Promoting Sensorimotor Response Generalizability: A Countermeasure to Mitigate Locomotor Dysfunction After Long-Duration Space Flight (Mobility) - 07.15.14
ISS Science for Everyone
Science Objectives for Everyone 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.
Science Results for Everyone
Astronauts returning to Earth sometimes have a hard time walking, standing, and seeing, which affects their ability to function normally for a short time. Researchers study returning crew members walking on a treadmill and negotiating an obstacle course to evaluate changes in their abilities and time needed for recovery. Walking difficulties go away within a few days, while some test subjects need about 2 weeks to return to normal on the obstacle course. Visual ability consistently improved during the week-long, post-flight recovery period. The data may be used to help develop an in-flight treadmill training program aimed at rapid recovery of functional mobility after long flights.
Johnson Space Center, Human Research Program, Houston, TX, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
June 2002 - April 2006
Previous 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.
- Promoting Sensorimotor Response Generalizability: A Countermeasure to Mitigate Locomotor Dysfunction After Long-Duration Space Flight (Mobility) will develop an inflight countermeasure built around the ISS treadmill exercise activities.
- By manipulating the sensory conditions of exercise (by varying visual flow patterns, body load and speed) this training regimen will systematically and repeatedly promote adaptive change in walking performance.
- This training program will assist the astronauts with adapting to Earth's gravity and to the gravity on Mars after long-duration space flight.
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.
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.
- Preflight and Postflight Testing
- Locomotor function will be assessed before and after space flight using two tests of gait function. The Integrated Treadmill Locomotion Test characterizes alterations in the integrated function of multiple sensorimotor subsystems. This test calls for subjects to walk on a motorized treadmill while we assess changes in dynamic postural stability, head-trunk coordination, visual acuity and lower limb coordination strategies. The Functional Mobility Test provides a corresponding assessment of the functional and operational changes in locomotor function by testing subject's ability to negotiate an obstacle course placed over a medium-density foam floor.
- Subjects walk at 6.4 km/h on a motorized treadmill while performing a visual task consisting of identifying the position of the gap in the letter "C" that is presented centrally on a laptop computer positioned 4 meters in front at eye level. Each trial lasts approximately 30 seconds and is repeated four times.
- Subjects also walk at 6.4 km/h on the treadmill while performing the same visual task described above but in this case with the letter "C" is presented centrally on a micro-display positioned 50 centimeters in front at eye level. Each of these trials last approximately 30 seconds and are repeated four times.
- While subjects are walking on the treadmill and performing the visual task 3-dimensional full-body motion data are acquired using a video-based motion analysis system; gait cycle timing is measured using foot switches placed in the shoes and dynamic visual acuity is assessed by the visual task described above.
- Subjects walk at a preferred pace through an obstacle course set up on a base of 10 cm thick medium density foam. The foam provides an unstable surface that increases the challenge of the test. The 6.0 m x 4.0 m course consists of several pylons and obstacles made of foam. Subjects are instructed to walk through the course as fast as possible without touching any of the objects on the course. This task is repeated three times in the clockwise direction and 3 times in the counterclockwise direction. The dependent measures are time to complete the course and the number of obstacles touched or knocked down.
Test 1: Integrated Treadmill Locomotion Test
Test 2: Functional Mobility Test
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.
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.
Mulavara AP, Feiveson AH, Fiedler J, Cohen HS, Peters BT, Miller CA, Brady R, Bloomberg JJ. Locomotor function after long-duration space flight: effects and motor learning during recovery. Experimental Brain Research. 2010. DOI: 10.1007/s00221-010-2171-0.
Peters BT, Miller CA, Brady R, Richards JT, Mulavara AP, Bloomberg JJ. Dynamic visual acuity during walking after long-duration spaceflight. Aviation, Space, and Environmental Medicine. 2011; 82(4): 463-466. DOI: 10.3357/ASEM.2928.2011.
Miller CA, Peters BT, Brady R, Richards JR, Ploutz-Snyder RJ, Mulavara AP, Bloomberg JJ. Changes in Toe Clearance During Treadmill Walking After Long-Duration Spaceflight. Aviation, Space, and Environmental Medicine. 2010; 81(10): 919-928. DOI: 10.3357/ASEM.2680.2010.
Ground Based Results Publications
Bock O, Schneider SM, Bloomberg JJ. Conditions for interference versus facilitation during sequential sensorimotor adaptation. Experimental Brain Research. 2001; 138(3): 359-365.
Miller CM, Mulavara AP, Bloomberg JJ. A quasi-static method for determining the characteristics of a motion capture camera system in a split-volume configuration. Gait and Posture. 2002; 16(3): 288-7.
Layne CS, McDonald PV, Bloomberg JJ. Neuromuscular activation patterns during locomotion after space flight. Experimental Brain Research. 1997; 113: 104-116.
Layne CS, Mulavara AP, McDonald PV, Pruett CJ, Kozlovskaya IB, Bloomberg JJ. The effects of long-duration spaceflight during self-generated perturbations. Journal of Applied Physiology. 2001; 90: 997-1006.
