title: [Circadian rhythm of the frequency of human cardiac contractions during head-down tilting].
abstract: The study of diurnal variations of heart rate of 7 healthy volunteers exposed to head-down tilting (-8 degrees) demonstrated that the absolute value decreased at the peak phase and in the daytime and increased at night; the amplitude of the diurnal variations declined. The experimental data indicate that heart rate may decrease in the morning and in the daytime beginning with the first days of the head-down position. Sometimes this decrease may be delayed and develop on head-down days 7-12.
mesh_terms: D002940:Circadian Rhythm; D004562:Electrocardiography; D006339:Heart Rate; D006801:Humans; D011187:Posture; D012890:Sleep / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology
vernacular_title: Sutochnyĭ ritm chastoty serdechnykh sokrashcheniĭ cheloveka pri antiortostaticheskom vozdeĭstvii.