Cardiovascular training effects in fighter pilots induced by occupational high G exposure

Introduction: A fundamental difference in the cardiovascular response to acceleration between a group of fighter pilots (FP) and a group of non-pilots (NP) has been demonstrated previously. This study investigated the longitudinal effects of repetitive occupational +G_z exposure on the cardiovascular response to acceleration. Methods: There were 6 FP and 6 NP subjects who underwent rapid +75° head-up tilt (HUT) on two separate occasions. The FP group were tested after a non-flying period of 5 wk (Test 1), and tested again after a period of repetitive exposure to high +G_z missions (Test 2). The NP group did not fly at all between Test 1 and Test 2. Mean arterial pressure (MAP), heart rate (HR), stroke volume (SV), and total peripheral resistance (TPR) were all determined non-invasively. SV was determined using impedance cardiography and calculated via the Kubicek equation. For each variable, resting values and the response to tilt for both HUT tests within and between each group were compared. Results: In the FP group, resting MAP was higher (86 mmHg) in Test 2 compared with Test 1 (78 mmHg). Between groups, FP resting MAP was only different from the NP resting MAP in Test 2. The FP HR response to HUT increased significantly between the two tests. Conclusions: These findings suggest a +G_z-induced cardiovascular training effect in the FP group. Repetitive exposure to +G_z results in an increased resting MAP and an elevated HR response to tilt, which may provide benefits to operational fighter pilots.