The elbows should be fully aligned under the shoulders. 

Action: 

1. Raise the body, forming a straight line from shoulders to heels and supporting body weight with the forearms. 

2. Hold the contraction of the abdomen and buttocks. 

3. Do not move or arch the back. 

4. In more advanced stages of difficulty, raise one leg 15 inches off the ground and hold the position for 20-30 seconds. 

5. Repeat with the other leg. 

6. Repeat the exercise three times.