Bodyweight Crunch

An oblique crunch is an exercise, which involves the oblique muscles, primarily the external and internal oblique. This exercise is performed lying on the floor or exercise mat on your back. The concentric portion of the exercise is flexion and rotation of the vertebral column, lifting the shoulder blade of one side off of the floor and rotating inward. The eccentric portion is extension and rotation of the vertebral column, which involves the descent of the body back to the floor.

The purpose of oblique crunches is to strengthen the oblique muscles while promoting the hypertrophy (increases in size) of this muscle group.

Promoting hypertrophy of the oblique muscles with trunk flexion and rotation helps define the surrounding area adjacent to the “6-pack” of the rectus abdominis. Training the obliques is essential to abdominal muscle aesthetics.

Strengthening the oblique muscles offers protective effects for the lower back as the obliques aid the lower back when bending over and bending sideways. Stronger obliques also complement exercise and sports performance as they can contribute to biomechanical efficiency (e.g. rotation) during physical activity and exercise.

The abdominal wall is made up of broad, flat sheet-like muscles that are layered. The oblique muscles are essential to trunk rotation and lateral flexion of the vertebral column (as with oblique crunches). They surround the rectus abdominis on both sides. The external oblique muscle runs downward and medially and forms the inguinal ligament of the groin area. Its origin is at the outer surfaces of the lower eight ribs and it inserts into the linea alba via a broad aponeurosis. Some of the fibers of the external oblique insert into the pubic crest and iliac crest.

The internal oblique, as its name suggests, is located below the superficial external oblique. Its fibers run in an upward and medial direction. Its origin is located at lumbar fascia, iliac crest and inguinal ligament. Its insertion is located at the linea alba, the pubic crest and the last three or four ribs.

The rectus abdominis aids the oblique crunch by rotating the lumbar region of the vertebral column. It is a vertical muscle that extends from the pubic crest and symphysis (at the pelvis) to the rib cage (xiphoid process and costal cartilages of ribs 5-7). The rectus abdominis is segmented by three tendinous intersections that run horizontally across the rectus abdominis. This tendon outlines the “6-pack” of the rectus abdominis along with the linea alba, a tendinous seam that runs down vertically, dividing the “6-pack” in half.

The transverse abdominis is the deepest muscle of the abdominal wall with fibers running horizontally. This stabilizing muscle compresses the abdominal contents. Its origin is located at the inguinal ligament, lumbar fascia, iliac crest and the cartilage of the last six ribs. It inserts at the linea alba and the pubic crest.

Trunk twists, oblique cable crunch.

The obliques are constantly assisting the lower back and abdominals with physical activity. Therefore, a greater overload stimulus is required to stimulate growth of the obliques when isolating them during exercise. One way to do this is – is to take shorter rest periods (e.g. 30 seconds) between sets. Another way is to hold the peak of the concentric contraction/upward phase for multiple seconds until volitional failure at the end of a set. Adding resistance by holding a plate or medicine ball can increase the intensity of oblique crunches.

Oblique crunches can be performed one side at a time per set or alternating between left and right oblique in one set.

Incorporating various oblique exercises complements the performance of oblique crunches, especially as you advance in exercise difficulty (e.g. trunk twists, oblique cable crunch).

Focus on each concentric portion of the contraction, concentrating on “squeezing” as the shoulder blades are lifting off of the floor completely.

Emphasis on eccentric contractions, prolonging the descent phase back to the mat, may also be incorporated with an abdominal training program focused on increasing strength of the obliques. This should be implemented accordingly and with adequate muscle recovery as eccentric contractions cause substantial damage to muscle tissue and/or delayed onset muscle soreness (DOMS).


It’s important to note that your repetition and set volume will depend on your goals (e.g. strength, hypertrophy, muscular endurance). Strategically varying your intensity, rest times and volume (number of repetitions in a set) will optimize oblique development with time.

It is common to see an individual use their hands to lift their head and neck when doing crunches. This minimizes the activation of the obliques. Keeping elbows flared out to the side is a reminder that your arms and hands do not contribute to the movement. Your oblique muscles should be responsible for lifting your shoulder blades off of the mat. Therefore, it is also important to control the concentric and eccentric contractions to avoid momentum minimizing abdominal activation.

When incorporating oblique training into your exercise regimen it is important to evaluate what other exercises you are doing in that training session. For example, it may not be best to train obliques on the same day as performing deadlifts and squats as the obliques work to stabilize the lower back. Training obliques before or after a training session that involves smaller muscle groups (e.g. calves, biceps, triceps) may be suitable, as it will not interfere with the quality of the overall training session.

While performing oblique exercises with added resistance can improve strength gains, increasing the weight beyond the lifter’s capacity can result in injury to the abdominal tissue or lower back.