Made available in DSpace on 2014-06-11T19:35:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-16Bitstream added on 2014-06-13T19:24:22Z : No. of bitstreams: 1 fernandes_la_dr_botfm.pdf: 1359001 bytes, checksum: a5448cd95987f70f2201ed53f0d8f36a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O obeso tem menor incidência de hipotermia intraoperatória em relação ao não obeso por apresentar limiar de vasoconstrição termorregulatória mais elevado. A combinação de métodos de aquecimento no intraoperatório parece ser melhor do que o uso isolado na prevenção de hipotermia. O objetivo da pesquisa foi avaliar se a combinação de permutador de calor e umidade (PCU) no circuito inspiratório com ar forçado aquecido ou aquecimento das soluções parenterais previne a ocorrência de hipotermia no período intraoperatório em obesas (OB) e não obesas (NOB) submetidas à anestesia venosa total. Quarenta pacientes submetidas à cirurgia abdominal ginecológica foram anestesiadas com propofol e remifentanil em infusão alvocontrolada. Todas as pacientes tinham um PCU acoplado no circuito inspiratório. As pacientes foram distribuídas aleatoriamente em 4 grupos de acordo com o índice de massa corporal (IMC) e com o manejo termal. Em 10 obesas (IMC de 30 a 34,9 kg.m-2) e 10 não obesas (IMC de 18,5 a 24,9 kg.m-2), utilizou-se ar forçado aquecido nos membros inferiores (WB). Dez obesas e 10 não obesas receberam aquecimento das soluções infundidas (HF). A temperatura central foi registrada nos momentos controle (0) e 15, 30, 60 90 e 120 minutos após instalação do circuito respiratório, e no final da cirurgia. Na Sala de Recuperação Pós-Anestésica (SRPA), a temperatura central das pacientes foi registrada durante o período de 1 hora. O IMC e a temperatura central foram correlacionados nos grupos que receberam o mesmo tratamento termal da hipotermia. O grupo OB/WB apresentou temperatura central intraoperatória mais alta em relação aos outros grupos (p<0,001). A proporção de pacientes normotérmicos no final da cirurgia e na admissão da SRPA foi mais alta em OB/WB do que nos outros grupos (p<0,05). Houve correlação positiva entre o IMC e a temperatura central no... / Obese individuals show less intraoperative (IOP) hypothermia than non-obese ones due to higher vasoconstriction threshold. A combination of warming methods may be better than an isolated one in preventing IOP hypothermia. Our aim was to evaluate whether the combination of a heat and moisture exchanger (HME) on inhaled gas with IOP forced air warming blanket (WB) or warming intravenous (IV) fluids (HF) prevents IOP hypothermia in obese (OB) and non-obese (NOB) women under intravenous anesthesia. Forty patients scheduled for gynecological abdominal surgery were anesthetized with propofol and remifentanil in a target controlled infusion. All patients had a HME on the inhaled gas. Patients were randomly distributed into 4 groups according to body mass index (BMI) and IOP thermal management. Ten OB grade I (BMI between 30 and 34.9 kg.m-2) and 10 NOB (BMI between 18.5 and 24.9 kg.m-2) had WB on the lower limbs. Ten OB and 10 NOB patients received IV HF. Core temperatures were recorded at baseline, after 15, 30, 60, 90, and 120 minutes of ventilatory system installation, and at the end of surgery. Core temperature was also followed for 60 minutes in the Post Anesthetic Care Unit (PACU). Core temperature and BMI were correlated in the groups with the same hypothermia treatment method. OB/WB group presented a higher IOP core temperature higher than the other groups (P<0.001). The proportion of normothermic patients at end of surgery and in PACU admission was higher in OB/WB than the other groups (P<0.05). There was a positive correlation between BMI and core temperature in the skin-surface warming groups (P<0.001). The combination of IOP skin-surface warming with HME on the inhaled gas in female obese patients, but not in non-obese ones, minimizes hypothermia. The combination of warming IV fluids and HME does not avoid IOP hypothermia in female obese or non-obese patients

Precooling, or a reduction in core temperature (Tc) has been demonstrated to be a potent enhancer of endurance running performance, however there is no known mechanism for this improvement. By holding the exercise workload constant, changes in variables such as running economy (RE), heart rate, and ventilation (VE) can be determined as a result of precooling. Improved running economy, or a reduced oxygen cost of a specific workload, is linked to improved exercise performance. Purpose: To determine the changes in flexibility, RE, heart rate, VE, and Tc during running at a constant workload following cool water immersion and to determine any sex-specific responses. Methods: Fourteen well-trained runners (8 males and 6 females) completed four treadmill runs at a sex-specific velocity (8.0 mph for females and 8.6 mph for males). The first two runs served as accommodation trials. The third and fourth runs were preceded by either cool water immersion (24.8oC) for 40 minutes or quiet sitting. Oxygen consumption, heart rate, Tc, VE, and flexibility were measured during both experimental trials. Results: Running economy did not change as a result of the precooling treatment, whereas Tc and heart rate were reduced by 0.4oC and 5 beats per minute, respectively. Minute ventilation was reduced in the female subjects only (1.4 liters/min). Sex differences were apparent in Tc, heart rate, VE, and flexibility response. Conclusion: While the precooling procedure was effective in reducing Tc and heart rate, RE did not change. Thus, improvements in RE cannot explain the dramatic enhancements of endurance running performance that often occur post-cooling. Differences between male and female subjects in response to precooling were identified, most notably in VE.

