Thermoregulatory changes induced during heat acclimatization by controlled hyperthermia in man

Hénane, R; Valatx, Jean–Louis

doi:10.1113/jphysiol.1973.sp010187

Cited by 66 publications

(45 citation statements)

References 11 publications

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“…Each woman was tested during four complete cycles with two sweating tests per cycle. The sweating tests were conducted in a temperaturehumidity controlled chamber, previously described (Henane & Valatx, 1973 procedure followed in the sweating tests comprised three phases ( Fig. 1): pre-heating period (neutral stage).…”

Section: Methodsmentioning

confidence: 99%

Comparison of thermal exchanges in men and women under neutral and hot conditions.

Bittel¹,

Hénane²

1975

The Journal of Physiology

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SUMMARY1. The thermoregulatory responses in unacclimatized men and women were analysed and compared by means of standard heat exposure tests which allowed evaporative losses, body temperatures, heat storage and the complete thermal balance to be continuously recorded in all subjects.2. The most pronounced differences were observed in delay before onset of sweating. Sweating always occurred faster with lower body temperatures in men than in women. The period immediately following ovulation was characterized by an increase in onset delay and a decrease in the sensitivity in sweating response compared with the pre-ovulation period.3. The evaporative rate in the steady state did not change significantly in the post-ovulation period and was found to be higher in men who consequently had lower mean skin temperatures. Skin conductances, different under thermo-neutral conditions, were the same in men and women under hot conditions. 4. Women showed a more definite increase of body temperatures and heat storage than men due to delayed sweating and decreased sweating sensitivity. The body heat content in the steady state increased more markedly in women than in men. Furthermore, the highest heat storage values were found during the post-ovulation period. A high degree of correlation was found between body heat content and absolute onset delay.5. The sweating kinetics and the transient phase just before the steady state of the thermal balance appeared to be decisive factors in the differentiation of the thermoregulatory behaviour in women before and after ovulation. Heat storage achieved during the transient phase and not made up by adequate evaporation seemed to be the cause of the large increase of body temperatures and heat content shown by women in hot environments.

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Section: Methodsmentioning

confidence: 99%

Comparison of thermal exchanges in men and women under neutral and hot conditions.

Bittel¹,

Hénane²

1975

The Journal of Physiology

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“…In the control experiment (C), the subjects remained in a sitting position for 2 h. Any loss of mass during these 2 h was replaced by water intake at the end of the period to maintain a euhydrated state. In the thermal dehydration experiment (D), the subjects were dehydrated for about 2 h by passive controlled hyperthermia in semi-recumbent posture (see Henane and Valatx 1973), until they had lost 2.8% of their M b (body mass). In the exercise dehydration experiment (E), the subjects, dressed in shorts, socks and sports shoes, exercised on a treadmill at 60% of VO 2max until M b had decreased by 2.8% in a mean duration of 2 h. The T db was 25±26°C with rh of 35%±45% and a wind speed that was modulated to maintain a rectal temperature of less than 39°C (see Melin et al 1994b).…”

Section: Experiments Protocolmentioning

confidence: 99%

Plasma volume changes during and after acute variations of body hydration level in humans

et al. 1999

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This study examined plasma volume changes (deltaPV) in humans during periods with or without changes in body hydration: exercise-induced dehydration, heat-induced dehydration and glycerol hyperhydration. Repeated measurements of plasma volume were made after two injections of Evans blue. Results were compared to deltaPV calculated from haematocrit (Hct) and blood haemoglobin concentration ([Hb]). Eight well-trained men completed four trials in randomized order: euhydration (control test C), 2.8% dehydration of body mass by passive controlled hyperthermia (D) and by treadmill exercise (60% of their maximal oxygen uptake, VO2max) (E), and hyperhydration (H) by glycerol ingestion. The Hct, [Hb], plasma protein concentrations and plasma osmolality were measured before, during and after the changes in body hydration. Different Hct and [Hb] reference values were obtained to allow for posture-induced variations between and during trials. The deltaPV values calculated after two Evans blue injections were in good agreement with deltaPV calculated from Hct and [Hb]. Compared to the control test, mean plasma volume declined markedly during heat-induced dehydration [-11.4 (SEM 1.7)%] and slightly during exercise-induced dehydration [-4.2 (SEM 0.9)%] (P < 0.001 compared to D), although hyperosmolality was similar in these two trials. Conversely, glycerol hyperhydration induced an increase in plasma volume [+7.5 (SEM 1.0)%]. These results would indicate that, for a given level of dehydration, plasma volume is dramatically decreased during and after heat exposure, while it is better maintained during and after exercise.

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“…The passive heating session was conducted in a climatic chamber so that the subjects might lose 2% of their initial body mass. This method was derived from the passive controlled hyperthermia technique described by Henane and Valatx (1973). The subjects were asked to lie down on a balance (TESTUT 9009, France) to measure the sweat loss (sensitivity 3 g).…”

Section: Experiments Protocolmentioning

confidence: 99%

Effects of different carbohydrate-electrolyte beverages on the appearance of ingested deuterium in body fluids during moderate exercise by humans in the heat

Koulmann

Melin

Jimenez

et al. 1997

European Journal of Applied Physiology

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To determine whether different forms of glucose (free and polymer) associated with sodium chloride influence the rate of water absorption during exercise in the heat, six men took part in five trials. Each trial included a passive heating session which resulted in a 2% loss of body mass, followed by 1h of treadmill exercise (at 50% of maximal oxygen uptake) in warm conditions (dry bulb temperature 35 degrees C, relative humidity 20%-30%). Immediately before exercise, the subjects were given either no fluid or a volume equal to 50% of the fluid previously lost (about 650 ml), chosen from among four D2O-labelled beverages: mineral water, a 6% glucose-electrolyte solution (GS), a 6% maltodextrin solution and a 6% maltodextrin-electrolyte solution. No significant differences were observed among these various beverages so far as temporal accumulation of deuterium in plasma, sweat and urine was concerned. During GS, the plasma volume was completely restored and the drifts of heart rate and rectal temperature were less marked than during other trials. These results would suggest that rehydration with GS was more efficient, probably because of an internal redistribution of water. The proportion of ingested water was twice as high in sweat as it was in urine. These findings may reflect the essential part played by circulatory adjustments in the transfer of plasma water into sweat and urine.

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Thermoregulatory changes induced during heat acclimatization by controlled hyperthermia in man

Cited by 66 publications

References 11 publications

Comparison of thermal exchanges in men and women under neutral and hot conditions.

Comparison of thermal exchanges in men and women under neutral and hot conditions.

Plasma volume changes during and after acute variations of body hydration level in humans

Effects of different carbohydrate-electrolyte beverages on the appearance of ingested deuterium in body fluids during moderate exercise by humans in the heat

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