cooling systems ( p < 0.05 ) . The Physiological Strain Index ( PSI ) was lower in MCC-TOTAL ( 2.4 ) than MCC-SHIRT ( 3.7 ) , PIC-SHIRT ( 3.8 ) , and PIC-TOTAL ( 3.3 ) after 45 min of heat exposure ( p < 0.05 ) . CONCLUSIONS Total body circulating liquid cooling was more effective than shirt-only cooling under the impermeable STEPO uniform , providing 
    Output:
    
When considering the literature available for cooling firefighters and hazardous material s technicians during emergency incident rehabilitation , widespread use of cooling devices does not appear to be warranted if ambient temperature and humidity approximate room temperature and protective garments can be removed .
In general , liquid-perfused suits appear to be superior to air-cooled garments , but both add weight to the firefighter , making current iterations less desirable .