The purpose of this study was to analyze the electromyography of rectus, obliquus externus and obliquus internus abdominis, erector spinae and biceps femoris of 10 men and 10 women while performing isometric crunches on a board in different positions: horizontal (0º), inclined 10º with the head at the bottom (-10º) and at the top of the bench (+10º), and inclined 20º with the head at the bottom (-20º) and at the top of the bench (+20º). The results showed a muscular activation increase when the slope increased in the negative inclinations (upside down). In the positive inclinations, increasing the slope from +10º to +20º reduced the rectus abdominis activation, but increased the activation of the oblique muscles, especially of the obliquus internus. Although men and women responded similarly to changes in the board inclination, women showed higher levels of obliquus internus activation.