Human responses to repeated high G stimulated aerial combat maneuvers

Five subjects wearing standard USAF anti-G suits and seated at a 65 degrees back angle were exposed to a simulated aerial combat maneuver (SACM) which was repeated 5 times with 4-min 1-G rests between each SACM exposure. The SACM was 122 s in duration with 10 s acceleration peaks of 10, 8, and 6 G; between these peaks, the subject was at 4 G for 15 s. This series of repeated SACM exposure fatigued four of the five subjects. Heart rate and rhythm, arterial oxygen saturation, expired gases, lactate, pyruvate, glucose, CPK enzymes and isoenzymes, blood volume, subjective fatigue measurements, and subject performance were examined relative to the development of fatigue, the energy cost of the M-1, and tolerance to the SACM. All physiologic-metabolic parameters were significantly affected by the repeated SACMs. However, only heart rate changes appeared to be correlated with developing fatigue. A significant amount of energy is required to perform the M-1. Subjects whose energy-metabolic and cardiovascular states are least disturbed by high G exposure are those persons who will perform best and become least fatigued during repeated aerial combat maneuvers.