Priming exercise, or the ‘warm-up’, is an accepted practice prior to exercise participation, physical training or sporting competition. Traditionally, low intensity exercise has been used prior to both short- and long-duration events in an effort to prepare the athlete, but not fatigue them. Recently, however, a more scientific approach to priming exercise has been considered important, with some research suggesting that a high intensity intermittent priming strategy may be optimal. However, given the paucity of performance focussed ‘warm-up’ studies, and that existing data regarding high-intensity priming strategies is inconclusive, the aim of this thesis was to determine the effects of three high-intensity intermittent priming strategies on physiological responses and subsequent 3km laboratory time-trial (TT) performance. Ten well-conditioned endurance-trained male cyclists (mean ± SD: age, 28.3 ± 8.4 yr, body mass, 81.8 ± 11.6 kg, stature, 1.8 ± 0.1 m, O2peak, 4.6 ± 0.5 L•min−1) were recruited for this study. After an initial incremental exercise test to exhaustion, participants completed four 3km time trials (TT) on four separate occasions, each preceded by a different priming strategy. These included a ‘self-selected’ (control) condition, and three high-intensity intermittent priming strategies of varying intensity (100% and 150% of the power at O2peak, and all-out) and fixed duration (15 minutes), each in predetermined random order. Five minutes passive rest separated each priming exercise condition from the experimental 3km-TT. Oxygen uptake ( O2) and heart rate (HR) were measured continuously, while blood lactate concentration ([BLa]) and core temperature (TC) were recorded at rest, post-priming exercise, and immediately prior to and following the 3km-TT. In an attempt to provide a mechanistic explanation for changes in performance, O2 kinetic variables were determined from the O2 data. Performance was quantified as a mean power (Wmean) and total time taken to complete the 3km-TT. Mean power output and time taken for each 500m segment of the 3km-TT were also calculated. Results demonstrated that the athletes self-chosen priming condition (378.6 ± 44.0 W) resulted in Wmean that was slightly greater than both the lowest (376.3 ± 44.9 W; 0.7%; p = 0.57) and moderate (373.9 ± 47.8 W; 1.5%, p = 0.30) intensity intermittent priming condition, but significantly greater than the ‘all-out’ intermittent sprint priming condition (357.4 ± 44.5 W; 5.8%, p = 0.0033). Similar differences were observed for time. While differences existed in the O2 deficit (however, mainly non-significant), these differences did not provide clear explanations for the differences in performance, with the moderate priming condition displaying a significantly reduced O2 deficit (59.4 ± 15.6 L, p < 0.05), despite the non-significant change in Wmean, compared to the self-chosen priming condition (73.3 ± 18.6 L). Additionally no significant differences were observed in either the time constant or the mean response time of O2. Significant findings with regard to HR, [BLa] and TC were observed, but consistent with O2 kinetic variables, they were not related to, nor explain performance changes. In conclusion, regardless of intensity, different high-intensity intermittent priming exercise did not improve 3km-TT performance more than the control condition (self-chosen). A priming strategy that is overly intense was detrimental to subsequent cycling performance. The observed finding that a self-chosen priming strategy resulted in a comparable performance suggests that athletes are able to self-select (consciously or sub-consciously) a ‘warm-up’ that is of appropriate intensity/duration. Further work utilising the priming strategies from the current study with events of shorter duration is required to further clarify how priming strategies of this nature may affect track cycling performance.

