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1.
Aviat Space Environ Med ; 83(6): 570-6, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22764611

RESUMO

INTRODUCTION: Wearing protective clothing can have deleterious effects on operational capacities and can cause non-compensable thermal stress. We studied the effects of moderate exercise on orthostatic tolerance while wearing protective clothing in eight healthy subjects tolerant to orthostatism. METHODS: Subjects performed a 60-min moderate exercise on a treadmill followed by a 45-min head-up tilt test. Subjects performed the moderate exercise either in a comfortable condition (control, CON) or wearing protective clothing (PRO) in a random order. RESULTS: Compared with the CON trial, exercise in the PRO trial induced higher body dehydration, heart rate, and rectal temperature and a decrease in plasma volume. Orthostatic tolerance was significantly reduced in the PRO trial (23.7 +/- 0.2 min) compared with the CON trial (40.7 +/- 1.0 min). Transition from supine to head-up position caused a significant decrease in blood pressure in the PRO compared with the CON. RR interval was smaller in the PRO trial compared with CON in both the supine and head-up positions. Spontaneous baroreflex sensitivity was decreased in the PRO, either supine or standing, compared to CON (4.6 +/- 0.5 ms x mmHg(-1) and 14.5 +/- 4.2 ms x mmHg(-1) in supine, and 3.3 +/- 0.6 ms x mmHg(-1) and 7.0 +/- 0.6 ms x mmHg(-1) in standing, for PRO and CON, respectively). DISCUSSION: These results suggest that the large decrease in the tolerance to orthostatism after exercise while wearing protective clothing was due to the impossibility of maintaining an adapted blood pressure induced by a conflict between the needs of peripherical vasoconstriction linked to the standing posture, the needs of vasodilatation linked to thermoregulation, and a drop in the sensibility of the spontaneous baroreflex.


Assuntos
Exercício Físico , Transtornos de Estresse por Calor/etiologia , Intolerância Ortostática/etiologia , Roupa de Proteção/efeitos adversos , Adulto , Estudos Cross-Over , Desidratação/complicações , Febre/complicações , Hemodinâmica , Humanos , Masculino , Distribuição Aleatória , Teste da Mesa Inclinada
2.
Eur J Appl Physiol ; 108(1): 49-58, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19756708

RESUMO

This experiment was designed to assess the effects of prolonged whole body immersion (WBI) in thermoneutral and cold conditions on plasma volume and hydromineral homeostasis.10 navy "combat swimmers" performed three static 6-h immersions at 34 degrees C (T34), 18 degrees C (T18) and 10 degrees C (T10). Rectal temperature, plasma volume (PV) changes, plasma proteins, plasma and urine ions, plasma osmolality, renin, aldosterone and antidiuretic hormone (ADH) were measured. Results show that compared to pre-immersion levels, PV decreased throughout WBI sessions, the changes being markedly accentuated in cold conditions. At the end of WBI, maximal PV variations were -6.9% at T34, -14.3% at T18, and -16.3% at T10. Plasma osmolality did not change during and after T34 immersion, while hyperosmolality was present at the end of T18 immersion and began after only 1 h of T10 immersion. In the three temperature conditions, significant losses of water (1.6-1.7 l) and salt (6-8 g) occurred and were associated with similar increases in osmolar and free water clearances. Furthermore, T18 and T10 immersions increased the glomerular filtration rate. There was little or no change in plasma renin and ADH, while the plasma level of aldosterone decreased equally in the three temperature conditions. In conclusion, our data indicate that cold water hastened PV changes induced by immersion, and increased the glomerular filtration rate, causing larger accumulated water losses. The iso-osmotic hypovolemia may impede the resumption of baseline fluid balance. Results are very similar to those repeatedly described by various authors during head-out water immersion.


Assuntos
Aldosterona/sangue , Temperatura Corporal/fisiologia , Homeostase/fisiologia , Imersão/efeitos adversos , Volume Plasmático/fisiologia , Adulto , Água Corporal , Temperatura Baixa , Humanos , Imersão/fisiopatologia , Masculino , Sódio/metabolismo , Temperatura , Vasopressinas
3.
Aviat Space Environ Med ; 79(12): 1096-9, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19070304

