[Show abstract][Hide abstract] ABSTRACT: A survival sojourn in a tropical climate exposes subjects to 2 main constraints: food restriction and tropical climatic conditions. We hypothesized that such a sojourn could modify anthropological characteristics and thermoregulatory responses to heat and cold on return.
Eight European male subjects were submitted to a sweating test (ST) for 90 minutes (dry bulb temperature [Tdb] = 47 degrees C, relative humidity (RH) = 10%, and wind speed = 0.8 m x s(-1)) and to a whole-body cold-air test (Tdb = 1 degrees C, RH = 40%, and wind speed = 0.8 m x s(-1)) for 120 minutes in thermoclimatic chambers both before and after a 4-week survival sojourn in French Guyana.
The survival sojourn resulted in a decrease in lean body mass (P < .05) without any significant change in body fat content. Heat thermoregulatory changes studied during the ST were characterized both by a lower mean skin temperature (Tsk) (P < .05) and a higher sweat rate measured after the sojourn than before it (m(sw); P < .05). Cold thermoregulatory changes were characterized by a higher T(sk) value (P < .05) and a decreased onset for continuous shivering without any significant change in internal temperature or metabolic heat production (M).
This study showed that this type of sojourn modifies not only biometrical characteristics of the subjects but also the thermoregulatory responses, inducing an adaptation of the thermoregulatory system to heat and an increase in the sensitivity of the thermoregulatory system to cold. This finding could have practical implications on return after such a sojourn.
No preview · Article · Mar 2002 · Wilderness and Environmental Medicine
[Show abstract][Hide abstract] ABSTRACT: To clarify the ventilatory effects of a 5-cm H2O positive end expiratory pressure (PEEP) in healthy men during incremental exercise in normoxic conditions, 22 subjects were subjected to a constant workload (0 W, 50 W, 100 W, 150 W and 200 W) on a cycle ergometer for periods of 8 min each, both with and without 5-cm H2O PEEP. Results show that PEEP increases inspiratory (TI) and expiratory (TE) duration and tidal volume (VT) and decreases breathing frequency (fB) at rest (p < 0.05). During exercise, TI is higher at 50 W and 100 W (p < 0.05), but not at 150 and 200 W. TE only increases at 50 W (p < 0.05). An increased VT (p < 0.05 at 50, 100 and 150 W) and a decreased fB (p < 0.05 throughout the experiment) were observed. However, mean inspiratory flow (VT/T1) and duty cycle (TI/TT) were unaffected by PEEP. In conclusion, this study shows that a 5-cm H2O PEEP slightly modifies the ventilatory parameters in healthy subjects during incremental exercise in normoxic conditions.
No preview · Article · Jan 2001 · Aviation Space and Environmental Medicine
[Show abstract][Hide abstract] ABSTRACT: Hand cooling is a cold pressor test, which induces general sympathetic stimulation. This cooling procedure is often performed to investigate cold induced vasodilatation (CIVD) in one finger. To investigate the effects of this sympathetic stimulation on local CIVD, 12 subjects immersed either the right index finger (T1), right hand (T2) or left hand and right index finger (T3) for 30 min in water at 5°C followed by 15-min recovery. Skin temperature and skin blood flow (Q˙
sk) measured by laser Doppler flowmetry on the right index finger, as well as heart rate (f
c) and mean arterial blood pressure (\(\)), were continuously monitored during the three tests. Cutaneous vascular conductance was calculated as Q˙
sk/\(\). Concentrations of plasma noradrenaline (NA) and adrenaline (AD) were measured at different times during the tests. The results showed no cardiovascular change in T1, whereas f
c and \(\) increased significantly at the beginning of both T2 and T3. Similarly, sympathetic stimulation was reflected in the NA concentrations, which increased significantly (P < 0.01) during T2 and T3 after 5 min of immersion, and remained elevated until the recovery period. The AD concentration did not change during the three tests. During T2, the CIVD appeared later and slower in comparison with T1 [CIVD onset: 12.81 (SEM 2.30) min in T2 and 5.62 (SEM 0.33) min in T1] . During T3, the CIVD onset was not delayed compared to T1 [6.38 (SEM 0.67) min], but the rewarming was lower [+5.40 (SEM 0.86)°C in T3 and +9.10 (SEM 1.31)°C in T1]. These results showed that CIVD could be altered by sympathetic stimulation but it also appeared that the onset of CIVD could be influenced by local cooling, independently of the general sympathetic stimulation.
