Foot sensitivity Foot neurosensitivity tests found no change over the course of bed-rest in the sensitivity feet. Plantar nerve sensitivity tested by the use of monofilaments found no significant difference at each time point.

Joint proprioception tests showed no effect of bed-rest results showed that subject had normal proprioception at all time points. The vibration identification test results found that the number of incorrect identifications doubled over baseline; however this change was not significant

Bone Density Scans have been performed on the non-dominant ankle by quantitative ultrasound. Broadband Ultrasound Attenuation (BUA) and Ultrasound Velocity (UV) are calculated from the raw data. Both are indicators of the structure and composition of the bone). The more dense the bone is, the more signal will be attenuated and slower the velocity will be. Thinner, less structured bone will attenuate signal less, and have an overall greater velocity. Correct scans of the second subject group were not possible at day 45 due to the evacuation of Galveston. Computed Tomography scans of the hips have been analyzed. Significant decreases in bone mineral density (BMD) were found in several areas of the hip. The largest loss of bone was seen in the trabecular bone. Analysis of the spine BMD is underway. Analysis of the CT scans of the hips found a 1.6 +/- 1.25% loss in muscle cross sectional area per month in the leg during bed rest.

Postural Control Postural control measurements are available only for the first group of four subjects. Results show that there was a significant increase in sway magnitude and velocity in both the anterior-posterior (AP) and medial-lateral (ML) directions. Maximum AP sway velocity increased significantly as well. Continued analysis of the postural control data are being performed, to identify the cause of the increase is sway. Increased sway is an indicator an increased risk of falling. Causes for an increased sway could be muscle loss, loss of sensation of the feet, and changes in the vestibular system. The neurosensitivity tests found no significant effect of bed-rest on the nerves of the feet. Present analysis is looking to identify if the changes are due solely to the muscle loss seen in the leg, or if there are changes in the vestibular system which could be affecting postural control.

Application of LMMS Application of LMMS will be achieved through the use of a harness system. A vibrating platform, which provides a 0.3 g, 30 Hz signal is hung perpendicularly from a sled, which can be moved from bed to bed [Figure 11]. Subjects put on a vest, which is attached to the plate through the use of two springs. The treatment is given for 10 minutes a day, during which the subject is free to perform normal activities as they see fit.

Our data so far shows baseline data for four healthy controls. Upon completion of the bed-rest study, we will be able to compare the bone mineral density of control subjects who under went 90 days of bed-rest simulating microgravity, and an experimental group who underwent the same bed-rest, but had daily treatments of 10 minutes of mechanical stimulation. If the data collected for bed-rest mirrors what we have seen in post-menopausal women as we hypothesize, there will be a significant drop in the loss of bone due to disuse. If this is the case, it may be possible to effectively reduce and/or stop the loss of bone seen in extended hypogravity. At present, exercise regimes in the ISS and shuttle have not been effective in decreasing the loss of bone in space. LMMS has been shown in multiple ground based models to reduce and/or prevent the loss of bone in at risk groups. Animal studies, as well as human studies of post-menopausal women and children with muscular dystrophy have shown significant improvement in bone density when compared to controls. By loading the experimental subjects with 60% of their body weight, we will be creating a short term load on their axial skeleton, which will be stimulated with the mechanical vibrations generated by the plate. Because the treatment only requires the astronaut to stand upright, they are free to perform other tasks which do not require extensive motion while they undergo treatment, such as reading, writing, or computer work. The plate itself isn’t much larger than a bathroom scale. Considering the confined volume of the ISS and any space vehicle, and the high value of crew time, the treatment method is an improvement over time intensive exercise regimes requiring large equipment.

Project Aims: 1) Show that application of low magnitude (0.3g), high frequency (30Hz) mechanical stimulation, will reduce the loss of bone seen with long term disuse 2) Show that application of low magnitude, high frequency mechanical stimulation will improve the postural control of subjects undergoing long term bed-rest 3) Determine if long term bed-rest affects the sensitivity of the lower extremities. 3.b) Determine if the application of low magnitude, high frequency mechanical stimulation will inhibit the changes if they exist

Although the exact mechanism is unknown, we are seeking to determine if our regimen of daily vibration treatment will improve the postural control and reduce bone loss after disuse when compared to controls. If the retention of balance control and bone quantity/quality in astronauts can achieved without pharmacologic treatment, there are multiple benefits. Firstly, the astronauts will be more able to safely and effectively complete tasks upon re-entry to a gravity environment. Secondly, if their postural control is improved, they are at a lower risk of falling. Considering the loss of bone seen in long term hypogravity, a reduction in the risk of falling will result in a reduction in the risk of bone fracture. If the treatment is also successful in the treatment of the loss of bone, then the risk of bone fracture from extended hypogravity will be reduced even more significantly.

Following one year of support, preliminary data have been collected from bedrest subjects (control), as the first stage in evaluating efficacy of a unique, non-pharmacologic countermeasure for disuse osteoporosis--extremely low magnitude mechanical stimuli (LMMS), or, vibration. This low magnitude (0.3g), high frequency (30Hz) mechanical signal has been shown to be anabolic to bone. Work will continue in the second year to collect baseline, 60d and 90d data from controls and subjects subject to 10 minutes per day of the vibration stimulus.

Project aims: 1) Show that application of low magnitude (0.3g), high frequency (30Hz) mechanical stimulation, will reduce the loss of bone seen with long term disuse; 2) Show that application of low magnitude, high frequency mechanical stimulation will improve the postural control of subjects undergoing long term bed-rest; 3) Determine if long term bed-rest affects the sensitivity of the lower extremities.; 3.b) Determine if the application of low magnitude, high frequency mechanical stimulation will inhibit the changes if they exist

[Ed. note: FY2004 record added in December 2010 for statistical reporting purposes]