Trunk postural control is the capacity to maintain both postural equilibrium (control of the center of mass over the base of support) and postural orientation between segments (within spine regions and between the spine and other body regions). Therefore, it is critical for executing human motion and completing everyday activities.
Trunk postural control is not simply core strength; it requires motor skill, the integration of kinematic (position and movement) feedback from visual, vestibular, and proprioceptive systems, and the generation of coordinated motor responses using an array of muscles.
Low back pain (LBP) is a multifactorial condition and is the leading cause of disability globally. Many times, it is of insidious onset with no pinpoint trauma or cause preceding it. These patients may need to self-manipulate; have frequent bouts of painful episodes that resolve on their own; pain with sudden trivial movements or when returning to an erect position from flexion; decreased lumbopelvic rhythm; and poor control of neutral spine upon movement.
The quality of trunk postural control has been suggested as a risk factor for LBP development, recurrence, and/or perpetuation, mediated by effects of suboptimal loading on spine tissue; and may be an explanation for this common insidious cause.1
Measuring the Quality of Postural Control
How do we measure the quality of someone’s postural control? Many studies use an unstable sitting paradigm to assess the contribution of the trunk to postural control by limiting contributions from the legs and arms. To maintain balance in this paradigm, the global position of the upper body is maintained via dynamic movements at the base/seat. Movements at the base/seat are attenuated by coordinated movements of the hip and spine to limit upper-body movements and maintain the overall center of mass close to the center of pressure (the location of the point of contact of the seat).
Many outcome measures from this paradigm have been reported to have acceptable to excellent test-retest reliability for assessing trunk postural control among individuals with or without LBP.
Insights From the Latest Research
In a recent meta-analysis,2 the authors analyzed 64 studies with 2,871 participants to determine whether trunk postural control differs between those with and without LBP, and whether the difference between groups is impacted by vision and potential confounding factors.
This systematic review indicated that trunk postural control differs between individuals with and without LBP in that individuals with LBP demonstrated poorer postural control of the trunk. Meta-analyses revealed that trunk postural control deteriorates more from removal of vision among individuals with than without LBP; and that older age and higher BMI have greater adverse impacts on trunk postural control among individuals with than without LBP.2
Why Do LBP Patients Demonstrate Poorer Postural Control?
Decreased sense of lumbar proprioception, increased trunk stiffness, and delayed onset or offset of trunk muscles activity are commonly seen in patients with LBP. Some plausible mechanisms may include the fact that those with LBP have less proprioceptive sensitivity, which may reduce the ability to coordinate or delay the trunk muscle response required to maintain balance – affecting not only the accuracy and precision of trunk movement, but also the detection of movement errors required to execute postural adjustments.
Alternatively, some LBP patients may adopt a distinct muscle activation strategy to control balance, such as increased muscle coactivation, either to reduce reliance on proprioception or to protect the spine from threat, resulting in trunk stiffness.
Corrective adjustments for postural control require contributions of the visual, vestibular, and senses, as indicated by the fact that decreased trunk postural control was seen in the absence of visual feedback, but was even greater for individuals with than without LBP.
The authors concluded that there is robust evidence that trunk postural control is compromised among individuals with LBP; however, they cannot discriminate whether changes in trunk postural control are a cause or consequence of LBP. Regardless, impaired trunk postural control should be diagnosed and treated as both a prophylactic mechanism to avoid insidious LBP as well as part of an active care plan for those suffering with LBP as well.2
How Do We Evaluate Postural Control?
First, start with a static posture evaluation from A-P and lateral vantage with the patient’s eyes open and eyes closed. Also look for postural sway. Next, check for increased tone or inhibition of the postural muscles such as the gastrocnemius, gluteus medius, TFL, Iliopsoas, and thoracic erector spinae.
Finally, we can perform scored tests such as the Trunk Impairment Scale, trunk stability push-up test, and rotary stability test. These tests are simple and can be performed on nearly every patient right in your office. For more conditioned, athletic patients, the Bourbon Trunk Muscle Strength Test and the Biering Sorensen Test may be indicated.3
How Do We Improve Trunk Postural Control?
There are many exercises that can be performed in the office or at home, from beginner to advanced, to improve trunk postural control. Starting with simple movements with intention and control of the core and progressing to more difficult exercises using unstable surfaces is imperative for improved function and patient challenge, which will increase patient compliance.
Prescribed exercises are based on the patient’s conditioning and ability. They may start with simple one-legged stands, abdominal bracing, pelvic tilts, wall rolls, side planks, curl-ups, and bird-dog exercises. Of course, reducing the patient’s pain through adjustments, muscle release techniques, stretching, and physiotherapy must be completed before any exercise program is implemented.
Identifying trunk postural control deficits and prescribing the correct exercises will lower the severity and number of painful episodes, and improve their movement and functional patterns – all contributing to a better quality of life.
References
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