No preview · Article · Mar 2000 · Arbeitsphysiologie
[Show abstract][Hide abstract] ABSTRACT: To study the physiological responses induced by immersing in cold water various areas of the upper limb, 20 subjects immersed either the index finger (T1), hand (T2) or forearm and hand (T3) for 30 min in 5 degrees C water followed by a 15-min recovery period. Skin temperature of the index finger, skin blood flow (Qsk) measured by laser Doppler flowmetry, as well as heart rate (HR) and mean arterial blood pressure (BPa) were all monitored during the test. Cutaneous vascular conductance (CVC) was calculated as Qak/BPa. Cold induced vasodilatation (CIVD) indices were calculated from index finger skin temperature and CVC time courses. The results showed that no differences in temperature, CVC or cardiovascular changes were observed between T2 and T3. During T1, CIVD appeared earlier compared to T2 and T3 [5.90 (SEM 0.32) min in T1 vs 7.95 (SEM 0.86) min in T2 and 9.26 (SEM 0.78) min in T3, P < 0.01]. The HR was unchanged in T1 whereas it increased significantly at the beginning of T2 and T3 [+13 (SEM 2) beats.min-1 in T2 and +15 (SEM 3) beats.min-1 in T3, P < 0.01] and then decreased at the end of the immersion [-12 (SEM 3) beats.min-1 in T2, and -15 (SEM 3) beats.min-1 in T3, P < 0.01]. Moreover, BPa increased at the beginning of T1 but was lower than in T2 and T3 [+9.3 (SEM 2.5) mmHg in T1, P < 0.05; +20.6 (SEM 2.6) mmHg and 26.5 (SEM 2.8) mmHg in T2 and T3, respectively, P < 0.01]. The rewarming during recovery was faster and higher in T1 compared to T2 and T3. These results showed that general and local physiological responses observed during an upper limb cold water test differed according to the area immersed. Index finger cooling led to earlier and faster CIVD without significant cardiovascular changes, whereas hand or forearm immersion led to a delayed and slower CIVD with a bradycardia at the end of the test.
No preview · Article · Feb 1997 · European Journal of Applied Physiology and Occupational Physiology
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was firstly to describe the physiological responses observed in 19 subjects during immersion of the arm up to the elbow in water at 5 degrees C (5 min) followed by a 10-min recovery and secondly, to correlate the observed physiological responses with biometrical characteristics of the subjects (maximal oxygen uptake, VO2max, percentage fat content of whole body, BF, and arm, forearm and hand skinfold thickness). The results showed that the time courses of changes in forearm and hand skin temperature were different compared to those of finger skin temperatures both during local cooling and during rewarming (P < 0.05). Cardiovascular responses (heart rate, systolic and diastolic blood pressures) and finger skin temperatures were not related to the biometrical characteristics of the subjects. However, at the end of the immersion, decreased hand skin temperature was correlated to VO2max (r = 0.45, P < or = 0.05) whereas decreased forearm skin temperature was correlated both to VO2max (r = 0.44, P < or = 0.05) and to skinfold thickness (r = -0.44, P < or = 0.05) but not to BF. During the beginning of the recovery period only, outside, inside forearm and hand skin temperatures were related to VO2max (r = 0.54, P < or = 0.05; r = 0.66, P < or = 0.01 and r = 0.45, P < or = 0.05, respectively) and all the skinfold thicknesses (r = -0.47 to -0.71, P < or = 0.05). It was concluded that the local skin temperature profiles differed according to the upper limb segment both during cooling and during early rewarming. Moreover, VO2max and upper limb skinfold thickness but not BF did influence the forearm and hand skin temperature changes during cooling and early rewarming but not the finger skin temperature changes and cardiovascular responses.
No preview · Article · Feb 1996 · European Journal of Applied Physiology and Occupational Physiology