Thermal and metabolic responses of military divers during a 6-hour static dive in cold water.

Background: Human thermal responses during prolonged whole-body immersion in cold water are of interest for the military, especially French SEALS. This study aims at describing the thermo-physiological responses.

Methods: There were 10 male military divers who were randomly assigned to a full immersion in neutral (34 degrees C), moderately cold (18 degrees C), and cold (10 degrees C) water wearing their operational protective devices (5.

Moderate exercise effects on orthostatic intolerance while wearing protective clothing.

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.

Whole body immersion and hydromineral homeostasis: effect of water temperature.

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.

Haemodynamic changes after prolonged water immersion.

Thermoneutral water immersion increases cardiac preload and changes the neuroendocrine settings of blood volume regulation. The resulting marked diuresis may lead to significant haemodynamic changes after the end of a prolonged water immersion. Ten volunteers underwent 6 h of complete thermoneutral water immersion.

Immune function during and after 60 min of moderate exercise wearing protective clothing.

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.

Consequences of prolonged total thermoneutral immersion on muscle performance and EMG activity.

We hypothesized that the changes in muscle temperature and interstitial pressure during thermoneutral immersion may affect the reflex adaptation of the motor drive during static contraction, assessed by the decrease in median frequency (MF) of electromyogram (EMG) power spectrum. Ten subjects were totally immersed for 6 h at 35 degrees C and repeated maximal voluntary contraction (MVC) and submaximal (60% MVC) leg extensions sustained until exhaustion. In vastus lateralis (VL) and soleus (SOL) muscles, the compound muscle potential evoked by muscle stimulation with single shocks (M-wave) was recorded at rest, and MF of surface EMG was calculated during 60% MVCs.

Effects of passive hyperthermia versus exercise-induced hyperthermia on immune responses: hormonal implications.

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.

Consequences of prolonged total body immersion in cold water on muscle performance and EMG activity.

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).

Fluid-regulatory hormone responses during cycling exercise in acute hypobaric hypoxia.

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.

Plasma compartment filling after exercise or heat exposure.

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.

Hyperhydration induced by glycerol ingestion: hormonal and renal responses.

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.