Lower back pain (LBP) patients present with a wide variety of motor control adaptations in response to, and in anticipation of pain. Though these adaptations manifest across a spectrum of functionality, studies have indicated two common phenotypes that represent the trunk posture and movement of most LBP patients. Further study 1 of these two phenotypes can help practitioners target more specific, effective treatments for their patients who have developed motor control adaptations that may undermine and contribute to their long-term spinal health.
Variations of Motor Control Adaptations in LBP Patients
People with LBP adapt the way they move to mediate pain or avoid pain. These adaptations may be conscious or unconscious processes, or a combination of the two, but the changes in posture and movement—what we refer to as “motor control”—involve the muscles, joints, nerves, senses, and integrative processes. Studies of how LBP affects posture and motor control have been inconsistent in the conclusions, perhaps because of the built-in redundancy and flexibility of the musculoskeletal system.
There are many ways to adapt posture and movement in response to pain or in anticipation and avoidance of pain. But because each adaptation creates not only short-term solutions, but potential long-term changes in biomechanics, which can become problematic, creating a cycle of disfunction, it is helpful to study the two most prominent phenotypes of motor function adaptions to create targeted treatment and information options for LBP patients presenting these adaptations.
Identified Motor Function Phenotypes
Tight Control: Some LBP patients exhibit increased excitability and accompanying tight control over their trunk movements, which increases reflex gains, attention to how they control movement, tissue loading, and muscle contraction. While having tight control over trunk movements can help the LBP sufferer from short-term injury by constraining movement, it may also contribute to trunk stiffness and increase the amount of force necessary to move. This may manifest in subtle ways or, in extreme cases, lead to a complete bracing of the trunk, making movement difficult and leading to fatigue.
Patients with extreme tight control over their motor control have been shown to experience a reduction in lumbar stiffness and pain after spinal manipulation. This could mean that the adaptation could, itself, be responsible for pain. These patients are also more likely to experience spinal compression due to increased loading. This compression may lead to a reduced fluid flow in the discs, which may contribute to degeneration over time.
Tight control creates low-level muscular activity, even when the spine is at rest. This can create muscle fatigue, pain, and discomfort. The lack of muscle variability and reduced movement associated with tight control of motor function may also compromise tissue health and compromise the load-sharing capabilities, balance, and movement task learning abilities inherent in the body’s structures.
Loose Control: At the opposite end of the spectrum are patients with loose muscle and posture control and less muscular excitability. This creates an increase in spinal movements and subsequent tissue loading. This may help prevent the short-term pain associated with muscle movement, but the spine is unstable and requires musculature to support movement. Less muscle control means potential failure of the mid-range lumbar vertebral alignment segments, which can cause tissue strain and pain. Spinal displacement due to loose control may cause LBP.
Clinical Implications for Loose or Tight Muscle and Posture Control in LBP
Understanding whether a LBP patient is exhibiting a loose or tight control muscle and posture adaptation in response to their pain can help practitioners tailor their treatment in a targeted and more beneficial way. Increasing movement and reducing excitability in later stages of LBP adaptive tight control models can help a patient integrate movement variation as their LBP improves. Likewise, exercises and therapies to help loose control patient models develop more control of their musculature and posture may help them avoid the potential long-term consequences of a proper lack of spinal support.
Assessing LBP patients carefully to identify their motor control phenotype prior to the onset of treatment may allow practitioners to more efficiently target and proactively treat potential complications of their particular adaptation due to actual or anticipated pain.
KEYWORD LONG TAIL PHRASES: motor control phenotyping may help target treatment for lower back pain patients, motor control adaptations in response to, and in anticipation of pain, common phenotypes that represent the trunk posture and movement of most LBP patients, two most prominent phenotypes of motor function adaptions, reduction in lumbar stiffness and pain after spinal manipulation.