EXERCISE AND SLEEP IN 4 AFRICAN SPORTSMEN LIVING IN THE SAHEL - A PILOT-STUDY

During both the cool and hot periods of the dry season of the Sahelian climate, sleep patterns of four African sportsmen from Niger (23 +/- 0.8 years old) were studied after square-wave cycle ergometer exercise . The sleep patterns were studied in the sedentary (Baseline) conditio n and under two exercise conditions, with and without rehydration. All conditions were randomly assigned. The exercise programme consisted o f 3 sequences of cycling, beginning with 10 min at 30% of maximal aero bic power (MAP), followed by an exhaustive supramaximal effort (130 % of MAP), and ending with a 10 min recovery at 30 % of MAP. Polysomnogr aphy was recorded for 2 consecutive nights in each condition. One adap tation night, to familiarize the subjects to the polysomnography proto col, preceded the first session. Baseline slow-wave sleep (SWS) and RE M sleep were high. In the hot season, there was an overall increase in SWS (p < 0.02), due primarily to an increase in Stage 4 (p < 0.01). S tage 2 sleep decreased (p < 0.01). This effect was also observed after exercise with rehydration, but was absent in the non-hydration condit ion. This distinction between the rehydrated and non-rehydrated condit ion is thought to be due to the greater stress which may accompany an exercise-induced relative dehydration. REM sleep decreased after exerc ise in the cool season (p < 0.001), but equalled baseline levels durin g the hot season. The results suggest a combined action of hyperthermi a, water balance and stress, and are further supportive of an underlyi ng hypothalamic control of human sleep.