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 fiv e pilots during and after normal training aerobatics flights of a mean dura tion 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 b y a miniature telemetric system (K2). Heart rate Cf,), the abdominal muscle electromyogram (EMG) and Gz levels were recorded synchronously on a magnet ic tape recorder. A tilt test was performed pre- and post-flight to evaluat e f(c) and blood-pressure variability. The left forearm blood flow was meas ured by strain-gauge plethysmography. The mean VO2 during flight was 1.2 lm in(-1), with a peak VO2 of 2.1 lmin(-1). f(c) ranged between 55 and 165 bea ts min(-1) and showed a progressive increase under the effect of + Gz, with a sudden fall during -Gz. The abdominal muscle EMG indicated the occurrenc e of muscle contraction under Ct load. Maximal responses were observed duri ng the -Gz phase. Comparison between pre- and post-flight data showed lower post-flight systolic blood pressure with higher f(c). Before flight, uprig ht tilt induced a significant increase in low/high frequency f(c), as asses sed using spectral analysis. This change was suppressed after flight. In su mmary, these data show that aerobatics flight leads to enhanced energy expe nditure, mainly because of increased skeletal muscle work. The post-flight tilt test showed that aerobatic flight favors parasympathetic drive and, co nsequently, modifies blood pressure regulation during recovery. This action may decrease + Gz tolerance to a second aerobatics flight performed shortl y after the first.