- Lie down on the ground (or bench).
- Bend the knees to a 45 degree angle.
- Position feet beneath a fixed object.
- Cross arms over chest (left hand to right shoulder, right hand to left shoulder) or hands placed behind ears.
- Inhale, and in a smooth, controlled motion bring the torso up until the arms connect with the upper thighs.
- Slowly lower the torso back down until the torso is just short of the floor and repeat.
- Repeat steps 5-6.
When bringing the torso to the up position, it is normal (and recommended) to have a slight bend to the spine. This is also know as rounding and is the chief method to alleviate stress placed on the lower spine.
The arms crossed over the chest method is the easiest method. To increase the difficulty, place one's fingers behind one's ears. To understand why this makes it harder we simply look to physics. However, to avoid a lesson in physics we can summate the concept as follows: the further the weight gets from the pivot point, the more difficult the movement becomes. Placing one's elbows pointing outwards (opposed to inwards, towards the knees) increases the difficultly of this exercises slightly more yet.
For a more intense workout, keep the spine from arching and focus on not touching the ground with your shoulder blade (scapula) in the lowering motion. Utilizing one's own body weight for exercises allows for greater repetitions. Depending on one's conditioning, repetition amounts should typically range from 25-100 per set. One may notice a variety of hip muscles are used while performing sit-ups. This occurs when the torso moves beyond a 45 degree angle on the upward motion. At this point, the hips are called into action to complete the rest of the exercise.
Generally, performing sit ups without securing the feet is easier for women due to women having less upper body mass than men in proportion to the legs.
Do not get into a "rocking" motion with this exercise. The curvature of the spine allow for this happen very easily and sometimes without even thinking about it. Slow and controlled movements are required to target the abdominal muscles. While you may be able to do more repetitions faster with rocking, it defeats the purpose of truly blasting one's abdominals.
Further, exercises involving the abdominal core (particularly the rectus abdominis) call for rounding the back. Indeed, this is likely contrary to advice that you have heard for weight lifting in general, but in the case of exercises that focus on the aforementioned muscle group, rounding the back is recommended to prevent injury.
Often, people will put themselves on insane abdominal programs to achieve the "6-pack" look. What many fail to realize is that while focusing on increasing abdominal stretch helps the muscles grow larger, the outer lay of fat between the abdominal and skin is what often prevents the "6-pack" from showing. So in some cases these individuals may have a great set of ripped abdominals that are concealed by adipose tissue (fat). See the Cardio and Nutrition sections for more information.