Advances in flight technologies and the demand for long range flight have increased
mission lengths for United States Army UH-60 Black Hawk aviators. Prolonged mission times have increased reports of pilots discomfort and symptoms of parathesia thought to be due to Black Hawk seat design and areas of locally high pressure. Discomfort created by the seat system decreases situational awareness putting our aviators and support crew at risk of injury.
Therefore, the purpose of this study was to examine the effects of prolonged restricted sitting and local pressure application in a Black Hawk helicopter on discomfort, sensory function, vascular, and neurological measures in the lower extremity.
Project one tested the effects of four hours of restricted sitting on discomfort, sensory, and vascular function in the lower extremity. The results demonstrated that during four hours of restricted sitting, subjective discomfort increases, lower extremity sensory function is diminished along the S1 dermatome, and skin temperature decreases. This suggests that prolonged sitting in a Black Hawk helicopter aviator seat does create increases in discomfort, potentially through a peripheral nervous or vascular system mechanism.
Project two examined the effects of local pressure application location on measures of discomfort, sensory function, and vascular function in the lower extremity. The results revealed that local pressure application increases discomfort regardless of location or magnitude. Pressure applied to the posterior thigh at a magnitude of 44 kilopascals created the greatest increases in discomfort. Skin temperature increased suggesting decreased venous return from the extremity during the test period.
Project three examined the effects pressure application to the ischial tuberosity or posterior thigh on discomfort, sensory, vascular, and neurological function in the lower extremity compared to a control condition. Mean peak-to-peak Hoffmann reflex amplitude significantly decreased, discomfort increased, skin temperature increased, and sensory function along the S1 dermatome decreased. The results suggest areas of locally high pressure created during prolonged sitting in the Black Hawk helicopter may create the discomfort and temporary parathesia by altered S1 nerve root function and decreased venous return.