Core body temperature is an important physiological parameter used to identify whether a patient displays a normal, hypothermic, or hyperthermic state. It is routinely monitored during cardiac surgeries and general anesthesia. Currently, the most effective methods for measuring core body temperature are also the most invasive. While select devices have been designed to enable surface recording of internal temperature, none have been implemented in U.S.-based hospitals. The objective of this study was to create a noninvasive core temperature sensor and evaluate its potential of becoming a widely used clinical tool. In tissue phantom and human-based experiments, the prototype performed effectively and posed no safety risk. Provided the prototype can be successfully translated into a more streamlined medical device, it stands to become a staple in operating rooms around the nation. / text

The cardiovascular effects of whole body heat stress during exercise are well established. However the independent contribution of elevated skin temperature (Tsk) or core temperature (Tc) on these responses remains unclear. The purpose of this study was to determine how increases in Tsk and Tc alone and in combination, impact cardiovascular responses during moderate intensity exercise. To accomplish this goal, eight healthy, recreationally active males were immersed to the neck in a cold (14 - 17°C) or hot (40 - 42.5°C) water bath for 20 to 25 min to alter Tc immediately prior to exercise with either cool Tsk (i.e. fans) or warm Tsk (i.e. heaters). Conditions during exercise were cool skin and cool core (CC), warm skin and cool core (WC), cool skin and warm core (CW), and warm skin and warm core (WW), and were conducted in a randomized crossover design. When data was combined (n=16), warm core conditions (CW and WW) were associated with significantly higher average heart rate (HR) and lower stroke volume (SV) during exercise compared to cool core conditions (CC and WC); 168.1 ± 3.2 vs. 152.2 ± 4.0 beats/min and 139.2 ± 7.3 vs. 147.7 ± 9.4 mL/beat, respectively. The approximate 9 mL/beat decline in SV and 16 beat/min increase in HR in warm core conditions tended to increase cardiac output (Q), 23.2 ± 0.6 vs. 22.2 ± 0.7 L/min, P=0.078. Similarly, warm Tsk conditions (WC and WW) were associated with significantly higher average HR and lower SV during exercise compared to cool Tsk conditions (CC and CW); 165.2 ± 3.3 vs. 155.1 ± 3.4 beats/min and 140.8 ± 7.8 vs. 146.0 ± 8.7 mL/beat, respectively. Additionally, there was also a trend for Q to be elevated with warm skin (23.0 ± 0.6 vs. 22.4 ± 0.6, P=0.075). Although combined data indicated that warm Tsk conditions significantly lowered average SV by ~6 mL/beat, there was no reduction in SV during exercise by warm Tsk, when Tes was cool (i.e. <37.0°C), as evidenced by identical values for SV in CC and WC, 147.7 ± 9.8 vs. 147.7 ± 9.0 mL/beat, respectively. In contrast, SV was significantly lower in WW compared with CW, 133.9 ± 7.0 vs. 144.4 ± 7.8 mL/beat, respectively. Therefore, the major reduction in SV by warm Tsk occurred during WW, when Tes was elevated (i.e. >38.0°C). Analyzing data independently for precooling and preheating conditions revealed that warm Tsk was associated with greater HR drift from 5 to 20 min of exercise, compared to cool Tsk, when esophageal temperature (Tes) was both cool or warm (23.9 ± 2.2 vs. 17.5 ± 2.3 and 12.3 ± 1.3 vs. 4.6 ± 1.7 beats/min, respectively). These observations demonstrate that both Tes and Tsk can directly influence cardiovascular responses during exercise, as indicated by elevations in HR during exercise with warm Tsk, with both warm and cool Tes. However SV is not compromised by warm Tsk if Tes is below 37.5°C. Furthermore, when both Tes and Tsk are elevated simultaneously, cardiovascular strain (i.e. increased HR and reduced SV) is much greater than when either is elevated alone. This is demonstrated by the finding that average HR was 175.8 ± 3.2 beats/min in WW, compared to 149.8 ± 4.0, 154.7 ± 4.1, and 160.3 ± 3.5 beats/min, in CC, WC, and CW, respectively, and the fact that SV was lowest during exercise in WW. In conclusion, individuals exercising in the heat should take measures to keep skin cool, especially when Tes is 39°C or greater to attenuate the cardiovascular strain that occurs with warm Tsk, when Tes is elevated. / text

