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.

Made available in DSpace on 2014-12-17T14:13:24Z (GMT). No. of bitstreams: 1 CarlosAAA.pdf: 153996 bytes, checksum: 5df16895ded0d4a8843735806657602d (MD5) Previous issue date: 2008-09-29 / Hyperhidrosis is an idiopathic condition characterized by excessive sweating. Symptoms generally begin in childhood or early adolescence, and rarely improve with age. The excessive localized sweating generally occurs either spontaneously, or in association with stressful or emotionally charged situations. This prospective study aimed to investigate predictive factors for compensatory hyperhidrosis after thoracoscopic sympathicotomy. From 2000 to 2002, 80 patients (53 female and 27 male) underwent hyperhidrosis surgery. The patients, ranging from 12 to 56 years old, were studied and followed-up for 42.51 ?5.98 months. A satisfaction grading using a visual analogue scale -VAS (0 = not at all satisfied, and 10 = fully satisfied) was used. The surgical procedure was performed bilaterally on the second ganglion (T2) for facial hyperhidrosis, on the third and fourth ganglia (T3 and T4) for axillary hyperhidrosis, and on the third ganglion (T3) for palmar hyperhidrosis. The results showed that, 68 patients (85%) presented with compensatory sweating (CS), which was classified as mild (33.8%), moderate (33.8%) and severe (32.4%). Considering the final surgical results, 70 patients (87.5%) were satisfied with the outcome of the operation, while 10 patients (12.5%) were dissatisfied. Degrees of satisfaction varied according to sex, age, BMI and extent of denervation. Moreover, the compensatory hyperhidrosis was more severe in abdomen and back than in legs. In conclusion, although CS is a frequent adverse effect of sympathicotomy, the degree of patient satisfaction was high. Some factors were related to the occurrence and severity of CS and the most adequate patients to be submitted to this operation are young adult women whose BMI is less than 24.9 / A hiperidrose prim?ria localizada ? um dist?rbio que atinge em algumas regi?es at? 4,6% da popula??o. Caracteriza-se por uma transpira??o em excesso, que vai al?m da necessidade de perda de calor corporal. Manifesta-se mais frequentemente nas m?os, face, axilas e p?s. Identifica de forma negativa o paciente no seu ?mbito familiar, profissional e psicol?gico, levando a uma queda na sua qualidade de vida. As pessoas acometidas limitam seu tempo despendido no ambiente do trabalho, em atividades sociais e recreativas, decorrente ao constrangimento. Muitas delas passam a ser reclusas e a ter problemas de conv?vio social, que pode culminar em fobia social. A simpatectomia tor?cica ? uma forma eficaz no tratamento da hiperidrose localizada. O trabalho visou investigar fatores preditivos para a hiperidrose compensat?ria ap?s a simpaticotomia tor?cica videoendosc?pica. Quanto ? metodologia, entre os anos de 2000 e 2002, 80 pacientes (53 mulheres e 27 homens) foram operados de hiperidrose e acompanhados durante 42,51 ? 5,98 meses, com idade variando de 12 a 56 anos. A satisfa??o destes pacientes quanto aos resultados do procedimento foi aferida por meio de uma escala de avalia??o. O procedimento foi executado bilateralmente no g?nglio T2 para a hiperidrose facial, nos g?nglios T3 e T4 para a hiperidrose axilar, e no g?nglio T3 para a hiperidrose palmar. De acordo com os dados obtidos, 68 pacientes (85%) apresentaram hiperidrose compensat?ria, que foi classificada como leve (33,85), moderada (33,8) e severa (32,4%). Quanto aos resultados da cirurgia, na avalia??o dos pacientes, 70 deles (87,5%) se consideraram satisfeitos, enquanto 10 pacientes (12,5%) disseram estar insatisfeitos. O grau de satisfa??o variou de acordo com o sexo, a idade, o IMC e a extens?o da opera??o. A hiperidrose compensat?ria foi mais intensa no abdome e dorso, comparando-se com as pernas. Em conclus?o, embora a hiperidrose compensat?ria seja um efeito adverso freq?ente ap?s a simpaticotomia, o grau de satisfa??o dos pacientes foi elevado. Alguns fatores foram relacionados ? ocorr?ncia e ? severidade deste problema. Pacientes mais adequados para essa opera??o devem ser mulheres adultas jovens com IMC inferior a 24,9. O car?ter multidisciplinar desse estudo fica atestado pela intera??o de profissionais de ?reas diversas como a epidemiologia, cirurgia geral, cirurgia experimental e cirurgia tor?cica

