Sleep loss, recovery sleep, and military performance

Ten experienced infantry soldiers completed a 9-day (216 hours) tactical defensive exercise, the aim of which was to determine whether soldiers are likely to remain militarily effective during a period of partial sleep loss following a period with no scheduled sleep at all. Assessments were made of shooting, vigilance, cognitive functioning, EEG activity and physical fitness. The results indicated that tasks with a vigilance and cognitive component began to deteriorate after one night without scheduled sleep. After 3|days (90hours) with no scheduled (and very little unscheduled) sleep, 4 hours block sleep had a marked beneficial effect upon performance. After a total of 12 hours sleep over 3 3/4 days (72 hours), performance had recovered (except for scores at 05.45 hours) from an approximate average level of 50 to 88% of control Values. One and a quarter days (30 hours) of rest, of which an average amount of 19 1/2 hours was spent asleep, eliminated any remaining decrement. Electroencephalography (EEG) recordings indicated that on the six nights following total sleep loss there was an increased percentage of stage 4 sleep. Stage REM percentage remained virtually unchanged, except for the first night after total sleep loss, when there was 8% less. The EEG results are discussed in relation to the work of other investigators.