This controlled trial was designed to investigate the influence of osteoporosis-related kyphosis (O-K) on falls. Twelve community-dwelling women with O-K (Cobb angle, 50-65 degrees measured from spine radiographs) and 13 healthy women serving as controls were enrolled. Mean age of the O-K group was 76 years (+/-5.1), height 158 cm (+/-5), and weight 61 kg (+/-7.9), and mean age of the control group was 71 years (+/-4.6), height 161 cm (+/-3.8), and weight 66 kg (+/-11.7). Quantitative isometric strength data were collected. Gait was monitored during unobstructed level walking and during stepping over an obstacle of four different heights randomly assigned (2.5%, 5%, 10%, and 15% of the subject's height). Balance was objectively assessed with computerized dynamic posturography consisting of the sensory organization test. Back extensor strength, grip strength, and all lower extremity muscle groups were significantly weaker in the O-K group than the control group (P <0.05), except right ankle plantar flexors (P =0.09). There was a significant difference in the anteroposterior and mediolateral displacements and velocities. The O-K subjects had less anteroposterior displacement, greater mediolateral displacement, reduced anteroposterior velocity, and increased mediolateral velocity compared with controls for all conditions of unobstructed and obstructed level walking. Obstacle height had a significant effect on all center-of-mass variables. The O-K subjects had significantly greater balance abnormalities on computerized dynamic posturography than the control group (P =0.002). Data show that thoracic hyperkyphosis on a background of reduced muscle strength plays an important role in increasing body sway, gait unsteadiness, and risk of falls in osteoporosis.

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Low-intensity back-strengthening exercise was effective in improving the quality of life and back extensor strength in patients with osteoporosis.

Concern about the risk of bone loss in astronauts as a result of prolonged exposure to microgravity prompted the National Aeronautics and Space Administration to convene a Bone Summit with a panel of experts at the Johnson Space Center to review the medical data and research evidence from astronauts who have had prolonged exposure to spaceflight. Data were reviewed from 35 astronauts who had served on spaceflight missions lasting between 120 and 180 days with attention focused on astronauts who (1) were repeat fliers on longduration missions, (2) were users of an advanced resistive exercise device (ARED), (3) were scanned by quantitative computed tomography (QCT) at the hip, (4) had hip bone strength estimated by finite element modeling, or (5) had lost >10% of areal bone mineral density (aBMD) at the hip or lumbar spine as measured by dual-energy X-ray absorptiometry (DXA). Because of the limitations of DXA in describing the effects of spaceflight on bone strength, the panel recommended that the U.S. space program use QCT and finite element modeling to further study the unique effects of spaceflight (and recovery) on bone health in order to better inform clinical decisions.

Aging and osteoporosis have been associated with skeletal changes. Back extensor strengthening exercises are highly recommended for management of back pain, especially back pain related to osteoporosis. To our knowledge, the correlation of thoracic kyphosis, lumbar lordosis, and sacral inclination with back extensor strength, physical activity, and bone mineral density has not been critically studied in healthy, active, estrogen-deficient women. In a study of 65 such women (ages 48-65 yr), back extensor strength, bone mineral density, and physical activity score were evaluated and measured. These factors were then correlated with radiographic factors: (1) vertebral body ratios (anterior/posterior height) calculated for each vertebra from T-4 through L-5; (2) kyphosis index determined by adding the anterior heights of each vertebral body, T-4 through T-12, and then dividing the total by the corresponding sum of the posterior heights of each vertebral body; (3) thoracic kyphosis; (4) lumbar lordosis; and (5) sacral inclination. Back extensor strength had a significant negative correlation with thoracic kyphosis (r = -0.30, P = 0.019) and a positive correlation with lumbar lordosis (r = 0.26, P = 0.048) and sacral inclination (r = 0.34, P = 0.009). However, bone mineral density and physical activity score did not show any significant correlations with the radiographic factors. The results indicate that the stronger the back extensor, the smaller the thoracic kyphosis and the larger the lumbar lordosis and sacral inclination. We conclude that back extensor strength is an important determinant of posture in healthy women. However, prescribing back extensor strengthening exercises alone may also increase lumbar lordosis, which is not desirable.

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