These studies determined the effects of sodium chloride supplementation on serum and sweat sodium concentration, cardiovascular function, and physical and cognitive performance. Sweat sodium losses, alone, caused a significant decline in serum sodium concentration (-6.4±1.6 mEq/L, p=0.001) during 3h cycling in the heat in endurance-trained athletes with high sweat sodium losses. However, sodium chloride supplementation matching sweat sodium losses (NA; 5.9±1.5g NaCl/h) maintained serum sodium concentration. Post-exercise maximal cycling power declined and was significantly lower than pre-exercise in placebo (PL; p=0.012), but power was not significantly different in NA (p=0.057). Pre- to post-exercise response time during a Stroop Test improved in NA (p=0.009), while there was no change in PL (p=0.597). Post-exercise postural sway was less in NA vs. PL (p=0.044). Three days of sodium chloride supplementation (~15 g NaCl/d) resulted in a significant increase in plasma volume in healthy untrained males at rest (5.9±7.6 %) and during exercise at 60%VO₂peak (8.6±5.2 %) compared to PL. During NA, stroke volume was 10% higher during exercise vs. PL (139±27 vs. 126±24 ml/beat, respectively, p=0.004). Cardiac output was 8% higher in NA during exercise vs. PL (21.0±3.1 vs. 19.4±2.6 L/min, respectively, p=0.013). Mean arterial pressure during exercise was not different in NA vs. PL (p=0.548) as total peripheral resistance decreased (p=0.027) with the increased cardiac output. Sweat sodium concentration was 9% higher in NA vs. PL during exercise in the heat (70.4±19.5 vs. 64.5±21.7 mEq/L, p=0.044). In summary, serum sodium concentration declines when high sweat sodium losses are not replaced while hydration status is maintained. Acute sodium chloride supplementation during exercise which matches sodium losses maintains serum sodium concentration. This maintenance of serum sodium concentration results in both physical and cognitive benefits compared to when serum sodium concentration declines. Chronic intake of sodium chloride for 3 days increases plasma volume in healthy untrained men and improves cardiovascular function, as both stroke volume and cardiac output are increased, while oxygen consumption and blood pressure are unchanged. Therefore, acute and chronic sodium supplementation positively alters fluid and sodium balance which results in beneficial effects on physical and cognitive performance and cardiovascular function during exercise. / text

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.

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.

Our aim was to understand mechanisms responsible for excessive electrolyte loss in the sweat gland and the potential impact on fluid balance during exercise in heat stress conditions. Human physiological testing under exercise/heat stress and immunofluorescence staining of sweat glands from skin biopsies were compared between healthy individuals (with normal and high sweat sodium chloride concentration, [NaCl]) and with cystic fibrosis patients (CF), who exhibit excessively salty sweat due to a defect of Cl- channel cystic fibrosis transmembrane conductance regulator (CFTR). Three novel findings are presented. First, excessively salty sweat may be associated with reduced expression of CFTR in the sweat gland reabsorptive duct of healthy individuals in addition to in those with CF; however, although a link to a CF gene mutation in healthy individuals with high sweat [NaCl] was not demonstrated, the possibility of an undetected CFTR mutation or polymorphism remains to be investigated as an underlying mechanism. Two, CF and healthy individuals with excessively salty sweat respond to moderate dehydration (3% body weight loss during exercise) with an attenuated rise in serum osmolality, greater relative loss in plasma volume, but similar perceived thirst compared to healthy individuals with "normal" sweat [NaCl]. However, individuals with CF respond to rehydration with hypotonic beverage by drinking less ad libitum in response to reduced serum [NaCl], suggesting that thirst-guided fluid replacement may be more appropriate for this population rather than restoring 100% of sweat loss following dehydration as is often recommended in healthy individuals.

