Analysis of lower limb circulation and muscle fatigue of divers at different crew positions in full ocean depth manned submersible

Objective To discuss the cabin design of full ocean depth manned submersible by analyzing the changes of blood flow and surface electromyogram of lower limbs of divers at different crew positions after maintaining irregular posture for long time. Methods This study focused on the sitting postures of main driver, co-driver, and observer. For all sitting postures of different divers, scheme 1 has baffle support, while scheme 2 has no baffle support. The duration of single test on main driver sitting posture was 2 hours, while that on co-driver and observer sitting posture was 1 hour. Lower limb blood flow and the surface electromyography of trapezius, erector spine and rectus femoris were measured in different divers respectively. Results Compared with those of main driver in resting posture, the lower limb blood flow of both two schemes showed increasing tendency; and the lower limb blood flow of the scheme 2 showed decreasing tendency as compared with that of the scheme 1. Compared with those of co-driver in resting posture, the lower limb blood flow of both two schemes of co-driver sitting posture and observer sitting posture showed significant increase (P<0.01). The mean frequency of erector spine muscle of the main driver in sitting posture of scheme 2 at 2 h was significantly higher than that of the scheme 1 (P<0.05). Compared with those of co-driver in resting posture, the mean frequencies and mean power of trapezius, erector spine, and rectus femoris of the co-driver and observer in sitting position of both two schemes showed significant increase (P<0.05 or P<0.01). Compared with those of the co-driver and observer in sitting posture of the scheme 1, the mean frequencies and mean power of rectus femoris of the schemes 2 showed increasing tendency. Conclusion If retractable movable baffles could be installed in the full ocean depth manned submersible cabin, they could meet the needs of the physiological characteristics of the co-driver and observer so as to reduce body fatigue and improve operational performance. Key words: Blood flow of lower limbs; Surface electromyogram; Full ocean depth manned submersible; Operational performance