Objective: To determine the influence of back extensor strength on vertebral fractures in 36 women with osteoporosis.
Design: We conducted a cross-sectional study of female patients with osteoporosis by assessing anthropometric variables, bone mineral density, muscle strength, level of physical activity, and radiographic findings in the spine.
Material and methods: The 36 study subjects with osteoporosis, who ranged from 47 to 84 years of age, satisfied specific inclusion and exclusion criteria that minimized confounding factors related to pathophysiologic features, diet, and medications. A physical activity score was determined for each subject on the basis of daily physical activities relating to homemaking, occupation, and sports.
Results: The range of the physical activity scores-from 2 to 13-indicated that no subject was involved in unusually demanding physical activities. Bone mineral density values ranged from 0.49 to 0.92 g/cm2. Thoracic kyphosis ranged from 31.0 to 84.0 degrees. Isometric strength of the back extensor muscles ranged from 7.3 to 34.0 kg. Statistical analysis demonstrated a significant negative correlation between the strength of the back extensor muscles and thoracic kyphosis. Significant negative correlations were also found between back extensor strength and the number of vertebral compression fractures and between bone mineral density and the number of vertebral fractures.
Conclusion: The negative association between back extensor strength and both kyphosis and number of vertebral fractures suggests that increasing back strength may prove to be an effective therapeutic intervention for the osteoporotic spine. In persons with stronger back muscles, the risk of vertebral fractures will likely decrease.