Effects of aerobatics flight on oxygen consumption and heart rate control: influence on autonomic cardiovascular regulation during recovery.
Oxygen consumption (VO2) and blood pressure regulation were measured on five pilots during and after normal training aerobatics flights of a mean duration of 35 min. The acceleration vector along the longitudinal axis of the body (Gz) ranged from + 6.5 Gz to -3.5 Gz. VO2 was continuously monitored by a miniature telemetric system (K2). Heart rate (fc), the abdominal muscle electromyogram (EMG) and Gz levels were recorded synchronously on a magnetic tape recorder. A tilt test was performed pre- and post-flight to evaluate fc and blood-pressure variability. The left forearm blood flow was measured by strain-gauge plethysmography. The mean VO2 during flight was 1.2 l x min(-1), with a peak VO2 of 2.1 l x min x fc ranged between 55 and 165 beats x min(-1) and showed a progressive increase under the effect of + Gz, with a sudden fall during -Gz. The abdominal muscle EMG indicated the occurrence of muscle contraction under Gz load. Maximal responses were observed during the Gz phase. Comparison between pre- and post-flight data showed lower post-flight systolic blood pressure with higher fc. Before flight, upright tilt induced a significant increase in low/ high frequency fc, as assessed using spectral analysis. This change was suppressed after flight. In summary, these data show that aerobatics flight leads to enhanced energy expenditure, mainly because of increased skeletal muscle work. The post-flight tilt test showed that aerobatic flight favors parasympathetic drive and, consequently, modifies blood pressure regulation during recovery. This action may decrease + Gz tolerance to a second aerobatics flight performed shortly after the first.
Guézennec
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CY
Department of Physiology, Institut de Médecine Aérospatiale du Service de Santé des Armées, Brétigny sur Orge, France. cyguezennec@imassa.fr
Louisy
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D000009:Abdominal Muscles / Q000502:physiology; D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D001359:Aviation; D001794:Blood Pressure / Q000502:physiology*; D004576:Electromyography; D005221:Fatigue / Q000503:physiopathology; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D018667:Tilt-Table Test