The Biomechanical and Clinical Significance of the Lumbar Erector Spinae Flexion-Relaxation Phenomenon: A Review of Literature

A comparative investigation of flexion relaxation phenomenon in healthy and chronic neck pain subjects

“…Movements in the spine are supported by a complex neuromuscular system involving active (muscle), passive (vertebrae, intervertebral discs, ligaments, tendons and fascia) and neural components [31]. During full flexion, this supporting role transfers from the superficial extensor musculature to other stabilisation systems [7,[9][10][11][12]. The relationship between pain and altered muscle activation patterns is also complex, and researchers use experimental pain models to explain how pain can change the motor control and load transfer between tissues [7,32].…”

“…During full flexion, this supporting role transfers from the superficial extensor musculature to other stabilisation systems [7,[9][10][11][12]. The relationship between pain and altered muscle activation patterns is also complex, and researchers use experimental pain models to explain how pain can change the motor control and load transfer between tissues [7,32]. Altered motor control strategies may be seen as compensatory mechanisms, such as reorganisation of activity among agonist, synergists and antagonist muscles to allow the movement in painful and painless conditions.…”

“…Neck pain patients demonstrated an altered pattern of muscle activation, such as deep cervical extensor and flexor muscles [5]. Surface electromyography (SEMG) provides a non-invasive and a objective tool to investigate the muscle activity in addition to the kinesiological analysis of movement disorders [6,7]. Previous studies have shown that the electrical activity in the lumbar erector spinae muscles is reduced after a certain amount of trunk flexion, which is known as flexion relaxation phenomenon (FRP) [8].…”

“…The FRP was first defined by Floyd and Silver [9] and refers to a reduced or sudden onset of myoelectric silence in erector spinae muscles during full trunk flexion. Three mechanisms have been proposed for this phenomenon: (a) transfer of the moment force of weight to passive structures of the spine [7,9,10], (b) transfer of the extension moment force from the superficial muscles to deeper muscles [11,12] and finally, (c) reflexive mechanisms involving tension mechanoreceptors which are in ligaments and other viscoelastic structures which may trigger the FRP [13], although the last suggested mechanism is questionable for it could only explain the FRP [14].…”

“…Some studies reported absence or delay of FRP during complete trunk flexion, which could be used to differentiate subjects with LBP from healthy or asymptomatic subjects [7,15,[17][18][19]. In contrast to LBP, there is still a lack of evidence about the changes that occur during FRP in chronic neck pain (CNP) patients.…”