The control of the body orientation and the center of mass position with respect to the feet was investigated under normo- and microgravity (space flight Altair), during erect posture and at the end of a forward or backward upper trunk movement.
It was observed that during erect posture, the trunk orientation with respect to the vertical was inclined some 6 ° forward in both subjects under microgravity, whereas it was vertical or slightly backward oriented under normogravity. Under microgravity, on the contrary, the initial position CM changed either backwards or forwards. This result suggests that the inclined trunk posture might be due to misevaluating the vertically under microgravity and that different control mechanisms are involved in orienting the trunk and placing the CM.
It was also noted that the final position of the CM at the end of the movement did not differ markedly between microgravity and normogravity. This result suggests that the kinematic synergies which stabilize the CM during uppertrunk movements may result from an automatic central control which is independent from the gravity constraints. 相似文献
Since the first French flight in space in 1982, the CNES has developed a wide range of instruments, especially in the field of Neurosciences. The design of these instruments has considerably evolved from rather simple equipment up to much more sophisticated tools that are being specially tailored for these missions. Four major phases can be identified: -a simple adaptation of an echographe leading to the first neurosciences experiments (the ARAGATZ'88 mission), -the ILLUSIONS and VIMINAL instruments used during the ANTARES'92 and ALTAIR'93 missions, -the COGNILAB instrument developed for the CASSIOPEE'96 mission, to be re-used in 1997 and in 1999, -a preliminary design of the 1999 mission payload, including virtual reality concepts, in a modular design to adapt to the European COF. Aside from the evolution of scientific requirements, the experience gained during the flights led to progressive improvements in the different technical parts, including visual system, body restraint systems, accessories, such as a force feedback joystick, computer and software, etc. This paper describes the technical evolutions in the CNES Neurosciences program. 相似文献
The cardiovascular function is one of the main disturbed by weightlessness: it is particularly affected by the astronaut's return to Earth, where symptoms linked to the cardiovascular deconditioning syndrom appear in the following forms: (1) orthostatic intolerance with its risk of syncope: (2) higher submaximal oxygen consumption for an equivalent work load. Lower Body Negative Pressure (LBNP) is intended to stimulate the venous system of the lower limbs; however, the specific effects of periodical LBNP sessions on the orthostatic intolerance have never been studied. With this objective in mind, 5 volunteers took part in two recent antiorthostatic bedrest experiments for 30 days. In the first experiment 3 subjects were submitted to several sessions of LBNP experiment per day and 2 others were controls; in the second experiment the LBNP group of the 1st one became controls and vice-versa. Two orthostatic investigations were performed: (1) 5 days before the bedrest; (2) at the end of the 30 day bedrest period. The results showed: (1) when the subjects were control, a high orthostatic intolerance post bedrest with 3 syncopes and one presyncopal state during the first minutes of the tilt test; (2) when the subjects were submitted to LBNP sessions, no orthostatic intolerance. 相似文献
The spontaneous baroreflex response was evaluated during supine rest and head up tilt (60 degrees) before and immediately after a 28 day 6 degrees HDT bedrest in 6 healthy adult men (age 30-42 years). Sequences of 3 or more beats where RR-interval and systolic blood pressure changed in the same direction were used to evaluate baroreflex response slope (BRS). Prior to bedrest, the mean BRS and RR-interval were 18.0 +/- 3.9 ms/mm Hg and 926 +/- 61 ms at rest and 10.5 +/- 2.5 ms/mm Hg and 772 +/- 63 ms during the first 10 min of 60 degrees tilt. Following bedrest, these values changed to 15.6 +/- 2.7 ms/mm Hg and 780 +/- 53 ms at rest, and to 6.5 +/- 1.2 ms/mm Hg and 636 +/- 44 ms during tilt. Thus, (1) the spontaneous baroreflex can be evaluated in human subjects during experiments of orthostatic stress; (2) the baroreflex slope was reduced on going from supine to the head up tilt position; and (3) 28 days of bedrest reduced the spontaneous baroreflex slope. 相似文献