Effects of modafinil on heat thermoregulatory responses in humans at rest

2002 ◽  
Vol 80 (8) ◽  
pp. 796-803 ◽  
Author(s):  
Jean-Claude Launay ◽  
Yves Besnard ◽  
Angélique Guinet ◽  
Germain Bessard ◽  
Christian Raphel ◽  
...  
Keyword(s):  
Heat Storage ◽  
Sweat Rate ◽  
Heat Exposure ◽  
Body Temperatures ◽  
Metabolic Heat ◽  
Thermoregulatory Responses ◽  
The Central Nervous System ◽  
Male Subjects ◽  
Skin Temperatures ◽  
Body Heat

The effects of modafinil on heat thermoregulatory responses were studied in 10 male subjects submitted to a sweating test after taking 200 mg of modafinil or placebo. Sweating tests were performed in a hot climatic chamber (45°C, relative humidity <15%, wind speed = 0.8 m·s–1, duration 1.5 h). Body temperatures (rectal (Tre) and 10 skin temperatures (Tsk)), sweat rate, and metabolic heat production (Mdot) were studied as well as heart rate (HR). Results showed that modafinil induced at the end of the sweating test higher body temperatures increases (0.50 ± 0.04 versus 0.24 ± 0.05°C (P < 0.01) for deltaTre and 3.64 ± 0.16 versus 3.32 ± 0.16°C (P < 0.05) for deltaTbarsk (mean skin temperature)) and a decrease in sweating rate throughout the heat exposure (P < 0.05) without change in Mdot, leading to a higher body heat storage (P < 0.05). DeltaHR was also increased, especially at the end of the sweating test (17.95 ± 1.49 versus 12.52 ± 1.24 beats/min (P < 0.01)). In conclusion, modafinil induced a slight hyperthermic effect during passive dry heat exposure related to a lower sweat rate, probably by its action on the central nervous system, and this could impair heat tolerance. Key words: modafinil, heat, human, thermoregulation.

Influence of Respiratory Heat Transfer on Thermogenesis and Heat Storage after Cold Immersion

1982 ◽  
Vol 63 (2) ◽  
pp. 127-135 ◽  
Author(s):  
J. B. Morrison ◽  
M. L. Conn ◽  
P. A. Hayes
Keyword(s):  
Heat Production ◽  
Heat Input ◽  
Heat Storage ◽  
Metabolic Heat Production ◽  
Central Temperature ◽  
The Core ◽  
Metabolic Heat ◽  
Male Subjects ◽  
Skin Temperatures ◽  
Cold Immersion

1. Ten male subjects were cooled on three occasions to a rectal temperature of 35°C by immersion to the neck in water at 11·3°C. The subjects were rewarmed for 60 min, once by metabolic heat production alone (shivering), once by inhalation rewarming with spontaneous breathing of saturated air at 47°C (control) and once by inhalation rewarming with ventilation regulated at 40 litres/min by respiring a controlled fraction of CO2 (hyperventilation). 2. Metabolic heat production was substantially reduced by inhalation rewarming (P < 0·05), from 913 kJ when shivering to 766 kJ (control) and 613 kJ when hyperventilating. The fall in metabolic heat production was greater than the corresponding respiratory heat gain, which increased from a loss of 41 kJ when shivering to gains of 85 kJ (control) and 169 kJ (hyperventilation). 3. As differences in mean skin temperatures were small (<1·0°C), it is concluded that the lower metabolic heat production in response to increased respiratory heat input must result from more rapid central temperature gains. This conclusion is supported by the relative values of rectal and tympanic temperatures. It was calculated that the percentage of the total heat supply which was donated to the core increased from 13% during shivering to 16% for the control and 23% in hyperventilation. Results imply that respiratory heat input is more efficient than metabolic heat production in elevating central temperature.

Effect of vapor pressure on physiologic strain and body heat storage

1963 ◽  
Vol 18 (4) ◽  
pp. 808-811 ◽  
Author(s):  
John F. Hall
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Vapor Pressure ◽  
Heat Storage ◽  
Sweat Rate ◽  
Human Subjects ◽  
Vapor Pressures ◽  
Physiologic Responses ◽  
Male Subjects ◽  
Body Heat

Physiologic strain, in terms of body heat storage, and other physiologic responses were measured and compared in two series of heat stress experiments performed on human subjects exposed to different ambient vapor pressures. One group of 75 experiments conducted on 5 healthy nonacclimatized male subjects exposed 5 times each to 38, 54, and 71 C at 10 mm Hg vapor pressure was compared with a series of 81 experiments performed on 10 similar subjects exposed 1–6 times each to 38, 41, and 54 C at 20 mm Hg vapor pressure. Subjects were sitting and wore 1.0 clo insulation. The data show relation between body heat storage and a) the modified Craig index of physiologic strain; b) over-all sweat rate; c) evaporative rate; d) sweat-evaporative ratio; e) mean skin and rectal temperatures; and f) change of heart rate at the respective vapor pressure levels. Statistically significant correlation between sweat-evaporative ratio and over-all sweat rate with body heat storage is shown. Use of the over-all sweat response as a physiologic strain index is suggested. Submitted on August 14, 1962