Priming exercise, or the ‘warm-up’, is an accepted practice prior to exercise participation, physical training or sporting competition. Traditionally, low intensity exercise has been used prior to both short- and long-duration events in an effort to prepare the athlete, but not fatigue them. Recently, however, a more scientific approach to priming exercise has been considered important, with some research suggesting that a high intensity intermittent priming strategy may be optimal. However, given the paucity of performance focussed ‘warm-up’ studies, and that existing data regarding high-intensity priming strategies is inconclusive, the aim of this thesis was to determine the effects of three high-intensity intermittent priming strategies on physiological responses and subsequent 3km laboratory time-trial (TT) performance. Ten well-conditioned endurance-trained male cyclists (mean ± SD: age, 28.3 ± 8.4 yr, body mass, 81.8 ± 11.6 kg, stature, 1.8 ± 0.1 m, O2peak, 4.6 ± 0.5 L•min−1) were recruited for this study. After an initial incremental exercise test to exhaustion, participants completed four 3km time trials (TT) on four separate occasions, each preceded by a different priming strategy. These included a ‘self-selected’ (control) condition, and three high-intensity intermittent priming strategies of varying intensity (100% and 150% of the power at O2peak, and all-out) and fixed duration (15 minutes), each in predetermined random order. Five minutes passive rest separated each priming exercise condition from the experimental 3km-TT. Oxygen uptake ( O2) and heart rate (HR) were measured continuously, while blood lactate concentration ([BLa]) and core temperature (TC) were recorded at rest, post-priming exercise, and immediately prior to and following the 3km-TT. In an attempt to provide a mechanistic explanation for changes in performance, O2 kinetic variables were determined from the O2 data. Performance was quantified as a mean power (Wmean) and total time taken to complete the 3km-TT. Mean power output and time taken for each 500m segment of the 3km-TT were also calculated. Results demonstrated that the athletes self-chosen priming condition (378.6 ± 44.0 W) resulted in Wmean that was slightly greater than both the lowest (376.3 ± 44.9 W; 0.7%; p = 0.57) and moderate (373.9 ± 47.8 W; 1.5%, p = 0.30) intensity intermittent priming condition, but significantly greater than the ‘all-out’ intermittent sprint priming condition (357.4 ± 44.5 W; 5.8%, p = 0.0033). Similar differences were observed for time. While differences existed in the O2 deficit (however, mainly non-significant), these differences did not provide clear explanations for the differences in performance, with the moderate priming condition displaying a significantly reduced O2 deficit (59.4 ± 15.6 L, p < 0.05), despite the non-significant change in Wmean, compared to the self-chosen priming condition (73.3 ± 18.6 L). Additionally no significant differences were observed in either the time constant or the mean response time of O2. Significant findings with regard to HR, [BLa] and TC were observed, but consistent with O2 kinetic variables, they were not related to, nor explain performance changes. In conclusion, regardless of intensity, different high-intensity intermittent priming exercise did not improve 3km-TT performance more than the control condition (self-chosen). A priming strategy that is overly intense was detrimental to subsequent cycling performance. The observed finding that a self-chosen priming strategy resulted in a comparable performance suggests that athletes are able to self-select (consciously or sub-consciously) a ‘warm-up’ that is of appropriate intensity/duration. Further work utilising the priming strategies from the current study with events of shorter duration is required to further clarify how priming strategies of this nature may affect track cycling performance.

