RESUMO
The influence of twelve selected abdominal exercises on the muscle action potentials (MAP) of the rectus abdominis--upper and lower portions--and rectus femoris was investigated. Twenty physical education students executed twelve exercises. The results showed that the elevation of the lower limbs from the long lying and from the forearm supported positions elicited significantly lower MAP for the upper rectus abdominis than all other exercises. Elevation of the lower limbs with the body suspended by hands and the V-sit exercises elicited significantly higher MAP for the lower rectus abdominis than all other exercises. The use of extended or flexed knees with supported or unsupported feet in a horizontal or inclined plane did not affect the MAP of the upper and lower rectus abdominis. The results for the rectus femoris showed five significantly different groups of exercises. The curl-up elicited the lowest MAP. The elevation of the lower limbs with the body suspended by hands and the sit-ups--with extended and also with flexed knees--in an inclined plane elicited the highest MAP for the rectus femoris. The results suggested that sit-ups executed with supported feet required higher MAP of the rectus femoris than sit-ups with unsupported feet, no matter whether hips and knees were extended or flexed. This trend was observed for exercises performed in an horizontal and in an inclined plane.
