Effects of relatively high accelerations on some biological systems

¹ Aerospace Medical Laboratory, Wright-Patterson Air Force Base, Ohio

Fasting male subjects were exposed to forward accelerations (12-degree back angle) at fatiguing levels varying both in amplitude and duration, nonfatiguing levels and mock runs, and to treadmill exercise. The following analyses were made: plasma bicarbonate, blood glucose, phosphorus and creatinine, urine creatinine, urine volume, urinalysis, and an estimate of creatinine clearance. The only consistent change noted after fatiguing accelerations was a small rise in blood creatinine (P < 0.05). Exercise, however, resulted in a marked (P < 0.01) decrease in bicarbonate, rise in blood creatinine, and drop in clearance. Accelerations in comparison to exercise showed little effect on either muscular or renal activity. No correlation was found between any of the biochemical measurements and acceleration intensity nor were there any differences noted between real and mock accelerations, indicating that none of these tests could index the severity of accelerative stress. The fatigue associated with high accelerations is not easily explainable in terms of increased muscular activity.