Resumo: O obeso tem menor incidência de hipotermia intraoperatória em relação ao não obeso por apresentar limiar de vasoconstrição termorregulatória mais elevado. A combinação de métodos de aquecimento no intraoperatório parece ser melhor do que o uso isolado na prevenção de hipotermia. O objetivo da pesquisa foi avaliar se a combinação de permutador de calor e umidade (PCU) no circuito inspiratório com ar forçado aquecido ou aquecimento das soluções parenterais previne a ocorrência de hipotermia no período intraoperatório em obesas (OB) e não obesas (NOB) submetidas à anestesia venosa total. Quarenta pacientes submetidas à cirurgia abdominal ginecológica foram anestesiadas com propofol e remifentanil em infusão alvocontrolada. Todas as pacientes tinham um PCU acoplado no circuito inspiratório. As pacientes foram distribuídas aleatoriamente em 4 grupos de acordo com o índice de massa corporal (IMC) e com o manejo termal. Em 10 obesas (IMC de 30 a 34,9 kg.m-2) e 10 não obesas (IMC de 18,5 a 24,9 kg.m-2), utilizou-se ar forçado aquecido nos membros inferiores (WB). Dez obesas e 10 não obesas receberam aquecimento das soluções infundidas (HF). A temperatura central foi registrada nos momentos controle (0) e 15, 30, 60 90 e 120 minutos após instalação do circuito respiratório, e no final da cirurgia. Na Sala de Recuperação Pós-Anestésica (SRPA), a temperatura central das pacientes foi registrada durante o período de 1 hora. O IMC e a temperatura central foram correlacionados nos grupos que receberam o mesmo tratamento termal da hipotermia. O grupo OB/WB apresentou temperatura central intraoperatória mais alta em relação aos outros grupos (p<0,001). A proporção de pacientes normotérmicos no final da cirurgia e na admissão da SRPA foi mais alta em OB/WB do que nos outros grupos (p<0,05). Houve correlação positiva entre o IMC e a temperatura central no ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Obese individuals show less intraoperative (IOP) hypothermia than non-obese ones due to higher vasoconstriction threshold. A combination of warming methods may be better than an isolated one in preventing IOP hypothermia. Our aim was to evaluate whether the combination of a heat and moisture exchanger (HME) on inhaled gas with IOP forced air warming blanket (WB) or warming intravenous (IV) fluids (HF) prevents IOP hypothermia in obese (OB) and non-obese (NOB) women under intravenous anesthesia. Forty patients scheduled for gynecological abdominal surgery were anesthetized with propofol and remifentanil in a target controlled infusion. All patients had a HME on the inhaled gas. Patients were randomly distributed into 4 groups according to body mass index (BMI) and IOP thermal management. Ten OB grade I (BMI between 30 and 34.9 kg.m-2) and 10 NOB (BMI between 18.5 and 24.9 kg.m-2) had WB on the lower limbs. Ten OB and 10 NOB patients received IV HF. Core temperatures were recorded at baseline, after 15, 30, 60, 90, and 120 minutes of ventilatory system installation, and at the end of surgery. Core temperature was also followed for 60 minutes in the Post Anesthetic Care Unit (PACU). Core temperature and BMI were correlated in the groups with the same hypothermia treatment method. OB/WB group presented a higher IOP core temperature higher than the other groups (P<0.001). The proportion of normothermic patients at end of surgery and in PACU admission was higher in OB/WB than the other groups (P<0.05). There was a positive correlation between BMI and core temperature in the skin-surface warming groups (P<0.001). The combination of IOP skin-surface warming with HME on the inhaled gas in female obese patients, but not in non-obese ones, minimizes hypothermia. The combination of warming IV fluids and HME does not avoid IOP hypothermia in female obese or non-obese patients / Orientador: José Reinaldo Cerqueira Braz / Coorientador: Leandro Gobbo Braz / Banca: Pedro Thadeu Galvão Vianna / Banca: Flora Margarida Barra Bisinotto / Banca: Jair de Castro Junior / Banca: João Abrão / Doutor

