We studied the relationship between bone mineral density (BMD) and history of habitual exercise in a group of university students comprising 41 athletes (27 males and 14 females) and 39 non-athletes (24 males and 15 females), ranging in age from 18 to 28 years. Their athletic history during elementray, junior and senior high schools was surveyed. Subjects who had engaged in athletic activities more than 3 days/week for more than two years at each school level were classified as a former physically active group, whereas the others were classified as controls. The BMD of the femur (femoral neck, Ward's triangle, trochanteric region) and vertebrae (L2-4) was ieasured using dual-photon absorptiometry with a ¹⁵³Gd source. The following results were obtained: 1) University athletes showed significantly higher BMD of the femur and L2-4 than non-athletes. 2) No significant difference was found for either sex between the physically active group on elementary school days and the control group with regard to BMD of the femur and L2-4. 3) The BMD of the femoral neck and trochanteric region in the male physically active group on junior high school days was significantly higher than that in the control group. The BMD of the femoral neck in the female physically active group on junior high school days was significantly higher than that in the control group. 4) The BMD of the femur and L2-4 in the female physically active group on senior high school days was significantly higher than that in the control group, whereas no difference was found between these two groups for males. These results suggest that regular exercise during puberty is effective for increasing BMD, especially in females. The finding that increased BMD in association with physical activity on senior high school days was observed only in females may be due to the synergistic effect of estrogen and exercise.

Bone mineral content (BMC), fat weight (FAT) and lean tissue weight (LTW) were determined by dual-energy X-ray absorptiometry (DEXA) in 20 young adults of both sexes who were performing habitual exercise. From these data, body weight, lean body weight (LBW) and the percentage of BMC relative to LBW (BMC%LBW) were obtained. First, body density based on a two-component model (D₂) was calculated using the values of FAT and LBW of the subjects and the fat and lean densities of the Reference Body, Then percentage body fat (%Fat₂) was calculated using the formula of Brozek et al. The body density for a three-component model (D₃) was then determined from the values of FAT, BMC and LTW of the subjects, and the fat, bone mineral and lean tissue densities of the Reference Body. Percentage body fat (%Fat₃) was also calculated in the same manner as %Fat₂. Analysis of the data indicated that (1) females had higher values of BMC%LBW than males, and that (2) subjects whose %Fat₂ exceeded %Fat₃ by more than 1% were exclusively females whose BMC%LBW values were more than 6.1%. In contrast, those whose %Fat₂ was lower than %Fat₃ by less than -1% were exclusively males who had BMC%LBW values less than 5.2%. It is concluded that male subjects develop their muscles more than their bones with habitual exercise, which results in a lower BMC%LBW value than in females, and that for those with BMC%LBW values exceeding 6.1% (females) or less than 5.2% (males), %Fat calculation from body density using the formula of Brozek et a1. will produce an error of more than 1% if BMC%LBW is not considered.

PURPOSE: A comparison of MRI and computed tomography-myelography (CTM) for lumbar intracanalar dimensions. To compare the capability and reproducibility of MRI and CTM in measuring the cross-sectional morphology of intracanalar lesions of the lumbar spine. MATERIALS AND METHODS: MRI and CTM of lumbar disc levels from 61 subjects with various lumbar spinal diseases were studied. Dural area, dural anteroposterior (AP) diameter, dural right-left diameter, and thickness of the ligamentum flavum were measured by two orthopedic surgeons. Each section was graded by degree of stenosis. Absolute value and intra- and inter-observer correlation coefficients (ICC) of these measurements and the associations between MRI and CTM values were determined. RESULTS: Except for MRI determination of ligament flavum thickness, CTM and MRI and intra- and ICC suggested sufficient reproducibility. When measurements of dural area, dural AP diameter, and RL diameter were compared, values in CTM were significantly (p = 0.01-0.004) larger than those in MRI (CTM/MRI ratios, 119%, 111%, and 105%, respectively). As spinal stenosis became more severe, discrepancies between CTM and MRI in measurements of the dural sac became larger. CONCLUSION: Both CTM and MRI provided reproducible measurements of lumbar intracanalar dimensions. However, flavum thickness may be more accurately measured by CTM. Because the differences in the measurements between CTM and MRI are very slight and there is very little data to suggest that the precise degree of stenosis is related to symptoms or treatment outcome, the usefulness of the CTM over MRI needs to be confirmed in future studies.
Aged ; Aged, 80 and over ; Female ; Humans ; Lumbar Vertebrae/*pathology/*radiography ; Magnetic Resonance Imaging/*methods ; Male ; Middle Aged ; Myelography/*methods ; Spinal Stenosis/*pathology/*radiography ; Tomography, X-Ray Computed/*methods