Overview

Development of a Gait Adaptability Training Program as a Countermeasure for Post-Flight Locomotor Dysfunction

Principal Investigator:
Jacob J. Bloomberg, Ph.D.

Organization:
NASA Johnson Space Center

Following their return to Earth, crewmembers experience disturbances in their ability to walk and maintain postural stability due to neural adaptation to the microgravity conditions of spaceflight. To counter this, Dr. Jacob J. Bloomberg is developing an in-flight Gait Adaptability Training Program to facilitate recovery of locomotor function. In this program, the subject learns to solve a class of motor problems rather than a specific motor solution to one problem. To develop the Gait Adaptability Training program, Bloomberg will conduct a ground-based study that will systematically investigate the training efficacy associated with exposing subjects to different combinations of sensory input during treadmill activities including alterations in visual flow, body loading and support surface stability. The goal of this training regimen is to enhance sensorimotor adaptability and facilitate re-adaptation to the gravities of Earth and Mars after long-duration spaceflight.

NASA Taskbook Entry

Technical Summary

During the acute phase of adaptation to novel gravitational environments on exploration-class missions, sensorimotor disturbances have the potential to disrupt the ability of astronauts to ambulate and perform functional tasks. The goal of this project was to develop a sensorimotor adaptability (SA) training program designed to facilitate recovery of locomotor and functional capabilities when astronauts transition to different gravitational environments and during the post-landing recovery period following return to Earth.

We have previously shown that training with task variability along with exposure to a variety of surrogate sensorimotor challenges leads to faster adaptation to new environments that have not been previously explored. By applying these concepts for training astronauts, we can enhance their ability to learn how to learn to adapt to new gravitational environments. To achieve the projects goal, we applied these adaptability motor-learning concepts to develop an astronaut SA training program. The project conducted a series of studies that investigated the efficacy of treadmill training combined with a variety of sensory challenges designed to increase adaptability, including alterations in visual flow, body loading and support-surface stability.

Findings
SA training using a treadmill (an analog to over-ground locomotion) was effective in producing increased adaptability in a more complex over-ground ambulatory task on an obstacle course. This confirms that for a complex task like walking, treadmill training contains enough of the critical features of over-ground walking to be an effective training modality.

Balance board training alone did not increase training efficacy demonstrating the limitations of training by showing that the training tasks must have certain critical features to allow full generalization.

Training that used constantly varying and challenging sensory input during each training session gave subjects a greater ability to rapidly reorganize appropriate response strategies when encountering a novel sensory environment and did not produce interference to motor learning. This indicates that training modes can be designed to maximally promote the rapid adaptability that would be required to deal with an emergency scenario requiring immediate responses soon after landing on a planetary surface.

To investigate the utility of body unloading as a training modality, we demonstrated that walking on a treadmill for 30 minutes while supported at 40 percent of body weight via a pneumatic harness produced adaptive alteration in head movement control, lower limb kinematics and gait cycle timing. These results indicate that alteration in body load can serve as an effective adaptability training modality.

Using a treadmill mounted on top of a six-degree-of-freedom motion base platform, we investigated locomotor training responses produced by subjects introduced to a dynamic walking surface. This study examined the strategies employed by subjects exposed to continuous, sinusoidal lateral motion of the support surface while walking on a treadmill. The results indicate that in order to optimize gait stability, some subjects depended more heavily on vision and others on proprioception. These results allow us to better design training modalities specifically targeted to an individual crewmembers sensorimotor biases.

In an associated study, we confirmed that SA training could be used to improve balance and locomotor performance in older adults and points to the general applicability of this type of training in different populations.

The data obtained in this project will aid in the design of a countermeasure system used to support exploration-class space missions. The operational version of this countermeasure will provide sensory challenges during regular exercise in both pre-and in-flight training modes to allow crew members to maximize their motor response adaptability facilitating the adaptive transition to partial or unit gravity.

Earth Applications

From a clinical perspective, exposure to varied sensorimotor stimuli during treadmill walking provides environmental enrichment to enhance gait and postural adaptability. A vast literature demonstrates that the central nervous system requires a rich and varied sensorimotor environment to maintain normal structure and function. Also, a converging body of evidence supports the use of environmental enrichment both before and after brain trauma, as an intervention to help restore behavioral function These studies indicate that exposure to environmental enrichment can play a central role in the restoration of functional mobility. Importantly, studies have shown that training comprised of challenging balance tasks compared to simple repetitive or treadmill exercises alone increases structural plasticity in the motor cortex and thalamus.

Within the context of locomotor functional training and rehabilitation, it is clear that an enriched and challenging environment provided by virtual reality devices provides the optimal conditions to explore variability and in that exploration to increase adaptability of motor function. Indeed, the concept of employing virtual reality technology as a tool for rehabilitation has become a topic of great interest among a number of researchers. A collateral benefit of the application of virtual reality technology, in this context, will be to make gait training programs for both spaceflight and rehabilitation more interesting, ultimately leading to increased adherence to prescribed training regimens.

In addition, the gait adaptability training program being developed by this project can be used to reduce the propensity of falling in the elderly. We have pursued this line of research in collaboration with Drs. Ronita Cromwell and Regina Buccello-Stout at the University of Texas Medical Branch in Galveston. This associated study compared a group of elders receiving the specialized treadmill adaptability training developed under NSBRI funding with a group that received the treadmill training only. Results from this study showed significantly improved gait function in elders that received the sensorimotor adaptability training (Buccello-Stout et al., 2008). This study clearly demonstrated the general utility of the training method beyond the NASA applications.

This project's funding ended in 2008