Bodyweight Trunk Twist

A trunk twist is an exercise, which involves the oblique muscles, primarily the external and internal oblique. This exercise is performed sitting on the floor or exercise mat with the upper body and legs suspended as the trunk rotates from side to side. The concentric and eccentric portions of this exercise entail rotation of the vertebral column.

The purpose of trunk twists 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 rotation helps define the surrounding area adjacent to the “6-pack” of the rectus abdominis. Training the obliques is essential to abdominal muscle aesthetics. Trunk twists also activate lower back muscles to stabilize the movement.

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 (as with trunk twists) and lateral flexion of the vertebral column. 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 trunk twist 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.

The upper body’s suspended nature in this exercise also requires stability from the back muscles. The quadratus lumborum forms part of the posterior abdominal wall located in the lumbar region (lower back). The iliocostalis is the most lateral of the erector spinae back muscles. It extends from the pelvis to the neck.

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 with trunk twists – is to take shorter rest periods (e.g. 30 seconds) between sets. It is advised that the individual learn the motion of the trunk twist before adding resistance. Adding resistance increases the intensity of trunk twists. Not allowing the weight to make complete contact with the floor may also advance the difficultly level of the exercise.

Incorporating trunk twists into an exercise regimen complements oblique strength and overall rotation performance.

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 individuals bouncing the weight off of the floor before rotating to the opposite side. It is important that the individual is in control of the movement the entire time. This means not allowing the weight to drop or bounce between rotations. This allows the individual to maximize their benefit from the exercise and prevent injury.
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.