Biofeedback method has been applied to the motor control training, of which aim is to keep a fixed constant surface EMG's signal during the flexor muscle contraction of the upper arm. The biofeedback method with the motor control has objected to make motor response with high sensibility and stability, and to give subjects the biofeedback training (BFT) in order to improve the covert sensory function. In the experiment, measuring items were as follows : integrated error values between the motor command and the controlled variable of suriace EMG (motor performance), the flexor muscle strength of the upper arm during an isometric contraction in the tracking (energy cost), and the spectrum analysis of error values (transfer function). The error spectrum should have been estimated to analyze the gain and the phase in the transfer function of the motor control. Adding the biofeedback training to the myoreflex control system, following results were obtained : 1) the gain in the motor control system increased efficiently, but the phase had no changes in the tracking after BFT. 2) the flexor muscle strength decreased with the low-cost energy of contraction after BFT. 3) motor performance had been improved with BFT significantly. 4) the covert sensory function might be elevated up to the overt sensory situation in the myoreflex control system.

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FM-AM tones

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Five young male subjects were exposed to simulated altitudes of 0 m (sea level), 2, 000 m and 4, 000 m in a hypobaric chamber under ambient temperatures of 16°C, 20°C, 24°C and 28°C. Oxygen uptake (Vo₂), cardiac output (Q ; CO₂ rebreathing method), arteriovenous O₂ difference (AVOD), heart rate (HR), and stroke volume (SV) were measured during two successive submaximal exercises after 2 hours of exposure. VO₂ and SV at high altitudes were similar to those at sea level. Q and HR at a given VO₂ Significantly increased at high altitudes, and AVOD decreased at high altitudes. No effect of ambient temperature on Q and AVOD was found, but HR showed a combined effect of temperature and altitude : at sea level and at an altitude of 2, 000 m, HR tended to increase when temperature increased ; but at an altitude of 4, 000 m, HR at low temperature was equal to the level at high temperature. These results indicated the possibility of vasodilation in the peripheral region even at low ambient temperature at high altitudes.

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Intentional and postural tremor were measured from four Japanese divers during a simulated heliox dive to 31ATA, including phases of predive, compression, depth, decompression, and postdive. The FFT power spectra of tremors were obtained in the frequency range of 0-31.5Hz with an incremental step of 0.5Hz. Attention was focused upon total power density because there were no remarkable changes in tremor frequency associated with ambient pressure. For postural tremor, two (subjects A and B) out of four divers showed significant increases in power density between 7 and 14Hz with increasing pressure. As for the other two divers, the power density remained fairly constant throughout the experiment. Increases in intentional tremor amplitude occurred only in subject B during dive. Adaptation to hyperbaric environment was not demonstrated during dive in subjects who showed increases in tremor amplitude. Under moderate helium pressure (31ATA), a variable individual composition is one of the important factors of tremors, although multifactorical causes have been implicated.

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The simulated experiment of heliox dive to 31ATA in four subjects was periormed for one month including the pressure holding for one week. In order to study the influence of hyperbaric environment on physical condition and level of consciousness, microvibration (MV) on thenar and eyelid and electroencephalogram (EEG) on T₄ and O₂ were measured at various atmosphere conditions. The power spectrum of MV and EEG were calculated : The peak frequency of power spectrum and the magnitude of power spectrum at the peak frequency were evaluated. The amplitude of MV increased after compression as compared with the value at pre-compression i.e., 1ATA, and the tendency was emphasized on eyelid MV at post-compression i.e., 1ATA, whereas the peak frequency of MV did not change significantly throughout the experiment. A rerharkable hyperbaric effect was found in the evaluation of EEG peak frequency ; The lowering of the peak frequency was recognized during the process of compression, pressure holding, and decompression. As the high pressure nervous syndrome (HPNS), especially during compression, was not recognized here, MV was not used as a detector of omen of HPNS, but the hyperbaric effect on skeletal muscle was found in ballistocardiogram cornponent of MV due to the increase of the amplitude at post-compression. EEG denoted the lowering of level of consciousness during pressure holding, so that the result meant calling one's attention to the operation in hyperbaric environment of 31ATA.

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Four male volunteers served as subjects for studies under hyperbaric helium-oxygen environments at 16 bar and 31 bar (simulated saturation dive). Tympanic membrane temperature, rectal temperature, ventilatory gas temperature, expiratory volume, respiratory frequency and cardiac frequency were measured during Cold Gas Inhalation (CGI : 20min) and recovery period (20min) in a warm hyperbaric chamber. Dyspnea and fall in deep body temperatures were evident during CGI (inspired gas temperature : 6°C at 31bar, 7°C at 16 bar). The change of tympanic membrane temperature during CGI and recovery period was more definite than rectal temperature. This phenomenon was induced by remarkable direct heat exchange between environment and body core, owing to high heat conductivity and high heat capacity of respiratory gas. Concerning safety and physiological functions of the deep sea diver and human exposed to hyperbaric helium-oxygen environment, not only rectal temperature monitoring is very important but also tympanic membrane temperature monitoring.

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In order to obtain the informations of fatigue and emotional state of divers living in hyperbaric (31 ATA, He-02) underwater simulation for long term, three questionaires-subjective sysmptoms of fatigue, mood adiective check list, , and State-Trait Anxiety Inventory (STAI), ware performed with appropriate intervals. Hyperbaric experiment was consisted of five phases, pre-dive control, compression, saturation at 31 ATA, decompression and post-dive observation. Four divers lived in this situation for about total of 30 days. Though there was variation between subjects, three indices revealed that fatigue, especially the physical one and state anxietny increased in the period of compression, though possitive or active mood was persisted throughout the experiment. Results lead us to the discussion that compression is a facter of both physical and emotional fatigue rather than decompression.

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In all of the saturation simulation dive that was given at Japan Marine Science and Technology Center, the Urine flow of the divers under hyperbaric exposure was increased. The results on the urine flow measurement In detail show that the increase of urine flow under hyperbaric conditions occurred especialy at night. The 300m saturation simulation dive cord-name "Seadragon-VI" was carried out from September to October in 1984. On this project, we examined the relationship bitween the water intake and the water loss of the divers. The results obtained are as follows : 1. A diver showed significant increase of the night urine flow have had much water intake, little urine flow before going to bed and also little insensible water loss with sweat during sleep. And the capacity of the bladder takes part in the frequency of night urine as well. 2. The water intake under 300m was less than the value of the surface.

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Four divers were compressed with He-O₂ (PO₂= 0.3 bar) at 25m/h to 300m(31 ATA). During the compression, all the divers answered a questionnaire and kept a personal log of their signs and symptoms including the time of onset and site of any arthralgias and fatigues. Symptoms of fatigue which include drowsiness, brain muddled and rigid or clumsy in motion appeared in all divers from 100m to 300m. The arthralgia and myalgia were deflnitely present but mild from a depth of 150m. At the same depth, the tremor appeared practically imperceptible. However, the symptom of tremor was not complained during the compression from 200m to 300m in the two divers (A and C). The nausea and dizziness associated with high pressure nervous syndrome (HPNS) were complained barely perceptible or minimal from a depth of 250m in the divers A, C and D. At the depth of 300m, these symptoms were kept on and the physical condition of the divers prevented them from working immediately. The feeling of adaptation in this environment was answered after 24h (diver D), 32h (diver A and C) and 80h (diver B) on the bottom. These results showed that there was a signiflcant interindividual variation in susceptibility to subjective signs and symptoms.

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