The independent influence of maximum oxygen consumption (VO2max) and running economy (RE) on thermoregulatory responses during treadmill exercise have not been isolated due to the complex interactions between VO2max, RE, body mass, body surface area (BSA), and metabolic heat production (Hprod). The purpose of the thesis is to determine whether large differences in VO2max and/or running economy independently alter thermoregulatory responses during running in a neutral environment. Seven aerobically unfit (LO-FIT: ~ 40 mlO2·kg-1·min-1) and sevn aerobically fit (HI-FIT: ~ 60 mlO2·kg-1·min-1) males, matched for body mass and BSA ran at 1) a fixed metabolic heat production of 640 W (FHP trial) and 2) 60%VO2max (REL trial). Also, seven high RE (HI-ECO: ~ 185 mlO2·kg-1·km-1) and seven low RE (LO-ECO: ~ 220 mlO2·kg-1·km-1) males, matched for body mass, BSA and VO2max (~ 60 mlO2·kg-1·min-1) ran at a 1) fixed Hprod of 640 W (FHP trial) and 2) fixed running speed of 10.5 km·h-1 (FRS trial). All trials were performed in a thermoneutral environment. The data was analyzed using a two-way mixed ANOVA, with the significance level set at an alpha of 0.05 for all comparisons. It was hypothesized that thermoregulatory responses (i.e., core temperature and sweating), during exercise will not be independently altered by VO2max, but will be altered by any differences in heat production and running economy. The FHP trial resulted in similar changes in esophageal temperature (∆Tes), changes in rectal temperature (∆Tre), and WBSL between the HI-FIT and LO-FIT groups, despite vastly different %VO2max. Whereas the REL trial resulted in greater ΔTeso, ΔTre, and WBSL in the HI-FIT group, in parallel with their greater Hprod. In groups greatly differing in RE, the FHP trial elicited similar ∆Tes, ∆Tre, and WBSL; however the HI-ECO group had to run faster to achieve the same heat production as their LO-ECO counterparts. Moreover, a FRS of 10.5 kmh-1 produced a greater Hprod, ∆Tes, ∆Tre, and WBSL in the LO-ECO group. In conclusion, thermoregulatory responses are determined by Hprod and RE, not VO2max, when differences in mass and BSA are eliminated between groups. Thus, these findings support the initially stated hypotheses.

Capacity to perform prolonged exercise is reduced in high ambient temperatures, but this premature fatigue is not adequately explained by peripheral mechanisms. The aim of this thesis was to examine some possible underlying mechanisms of central fatigue operating during prolonged exercise in a warm environment. The first series of experiments investigated the effect of nutritional manipulation of central serotonergic activity through alterations to the plasma concentration ratio of free-tryptophan to branched-chain amino acids (f-TRP:BCAA). In contrast to previous reports, acute BCAA supplementation failed to alter perceived exertion and delay the onset of fatigue (Chapter 3). This response was similar when exercise was preceded by an exercise and diet regimen designed to reduce glycogen availability (Chapter 4). The ingestion of meals containing added carbohydrate and fat did not alter f-TRP:BCAA at rest (Chapter 5). Acute dopaminergic / noradrenergic reuptake inhibition with bupropion increased exercise perfonnance by 9 % in warm conditions (30C), but this effect was not apparent at 18C (Chapter 6). This response was accompanied by attainment of a higher core temperature and heart rate towards the end of the bupropion trial in the heat despite no detectable difference in perceived exertion and thermal stress. These data suggested that maintenance of catecholaminergic activity may dampen inhibitory signals from the CNS due to the attainment of a high core temperature, allowing power output to be maintained. The blood-brain barrier (BBB) regulates the exchange of substances between the cerebral interstitial fluid and the blood to maintain a stable environment for the CNS. If the BBB is compromised this may adversely influence nonnal brain function. Serum S1OOb, a proposed peripheral marker of BBB penneability, was increased following exercise in a warm environment (Chapter 7). These data indicate that exposure to combined exercise and heat stress may result in a loss of BBB integrity.

This thesis examined why NCAA Division 1 American football “linemen” experience greater heat strain than “backs” during summer training camps. In study #1, exercise at a heat production of 350 W/m2 in a hot environment (Tdb:32.4±1.0ºC; Twb:26.3±0.6ºC) resulted in greater local sweating on the upper body (head, arm, shoulder and chest; all <0.05) and a greater core temperature (P=0.033) in linemen despite a ~25% lower heat production per unit mass (L:6.0±0.5 W/kg; B:8.2±0.8 W/kg). In study #2, greater convective and evaporative heat transfer coefficients (P<0.05) were found in backs during live summer training camp drills, but these did not lead to a greater dry heat transfer or evaporative capacity. However, the maximum metabolic rate per unit mass was lower in linemen due to differences surface area-to-mass ratio. In conclusion, the greater heat strain previously reported in linemen likely arises, in part, from differences in sweating efficiency and body morphology.