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Exercice physique et sommeil en climat tropical sec: étude préliminaire chez trois sujets africains

1990; Elsevier BV; Volume: 5; Issue: 2 Linguagem: Francês

10.1016/s0765-1597(05)80211-4

1778-4131

Alain Buguet, R Gati, M Soriba, B. Melin, Alain Montmayeur, S Alou, B Wamba, Pascal Bogui, J. Lonsdorfer,

Sleep and related disorders

Trois sujets africains sédentaires (âge moyen: 25 ± 1,7 ans) ont participé à l'étude des effets d'un entraînement physique progressif sur les états de sommeil en période fraîche et en période chaude de la saison sèche du climat sahélien. L'entraînement a consisté en un exercice en créneaux répété 3 fois par semaine pendant 6 semaines (plateaux de 4 min à puissance sous-maximale, pic à puissance maximale la cinquième minute). Le nombre de créneaux a été augmenté de 5 la première semaine à 7 la deuxième semaine puis à 9 les 4 semaines suivantes et la puissance développée a été accrue progressivement lors des 3 dernières semaines. L'amélioration des performances physiques a été estimée par une épreuve triangulaire réalisée avant l'entraînement, et après les troisième et sixième semaines d'exercice. Le programme d'entraînement a été réalisé en période fraîche et répété en période chaude après 2 mois 1/2 sans exercice physique. Les examens polygraphiques du sommeil ont été réalisés avant l'entraînement (3 nuits consécutives) et pendant les quatrième et sixième semaines (2 nuits consécutives). La période de contrôle en saison fraîche a été considérée comme période de référence, chaque sujet constituant son propre témoin. L'efficacité du sommeil a été améliorée par l'entraînement, avec surtout une augmentation du nombre de phases de sommeil delta (stades 3 et 4), conduisant à un accroissement de cet état. Ces changements ont été plus importants en période chaude. Au contraire, le sommeil paradoxal n'a pas varié avec les conditions climatiques, mais avec l'intensité de l'exercice. Il a diminué lors de la sixième semaine par rapport à la quatrième. En conclusion, l'augmentation du sommeil delta est en rapport avec la charge thermique supportée par le sujet, le sommeil paradoxal étant sensible au stress lié à l'intensité de l'exercice pratiqué. The effects of physical exercise on sleep patterns are still subject to controversy. Exercise can induce sleep disturbances through a stress effect, such as a decrease in sleep efficiency and reduced amounts of REM sleep or delta sleep (stages 3 and 4 of Non-REM sleep). When no stress effect occurs, diurnal exercise is followed by an increase in sleep efficiency and in delta sleep during the following night. This delta sleep enhancement has been attributed to a hyperthermic effect of exercise. Indeed, when the subject is cooled during exercise, there is no change in delta sleep, which is also known to increase after heat exposure. In order to minimize the stress component, we examined the effects of a progressive training programme on the sleep of sedentary subjects, along with the effects of the external load due to the dry tropical climate in a sahelian country. Three African subjects (25 ± 1.7 years old) volunteered for a study on the effects of progressive physical training on sleep stages during the cool and hot periods of the dry sahelian season. They had been subjected to the dry tropical sahelian climate since they were born. They were not practicing any sport, and were thus considered as sedentary subjects. The training programme (fig 1) consisted of a 6-wk square-wave endurance exercise test (SWEET) performed 3 times a wk. The test was made of the repetition of 5 min blocks with a 4-min submaximal plateau (50% of V̇O2 max) followed by a 1-min maximal peak. The number of blocks was increased from 5 in the first wk to 7 in the second wk, then to 9 during the following 4 wks. The improvement of physical performance was judged using a triangular maximal test with 25 W increments every 2 min. The maximal test was performed before the training programme and after the 3rd and 6th wks of training. The 3rd wk triangular test served to adjust the work load to the improved level of V̇O2 max. All the exercise tests were performed at laboratory temperatures of 24–25 °C. The training programme was realized twice, during the cool season and the hot dry season of the sahelian dry tropical climate, with an interval of 10 wks during which routine sedentary activity was resumed. Baseline polysomnographic recordings were taken during 3 consecutive nights, preceding the training session. During the 4th and 6th wks of each exercise period, sleep recordings were performed during the last 2 consecutive nights following day exercise. All recordings were referred to the baseline recordings of the cool season, each subject being regarded as his own control. The subjects experienced a seasonal acclimatization to heat, with lower initial rectal temperatures (Tre) in the hot vs the cool season. However, the exercise-induced increase in Tre was of similar amplitude in the cool vs the hot season. Physical fitness improved during each training session (table I). However, the 10 wk interruption in the training programme was sufficient to cancel the improvement due to the first training session. Sleep efficiency was enhanced by training during the hot season (table IV), an increase in slow-wave sleep (stages 3 and 4) occurring during both experimental sessions (table V). This increase was prominent during the hot season and was due to an increased number of slow-wave sleep phases (table VI). Contrarily, REM sleep did not change with climatic conditions, but was affected by exercise intensity, being decreased during the 6th vs the 4th wk (table V). In conclusion, the training protocol led to a similar improvement of physical fitness during the cool and the hot seasons of the sahelian climate. Seasonal heat acclimatization occurred in the 3 subjects. Training induced an increase in slow-wave sleep, which was also related to the level of the climatic thermal load experienced by the subject, while REM sleep was sensitive to the stress induced by the exercise intensity.