Heart rate response of aircrew during recovery from gradual onset rate +Gz exposures

A quantitative study of cardiac recovery from +Gz was accomplished to define recovery heart rate (HR) of aircrew exposed to the acceleration environment in the centrifuge. Electrocardiographic data from 30 pilots were analyzed. The profiles considered were gradual onset rate exposure of 0.1 G/s. Continuous R-R interval measurements were recorded prior to +Gz and immediately after peak +Gz was attained. In 57% of the subjects, HR decreased 57 +/- 18 bpm an average of 11 +/- 4 s after maximum HR was attained. This rate was maintained for 17 +/- 5 s. The remaining 43% of the subjects exhibited a gradual decline in HR until reaching a steady state 60 s after the exposure. Heart rate was also observed to oscillate 42 +/- 15 bpm about the mean values before achieving a steady state during both types of recovery. The oscillatory HR did not have fixed upper and lower limits. Description of the recovery HR during +Gz exposures establishes a baseline for comparison with atypical responses and a basis for describing cardiovascular response to alternate and more complex +Gz profiles.