Human skin wettedness and evaporative efficiency of sweating

1979 ◽  
Vol 46 (3) ◽  
pp. 522-528 ◽  
Author(s):  
V. Candas ◽  
J. P. Libert ◽  
J. J. Vogt
Keyword(s):  
Sweat Rate ◽  
The Body ◽  
Body Temperatures ◽  
Skin Wettedness ◽  
Evaporative Heat Transfer ◽  
Evaporative Heat Transfer Coefficient ◽  
The Relationship ◽  
Male Subjects ◽  
Skin Temperatures ◽  
Different Levels

Rates of evaporation and sweating were recorded for three acclimatized male subjects in hot humid conditions, the ambient parameters of which were set so that the various imposed evaporative rates required the same skin wettedness at different levels of sweating. Rectal and skin temperatures were measured. Results showed that during steady state occurring during the 2nd h of exposure each subject reached the required evaporative rate by means of increases in skin wettedness regardless of the level of sweating; the sweat evaporative efficiency, defined as the ratio between evaporative rate and sweat rate, decreased as skin wettedness increased, in a range between 0.74 and 1.0 Sweat efficiency fell to 0.67 for fully wet skin. The body temperatures did not increase with time if skin wettedness was less than unity. Evaporative heat transfer coefficient (he), maximum evaporative capacity, and wettedness were estimated on the basis of the observed decrease of sweat efficiency. The relationship between skin wettedness and sweat efficiency was interpreted as a combined effect of differences in local he as well as in local sweat rates.

Physiological index of strain and body heat storage in hyperthermia

1960 ◽  
Vol 15 (6) ◽  
pp. 1027-1030 ◽  
Author(s):  
John F. Hall ◽  
J. W. Polte
Keyword(s):  
Heat Storage ◽  
Sweat Rate ◽  
Individual Variability ◽  
Physiological Strain ◽  
Strain Index ◽  
Stress Levels ◽  
Group Variation ◽  
The Relationship ◽  
Male Subjects ◽  
Body Heat

Individual variability of a modified Craig index of physiological strain and body heat storage was determined, and the relationship between these parameters defined for five healthy, nonacclimatized male subjects exposed five times to each of three heat stress levels: 38°C, 54°C and 71°C at a vapor pressure of 10 mm Hg. This index contains the variables of heart rate, sweat rate and rate of rectal temperature change, measured by EKG, nude pre- and post-experimental weighings, and a rectal thermistor, respectively. Body heat storage was calculated from initial and terminal weighted mean skin and rectal temperatures. Subjects were sitting and wore 1 clo of body insulation. Individual and group variation for strain index and body heat storage was determined. The data show a linear relationship between these expressions over the thermal stress range investigated although individual variability was considerable at the higher stress levels. A statistically significant correlation between strain index and body heat storage is shown. Submitted on May 16, 1960

scholarly journals Type 2 diabetes does not exacerbate body heat storage in older adults during brief, extreme passive heat exposure

Temperature ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 263-269 ◽  
Author(s):  
Martin P. Poirier ◽  
Sean R. Notley ◽  
Pierre Boulay ◽  
Ronald J. Sigal ◽  
Brian J. Friesen ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Older Adults ◽  
Heat Storage ◽  
Heat Exposure ◽  
Body Heat

Metabolic, thermoregulatory, and perceptual responses during exercise after lower vs. whole body precooling

2003 ◽  
Vol 94 (3) ◽  
pp. 1039-1044 ◽  
Author(s):  
Andrea T. White ◽  
Scott L. Davis ◽  
Thad E. Wilson
Keyword(s):  
Heat Storage ◽  
Thermal Sensation ◽  
Submaximal Exercise ◽  
Whole Body ◽  
Lower Body ◽  
Mean Body Temperature ◽  
Thermal Discomfort ◽  
Healthy Men ◽  
Metabolic Heat ◽  
Body Heat

The purpose of this investigation was to compare the thermoregulatory, metabolic, and perceptual effects of lower body (LBI) and whole body (WBI) immersion precooling techniques during submaximal exercise. Eleven healthy men completed two 30-min cycling bouts at 60% of maximal O2uptake preceded by immersion to the suprailiac crest (LBI) or clavicle (WBI) in 20°C water. WBI produced significantly lower rectal temperature (Tre) during minutes 24–30 of immersion and lower Tre, mean skin temperature, and mean body temperature for the first 24, 14, and 16 min of exercise, respectively. Body heat storage rates differed significantly for LBI and WBI during immersion and exercise, although no net differences were observed between conditions. For WBI, metabolic heat production and heart rate were significantly higher during immersion but not during exercise. Thermal sensation was significantly lower (felt colder) and thermal discomfort was significantly higher (less comfortable) for WBI during immersion and exercise. In conclusion, WBI and LBI attenuated Tre increases during submaximal exercise and produced similar net heat storage over the protocol. LBI minimized metabolic increases and negative perceptual effects associated with WBI.

