DESCRIPTION OF THE TRUNK CURL OR SIT UP

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Abdominal strength is crucial for the maintenance of optimal posture and to counteract the forces of the spinal muscles (plus they look great on a chiseled body!).  The main purpose of the abdominals is to cause spinal flexion or the forward curving of the spine toward the pelvis.

The trunk curl is an appropriate name for this exercise as this aptly describes the purpose of the exercise – that is to curl the trunk off the floor towards the pelvis.  This exercise is great for targeting the rectus abdominis (six pack ab), and the internal and external oblique muscles.  Although the oblique muscles do cause trunk rotation and side flexion, they also significantly contribute to flexion of the spine too.

Starting Position

• Lay face up on the floor or on a thin exercise mat 
• Flatten your lower back into the floor with a backwards tilting of the pelvis - imagine squashing a grape on the floor with your low back through the entire exercise
• Bend your knees and hips only enough to allow your low back to flatten onto the floor.  Do not bend the knees and hips excessively, especially if you have tight hip flexors (groin muscles) as this may cause them to shorten and tighten even more
• Do NOT fix the feet under a bed, door, Roman Chair or have anyone hold your feet down.  As explained in our article Ten Mistakes to Avoid When Exercising the Abdominals fixing the feet causes the hip flexors to contribute significantly more to the exercise and may cause straining of your back.
• Place your hands in one of four positions depending on the difficulty you experience.  The positions are in order of increasing difficulty: arms straight out next to your sides on the floor/thighs, arms crossed over the chest, fingers touching the ears or arms held straight above the head.

Upward Movement:

A good way to visualize the movement is to imagine having double-backed tape stuck to the floor and the back of your head down to the middle spine.  Visualize “peeling” yourself off the floor slowly in a sequential fashion.

·        Begin by curling your neck towards your chest.  Resist the urge to pull on your neck (or the ears!) or poke your chin

·        If your hands are on your thighs or the floor, imagine trying to touch your knees or a line 3 inches away from your fingers

·        Continue the curl by flexing/rounding your upper spine and middle back to approximately 60 degrees (try to avoid curling all the way to 90 deg. or more as this has a tendency to stretch the posterior-lateral fibers of the external oblique muscle)

·        Once you reach the 60 degree angle pause for a second or two

Downward Movement

The downward movement is the exact opposite of the upward movement in that the mid-spine will contact the floor then the upper spine and then the back of the head. 

• As in the upward movement, it is important that the curved position of the spine be retained as the spine progressively “uncurls” or straightens until the back of the head is on the mat
• Do not allow your trunk to “slop” back on the floor – control the eccentric contraction too

Pointers for performing the trunk curl or sit-up

1. If your abdominals are too weak to allow you to curl from the floor, prop your entire spine up on an angled board/ramp or even an incline bench, adjusting the incline until you can curl and flex the spine correctly
2. Avoid performing crunches exclusively as these exercises work through such a small range of motion and target appropriately less muscle fibers and allow for less muscle strength and development
3. Again as mentioned earlier, never fix the feet or knees – the feet/knees can be fixed after initiation of the exercise (like in a crunch), once the low back has reversed and is now pressing into the mat surface