RESUMO

INTRODUCTION: Previous human studies reported that platelet count (PC) is decreased following decompression. Platelet aggregation and adherence to the bubble surface has been demonstrated in severe decompression sickness (DCS). The present study was designed to clarify the relationship between post-dive changes in blood PC and the level of bubble formation in divers. METHODS: There were 40 healthy experienced divers who were assigned to 1 experimental group (N = 30) with an open-sea air dive to 30 msw for 30 min in field conditions and 1 control group (N = 10) without hyperbaric exposure. Bubble grades were monitored with a pulsed Doppler according to the Spencer scale and Kissman integrated severity score (KISS). Blood samples for red blood cell counts (RBC), hematocrit (Hct), and PC were taken 1 h before and after exposure in two groups. RESULTS: None of the divers developed any signs of DCS. In two groups, the results showed significant increase in RBC count and Hct related with hemoconcentration and no change in PC. Divers with a high KISS score (39 +/- 5.8; mean +/- SD) presented a significantly more pronounced percent fall in PC than divers with a lower KISS score. We found a significant correlation between the percent fall in PC after a dive and the bubble KISS score. DISCUSSION: The present study highlighted a relationship between the post-dive decrease in PC and the magnitude of bubble level after decompression. Our primary result is that the post-dive decrease in PC could be a predictor of decompression severity after diving.


Assuntos
Doença da Descompressão/etiologia , Descompressão/efeitos adversos , Mergulho/efeitos adversos , Embolia Aérea/sangue , Embolia Aérea/etiologia , Contagem de Plaquetas , Adulto , Doença da Descompressão/sangue , Indicadores Básicos de Saúde , Humanos , Masculino , Agregação Plaquetária , Pressão , Estudos Prospectivos , Fatores de Tempo
4.
Aviat Space Environ Med ; 79(6): 570-6, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18581940

RESUMO

INTRODUCTION: As exercise while wearing protective clothing exacerbates body heat storage compared to exercise in the heat, and as exercise alters immune responses, it appeared worthwhile to examine immune and stress responses while wearing protective clothing during moderate exercise. METHODS: Eight subjects completed two bouts of exercise at 45% Vo2(max) in a thermoneutral environment: once while wearing shorts only (Control trial, CON) and again while wearing protective clothing (PRO). Venous blood samples were taken to analyze TNF-alpha mRNA by RT-PCR in LPS stimulated blood, plasma catecholamines, and cortisol. Blood cell count was analyzed by flow cytometry. Rectal temperature (T(re)) was monitored continuously. RESULTS: Exercise with PRO resulted in significantly greater increases in T(re) (39.2 +/- 0.2 degrees C in PRO vs. 38.0 +/- 0.1 degrees C in CON) and plasma epinephrine and norepinephrine (+70% and 150%, respectively). Plasma cortisol increased only at the end of PRO exercise (+33%). Leukocyte and lymphocyte cell count was 14% and 18% higher, respectively, but there were no significant changes in T cytotoxic and NK cell counts compared to the CON trial. Only T helper lymphocyte count was lower (-29%). During both exercise trials, T helper lymphocytes were significantly decreased at the end of exercise and recovery. With or without protective clothing, exercise was associated with an inhibition of TNF- alpha expression in stimulated monocytes (approximately -50% at min 20 and 40, and approximately -30% at min 60). DISCUSSION: Protective clothing wearing induces significant thermal challenge during exercise. The inhibition of TNF-alpha appears to be mediated primarily by exercise and not the added thermal load associated with protective clothing.


Assuntos
Exercício Físico/fisiologia , Febre/imunologia , Roupa de Proteção/efeitos adversos , Fator de Necrose Tumoral alfa/sangue , Adulto , Catecolaminas/sangue , Estudos Cross-Over , Teste de Esforço , Humanos , Hidrocortisona/sangue , Masculino , Subpopulações de Linfócitos T/fisiologia
5.
Eur Cytokine Netw ; 18(3): 154-61, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17823084

RESUMO

UNLABELLED: Different stress hormones are released during prolonged exercise and passive hyperthermia. We hypothesized that these different hormonal responses could contribute to the different changes in the immune response during these two challenges. METHODS: Eight subjects completed three trials in a randomized order. In the control trial (C), the subjects remained in a sitting posture for three hours in thermoneutral conditions. In the exercise hyperthermia trial (E), they exercised for two hours on a treadmill at 65% max in thermoneutral conditions, followed by 1-h recovery in thermoneutral conditions; in the passive hyperthermia trial (PH), the subjects remained in a semi-recumbent position in a climatic chamber for two hours in hot conditions, followed by 1-h recovery in thermoneutral conditions. During the E and PH trials, wind speed and thermal conditions were modulated to reach a rectal temperature (Tre) of 38.5 degrees C at 60 min and 39 degrees C at 120 min. The subjects did not drink during the experiments. Blood samples (10 mL) were taken at 0, 60, 120 and 180 min of each trial. The total white cell count and its subsets were measured; plasma catecholamines, cortisol and prolactin were assayed. In a whole blood assay, blood leukocytes were stimulated by lipopolysaccharide (LPS) or phytohemagglutinin (PHA) for 24 and 48 hours, respectively. Cytokines, such as TNF-alpha, IL-10 and INF-gamma were measured in the culture supernatant. RESULTS: The plasma levels of catecholamines were increased only during E, prolactin was increased only during PH, and cortisol was increased in both E and PH. Only the exercise caused a mobilization of blood leukocytes and leukocyte subsets. The INF-gamma and TNF-alpha production by PHA- and LPS-stimulated blood, respectively, were inhibited in a substantial way in both E and PH compared to control when Tre reached 39 degrees C. Only LPS-induced IL-10 production was enhanced during the exercise. The effects of the challenges were increased with 39 degrees C compared to 38.5 degrees C. CONCLUSIONS: Catecholamines play a major role in the mobilization of immunocompetent cells and the production of IL-10 during exercise. Prolactin and catecholamines have adverse role on the immune response, whereas cortisol exerts similar effects during both trials. The consequence could be a protection against inflammatory overshooting.