Studies show that vasomotor and sudomotor activity is compromised in individuals with Type 1 Diabetes (T1DM) which could lead to altered thermoregulatory function. However, recent work suggests that the impairments may only be evidenced beyond a certain level of heat stress. We therefore examined T1DM-related differences in heat loss responses of sweating and skin blood flow (SkBF) during exercise performed at progressive increases in the requirement for heat loss. Participants were matched for age, sex, body surface area and fitness cycled at fixed rates of metabolic heat production of 200, 250, and 300 W•m-2 of body surface area, each rate being performed sequentially for 30 min. Local sweat rate (LSR), sweat gland activation (SGA), and sweat gland output (SGO) were measured on the upper back, chest and forearm while SkBF (laser-Doppler) was measured on the forearm and upper back only. We found that despite a similar requirement for heat loss, LSR was lower in T1DM on the chest and forearm only, relative to Control and only different at the end of the second and third exercise periods. Differences in chest LSR were due to reduced SGA whereas the decreased forearm LSR was the result of a decrease in SGO. SkBF did not differ between groups. The reduction in the sweating response in the T1DM group was paralleled by a greater increase in core temperature. We show that T1DM impairs heat dissipation as evidenced by reductions in LSR and not SkBF. A compromised thermoregulatory response during and following physical exertion is of considerable concern due to the associated increased risk of post-exertion heat-related injury.

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.

Four studies were performed to evaluate the independent influence of core temperature and heat acclimation on sweating responses when exercise is fixed for a given evaporative heat balance requirement (Ereq) during compensable and uncompensable heat stress. By using circadian rhythm to modulate absolute core temperature, study 1 investigated whether absolute core temperature altered the steady-state sweat rate during compensable heat stress at a fixed Ereq. Study 2 compared the influence of partial and complete heat acclimation on core temperature and sweating responses between a compensable and uncompensable heat stress condition. Study 3 quantified how maximum skin wettedness is altered with partial or complete heat acclimation. Study 4 determined whether aerobic fitness (i.e. maximum rate of oxygen consumption; VO2max) per se independently alters the sweating and core temperature responses to uncompensable heat stress or if the frequent bouts of exercise-induced heat stress that accompany aerobic training are required to augment thermoregulatory capacity. Study 1 demonstrated that when absolute core temperature is different between AM and PM by ~0.2°C, steady-state sweat rates were the same for a fixed Ereq. Only when a different level of Ereq was attained, were differences in steady-state sweating observed. Moreover, steady-state sweat rates were similar despite differences in skin and core temperature when exercise intensity was matched to elicit a fixed Ereq in two different ambient temperatures (23°C and 33°C). In study 2, neither partial nor complete heat acclimation altered the core temperature response to compensable heat stress despite a marginally greater sweat rate compared to an unacclimated state. However, the sudomotor adaptations associated with heat acclimation were evident during uncompensable heat stress and mitigated the rise in core temperature during 60 minutes of exercise compared to an unacclimated state. Study 3 determined that the biophysical parameter that defines the upper limit for evaporative heat loss, that is the maximum skin wettedness achievable, increased following partial (0.84±0.08) and complete heat acclimation (0.95±0.05) compared to unacclimated (0.72±0.06) which directly explains the reduced change in core temperature reported in study 2 during uncompensable heat stress. Lastly, study 4 demonstrated that VO2max per se does not alter the sudomotor responses to uncompensable heat stress. Rather, it is the repetitive exercise-induced heat stress experienced during aerobic training that induces a partial heat acclimation thereby mitigating the rise in core temperature during uncompensable heat stress. Taken together, when exercise is prescribed in a compensable environment, the steady-state sweat rate observed will be primarily determined by Ereq independent of absolute core temperature, while heat acclimation will slightly increase the sweat rate despite providing no additional reduction in the change in core temperature. However, progressive heat acclimation increases the upper limit of compensability via a greater maximum skin wettedness thereby mitigating the rise in core temperature during uncompensable heat stress.

