Gender Differences in the Curl-up and the Double-leg-lower Tests

[Purpose] The aim of this study was to quantitatively investigate gender differences in trunk muscle strength and activity and to verify the two proposed field tests for screening the muscle strength of trunk flexors by use of surface EMG (sEMG). [Subjects and Methods] Fifty-four healthy young volunteers participated in this study and RA strength was evaluated using the curl-up (CU) and double-leg-lower (DLL) tests. All muscle activity that occurred in the upper and lower RA sites during the two tests was recorded using sEMG. The sEMG data were then normalized using the maximum voluntary contraction. To investigate the validity of the two tests, the ratio of muscle activity between the upper and lower RA sites was calculated. [Results] The reliability of the CU and the DLL tests were estimated using the intraclass correlation coefficient and the values ranged from 0.84-0.96 and 0.93-0.98, respectively. Muscle activity was significantly higher in females than in males in all tests except one of the DLL tests. The activity ratio with respect to each muscle grade was constant between the CU and the DLL tests. [Conclusion] Our results indicate that trunk muscle activity is affected by gender, and the tests should be selected according to purpose.