To evaluate the effect of back-strengthening exercise on posture in 60 healthy estrogen-deficient women. The 60 study subjects were randomly assigned to either an exercise or a control group, and various factors were assessed at time of enrollment in the study and at 2-year follow-up. The 32 women in the exercise group were instructed in progressive back-strengthening exercises, whereas the 28 women in the control group had no exercise prescription and were asked to continue their usual physical and dietary activities. At baseline and 2-year follow-up examinations, back extensor strength was measured with a strain-gauge dynamometer, and lateral roentgenograms of the thoracic and lumbar areas of the spine were obtained to measure the angles of thoracic kyphosis, lumbar lordosis, and sacral inclination. The changes in radiographic measurements and back extensor strength were analyzed statistically. Back extensor strength increased significantly in both the exercise and the control groups, but no radiographic measurements were significantly different between these groups. The significant increase in back extensor strength in both groups of healthy women suggested that the original grouping did not accurately reflect the amount of exercise. Thus, the 60 subjects were reclassified for comparison on the basis of increase in back extensor strength—27 with more than or equal to the mean increase of 21.1 kg and 33 with less than 21.1 kg. Furthermore, each of these groups of subjects was subdivided on the basis of degree of thoracic kyphosis. Among the subjects with substantial thoracic kyphosis, those with a significant increase in back extensor strength had a significant decrease in thoracic kyphosis (−2.8 ± 4.2°; P = 0.041), whereas those with a small increase in strength had a nonsignificant increase in thoracic kyphosis (1.8 ± 5.3°). The increase in back extensor strength did not seem to affect mild degrees of kyphosis. Increasing the back extensor strength in healthy estrogen-deficient women helps decrease thoracic kyphosis.
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