Sagittal Spinal Mobility and Back Extensor Muscle Function in Older Females with Age-Related Hyperkyphosis

Spinal range of motion (ROM) is a potential and modifiable variable that may contribute to the maintenance of upright sagittal alignment. The present study aimed to compare spinal ROM in older females with and without hyperkyphosis and investigate associations between thoracic kyphosis and spinal ROM, back extensor strength (BES), and back extensor endurance (BEE).

Sagittal spinal curvature and ROM were measured with the Spinal Mouse. Also, BES and BEE were assessed with a load cell. Variables were compared between older females with and without hyperkyphosis with the independent sample t test. We used the Pearson correlation coefficient to calculate associations between variables. Multiple linear regression was used to find which variable is best associated with kyphosis.

Lumbar and total spinal ROM were lower in the hyperkyphosis compared to the normal group (P<0.05). Thoracic kyphosis was associated with total lumbar ROM (r=-0.30, P=0.03), total spinal ROM (r=-0.35, P=0.01), BES (r=-0.73, P< 0.001), and BEE (r=-0.60, P< 0.001). Multiple linear regression analysis after adjusting for age, weight, and BMI showed that BES (P<0.001) and BEE (P=0.01) but not spinal ROM (P=0.16) were significantly associated with thoracic kyphosis.

Females with hyperkyphosis had lower spinal ROM than those with normal kyphosis. While thoracic kyphosis was significantly associated with total lumbar ROM, total spinal ROM, BES, and BEE, multivariate regression showed that ROM was not a significant contributor to thoracic kyphosis. BES and BEE were significant contributors to thoracic kyphosis and should be targeted in the rehabilitation of hyperkyphosis.