Le travail en ambiance chaude - Principes, méthodes, mise en oeuvre

Book published by Masson (1990)

Reproducibility of intra-abdominal pressure when lifting

in Scandinavian Journal of Rehabilitation Medicine (1988), 20(2), 83-8

Reproducibility of intra-abdominal pressure (IAP) variation was investigated in fifteen young male subjects when lifting three loads, 49, 98 and 147 N, with three speeds of movement, slow, fast and ... [more ▼]

Reproducibility of intra-abdominal pressure (IAP) variation was investigated in fifteen young male subjects when lifting three loads, 49, 98 and 147 N, with three speeds of movement, slow, fast and spontaneous, and starting from four standing postures: trunk erect, trunk forward flexed at 30, 60, and 90 degrees of dorsolumbar inclination. Each lift was replicated five times successively and the whole protocol was replicated at one a week interval. The intra-individual variability in IAP response was assessed using the standard deviation of each series of ten lifts. Results showed that variability of peak IAP increased with the load and with the lifting speed. This effect of speed was especially observed for light loads and in forward bending postures. Trunk posture had in itself no significant effect on IAP reproducibility. However, when the variations in the moment acting at lumbar level were taken into account by considering the IAP to moment ratio, the reproducibility of the response was not affected by the load but only by the trunk posture. Reproducibility was lower in the erect posture than in the three flexed positions. It is suggested that this difference relates to the importance in each posture of the moment acting at the shoulder with respect to the total moment acting at lumbar level. [less ▲]

Physiological factors associated with the onset of sweating

in Japanese Journal of Physiology (The) (1987), 37(4), 699-714

The influence of esophageal (Tes) and skin temperature (Tsk) variations, body heat storage, and individual parameters on the initiation of sweating was investigated in 9 unacclimated subjects during ... [more ▼]

The influence of esophageal (Tes) and skin temperature (Tsk) variations, body heat storage, and individual parameters on the initiation of sweating was investigated in 9 unacclimated subjects during thermal transients induced by exercise (25, 50, or 75 W) and by a step change in ambient temperature from 28 degrees C to 23, 28, 36.5, 45, or 50 degrees C. Seventy-four onsets of sweating were observed during the exposures, the sweating delay averaging 3 min at 45 and 50 degrees C, 6 min at 36.5 degrees C, and 9.5 min at 28 degrees C. In warm conditions (36.5 to 50 degrees C), the onset of sweating could mainly be related both to the level of Tsk and its rate component, whereas in cooler conditions (28 and 23 degrees C), the onset of sweating could only be related to a positive rate of Tes variation, the Tsk level being low and steady. On the whole set of data, the Tes changes at the onset were inversely related to the Tsk changes. The cumulated heat storage at the onset of sweating was 37 kJ/m2 (S.D. 25). It varied not only among subjects (range: 11-66 kJ/m2) but also within subjects even when differences in thermal state prior to exercise were accounted for. Among the individual parameters investigated, the magnitude of the decrease in Tes observed in response to the start of exercise was found to have a significant effect on the sweating delay. The Tes decrease was inversely related to the subject's skinfold thickness, and in a given subject, inversely related to the preexercise Tsk. It is concluded that the results are in agreement with a summation model of internal and mean skin temperatures on the sweating drive but that they do not verify the hypothesis of a critical level of heat storage at the onset of sweating. [less ▲]

Serum creatine kinase relationship to postural constraints in manual work

in International Archives of Occupational and Environmental Health (1986), 58(1), 61-8

Serum creatine kinase (CK) variations during work and subjective assessments of postural discomfort were analysed in 30 workers assigned to three different tasks in a rolling mill. After four days of work ... [more ▼]

Serum creatine kinase (CK) variations during work and subjective assessments of postural discomfort were analysed in 30 workers assigned to three different tasks in a rolling mill. After four days of work, serum CK levels were significantly increased above control levels. No difference was found between the tasks studied. Inter-individual variability in CK response was large: a marked CK increase was only seen in 21 workers, while 5 workers showed a marked CK decrease. The postural discomfort sensations increased with work in each group, with their location in the body being related to the characteristics of each task or workplace. No relationship was found between the postural discomfort scores and CK changes. Results showed that determination of an individual baseline CK level was difficult to achieve in an occupational setting. It is concluded that CK variations cannot reliably be used in the field for detection of individuals exposed to excessive postural constraints. Their use as a screening tool in groups of workers assigned to similar tasks deserves further study. [less ▲]

Prediction of strain for intermittent heat exposures

in Ergonomics (1986), 29(7), 913-23

Validité de la prédiction de la consommation maximale d'oxygène

in Archives des Maladies Professionnelles de Médecine du Travail et de Sécurite Sociale (1985), 46(6), 379-384

Physiological and perceptual responses to cyclic heat stress variations

in Aviation, Space and Environmental Medicine (1984), 55(10), 935-40

The effect of the time presentation of a given external heat load was examined on five subjects exercising at a constant work load (50 W). The subjects, dressed in briefs, were exposed to cyclic ... [more ▼]

