Abstract
Purpose The study was intended to determine if different portions of abdominal muscles are characterized by accordingly differing activation patterns during walking. Further, the influence of walking speed and sex were considered as well. Method For this 53 healthy subjects of both sexes (26 females, 28.1 ± 10 years; 27 males, 26.8 ± 7.0 years) were enrolled in the study. They walked on a treadmill at speeds of 2 to 6 km/h. Surface EMG was taken from three abdominal muscles of both sides using two electrode locations per muscle: one at the recommended position and one at a systematically shifted position. Muscles studied were: rectus abdominis, internal oblique, and external oblique abdominal muscles. From the grand averaged amplitude curves mean amplitudes and Minimum to Maximum Range values were derived and compared between the respective positions. Results According to the ANOVA, position systematically influenced mean amplitude and Range levels for RA and EO, but not for IO. The mentioned differences were all in favor for the shifted positions. Significant differences between amplitude curves occurred in all muscles. These differences were more pronounced in males for RA and EO and decreased with increasing walking speed. Females in contrast to males showed positive and negative differences of the shifted positions within muscles whereas in males the observed differences remained either constantly positive for RA and EO or negative for IO. The observed differences mostly seem to augment situational stability during gait, indicating a finely tuned and situational adequate shift between mobilizing and stabilizing functions. Conclusion Therefore, a general assignment of abdominal muscles to only stabilizing or mobilizing functions seems to be inappropriate.