Changing physiological relationships in men under acute cold stress

1970 ◽  
Vol 48 (1) ◽  
pp. 1-10 ◽  
Author(s):  
James F. O'Hanlon Jr. ◽  
Steven M. Horvath
Keyword(s):  
Rectal Temperature ◽  
Heat Production ◽  
Cold Exposure ◽  
Heat Content ◽  
Body Temperatures ◽  
Older Subjects ◽  
Skin Temperatures ◽  
Different Levels ◽  
Body Heat ◽  
Thigh Temperature

Thirty-four men were exposed to 8 °C for 2 h. Their reactions were studied to indicate how physiological relationships change during exposure to cold. Measurements of various body temperatures, MST, MBT, body heat content (BHC), [Formula: see text], heat production, and heart rate (HR) were made before the onset of and periodically during cold exposure. Various skin temperatures fell to different levels while rectal temperature rose slightly, then fell 0.3 °C by the end of the exposure. BHC declined by 6%, [Formula: see text] nearly doubled, [Formula: see text] and heat production increased by 66 and 75% respectively, and HR changed little during cold exposure. Relationships which changed most significantly during cold exposure were those between MST and rectal temperature, certain skin temperatures and rectal temperature, [Formula: see text] (also heat production) and BHC, [Formula: see text] and rectal temperature, and finally, those between every body temperature and the age of the subjects. Relationships which also changed were those between finger and toe temperature as well as those between [Formula: see text] (also heat production) and each of the following: [Formula: see text], rectal temperature, thigh temperature, HR, and age. These results indicated that (1) temperature in the upper extremities was actively maintained at a higher level than temperature in the lower extremities, (2) increased metabolism became a progressively more effective adaptation than redistribution of blood volume, (3) subjects with the lowest BHC tended to increase their metabolism the most, (4) [Formula: see text] was inversely related to core temperature after the latter fell below normal, (5) HR was unrelated to the increase in [Formula: see text], (6) the usual inverse relationship between age and metabolism was not found in the cold, and finally, (7) older subjects generally tended to maintain higher body temperatures than younger subjects.

Effects of oxygen inhalation on responses to cold exposure

1961 ◽  
Vol 16 (4) ◽  
pp. 627-632 ◽  
Author(s):  
D. M. Maccanon ◽  
D. D. Eitzman
Keyword(s):  
Cold Exposure ◽  
Ventilatory Response ◽  
Carbon Dioxide Production ◽  
Metabolic Responses ◽  
Body Temperatures ◽  
Healthy Male ◽  
Metabolic Heat ◽  
Oxygen Breathing ◽  
Oxygen Inhalation ◽  
Male Subjects

The effects of oxygen inhalation on shivering and thermal and metabolic responses to exposure to cold (10 C) were determined in ten healthy male subjects. The results showed that oxygen breathing reduced shivering and promoted a feeling of greater comfort. The ventilatory response to cold was diminished, and oxygen consumption was significantly lower during the later periods of the cold exposure. Carbon dioxide production was reduced and the mobilization of nitrogen during the initial periods of cold exposure was also noted. Since body temperatures and their rates of fall were not significantly altered by oxygen inhalation, a shift to more efficient metabolic heat production seems indicated. Submitted on February 6, 1961

scholarly journals Autonomic thermoregulatory dysfunction in neurofibromatosis type 1

2016 ◽  
Vol 74 (10) ◽  
pp. 796-802 ◽  
Author(s):  
Luciana G Madeira ◽  
Renata LF Passos ◽  
Juliana F de Souza ◽  
Nilton A Rezende ◽  
Luiz O. C. Rodrigues
Keyword(s):  
Neurofibromatosis Type 1 ◽  
Diastolic Pressure ◽  
Sweat Rate ◽  
Heat Exposure ◽  
Neurofibromatosis Type ◽  
Passive Heating ◽  
Thermoregulatory Responses ◽  
Sweat Function ◽  
Eccrine Sweat

ABSTRACT Objective Neurofibromatosis type 1 (NF1) causes neural and cutaneous disorders and reduced exercise capacity. Exercise/heat exposure increasing internal temperature must be compensated by eccrine sweat function and warmed skin vasodilation. We suspected NF1 could adversely affect eccrine sweat function and/or vascular thermoregulatory responses (VTR). Methods The eccrine sweat function and VTR of 25 NF1 volunteers (14 males, 11 females; 16–57 years old) were compared with 23 non-NF1 controls matched by sex, age, height and weight (CG). Sweating was induced by 1) pilocarpine 1% iontophoresis (PILO); and 2) by passive heating (HEAT) via the lower third of the legs being immersed in 42°C water for one hour. Previously established eccrine sweat function and VTR protocols were used. Results The NF1 group showed: a) lower sweat rate than the CG group during PILO; b) a smaller diastolic pressure decrease; and c) higher tympanic temperatures than controls during HEAT (p < 0.05). Conclusion Reduced sweating and vascular thermoregulatory responses suggest autonomic dysfunction in NF1 individuals.

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