Anaerobic energetics of the simulated aerial combat maneuver (SACM)

The role of anaerobic metabolism in +Gz duration tolerance was measured using venous blood lactate concentrations before G exposure and after subjects had been fatigued from exposure to one of several levels of G: low (4.5 G) sustained G (LSG); high (7-9 G) sustained G (HSG); and simulated aerial combat maneuver (SACM) of 4.5/7 G levels. A mean +/- S.E. blood lactate of six subjects fatigued from LSG was 29.8 +/- 4.0 mg%. Four subjects fatigued from HSG had blood lactates of 42.4 +/- 3.2 mg%, and six had blood lactates of 46.7 +/- 7.2 mg% from the SACM. Blood lactates appeared to correlate directly (on a group basis) with maximum heart rates found during G exposures. Six subjects exposed to 8 or 9 G for 10 s or less demonstrated an anaerobic alactate capacity. These G findings were related to fatigue produced with isometric muscle contraction in physiologic studies conducted at 1 G. We concluded that anaerobic metabolism and isometric exercise physiology are directly related to duration tolerances of fatigue at all levels of +Gz.