I often see other trainers instruct members to perform a combination of lateral trunk bend with rotation. What is the correct technique for this exercise, if any? Does this compromise the lumbar region because it limits range of motion, making the client susceptible to lower back injury?
From the way you are describing the movement, “lateral trunk bend with rotation,” I fail to see the “real world” purpose in the exercise. Lateral flexion or side bending of the lumbar spine is a movement that an individual with good structural alignment (and without an existing pathology) should be able to do symmetrically to both sides. Lateral flexion itself requires rotation to occur. If for instance your client is laterally flexing to the right, the rotation of the lumber vertebrae is to the left or toward the convexity of the curve. In the thoracic spine, the coupled motion causes the vertebrae to rotate to the right, or toward the concavity of the curve. Keep in mind however, that the rotation that occurs at the lumber spine is minimal. The majority of trunk rotation occurs at the thoracic spine.
Once in the laterally flexed position, there is the potential for injury if rotation is added. In our example above with the client laterally flexed to the right, if the trunk is rotated forward or backward there is the possibility of causing an injury. The client is at risk of creating derangement at certain facet joints, reducing the tautness of the restraining ligaments and compromising the inter-vertebral foramen. None of which are good for the client.
You may also now be seeing other trainers using spinal flexion with rotation. This is done either with both feet fixed and hip width apart, or combined with a lunge on the opposite leg. This once “taboo” movement is gaining popularity. The reason for this is the undeniable fact that we must flex and rotate our spine regularly to perform activities of daily living (ADLs). Done incorrectly or without the appropriate progressions, this movement can put the client at risk for a back injury.
This exercise should be performed with slight to moderate flexion of the knees. This reduces the opportunity for tight hamstrings to interfere with normal lumbo-pelvic rhythm, which may then stress the inert structures of the lumbar spine. Resistance should never be added to this movement until the client can demonstrate adequate range of motion for the movement. Resistance should also not be added until muscular endurance is achieved with this movement. The client should be able to successfully complete three sets of 15 repetitions of this movement without any pain or limitations before resistance is added. Remember, these are muscle groups whose most important role is to provide spinal stabilization.
This exercise should never be given to a client with an existing back injury unless clearance for this type of movement was provided by the treating physician or therapist.