Assuntos
Citocinas/biossíntese , Exercício Físico/fisiologia , Hormônios/biossíntese , Estresse Fisiológico/sangue , Estresse Fisiológico/imunologia , Adulto , Temperatura Corporal/fisiologia , Catecolaminas/sangue , Catecolaminas/imunologia , Citocinas/sangue , Hormônios/sangue , Temperatura Alta/efeitos adversos , Humanos , Hidrocortisona/biossíntese , Hidrocortisona/sangue , Hipertermia Induzida/efeitos adversos , Interferon gama/biossíntese , Interferon gama/sangue , Interleucina-10/biossíntese , Interleucina-10/sangue , Leucócitos/imunologia , Leucócitos/metabolismo , Lipopolissacarídeos/farmacologia , Resistência Física/fisiologia , Fito-Hemaglutininas/farmacologia , Prolactina/biossíntese , Prolactina/sangue , Projetos de Pesquisa , Fator de Necrose Tumoral alfa/biossíntese , Fator de Necrose Tumoral alfa/sangue
6.
Pflugers Arch ; 452(1): 91-101, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16328455

RESUMO

The consequences of a prolonged total body immersion in cold water on the muscle function have not been documented yet, and they are the object of this French Navy research program. Ten elite divers were totally immerged and stayed immobile during 6 h in cold (18 and 10 degrees C) water. We measured the maximal voluntary leg extension (maximal voluntary contraction, MVC) and evoked compound muscle potential (M wave) in vastus lateralis and soleus muscles at rest, after a submaximal (60% MVC) isometric extension allowing the measurement of the endurance time (Tlim). The power spectrum of surface electromyograms (EMG) was computed during 60% MVCs. MVCs and 60% MVC maneuvers were repeated four times during the immersion. Data were compared with those obtained in a control group studied in dry air condition during a 6-h session. Total body cooling did not affect MVC nor Tlim. The M wave duration increased in the coolest muscle (soleus), but only at 10 degrees C at rest. There were no further fatigue-induced M wave alterations in both muscles. During 60% the MVCs, a time-dependant increase in the leftward shift of the EMG spectrum occurred at the two temperatures. These EMG changes were absent in the control group of subjects studied in dry air. The plasma lactate concentration was elevated throughout the 18 and mostly the 10 degrees C immersion conditions. Throughout the 18 degrees C immersion study, the resting potassium level did not significantly vary, whereas at 10 degrees C, a significant potassium increase occurred soon and persisted throughout the study. Thus, total body immersion in cold water did not affect the global contractile properties of leg muscles during static efforts but elicited significant alterations in electromyographic events which may be related to the variations of interstitial fluid composition.


Assuntos
Imersão/fisiopatologia , Músculo Quadríceps/fisiologia , Adulto , Temperatura Corporal/fisiologia , Mergulho/fisiologia , Eletromiografia , Humanos , Masculino , Músculo Esquelético/fisiologia , Neopreno , Roupa de Proteção
7.
Med Sci Sports Exerc ; 36(10): 1730-6, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15595294

RESUMO

PURPOSE: This study was designed to describe the responses of fluid-regulating hormones during exercise in acute hypobaric hypoxia and to test the hypothesis that they would be dependent on the relative intensity of exercise rather than the absolute workload. METHODS: Thirteen men cycled for 60 min on four occasions in the same individual hydration status: in normoxia at 55% and 75% of normoxia maximal aerobic power (N55 and N75, respectively), in hypoxia (PB = 594 hPa) at the same absolute workload and at the same relative intensity as N55 (H75 and H55, respectively). VO2, heart rate, and rectal and mean skin temperatures were recorded during exercise. The total water loss was measured by the difference in nude body mass adjusted for metabolic losses. Venous blood samples were drawn before and 15, 30, 45, and 60 min after the beginning of exercise to measure variations in plasma volume, osmolality, and concentrations in arginine vasopressin (AVP), atrial natriuretic factor (ANF), plasma renin activity (ARP), aldosterone (Aldo), and noradrenaline (NA). RESULTS: During N55 and H55, AVP, Aldo and ARP did not change, whereas ANF increased slightly. Increases in AVP, Aldo, ARP, and NA were greater during N75 than during H75, whereas the increase in ANF was greater during H75 than N75. CONCLUSION: Plasma levels of AVP, Aldo, and ARP increase during exercise when a threshold is reached and thereafter are dependent on the absolute workload, without any specific effect of hypoxia. The time course of ANF appears to be different from that of the other hormones.


