Development of Training Programs to Mitigate Post Space Flight Gait Dysfunction

Abstract

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. We have previously shown that astronauts returning from space flight show disturbances in locomotor control manifested by changes in various sub-systems including head-trunk coordination, dynamic visual acuity, lower limb muscle activation patterning and kinematics (Glasauer, etal., 1995; Bloomberg, et al., 1997; McDonald, et al., 1996; 1997; Layne, et al., 1997; 1998, 2001; Newman, et al., 1997; Bloomberg and Mulavara, 2003). These postflight changes in locomotor performance affect the ability of long-duration crewmembers to egress their vehicle soon after landing on Earth or following a landing on the surface of Mars. At present, no operational training intervention is available to mitigate postflight locomotor disturbances. The goal of our present research is to develop an inflight balance and gait training program that will facilitate recovery of locomotor function after long-duration space flight. The training regimen we are developing is based on the concept of variable practice. During this type of training the subject gains experience producing the appropriate adaptive motor behavior under a variety of sensory conditions and response constraints. Astronauts will conduct their nominal inflight treadmill exercise while being exposed to variations in visual flow patterns, body load and speed. These variations will challenge the locomotor system repeatedly, thereby promoting adaptive reorganization in locomotor behavior. As a result of this training a subject learns to solve a class of motor problems, rather than a specific motor solution to one problem; i.e., the subject learns response generalizability or the ability to “learn to learn” under a variety of environmental constraints. We anticipate that this training will accelerate recovery of locomotor function during readaptation to gravitational environments following spaceflight, thus facilitating neural adaptation to unit (Earth) and partial (Mars) gravity after long-duration spaceflight. To date, we have collected pre and postflight locomotion data from International Space Station Expeditions 5–9 (n =12) who will serve as part of the control group for this study. Preliminary results show that recovery of postflight locomotor function may occur through adaptive mechanisms that lead to either restitution or substitution of function. Understanding the modes of postflight readaptation has implications for development and testing of inflight training regimens.