Rossi, a psychology researcher and disciple of clinical hypnotherapist Milton Erickson, introduces the concept of ultradian rhythms, or biological cycles of rest and activity that regulate physical and mental health. Approximately every 90-120 minutes, he asserts, the mind and body give clues signaling the need for rest and change in physical and mental activity. Rossi shows that ignoring these signals may lead to fatigue, stress, and ultimately psychosomatic illness. He recommends taking 20-minute breaks that lead to renewed energy and improved performance. He provides guidelines for monitoring one's own ultradian rhythms to aid in physical training, weight reduction, improving family and sexual relations, and managing stress. Recommended for popular psychology and consumer health collections.-- Lucille Boone, San Jose P.L., Cal.