Assuntos
Altitude , Teste de Esforço , Hipóxia/sangue , Adulto , Aldosterona/sangue , Arginina Vasopressina/sangue , Fator Natriurético Atrial/sangue , Temperatura Corporal/fisiologia , Frequência Cardíaca/fisiologia , Humanos , Hipóxia/fisiopatologia , Masculino , Norepinefrina/sangue , Concentração Osmolar , Oxigênio/sangue , Consumo de Oxigênio/fisiologia , Volume Plasmático/fisiologia , Renina/sangue , Suor/metabolismo
9.
Med Sci Sports Exerc ; 34(10): 1624-31, 2002 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-12370564

RESUMO

PURPOSE: The present study was assessed to study the restoration of the vascular compartment by rehydration after heat exposure or exercise. METHODS: Eight subjects completed four trials in a randomized order: 2.7% dehydration of body mass by passive controlled hyperthermia once with rehydration and once without rehydration during recovery, and 2.7% dehydration of body mass by treadmill exercise once with rehydration and once without rehydration during recovery. An isotonic glucose electrolyte beverage was provided twice during the recovery period for a total volume, which was equivalent to the target value of body mass loss during dehydration procedures. Plasma volume (PV) was measured using Evans Blue dilution technique, and PV changes (deltaPV) were determined using hematocrit and hemoglobin measurements. RESULTS: PV was better maintained during exercise than during heat exposure, and the difference in deltaPV between the two patterns of dehydration was maintained during the first 3 h of recovery. Plasma protein seemed to be accountable for the difference in deltaPV during heat exposure and exercise but not during the 270 min of recovery. Rehydration partly restored body fluid losses, but the plasma compartment was privileged, because 26-30% of the net fluid gain was found in the plasma compartment (about 300 mL). Rehydration restored plasma osmolality and diminished the drive for arginin-vasopressin response. CONCLUSION: The similar selective retention of water in the plasma compartment might essentially be explained by osmotic factors provided by the beverage. As PV was completely restored by rehydration after exercise and only partly restored after heat exposure, the volume of ingested beverage should be higher after heat exposure to completely restore the plasma compartment.


Assuntos
Regulação da Temperatura Corporal/fisiologia , Desidratação/etiologia , Esforço Físico/fisiologia , Adulto , Proteínas Sanguíneas/análise , Volume Sanguíneo , Desidratação/fisiopatologia , Desidratação/terapia , Azul Evans , Hidratação , Temperatura Alta , Humanos , Masculino , Concentração Osmolar , Fatores de Tempo
10.
Can J Physiol Pharmacol ; 80(6): 526-32, 2002 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12117301

RESUMO

The simultaneous time courses of hydromineral hormones (renin-aldosterone system, arginine vasopressin, and atrial natriuretic peptide) and renal responses were examined during and after the completion of hyperhydration induced by glycerol and fluid ingestion. Eight healthy young male Caucasian subjects participated in two separate trials, each including three consecutive phases in a thermoneutral environment. Phases 1 and 3 involved a 90-min period at rest, while phase 2 involved a 120-min period at rest designed to provide either (i) euhydration (control trial) or (ii) hyperhydration induced by ingestion of glycerol (1.1 g/kg body mass) and fluid (21.4 mL/kg body mass). During the 2-h time period of glycerol and fluid ingestion, urine flow, urine osmolality, and plasma levels of hydromineral hormones remained at basal values. In contrast, after hyperhydration completion during phase 3, the diuresis increased markedly together with a dilution of the urine (p < 0.05) while hormonal responses did not change. These results indicate significant differences in renal responses during and after hyperhydration completion and suggest that these changes are independent of fluid-regulating hormonal responses.


Assuntos
Glicerol/farmacologia , Hormônios/metabolismo , Rim/metabolismo , Intoxicação por Água/fisiopatologia , Adulto , Aldosterona/sangue , Algoritmos , Arginina Vasopressina/sangue , Fator Natriurético Atrial/sangue , Peso Corporal/efeitos dos fármacos , Eletrólitos/sangue , Taxa de Filtração Glomerular , Glicerol/sangue , Glicerol/urina , Humanos , Rim/efeitos dos fármacos , Masculino , Concentração Osmolar , Renina/sangue , Urodinâmica/efeitos dos fármacos , Equilíbrio Hidroeletrolítico/efeitos dos fármacos
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