The experimental approach to meet the goals of this study was to collect functional performance data from International Space Station (ISS) astronauts exposed to the spaceflight environment for a long-duration (>90 d) who performed simulated critical exploration mission tasks and measure a corresponding set of interdisciplinary physiological measures targeting the sensorimotor, cardiovascular, and neuromuscular adaptations known to be affected by spaceflight.
Ultimately, this information could be used to assess performance risks and inform the design of countermeasures for National Aeronautics and Space Administration (NASA) exploration class missions. We hypothesize that adaptation to the microgravity environment during long-duration spaceflight will cause changes in cardiovascular, neuromuscular, and sensorimotor function, and these changes will impact the performance of mission critical tasks in a differential manner related to the nature of the task. Therefore, the goal of this study was to determine the effects of spaceflight on the performance of functional tests that are representative of critical exploration mission tasks and to identify the changes in sensorimotor, cardiovascular, and neuromuscular factors that would likely affect the changes in performance of critical mission tasks. To date, no studies have been performed that integrated testing before and after spaceflight with the specific intent to determine how alterations in individual physiological systems impact functional performance of critical exploration mission tasks. To be able to define an effective and comprehensive countermeasure strategy for preserving performance of functional tasks after prolonged spaceflight, there is a need to understand the contributions of the changes in different physiological systems to the changes observed in functional task performance. These tasks place varying levels of demands on the functioning of physiological systems. Such tasks that are required during operations after landing on a planetary surface or after the return to Earth are generally identified as critical mission tasks. Therefore, we used the 6° head-down tilt (HDT) bed rest model to investigate and explain these multifactorial effects in isolation from other factors (e.g., isolated environment, vestibular changes, elevated environment CO 2 levels) and compare them with results obtained from spaceflight.įunctional tasks can be part of activities performed inside or outside of a space vehicle in different operational scenarios. Further, previous bed rest research focused on sensorimotor alterations suggests that data from prolonged bed rest can be used to help separate modifications within the vestibulospinal system in response to spaceflight from changes in the somatosensory-spinal system driven by axial unloading ( 11). Changes in muscle properties due to disuse and atrophy can also lead to loss in mobility and contribute to falls as seen in the elderly ( 14). Orthostatic intolerance is present after both real and simulated microgravity exposures and is associated with hypovolemia, cardiac remodeling, and decreased systolic and mean arterial blood pressure ( 12, 13).
Thus, similar to spaceflight, the effects on human physiology as a result of prolonged exposure to a bed rest environment are multifactorial. A combination of sensorimotor alterations, reduced muscle strength, or presyncopal symptoms caused by orthostatic intolerance may inhibit timely execution of the egress.īed rest is a well-accepted spaceflight analog ( 8) to understand the implications of muscle disuse ( 9), cardiovascular deconditioning ( 10), and to simulate the axial unloading experienced by the sensorimotor system ( 11). For example, mobile mission tasks after landing on a planetary surface may include a rapid egress from a vehicle. These adaptations are often manifested in balance and gait disturbances ( 1, 2), cardiovascular deconditioning ( 3, 4), and loss of muscle mass, muscle coordination, and strength ( 5– 7). Multiple studies have demonstrated that exposure to spaceflight produces adaptations in sensorimotor, cardiovascular, and neuromuscular systems that are maladaptive upon return to 1 g. Physiological responses to microgravity have been studied over the history of human spaceflight.
0 kommentar(er)
