One measure of respiratory effort is movement of the abdomen which reflects movement of the diaphragm.
Abdominal movement is recorded in diagnostic sleep studies.
Accordingly, the sleep phase occurs well ahead of the conventional bed time. Also associated with the tendency to wake up too early. It indicates the awake state in most normal individuals. Alpha Sleep - Sleep in which alpha activity occurs with sleep EEG patterns. Ambulatory Monitor - Portable system used for the continuous recording of multiple physiological variables during sleep.