The degree to which the musculoskeletal system will maintain its integrity during prolonged sojourns in the reduced gravity of the lunar surface is presently unknown. It is, however, likely that without countermeasures there will be adaptive changes in muscle strength, bone mineral density, bone geometry and sensorimotor status. When the combined effects of these changes are considered in the context of the construction and exploration tasks that will be performed at the lunar base or at other lunar sites, the risk of injury secondary to a fall is likely to be elevated. To address this fundamental problem, we have constructed a compact platform that integrates a time-efficient integrated battery of countermeasures that can be conducted in the confines of the lunar habitat to minimize the risk of musculoskeletal injury. Ultimately, we expect that this battery of countermeasures will be validated using a 10 degree head-up bed-rest simulation of a lunar mission, although it could also be tested in the standard 6 degree head down- simulation.

Specific Objectives of Countermeasure Battery

1. To preserve muscle strength and cardiovascular fitness.
2. To minimize decrements in postural stability, dynamic balance and the ability to make corrective actions prior to a fall.
3. To preserve functional performance on mission relevant tasks.
4. To minimize bone loss in the proximal femur.

Also, in the coming year, we plan to carry out a sub-study testing the balance training function of our device in subjects with sensorimotor deficits. We believe that this study will establish that the gains in muscle strength and V02max, when the device is used with an exercise prescription simulating its function in bed rest and spaceflight, will be comparable to historical studies in which resistive and cardiovascular exercises have been performed in parallel. We hypothesize that the combined effect of this multi-faceted intervention will be to significantly reduce the risk of a work-related falls and subsequent injury. Ultimately, we expect to test our hypothesis in a bed-rest study by randomizing half of our subjects to a group which will undergo the integrated countermeasure and the other half to a control group. Pre-and post-bed rest, we will compare indices of balance, muscle strength and skeletal density as well as function using a combination of functional and strength tests, serum and urine bone markers and computed tomography (CT) and dual energy X-ray (DXA) imaging of the hip, spine and tibia.

Earth-based Applications of Research Project
Outside of the space medicine community, there is a growing appreciation of the importance of an integrated musculoskeletal approach towards prevention of age-related skeletal fractures. Hip fractures, which represent the most serious manifestation of osteoporosis, rarely occur without falls, and the exercise strategies developed here could potentially be adapted to an older demographic, with the same compact exercise and balance countermeasures geared towards reduction of falls and bone loss in the growing population of elderly.

We believe that the compact characteristics of the combined countermeasure devise which are optimal for the spaceflight environment will also fulfill the needs for an in-house exercise device or for a nursing home. It is well known that impaired balance is associated with aging and with an increased risk of falling. Balance training exercise in the elderly has been shown to reduce risk of falls. In particular, resistive exercise has been shown to increase muscle strength in the elderly, and increases in muscle strength and balance are associated with improvements in performance and mobility, which are important determinants of quality of life in the elderly. Finally, by focusing on resistive exercise in the abductor and adductor muscle groups, this device is expected both to improve lateral balance and reduce the rate of age-related bone loss by stressing those muscle groups that attach at the hip and thus providing significant mechanical loads on the proximal femur.

Project Description
NASA Task Book Entry