Relationship between Cross-Sectional Area and Function of Core Muscles: An MRI Study

Background Particular attention has been paid to the core muscles because they serve as a muscular corset that works as a unit to stabilize the body and spine. Training programs for improving core stability often target improving core strength and endurance. Increased muscle size is also an expected effect of training programs. However, the relationship between core muscle cross-sectional area (CSA) and strength, stability, and clinical core test scores has not been identified. Purpose To investigate the relationship between core muscle CSA and muscle functions (strength, endurance, and stability). Study design A cross-sectional study Methods Fifty healthy participants (24 men, 26 women) participated in this study. The CSA of core muscle was measured using MRI. Maximal isometric trunk flexor strength, endurance, the score of double leg loading test were used to measure core muscle function. The relationship between core muscle CSA and muscle function was examined by Pearson’s correlation coefficient and Spearman rho correlation coefficient. Results Maximal isometric trunk flexor strength and side bridge strength were positively correlated with core muscle CSA. The isometric endurance test scores also showed a positive correlation with core muscle CSA except for the score of trunk flexor endurance test. Conclusions Only core strength showed moderate to excellent correlation with core muscle CSA. These findings indicate that core training to achieve muscle hypertrophy could lead to improved core strength but not core endurance.