Contribution of skeletal muscle activity to the natural history of acceleration-induced loss of consciousness (G-LOC)

G-LOC and the ensuing incapacitation represents an ever present threat to modern fighter aircraft and aviators. Of the techniques developed to combat gravitational induced stress, particularly such stress acting along the head to foot axis (+G z), a variety of straining maneuvers have assumed prominence. All the latter techniques involve voluntary skeletal muscle tensing to a varying degree. It is hypothesized that the basis for the importance of skeletal muscle activity in improving G tolerance predominantly lies in the increased muscle spindle afferent activity to the reticular activating system. It is also hypothesized that the natural history of G-LOC can be significantly improved by supplementing muscle spindle activity via active and passive skeletal muscle activity.