Quantification and Prediction of Male and Female Spine Loading Muscles

Abstract

In order to predict muscle forces in EMG-assisted biomechanical models, it is necessary to be able to predict the muscle size and still account for individual differences. Magnetic resonance imaging scans through the vertebral bodies from T₈ through S₁ were performed on twenty females and ten males. Muscle fiber angle corrected cross-sectional areas were recorded at each level present, with the largest fiber-corrected cross-sectional area for each muscle used to represent the physiological cross-sectional area. Female and male physiological cross-sectional areas were statistically compared, both in magnitude as well as for differences in prediction potential via externally measured anthropometric variables. Results indicated that for each muscle, males demonstrated significantly larger physiological cross-sectional areas than females, with an overall average of 56.1% larger. Anthropometric measures about the xyphoid process were significant predictors of most muscles of interest for females, whereas combinations of height and weight were significant predictors of most muscles of interest for males. Although females exhibit smaller muscles than males, the female erector spinae and internal oblique could not be predicted from the male prediction equations for these muscles, indicating that gender specific prediction equations should be utilized when predicting muscle force producing capability in EMG-assisted biomechanical models.