Mulavara AP, Verstraete MC, Bloomberg JJ. Modulation of head movement control in humans during treadmill walking. Gait and Posture. 2002; 16(3): 271-282.
Layne CS, Mulavara AP, McDonald PV, Pruett CJ, Kozlovskaya IB, Bloomberg JJ. Alterations in human neuromuscular activation during overground locomotion after long-duration spaceflight. Journal of Gravitational Physiology. 2004; 11(3): 1-15.
Reschke MF, Bloomberg JJ, Huebner WP, McDonald PV, Peters BT, Layne CS, Berthoz A, Glasauer S, Newman DJ, Jackson DK. Effects of Spaceflight on Locomotor Control, published in Extended Duration Orbiter Medical Project. NASA Special Publication; 1999.
Richards JT, Mulavara AP, Bloomberg JJ. Postural stability during treadmill locomotion as a function of the visual polarity and rotation of a three-dimensional virtual environment. Presence: Teleoperators and Virtual Environments. 2004; 13(3): 371-384.
Layne CS, Lange GW, Pruett CJ, McDonald PV, Merkle LA, Mulavara AP, Smith SL, Kozlovskaya IB, Bloomberg JJ. Adaptation of neuromuscular activation patterns during treadmill walking after long-duration space flight. Acta Astronautica. 1998; 43(3-6): 107-119.
Seidler RD, Seidler RD, Bloomberg JJ, Stelmach GE. Patterns of transfer of adaptation among body segments. Behavioral Brain Research. 2001; 122(2): 145-157.
Roller CA, Cohen HS, Kimball KT, Bloomberg JJ. Variable practice with lenses improves visuo-motor plasticity. Cognitive Brain Research. 2001; 12(2): 341-352.
Bloomberg JJ, Mulavara AP. Changes in walking strategies after spaceflight. IEEE Aerospace and Electronic Systems Magazine. 2003; 22(2): 58-62.
Reschke MF, Bloomberg JJ, Harm DL, Paloski WH, Layne CS, McDonald PV. Posture, locomotion, spatial orientation, and motion sickness as a function of space flight. Brain Research Reviews. 1998; 28: 102-117.
Bloomberg JJ, Peters BT, Smith SL, Huebner WP, Reschke MF. Locomotor head-trunk coordination strategies following space flight. Journal of Vestibular Research. 1997; 7: 161-177.
Bloomberg JJ, Mulavara AP, Cohen HS. Developing sensorimotor countermeasures to mitigate postflight locomotor dysfunction. Conference and Exhibit on International Space Station Utilization, Cape Canaveral, FL; 2001 4941.
Moore ST, MacDougall HG, Peters BT, Bloomberg JJ, Curthoys IS, Cohen HS. Modeling locomotor dysfunction following spaceflight with Galvanic vestibular stimulation. Experimental Brain Research. 2006; 174: 647-659.
Newman DJ, Jackson DK, Bloomberg JJ. Altered astronaut lower-limb and mass center kinematics in downward jumping following space flight. Experimental Brain Research. 1997; 117: 30-42.
McDonald PV, Basdogan C, Bloomberg JJ, Layne CS. Lower limb kinematics during treadmill walking after space flight: Implications for gaze stabilization. Experimental Brain Research. 1996; 112: 325-334.
Cavanagh PR, Cavanagh PR, Licata AA, Rice AJ. Exercise and Pharmocological Countermeasures for Bone Loss During Long-Duration Space Flight. Gravitational and Space Biology. 2005; 18(2): 39-58. PMID: 16038092.
International Space Station Medical Project (ISSMP)
Life Sciences Data Archive
Shuttle-Mir History - Biomechanics of Movement During Locomotion
NASA Fact Sheet
NASA Image: JSC2002E33152 - A participant performs a treadmill motion analysis test. This test tracks the participant's body placement and balance, elements of locomotion that undergo alterations during space flight. Mobility participants will undergo similar testing before and after their expedition.
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NASA Image: JSC2002E33153 - A participant performs a treadmill motion analysis test. This test tracks the participant's body placement and balance, elements of locomotion that undergo alterations during space flight. Mobility participants will undergo similar testing before and after their expedition.
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NASA Image: JSC2002E33157 - A test subject performs the functional mobility test. This test uses foam pylons as obstacles.
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NASA Image: JSC2002E47041 - A close up of a participant performing the variable training protocol. This test is only performed by the experiment subjects while in space.
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NASA Image: JSC2002E47040 - A participant performs the variable training protocol. This test is only performed by the experiment subjects while in space.
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NASA Image: ISS010E24001 - Astronaut Leroy Chiao, Expedition 10 commander and NASA ISS science officer, equipped with a bungee harness, exercises on the Treadmill Vibration Isolation System (TVIS) in the Zvezda Service Module of the International Space Station (ISS). Crewmembers completing standard exercise protocols on ISS are the experimental controls for the Mobility experiment.
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NASA Image: JSC2004E51814 - On November 24, 2004, Astronaut John L. Phillips (left), Expedition 11 NASA space station science officer and flight engineer, participates in a mobility session of the Integrated Treadmill Locomotion Test (ITLT) at Johnson Space Center. Jacob Bloomberg (center) and Brian Peters assisted Phillips.
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