Voluntary and reflex control of human back muscles during induced pain

Abstract

Low back pain is a common disabling musculoskeletal disorder, whose prevention and treatment are problematic. The main reason is that current imaging techniques do not identify the source of pain in the vast majority of cases. The diagnosis of low back disorder is, therefore, often based on non-specific signs, such as deep tissue pain and altered motor patterns. Unfortunately, there is little agreement on how these patterns change with pain. While most authors agree that force generated by the muscles is usually diminished (the mechanism is unknown), electromyographic (EMG) recordings are equivocal -both hyper-and hypoactivity have been reported (Ahern et al. 1988). The contradictory results may reflect two major disadvantages connected with clinical studies. First, as a direct consequence of the difficulty of localizing the primary tissue damage, the clinical studies may involve heterogeneous populations of patients with different primary afflictions (affecting intervertebral disks, ligaments, facet joints, muscles, etc.). Second, in clinical studies there is no healthy 'norm' to which the patients could be compared. Data from the individual's pain-free history are rarely available and there is a certain inter-individual variability in motion patterns even within the healthy population. Uncontrolled factors such as these are responsible for the current poor understanding of the

Paraspinal muscle control in people with osteoporotic vertebral fracture

“…Inhibition of muscle function due to pain may be attributable to symptomatic fractures, while subtle changes in thoracic kyphosis may have altered the mechanical properties of the muscles [39]. Previous research has confirmed changes in muscle recruitment as a consequence of pain [19,21,23,48]. Other factors related to vertebral fractures such as decreased mobility and fear of falling could also influence muscle activation characteristics [35].…”

The Association between Risk Factors and Low Back Pain among Commercial Vehicle Drivers in Peninsular Malaysia: A Preliminary Result

“…The frequencies of postures of bus drivers may be affected by an adaptation of posture to reduce LBP as suggested by Shirado et al 1) , Hodges and Moseley 35) and Zedka et al 37) that, to reduce pain, the erector spinae muscle remained inactive (flexion-relaxation response) 1) and muscle becomes stiff (pain adaptation model) limiting trunk muscle movement. Therefore, a high frequency of sitting straight and leaning posture might indicate adaptation in reducing the pain feeling.…”

Effect of Experimental Muscle Pain on Motor Unit Firing Rate and Conduction Velocity

“…Synergistic muscles may indeed increase their activity to compensate for the decrease in the force produced by the painful muscle. Effect of pain on muscles other than the painful one (i.e., antagonist and synergist) has been documented in dynamic contractions (Graven-Nielsen et al 1997;Zedka et al 1999) but direct extrapolation of results from dynamic tasks to isometric conditions is not possible. Indeed, the activity of synergic muscles is also decreased by experimental muscle pain during isometric contractions (Ciubotariu et al 2004).…”