Astronauts experience alterations in multiple physiological systems due to exposure to the microgravity conditions of space flight. These physiological changes include, among others, sensorimotor disturbances, cardiovascular deconditioning, and loss of muscle mass and strength. Changes in these systems clearly lead to disruption in the ability to ambulate and perform functional tasks during the initial reintroduction to a gravitational environment following a prolonged weightless transit and may cause significant impairments in performance of operational tasks immediately following landing on a planetary surface. Severe impairments may lead to loss of mission. To date changes in functional performance have been systematically studied for short-duration space flights and has recently begun on the long duration International Space Station (ISS) space flights. As important as these observed postflight functional changes have been, responses within hours following landing and a recovery time constant beginning as near to the time of landing as possible through full functional recovery has never been investigated or established for long-duration flights. The objective of this study is to address this gap in knowledge, allowing investigators to understand the impact on functional performance on tasks that are representative of critical mission requirements that the crews of exploratory missions will be expected to perform after an unassisted landing following flights from 6 to 12 months in duration. Findings from this investigation will provide the information needed for planning future Mars, or other deep space missions, with unassisted landings, including water landings.
The primary goal of this study is to determine functional performance in long duration space flight crews beginning as soon after landing as possible with one to three immediate follow-up measurements on the day of landing. This goal has both sensorimotor and cardiovascular elements including an evaluation of NASA’s new Gradient Compression Garment (GCG) and the Russian traditional Kentavr garment.
Preflight and postlight, subjects will complete familiarization sessions, with the data collection team giving a thorough explanation of each test as the subject completes it. The subject will arrive in Building 266 and begin the test session with Computerized Dynamic Posture. For this test, the subject will be instructed to maintain stable upright posture for 20 second trials with feet positioned shoulder width apart, eyes closed, and arms folded across the chest while positioned on a sway-referenced support surface intended to disrupt somatosensory feedback. Three trials will be obtained with the head upright and then with the head moving. Inertial sensors will be placed on the head, torso and lower leg to capture body kinematics. The subject will then be transported to a different room where they will complete Postural Muscle Tone/Compliance. The subject will lie relaxed in a prone position with the myotonometer applied to the skin overlying the muscle to be measured. Vibration is applied to the muscle and the muscle vibration response is measured. Next the subject is instrumented with the remaining hardware (motions sensors, heart rate monitor, Portapres, pressure sensors, electrodes) and the following tests will be conducted. Hand/Eye Coordination will consist of rapid and accurate target acquisition with the finger, or stylus, on a computer touch screen. For Sit-to-Stand, the subject will transition from an upright seated position to a standing position and remain stationary for approximately 10 seconds. For Recovery from Fall, the subject will be asked to lie down on a foam mat face down for two minutes and then asked to stand up again as quickly as possible when a command to stand is issued, after which subject will stand quietly on a stable surface for three minutes. Three Cerebellar Function Tests will be conducted. The first requires the subject to touch their finger to the operator’s finger, then to touch their own nose, repeating this several times with one hand, then with the other hand. The second test requires the subject to follow the operator’s finger with their eyes only, keeping their head still. The third test requires the subject to hold one arm out to the side, shoulder height, and to resist when operator pushes their arm down, repeating it with the other arm. Seat Egress and Walk Test involves beginning in an upright seat. Once the subject has assumed a vertical stance, he or she will be asked to remain stationary for approximately 5 to 10 seconds, walk approximately 10 steps, turn, and then walk back to the chair. On the traverse back to the chair, the subject will be required to step over a barrier that increases in height with each subsequent trial. Three trials will be conducted and test will be terminated if an obstacle is knocked over. For Tandem Heel-to-Toe Walk, the subject will attempt to walk 10 steps on the floor with their eyes closed, with arms and hands folded across the chest while placing their feet in the traditional tandem heel-to-toe position first with their eyes closed for three trials and then with their eyes open for one trial. Push Test consists of the subject standing upright with arms crossed in front of the chest and eyes closed. Using a push stick, a random force is applied approximately every 10 seconds to a plastic plate fixed at the center of the chest, and the subject is asked to try and maintain balance. Dynamic Visual Acuity entails the subject using a hand-held joystick to indicate the perceived orientation of the gap in a series of letter Cs that are presented on a computer screen using both “accurate and quick” guidelines. The subject will sit in a spring-suspended portable seat and perform the task first without moving, then again with the chair oscillating vertically at 2 Hz, ±2 cm. Force Discrimination (Foot and Hand) measures the ability of the subject to differentiate between forces that are self-generated. The subject will attempt to increase force from one cycle to the next. For the foot, the subject will press down on a foot pedal, and for the hand the subject will squeeze a hand dynamometer. In Jump Down Test, the subject will use a two-footed hop to jump from a height of 30 cm (taking care to ensure that both feet leave the platform together) and land on a force plate to measure the peak vertical impact force on landing. For Simulated Rock or Payload Translation, the subject will pick up one of three weights (2.7, 4.5, 9 kg) and will carry the weight at their side a distance of 2.5 m and place it in a receptacle positioned at 51 cm above the floor. This procedure will be repeated until all three weights have been individually transferred to the receptacle. Then the subject will return each weight one-by-one to its original location. Finally, the subject will be de-instrumented and the baseline data collection (BDC) session will be complete.
On landing day after removal of the Sokol suit, the subjects that have been designated to wear the GCG will remove the Kentavr and don the GCG prior to testing. While changing clothes, Postural Muscle Tone/Compliance will be collected on the calf muscle (before the GCG is donned) and on the lower back. Subjects that do not wear the GCG, Postural Muscle Tone/Compliance will only be collected on the lower back. Subjects will be encouraged to wear the GCG during the return to the US or Star City. If the subject chooses to doff the compression garments, they will don them again prior to testing on R+0. At the completion of each task, subjects will be asked to rate their level of motion sickness.
A subset of the tests performed on the 1R session will be collected in the ACQ upon return to JSC before the subject goes to sleep. If the compression garment has been removed, it must be donned prior to testing. At the completion of each task, subjects will be asked to rate their level of motion sickness.
This experiment is in progress.