Relationship between trunk extensor muscle's endurance and static postural stability in hyperkyphotic and normal kyphotic women with osteoporosis

Background: Considering the Importance of Back Extensor Muscles on the Postural Control and Risk of Falling in Osteoporotic Postmenopausal Women, We Investigated the Effects of Back Extensor Endurance on the Thoracic Kyphosis and Static Balance Control in Hyper and Normal Kyphotic Women with osteoporosis.

Methods: a total of 22 Osteoporotic Women, based on the Kyphosis Degree, were evaluated in two groups: Hyperkyphotics (No=10) and Normal Kyphotics (No=12). The Kyphosis Degree Measured by Flexi curve ruler. The Isometric Strength of the Back Extensors measured by a Digital Hand-held Dynamometer. Modified Sorensen Test was used for Back Extensor Endurance Evaluation. Static Balance Parameters Evaluated in Double Stand Position by Force plate.

Results: In the Hyperkyphotic Group, the time duration of Modified Sorensen Test was Significantly Lower than that in the Normal Kyphotic Group (P=0.029), there was also a significant negative correlation to the Medio-Lateral Displacement of the center of pressure (Correlation Coefficient: - 0/521, P = 0.047). The Multiple Regression test showed a significant effect of the modified Sorensen's time Duration on the increase of thoracic kyphosis (P = 0.044). In Hyperkyphotic Group, Standard deviation of the Anterior-Posterior of the Center of Pressure displacement was significantly higher than that in the normal kyphotic Group (P = 0.05).

Conclusion: Regarding to the negative correlation between the Trunk Extensor Endurance and Thoracic Hyperkyphosis and also medio-lateral of COP displacement, it suggests the Trunk Extensor Endurance exercise be considered in therapeutic programs of osteoporotic women.