The effect of the time presentation of a given external heat load was examined on five subjects exercising at a constant work load (50 W). The subjects, dressed in briefs, were exposed to cyclic variations for 120 min in air temperatures between 51 degrees C and 23 degrees C, under three different schedules involving heat pulses of 10-min, 20-min and 30-min duration, respectively. The strain induced by each of these conditions was compared in terms of both physiological and perceptual criteria. Results showed that between conditions, there were significant differences in skin temperature levels but not in core temperature levels, body heat storage, or body weight loss. Perception of effort and thermal sensation ratings both exhibited similar changes in all three conditions. Due to the time constant of the sweating response, sweating rates and skin wettednesses at the end of the heat pulses were lower for 10-min heat pulses than for those of 20- and 30-min duration, and these differences were perceived by the subjects. Lower perceived skin wettedness ratings are thus suggested as the main factor to explain why all subjects rated the 10-min heating-cooling cycle as the least strenuous and uncomfortable condition. It is concluded that under the conditions of this study, perceptual criteria associated with physiological criteria represent a useful means of discriminating slight differences in strain. [less ▲]

Indicateurs physiologiques de la charge mentale : leur utilité pour le médecin du travail

in Archives des Maladies Professionnelles de Médecine du Travail et de Sécurite Sociale (1984), 45(2), 101-110

Oral temperature as an index of core temperature during heat transients

in European Journal of Applied Physiology and Occupational Physiology (1983), 50(3), 331-41

Rectal (Tre), oral (Tor) and oesophageal (Tes) temperatures were measured in five exercising subjects exposed for two hours to five conditions (1) a steady condition (WR) involving a constant work load ... [more ▼]

Rectal (Tre), oral (Tor) and oesophageal (Tes) temperatures were measured in five exercising subjects exposed for two hours to five conditions (1) a steady condition (WR) involving a constant work load (50 W) at a constant air temperature (Ta = 36.5 degrees C); (2) air temperature variations (delta Ta) between 28 degrees C and 45 degrees C and (3) between 23 degrees C and 50 degrees C at constant work load (50 W); (4) and (5) to work load variations (delta W) between 25 W and 75 W at a constant Ta (= 36.5 degrees C). Oral temperature recordings were taken sublingually and were either continuous or discontinuous. When discontinuous, the time needed for Tor to stabilize after the mouth opening was taken into account. The respective reliability of Tor and Tre as estimates of Tes were compared in each condition. Results showed that the resting (Tor - Tes) difference (+ 0.12 degrees C) was barely modified after two hours of exposure, whereas Tre overestimated Tes by 0.2 degrees C to 0.4 degrees C depending on the condition. The Tor variations were highly correlated with Tes variations under steady condition and under air temperature variations. In these conditions, Tor represented the best estimate of Tes. Under work-load variations, Tor was less closely related to Tes than was Tre. It is suggested that the relative inertia of Tor to step changes in exercise intensity could be ascribed to work induced variations in mouth blood flow. [less ▲]

Evaluation des effets d'un vetement refroidissant sur l'adaptation aux efforts prolonges realises a haute temperature par des ouvriers mineurs.

in Revue de l'Institut d'Hygiène des Mines (1977), 32(3), 99-122

In order to improve the working conditions of coalminers exposed to high ambient temperature, the authors have studied the effects of wearing an under-vest and a cowl covering the head and shoulders made ... [more ▼]

In order to improve the working conditions of coalminers exposed to high ambient temperature, the authors have studied the effects of wearing an under-vest and a cowl covering the head and shoulders made in sponge-cloth and soaked with cold water (cooling clothes). Eight coalminers volunteered for this study which included three sessions of prolonged intermittent exercise performed in a climatic room with the following ambient temperatures:--experiment A (comfortable environment): td = 28 degrees C; twb = 20 degrees C; bare head and bare torso;--experiment B (hot environment) :td = 38 degrees C; twb = 30 degrees C; bare head and bare torso;--experiment C (hot environment and cooling clothes) : td = 38 degrees C; twb = 30 degrees C; wet undervest and cowl soaked with cold water (16 degrees C) every 15 minutes. Each experiment included 5 periods of exercise each lasting 15 minutes separated by periods of rest lasting 15 minutes; the exercises were performed on a bicycle ergometer or on a treadmill and their intensity corresponded to 50% of the maximal oxygen intake. In the comfortable environment (experiment A), all subjects completed the experiment without undue fatigue; the final heart rate was 81/min and the final rectal temperature was 37.6 degrees C; the weight loss never exceeded 1 Kg. In the hot environment (experiment B), all subjects were exhausted at the end of the study which had to be shortened in 2 cases. The final heart rate was 125/min and the final rectal temperature 38.8 degrees C; the weight loss was above 2 Kg. The use of the "cooling clothes" in the hot environment (experiment C) resulted in significantly (p less than 0.001) lower heart rate (104/min), rectal temperature (38.3 degrees C) and weight loss (1.5 Kg); all subjects completed the experiment, none was exhausted and the "cooling clothes" were appreciated by all subjects. We conclude that the "cooling clothes" tested in the present study significantly reduce the physiological and subjective strain due to intermittent work in a hot environment; this cooling system is simple, of low cost and our results indicate that it is will be very useful in climatic conditions similar to those adopted in the present experimental protocol. Its usefulness in less severe climates has to be established but it might be limited by the subjective reactions of the subjects to the transient but sudden sensation of cold given by the "cooling clothes". [less ▲]