Objectives
Gravity supplies a frame of reference for the human sensory-motor response. In the absence of gravity, such as during space flight, several systems are hindered. These disturbances are compensated for by the brain, and ultimately, the body adapts to the weightless environment. Balance and locomotion are temporarily disturbed after return to Earth, but eventually return to preflight levels. Postural problems reported by crewmembers include increased sway while standing, difficulty in rounding corners and increased body movement during locomotion. This investigation assessed the impact of microgravity on neuromuscular anticipatory postural activity and examined the changes, intending to provide a better understanding of balance and locomotion in humans and to design countermeasures which could reduce the time course of re-adaptation to gravity on Earth.
Five objectives were examined during this study. These were:
(1) to determine how long-duration space flight altered the anticipatory neuromuscular activity associated with arm movement,
(2) to perform proof-of-concept research to determine whether foot sensory input modified neuromuscular responses during space flight,
(3) to determine the time course of adaptation during long-duration space flight to foot sensory input as measured by patterns of neuromuscular activation,
(4) to determine whether long-duration space flight modified anticipatory neuromuscular postural activity in the immediate postflight period, and
(5) to determine whether modifications in anticipatory neuromuscular postural activity associated with long-duration space flight were correlated with postural instability immediately after landing and during the recovery period.
Shuttle-Mir Missions Approach
During inflight data collection, the BPAS vest assembly was used to collect EMG and acceleration data during a series of arm raises. Inflight testing involved four test conditions: (1) 15 arm raises while free-floating, (2) 15 arm raises while free-floating with the addition of foot pressure, (3) 15 arm raises while attached to the Mir support surface, (4) 15 arm raises while bunged to the Mir treadmill. The foot pressure boots were worn during test conditions 2 and 3. No force plate or motion analysis data was obtained in flight.
Results
Free-floating arm movements performed with the addition of foot pressure (provided by the pressure boots) resulted in the lower limb muscle activation always observed prior to arm movements made while upright in unit gravity.
Postflight, the crewmembers were unable to optimally perform the arm raise task and demonstrated less postural control during the arm motion after space flight. The data indicated that the precise neuromuscular activation patterns necessary for optimal arm movement were not produced after space flight.
In conclusion, evidence suggested that there were a wide range of individual responses of the movement control system to space flight and the ground-based Posa test could be utilized to characterize this response range. The ability to generate the same neuromuscular activation patterns used to perform preflight movement was compromised after space flight. No preliminary conclusions concerning inflight data can be drawn at this time. However, evidence from previous flights has consistently indicated that the addition of foot pressure results in enhanced neuromuscular activation.
Earth Benefits Publications
Layne, C.S., McDonald, P.V., Mulavara, A.P., Kozlovskaya, I.B., and Bloomberg, J.J. Adapting neuromuscular synergies in microgravity. Bernstein's Traditions in Motor Control Conference, Pennsylvania State University, University Park, PA, August, 1996.
Layne, C.S., McDonald, P.V., Pruett, C.J., Mulavara, A., Kozlovskaya, I.B., Voronov, A.V., and Bloomberg, J.J. The impact of space flight on anticipatory muscle activation. Annual Meeting of the American Institute of Aeronautics and Astronautics, Houston, TX, March, 1996.
Layne, C.S., Mulavara, A.P., McDonald, P.V., Pruett, C.J., and Bloomberg, J.J. Somatosensory input enhances neuromuscular activation during movements performed while free-floating in microgravity. Society for Neuroscience Annual Meeting, Washington, D.C. November, 1996.
Mulavara, A.P., McDonald, P.V., Layne, C.S., Poliner, J., Pruett, C.J., and Bloomberg, J.J. Quantifying adaptive preparatory postural adjustments that occur following space flight. 14th Annual Houston Conference on Biomedical Engineering Research, Houston, TX, February, 1996.
Layne, C.S., Spooner, B.S. Microgravity effects on "postural" muscle activity patterns. Adv. in Space Res. 1994 (in press).
Layne, C.S., McDonald, P.V., Mulavara, A.P., and Bloomberg, J.J. ''Adaptations in movement control after space flight..'' Annual Meeting of the North American Society for Psychology of Sport and Physical Activity, St. Charles, IL, June, 1998.
Layne, C.S., Mulavara, A.P., McDonald, P.V., Pruett, C.J., Kozlovskaya, I.B., and Bloomberg, J.J. ''The impact of long-duration space flight on upright postural stability during unilateral arm raises.'' Annual Meeting of the Society for Neuroscience, New Orleans, LA, October, 1997.
Layne, C.S., Mulavara, A.P., Pruett, C.J., McDonald, P.V., Kozlovskaya, I.B., and Bloomberg, J.J. ''The use of inflight foot pressure as a countermeasure to neuromuscular degradation.'' Acta Astronautica, vol. 42, no. 1-8, 231-246 (1998).
Principal Investigators
Inessa B. Koslovskaya, M.D. Co-Investigators
Mir-21/NASA-2
During all ground-based data collection, subjects wore shorts, T-shirts and stocking feet with electrodes and accelerometer leads attached to the body with adhesive tape (Belt Pack Amplification System (BPAS) vest assembly). An accelerometer was attached to a wrist splint worn by the subject. The subject stepped onto a force plate, assumed an upright position with feet shoulder-width apart and arms resting comfortably at the sides. With eyes closed, the subject performed 15 rapid, 90-degree shoulder flexions, keeping the arm and wrist locked throughout the movement. The movements were self-initiated and the subject regained stability before performing the next movement. The Flock of Birds motion analysis system was used during this testing to obtain measures of body segmental motion.
In flight, the addition of foot pressure resulted in increased muscle co-contraction relative to movement conditions without the pressure boots. This measure was a further reflection of the increase in muscle activation caused by the addition of foot pressure. Free-floating arm movements performed without foot pressure resulted in the elimination or severe reduction of the lower limb muscle activation always observed prior to arm movements made while upright in unit gravity.
This project has the potential to increase the understanding of processes whereby sensory input results in neuromuscular activation. It is suggested that many of the processes that contribute to muscle atrophy on Earth also contribute to the atrophy associated with space flight. It is anticipated that foot pressure will be regularly used to lessen lower limb muscle atrophy and maintain the functional state of muscles in bedridden patients.
Layne, C.S., Bloomberg, J.J., McDonald, P.V., Mulavara, A.P., and Pruett, C.J. The use of foot pressure to enhance neuromuscular activation during space flight. Annual Meeting of the American Institute of Aeronautics and Astronautics, Houston, TX, March, 1996.
Charles S. Layne, Ph.D.
University of Texas at Austin
Institute of Biomedical Problems
Jacob J. Bloomberg, Ph.D.
Vernon P. McDonald, Ph.D.
Andrei A. Voronov, Ph.D.
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Curator:
Julie Oliveaux
Responsible NASA Official: John Uri |
Page last updated: 07/16/1999
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