Estratégias de aclimatização ao calor e recomendações de segurança à saúde para crianças e jovens que se exercitam no calor são enfatizadas na literatura, devido principalmente à limitação da perda de calor pela sudorese, em comparação aos adultos; e acredita-se que, nos meninos obesos, essa resposta possa ser mais prejudicada. Aspectos relacionados à termorregulação e à sudorese, além de recomendações para a prática prolongada de exercícios no calor, em crianças e jovens, incluindo obesos, foram revisados na literatura; e um estudo experimental foi realizado. Objetivo: Comparar a temperatura retal (Tretal), a sudorese e a sensação subjetiva de calor (SSC) entre meninos púberes obesos e não-obesos que pedalam em uma similar intensidade relativa de esforço e na mesma condição ambiental. Métodos: No estudo experimental, meninos púberes fisicamente ativos foram alocados em dois grupos (obesos, n = 17; e não-obesos, n = 16). Ambos pedalaram dentro de uma câmara ambiental (35°C, 40-45% UR) por 30 min, a 50-60% do VO2pico; e, após 10 min de repouso, pedalaram até a exaustão (90% do VO2pico). A Tretal, a frequência cardíaca (FC), a sudorese, a taxa de percepção de esforço (TPE) e a SSC foram avaliadas durante os 30 min de pedalada; e a Tretal e a FC, durante a pedalada mais intensa. Resultados: O aumento da Tretal e da FC, assim como as respostas da sudorese foram similares entre os grupos, durante os 30 min de pedalada. A TPE foi maior nos obesos dos 25 aos 30 min de pedalada; e a SSC, durante os 30 min de pedalada. Obesos pedalaram intensamente (90% do VO2pico) por menos tempo que os não-obesos, e a ΔTretal foi maior nos não-obesos. Conclusão: A prescrição do exercício nas condições do protocolo seguido no presente estudo pode ser fisiologicamente segura para meninos púberes obesos fisicamente ativos e aclimatizados ao calor; mas não generalizadas a meninos obesos sedentários e/ou não-aclimatizados ao calor. O maior desconforto térmico dos meninos obesos ressalta a importância das mensurações subjetivas no auxílio à escolha da modalidade de exercício mais adequada para os meses do verão, o que pode prevenir riscos de doenças relacionadas ao calor. / Strategies of acclimatization to the heat and health safety recommendations for children and adolescents exercising in the heat are emphasized in the literature, particularly due to the limitation of heat loss through sweating as compared to adults; moreover, it is thought that this response may be impaired in obese children. Aspects relevant to thermoregulation and sweating, as well as recommendations for the prolonged practice of exercises in the heat by children and adolescents, including obese ones, were reviewed in the literature, and an experimental trial was performed. Aim: To compare the rectal temperature (Trect), sweat rate, and subjective sensation of heat (SSH) between obese and non-obese pubertal boys who cycled at a similar relative effort intensity and in the same environmental conditions. Methods: In the experimental trial, physically active pubertal boys were placed in two groups (obese, n = 17; and non-obese, n = 16). Both cycled inside an environmental chamber (35°C, 40-45% RH) for 30 min. at 50-60% VO2peak, rested for 10 min., and then cycled to exhaustion (90% VO2peak). Trect, heart rate (HR), sweat rate, rate of perceived exertion (RPE) and subjective sensation of heat (SSH) were assessed during the 30 min. of cycling; and Trect and HR during the most intense cycling. Results: The increase in Trect and HR as well as the sweating responses were similar between the groups during the 30-minute cycling. The RPE was greater in the obese at 25-30 minutes of cycling; and the SSH throughout the 30 minutes. The obese cycled intensely (90% VO2peak) for shorter than the non-obese, and Trect was greater in the non-obese. Conclusion: The prescription of exercise in the protocol conditions used in the present study may be physiologically safe for physically active, heat acclimated obese pubertal boys, but it cannot be generalized to obese boys who are sedentary and/or non-acclimated to the heat. The greatest thermal discomfort of obese boys highlights the importance of including subjective assessments in selecting the most suitable exercise modality for the summer months, which may avoid risks and prevent heat-related disorders.