| Purpose. To compare the effects of short-term training on the strength and coordination of abdominal musculature. Methods. 11 subjects matched for age, weight, and height (8 experimental and 3 control) were randomized to either one of two experimental groups (trunk flexion (TF) or core stabilization (CS)) or a control group. Experimental subjects were required to perform abdominal training for 5 weeks. Force production was acquired via surface electromyographic (EMG) activity of the rectus abdominus (RA) and external oblique abdominus (EO) muscles. EMG activity was normalized to maximum voluntary isometric contraction (%MVIC) of RA and EO during a two-minute pelvic tilting (PT) exercise and abdominal hollowing (AH) exercise. Subsequently, the ratios of EO to RA activity (EO/RA) were calculated. A 2 x 2 ANOVA was implemented to detect the effects of training. Results. No significant training effects on MVIC were noted in both TF and CS groups. During two-minute AH exercises, the %MVIC of EO in post-test were slightly higher than in pre-test in the CS group, resulting in increases in the EO/RA (1.21 +/- 0.72 in post-test versus 0.76 +/- 0.23 in pre-test, p = 0.11). Conversely, during two-minute PT exercise, the EO/RA in post-test was significantly lower than in pre-test in the TF group (0.88 +/- 0.33 in post-test versus 1.16 +/- 0.36 in pre-test, p = 0.04). Conclusion. The EO is one of the stabilizers in the abdominal musculature. Thus, the CS group might enhance the function of stabilizers and coordination in the abdominal musculature compared with the TF group. However, there was no significant difference between the CS and TF group. This would be because these exercises were performed in supine position and activity of the EO was measured. Measurement of activity of the RA and IO and IO/RA in quadruped position is recommended.;Key words. Core stability, abdominal muscles, EMG, muscle coordination, Ratios of the EO activity to RA activity (EO/RA). |
