Effect of Hindlimb Unloading of the Mechanical Properties of Bone in Mature Adult Male Rats: with Emphasis on the Bone Strength / 항공우주의학회지

BACKGROUND: The purpose of this study was to examine site-specific bone strength changes induced by hindlimb unloading in mature adult male rats. METHODS: Eight month old (390-410 g) 26 male Sprague-Dawley rats were weight-mated assigned to either a Ground control (CON) or a Hindlimb Unloading (HU) for 24 days. Daily body weight was watched for status of animal. Weight, BMD, strength, geometry of femur, tibia and humerus were examined in both groups. RESULTS: The 24-day hindlimb unloading of HU showed no significant change of body weight, total bone mineral, and bone geometry compared to CON. HU showed that the upper limb had maintained total bone mineral, bone geometry, and bone mechanical strength compared to CON. The hindlimb of HU had significantly decreased bone strength and ultimate stress (F/B) compared to CON. DEXA analysis of BMD and BMC in HU showed inconsistent changes at femur and tibia, although a relatively constant increase was shown in humerus. In HU rats, mechanical stress testing of compulsive fracture showed that more significant decreases in UL (ultimate load) and ultimate stress (F/B) was seen in femur than in tibia. CONCLUSION: These results support the theory that hindlimb unloading contribute to deleterious effects in femur rather than in tibia. It induced higher loss of mechanical bone strength in femur. In testing for BMD, pQCT, 2D, or 3D is recommended. DEXA is not recommended because it has inconsistent results and limitation with respect to the characteristics of area BMD (g/cm2) as a surrogate of volume BMD (g/cm3).

Analysis of Risk Factors on the G-induced Loss of Conscious in ROKAF Pilots / 항공우주의학회지

Of all the aeromedical treats to flying safety, G-induced loss of consciousness (G-LOC) must be one of the most important. The present study is undertaken to acquire the physiological normative data (including lifestyle and physical fitness) of KAF pilots and to investigate the factors that will be related with G-LOC. From 15 May through 27 Nov 2000, 464 KAF pilots underwent high G training and flight performance tests at the Aeromedical Research and Training Center are checked CBC, total cholesterol, PFT, physical fitness battery tests-muscular strength, muscular endurance, power, and flexibility. High G training and 2 kinds (before and after the G-training) of questionnaire were tried. Pilot's attitude for health promotion was relatively passive and the proportions as of high and borderline risk for atherosclerosis in total cholesterol level were 4.98% and 22.1%, respectively. 17.6% of the pilots had G-LOC and three quarters of them fell into G-LOC within the first 5 seconds. Variables showing significant correlation (p<0.05) with G-LOC were as follows; height, age, total flying time, and high G-training times. Trunk extension had positive correlation and curls ups had negative correlation, but the reasons are needed more following study. Also, the judgments of pilots and a supervisor in skillfulness of L1 maneuver were significant with G-LOC.