Planks, bicycle crunches and the crossover crunch lead a list of good abdominal exercises, according to exercise physiologist and sports medicine expert Elizabeth Quinn. She states that performing these exercises three to five times a week can improve abdominal strength.
Planks involve hovering with only the forearms and toes touching the ground. For correct form, the body must stay straight, reports Quinn. Bicycle crunches use the obliques and involve laying on the floor with the core contracted, raising the legs and moving them in a bicycle motion while touching the elbows to the knees. Crossover crunches also engage the obliques, and Quinn performs them by crossing one leg over the other, then contracting into a crunch while rotating to touch the opposite elbow to the knee.