Abdominal Crunch

Promoting hypertrophy of the abdominal muscles with trunk flexion helps define the “6-pack” of the rectus abdominis. Strengthening the abdominal muscles offers protective effects for the lower back as the abdominals play a role in stabilizing the torso. Stronger abdominals also complement exercise and sports performance as they can contribute to biomechanical efficiency during physical activity and exercise.

The abdominal wall is made up of broad, flat sheet-like muscles that are layered. The rectus abdominis 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 oblique muscles assist the rectus abdominis with flexion of the vertebral column. 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 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.

Toe reaches, Bent-knee abdominal crunches, V-ups, hanging leg raises, reverse crunches.

The abdominal muscles are working all day, every day, when you are physically active. For example, the rectus abdominis stabilizes the pelvis when you’re walking. Therefore, a greater overload stimulus is required to stimulate growth of the abdominals 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 can increase the intensity of abdominal crunches.

You may increase the difficulty of this exercise by flexing at the hips and bending at the knees (lower legs will be parallel to the floor). This position will also emphasize activation of the muscle fibers in the lower region of rectus abdominis.

Incorporating various abdominal exercises complements the performance of abdominal crunches, especially as you advance in exercise difficulty (e.g. V-ups, hanging leg raises).

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. 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 abdominal 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 abdominals. Keeping elbows flared out to the side is a reminder that your arms and hands do not contribute to the movement. Your abdominal 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 abdominal 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 abdominals on the same day as performing deadlifts and squats as those exercises fatigue the abdominals substantially. Training abdominals 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 abdominal exercises with added resistance can improve strength gains, increasing the weight beyond the lifter’s capacity can result in injury to the abdominal tissue.