What is the purpose of holding a ball between the knees during the seated thoracic rotation test?

Also Known As: Supine trunk rotation

Targets: Obliques, rectus abdominis, and lumbar multifidus (low back stabilizing muscle)

Level: Beginner

Trunk rotation is an exercise used to improve core strength, stability, flexibility, and greater mobility of the spine. The exercise can be done in a variety of ways allowing you to progress, challenge yourself, and perform what works best for you.

Trunk rotation is used during many functional daily activities as well as while participating in sports. You perform a trunk rotation by lying on the ground, bending your knees by engaging your core, and rotating your knees from side to side. You'll feel the stretch in your lower back, obliques, and abs.

Performing trunk rotation is a popular exercise to improve the strength and function of the trunk muscles. That said, and as with any exercise, it’s important to work at your fitness level for this type of movement. The following steps will help you perform the exercise safely and effectively:

1. Start in a supine position (lying on back) on an exercise mat.
2. Keep your knees bent and feet flat on the floor.
3. Maintain your shoulders and upper body firmly against the floor.
4. Outstretch your arms and press them into the floor to help with balance during the movement.
5. Engage/tighten the abdominal muscles.
6. Rotate the knees slowly to one side with control, working within your range of motion. Your feet will shift but remain on the floor.
7. Hold the position for 3 to 5 seconds.
8. Engage/tighten the abdominal muscles to move your legs to the opposite side.
9. Hold for another 3 to 5 seconds.
10. Stay focused and breathe normally through the exercise.
11. Repeat the exercise for a determined amount of reps, such as 10 times on each side.

The trunk muscles play a vital part in any motion the body performs. They help you walk, maintain balance, and provide body stability. Improving trunk mobility and strength through a rotation exercise like this can provide general fitness as well as sports performance benefits.

Additionally, trunk rotation is also a popular rehabilitative exercise to reduce low back pain. Having low back pain is a common problem among athletes and non-athletes alike. Improving trunk mobility and learning how to control the motion of your trunk can be very beneficial if you're experiencing back pain.

Trunk rotation can be easily added to your existing core routine. It enhances your workout program, targets specific trunk muscles, and improves the quality of your fitness in and out of the gym. Trunk rotation is a movement that involves the thoracic and lumbar vertebrae and surrounding muscles.

As you twist and turn your body, the trunk muscles are often the first ones activated to help maintain stability. In fact, research indicates the importance of exercises to help maintain the optimal function of these muscles. Trunk rotation exercises also can help improve strength, function, and mobility of the trunk muscles.

Adding this trunk training exercise into your regular fitness routine can provide the following benefits:

• Increase trunk rotation, flexibility, and range of motion (ROM)
• Decrease the risk of injury
• Improve functional fitness (daily activities)
• Relieve back tension
• Reduce low back pain
• Increase the ability to obtain peak fitness levels
• Improve athletic performance
• Improve stability
• Improve core strength
• Improve balance and gait (walking)
• Increase low back and hip flexibility
• Improve spinal mobility
• Improve posture

Trunk rotation is a progressive exercise that can be performed in a variety of ways to accommodate your fitness level and specific needs. If you are new to exercise and training your trunk muscles, you may want to use these variations and modifications to fully engage with the exercise.

Practice core engagement by tightening your abdominals (think about pressing your navel toward your spine) without moving your legs to opposite sides. This will help with body awareness and muscle control during trunk rotation. Once you have the hang of tightening your core, then progress to moving your legs during the exercise.

Perform pelvic tilts to help relax tight back muscles and increase flexibility. These are done in the same supine position with knees up and feet flat on the floor. Tighten your core (think navel to spine) as you tilt your pelvis up toward the ceiling and back again.

Perform a trunk rotation in the supine position but with your feet raised off the floor and knees bent at a 90-degree angle. This movement increases the intensity of the exercise by activating greater abdominal contraction during the movement.

Perform trunk rotation in the supine position but with legs extended at the knees. This advanced modification engages the core muscles even more during the movement. The focus remains on working slowly and with control.

To further change up the move as you advance, perform the trunk rotation in the supine position with knees up and feet flat on the floor. As you move the outer knee toward the opposite side, extend the other leg flat along the floor. Then, bring both legs back to the starting position.

Seated trunk rotation is another variation to consider and can be performed sitting on your exercise mat with legs extended in front of you. Engage your core as you twist your upper body, touching the floor on one side and moving with control to the opposite side.

Standing trunk rotation is considered an intermediate form of this exercise and sometimes, is a better option for those who feel discomfort or pain in a seated position. Follow the same rules for core engagement during this and all variations of the movement.

However, in this version of the exercise, rather than moving the legs, move the upper body to one side while keeping the hips on down still. Arms can be bent at the elbow with hands clasped together at the chest or hold arms extended out in front of you.

In either arm position, move the arms with the upper body as it twists. For an additional challenge, hold a weighted medicine ball in your hands (either right in front of the chest or extended out from the chest).

Performing trunk rotation may appear to be an easy bodyweight exercise, but it does require attention to good form and technique. The following are common mistakes to avoid while performing this exercise.

Trunk rotation, as with any exercise, requires working at the appropriate fitness level and attention to detail. The exercise should provide an effective challenge without overloading the muscle tissue.

Because it’s a bodyweight exercise, some people tend to overexert themselves causing more harm than good. Start slow and let yourself progress over time as you gain strength and spinal mobility.

Tightening your abdominal core muscles throughout the trunk rotation movement is an important part of the exercise. If you’re only moving your legs back and forth without activating your core muscles, the exercise is being done incorrectly.

Not engaging the right muscles may not feel good on your low back either. Focus on engaging your core to help relieve any discomfort.

Trunk rotation is a slow, controlled, and small movement. The goal is not to see if you can touch your knees to either side of the floor. The goal is to control the motion, rather than performing a big movement. Work within an appropriate range of motion for a properly executed and effective exercise.   

Trunk rotation is shown to be an effective exercise to improve spinal mobility, flexibility, and core strength. The following tips will reduce the risk of injury and help you apply proper form during the movement:

• Maintain body awareness during the exercise for proper form and technique.
• Engage your core during the exercise to effectively execute the movement without risk of low-back discomfort/injury. Think navel sucked into your spine.
• Perform the movement slowly and with control. Complete 10 reps on each side.
• Focus on controlling the motion, not increasing the motion. Think a smaller range of motion (ROM) for stronger trunk muscles.
• Perform the exercise at your fitness level and spinal range of motion.
• Apply appropriate exercise progression principles (add challenge when you have mastered the basic movement).
• Stop the exercise if you experience increased pain or discomfort that doesn’t feel right during the movement.

Incorporate this move and similar ones into one of these popular workouts: