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Bent-Knee Sit-up / Crunches

4 out of 5 stars
(2 Comments & Ratings)

Target Body Part: Abs
Primary Muscles: Rectus Abdominus (abs), Transverse Abdominus
Secondary Muscles:
(Synergists/Stabilizers)		 Obliques
Equipment Needed: No Equipment

Step 1

Starting Position: Lie on your back on a mat with your knees bent, feet flat on the floor and heels a comfortable distance (12-18") away from your seat.

 

Step 2

Place your hands behind your head. Pull your shoulder blades together and your elbows back without arching your low back or causing your ribs to splay out. This elbow position should be maintained throughout the exercise. Your head should be aligned with your spine.

 

Step 3

Upward Phase: Exhale. Engage your abdominal and core muscles. Nod your chin slightly as you slowly curl your head and shoulders off the mat. Pull your rib cage together and toward your pelvis. Keep the neck relaxed. Your feet, tailbone and lower back should remain in contact with the mat at all times. Continue curling up until your upper back is lifted off the mat. Hold this position briefly.

 

Step 4

Downward Phase: Gently inhale and lower your torso back toward the mat slowly and with control. Keep your feet, tailbone and low back in contact with the mat.
Proper form is important for this exercise to prevent excessive stress on your low back. Individuals typically perform this movement too rapidly and recruit the hip flexors to assist with the upward phase. Doing this should be avoided as it causes the pelvis to tilt anteriorly, increasing the stress on the low back. The abdominals connect the rib cage to the pelvis so the movement should focus on bringing these two body parts closer together while keeping the neck and shoulders relaxed.

Step 1

Starting Position: Lie in a supine (on your back) position on a mat with your knees bent, feet flat on the floor and heels 12 - 18" from your tailbone.

 

Step 2

Place your hands behind your head, squeezing your scapulae (shoulder blades) together and pulling your elbows back without arching your low back. This elbow position should be maintained throughout the exercise. Align your head with your spine, but allow it to move into slight flexion (moving the chin towards the chest) during the upward phase of the exercise.

 

Step 3

Upward Phase: Exhale, contract your abdominal and core muscles and flex your chin slightly towards your chest while slowly curling your torso towards your thighs. The movement should focus on pulling your rib cage towards your pelvis (the neck stays relaxed while the chin is tucked towards the neck). Your feet, tailbone and lower back should remain in contact with the mat at all times. Continue curling up until your upper back is lifted off the mat. Hold this position briefly.

 

Step 4

Downward Phase: Gently inhale and slowly uncurl (lower) your torso back towards the mat in a controlled fashion keeping your feet, tailbone and low back in contact with the mat.

Proper form is important for this exercise to prevent excessive stress on your low back. Individuals usually perform this movement too rapidly and recruit the hip flexors to assist with the upward phase. This technique tilts the pelvis anteriorly, increasing the stress on the low back and should be avoided. The abdominals connect the rib cage to the pelvis so the movement should focus on bringing these two body parts closer together while keeping the neck and shoulders relaxed.


For professional guidance in your exercise program,
find an ACE-certified Personal Trainer in your area. Before beginning any fitness program, always see a qualified healthcare provider for advice and to address any questions or concerns. The exercises presented on this website are for suggestion only and should not be substituted for medical diagnosis or treatment. Participate at your own risk and stop if you feel faint or experience shortness of breath.



Comments & Ratings

Average Customer Rating: 4 out of 5 stars (2 Comments & Ratings)
00
Rated by: Andrew (ACE-certified Professional)

Would Recommend this to others?:

Comments: I have a tall/heavy upper body compared to my legs and I find this exercise difficult to perform without recruiting the legs. A great modification I learned from ACE's Practical Guide to Exercise Coaching is to place the hands on top of the forehead instead of underneath. Then extend one of your bent legs and perform the exercise a couple of times before switching legs. This reduces stress on the neck and the lower back and produces a similar effect.
10
Rated by: Erik

Would Recommend this to others?: Definitely

Comments: Thanks for the detailed explanation.
 
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