[Optimization of human walk speed at minimum energy expenditure--the function of leg own oscillation frequency on the transfer phase].

Equations were developed to determine the work of transferring the body gravity center for a unit mass in a path unit, and to estimate walk speed at a minimum energy expenditure. It was demonstrated that minimum energy expenditure can be achieved by walking at the pace that corresponds to leg own oscillation frequency.

[Adaptation of humans to walking in semi-hard and flexible space suits under terrestrial gravity].

The spacesuit donning-on procedure can be viewed as the combining of two kinematic circuits into a single human-spacesuit functional system (HSS) for implementation of extravehicular operations. Optimal human-spacesuit interaction hinges on controllability and coordination of HSS mobile components, and also spacesuit slaving to the central nervous system (CNS) mediated through the human locomotion apparatus. Analysis of walking patterns in semi-hard and flexible spacesuits elucidated the direct and feedback relations between the external (spacesuit) and external (locomotion apparatus and CNS) circuits Lack of regularity in the style of spacesuit design creates difficulties for the direct CNS control of locomotion. Consequently, it is necessary to modify the locomotion command program in order to resolve these difficulties and to add flexibility to CNS control The analysis also helped trace algorithm of program modifications with the ultimate result of induced (forced) walk optimization. Learning how to walk in spacesuit Berkut requires no more than 2500 single steps, whereas about 300 steps must be made to master walk skills in spacesuit SKV.

[Biochemical profile of human-spacesuit interaction].

The article discusses and analyzes the issues of optimizing energy, kinematic and dynamic structures of the process of human-spacesuit system movement. Recommendations concerning system stabilization during posture acquisition and motion are made; the biomechanic requirement for spacesuit R&D is that joints with preset frequencies must be designed.

[Temporal pattern of walking on various training facilities under the conditions of the earth's and simulated lunar gravity].

Eight test-subjects participated in 120 treadmill tests (drive power of 10 and 85 kW) aimed to compare the walking patterns at 1 and reduced gravity. The temporal pattern of steps was noted to change significantly on the low-power treadmill. On the strength of convergence of calculated and experimental data the suggestion has been made that the leg transfer movement follows the pattern of spontaneous oscillations.

[Human walk in spacesuit as a self-oscillating process].

A series of 40 biomechanic and physiological tests of semi-rigid and flexible spacesuits as possible candidates for Moon explorations purposes were conducted with involvement of 20 volunteered subjects. Ability to walk in the spacesuits with the internal positive pressure of 0.4 kg/cm2 in the normal gravity was assessed simultaneously with energy expenditure for moving over preset distances. Also, mating of the leg movements with the spacesuit shell was investigated The longest distance test elicited the fact of acquisition of stable motor skills in the unusual circumstances. The acquired motor skills bring about restructuring of step kinematics and make equal knee flexures during leg transfer and stepping on platform (matching the angular movement of the spacesuit knee joint) to an accuracy of tenths of degree. This phenomenon is used by the authors as the ground for proposing a reasoned optimization of the walk pattern in spacesuits as a self-oscillating process.

Human adaptation to simulated gravitational fields.

We present the resuIts of manned studies in which test subjects were exposed to simulated zero g (water immersion or head-down tilt at -6 degrees) and head-to-feet acceleration. The findings give evidence that humans have different individual tolerances to an acceleration of +3 Gz after exposure to zero g, whether simulated by immersion or by head-down tilt. The paper discusses the role of functional relationship between water balance and cardiac output in the establishment of adaptive reactions to simulated zero g.

Human adaptation to simulated gravitational fields.

We present the results of manned studies in which test subjects were exposed to simulated zero g (water immersion or head-down tilt at -6 degrees) and head-to-feet acceleration. The findings give evidence that humans have different individual tolerances to an acceleration of +3 Gz after exposure to zero g, whether simulated by immersion or by head-down tilt. The paper discusses the functional relationship between water balance and cardiac output in the establishment of adaptive reactions to simulated zero g.

Physiological reactions during acute adaptation to reduced gravity.

Experiments were carried out on healthy volunteers exposed to a 7-day water immersion. The subjects were kept dry by use of a water proof, highly elastic cloth. During the experiment different cardiovascular, fluid-electrolyte and biochemical parameters were recorded. During the 7-day immersion, physiological parameters changed on a phasic basis. An acute period of adaptation began within the first minutes of immersion and ended by the third day. Later some of the parameters showed relative normalization. The experimental results suggest that the hypophyseal-adrenal system and renal function are closely coupled regulatory mechanisms for adaptive reactions of the cardiovascular system and for fluid-electrolyte metabolism during acute adaptation of the human body to reduced gravity.

Comparison of physiological effects of head-down tilting and immersion on the human body.

Among the methods simulating weightlessness, effects on the human body, head-down tilting and water immersion are very useful. The purpose of the present investigation was to carry out a comparative study of water balance and water-protein composition of the blood using the above two methods to simulate the physiological effects typical of an acute stage of weightlessness adaptation. The results of the 7-d head-down tilting and immersion experiments allow the following conclusions: More pronounced changes in water balance and water-protein composition of the blood during immersion seem to indicate that immersion produces a greater effect on the human body; The pattern of changes during immersion and tilting suggests that the adaptation period to immersion takes a longer time; These findings give evidence that immersion, compared with head-down tilting, reproduces more closely effects of acute adaptation to simulated weightlessness.