Promoting Sensorimotor Response to Generalizability: A Countermeasure to Mitigate Locomotor Dysfunction After Long-duration Spaceflight (Mobility) studies changes in posture and gait after long-duration spaceflight. Anticipated results may help in the development of an in-flight treadmill training program for International Space Station (ISS) crewmembers, which could facilitate rapid recovery of functional mobility after long duration space flight.Principal Investigator(s)
Johnson Space Center, Human Research Program, Houston, TX, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)Research Benefits
Information PendingISS Expedition Duration:
June 2002 - April 2006Expeditions Assigned
5,6,7,8,9,10,11,12Previous ISS Missions
Similar protocols, performed by the Mobility control group, were performed during STS-71/Mir-18 and STS-74/Mir-19.
Following space flight, astronauts experience disturbances in balance and walking control during the postflight readaptation period, due in part to changes in the way the central nervous system processes sensory information as a result of prolonged exposure to microgravity. The goal of this study is to develop an inflight treadmill training program that facilitates recovery of locomotor function after long-duration space flight.
The proposed training program is based on the concept of adaptive generalization. During this type of training, the subject gains experience producing the appropriate adaptive behavior under a variety of sensory conditions and balance challenges. As a result of this training, the subject learns to solve a class of balance and walking problems rather than producing a single solution to one problem. Therefore, the subject gains the ability to "learn to learn" under a variety of conditions that challenge the balance and walking control systems.
Mobility will develop an inflight countermeasure built around ISS treadmill exercise activities. By manipulating the sensory conditions of exercise (e.g., varying visual flow patterns during walking), this training regimen will systematically and repeatedly promote adaptive change in walking performance, improving the ability of the astronaut to adapt to a novel gravity environment. It is anticipated that this training regimen will facilitate neural adaptation to unit (Earth) and partial (Mars) gravity after long-duration space flight.
All participating subjects perform two tests of locomotor performance both preflight and postflight: the Integrated Treadmill Locomotion Test and the Functional Mobility Test.
Following long-duration space flight, crewmembers have trouble standing and walking. The magnitude and duration of postflight instability increases with longer exposure to microgravity and can pose a risk to crew safety and to mission objectives during extravehicular operations during planetary exploration. Presently, no operational countermeasure is available to mitigate these balance and locomotor disturbances. This study proposes to develop a unified, multi-disciplinary countermeasure system designed to enhance postflight adaptive locomotor function that can be easily integrated with the existing International Space Station (ISS) treadmill procedures, without requiring more commitment of valuable crew resources. If successful, this experiment will provide methods for mitigating one of the most significant obstacles to long-term space flights, including trips to the Moon and Mars.Earth Applications
As people age on Earth, they sometimes experience instabilities in standing and walking. The development of unique walking and balance training procedures like the ones proposed in this study can be used to help prevent falling and injury in the elderly population.
A minimum of nine subjects are needed to perform the preflight and postflight baseline data collection for this investigation.Operational Protocols
Following their return to Earth, astronauts experience disturbances in their ability to walk and maintain postural stability due to neural adaptation to the microgravity conditions of space flight. These changes can impact the ability of crewmembers to complete mission critical tasks following the initial introduction to a novel gravitational environment following a landing on a planetary surface. The goal of this project was to characterize the effects of long-duration space flight on astronaut locomotor control and functional mobility.
The Mobility investigation was conducted with 18 ISS crewmembers over the course of Expeditions 5-12. Locomotor function was assessed before and after space flight using two tests of gait function. The first test characterized alterations in several systems responsible for the control of locomotion. For this test subjects walked on a treadmill to assess changes in dynamic visual acuity and lower limb coordination strategies. The second test provided a corresponding assessment of overall functional mobility by testing the subjects' ability to negotiate a complex obstacle course.
Toe clearance (minimum height of the toe as the foot swings forward) during treadmill walking was assessed to determine whether astronauts are at an increased risk of tripping after their return from long-duration space flight. Test performed on landing day indicated reduced toe clearance and an increased risk of tripping during walking one day after space flight. However, tripping risk on subsequent days was not different than preflight (Miller et al., 2010). Postflight changes in gaze control produced decreases in the ability to see clearly during walking. Recovery in visual performance occurred during the two-week postflight recovery period (Peters et al., 2011). Results from the obstacle course indicated that adaptation to space flight led to a 48% increase in time to traverse the course one day after landing, and recovery of function took an average of 15 days to return to within 95% of their preflight level of performance. This recovery was characterized by a two stage re-adaptation process characterized by a fast learning response using cognitive supervision followed by a slower learning process designed to ultimately automate re-learned gait patterns (Mulavara et al., 2010).
Dynamic visual acuity (DVA) data from 14 crewmembers after their return from long-duration (6 months) stays in space show changes in gaze control. These changes can affect the ability of crewmembers to clearly see visual targets while moving after space flight. Acuity assessments were made while seated (static condition) and walking (dynamic condition) on a motorized treadmill. Static and dynamic acuity differences measure the ability to maintain gaze fixation on a visual target while in motion. A decrease in postflight dynamic visual acuity was found during walking. The population mean showed a consistent improvement in DVA performance during the week-long postflight recovery period, although the individual recovery rates varied. When adjusted for previous long-duration flight experience, the averaged results showed an unexpected DVA degradation during the readaptation curve that has also been observed in prism adaptation studies. When data for the seven subjects with previous long-duration space flight experience were shifted by a day, group recovery curves aligned in a manner that suggests these subjects were 1 day ahead of the others in their recoveries. Because these results were produced during the actively-controlled process of walking, researchers believe that they may significantly underestimate the decrements in visual performance that could be experienced during passive movements like the vehicle vibrations present during, and immediately following, landing (Peters et al. 2011).
This research provides valuable data on the extent of postflight locomotor dysfunction, the rate of improvement, and the expected duration of dysfunction of crewmembers following long-duration space flight. Results will be important in the design of interventions to mitigate space flight related locomotor disturbances.
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Cohen HS, Kimball KT, Mulavara AP, Bloomberg JJ, Paloski WH. Posturography and locomotor tests of dynamic balance after long-duration spaceflight. Journal of Vestibular Research. 2012 January 1; 22(4): 191-196. DOI: 10.3233/VES-2012-0456. PMID: 23142833.
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