The relative timing of trunk muscle activation is retained in response to unanticipated postural-perturbations during acute low back pain

Abstract

The purpose of this study was to assess the activation of the erector spinae (ES) and external oblique (EO) in response to unanticipated, bi-directional postural perturbations before and after the induction of acute low back pain (LBP) in healthy individuals. An experimental session consisted of a baseline, control, and an acute LBP condition. For the control and acute LBP condition, isotonic or hypertonic saline (HS), respectively, was injected into the right ES muscle. In each condition, participants stood on a moveable platform during which 32 randomized postural perturbations (8 repetitions of 4 perturbation types: 8 cm anterior slides, 8 cm posterior slides, 10° anterior tilts, and 10° posterior tilts) with varying inter-perturbation time intervals were performed over a period of 4–5 min. Bilateral surface electromyography (EMG) was recorded from the ES and EO in addition to subjective pain records. During the acute LBP condition: (1) the onset time of the ES and EO was delayed for the forward and backward sliding perturbations (P < 0.05); (2) EMG amplitude was reduced bilaterally for all perturbations (P < 0.05); (3) the order of activation and interval between the onset times of the ES and EO were unaltered and (4) ES, but not EO, activity was adjusted to account for the directional differences between the perturbations. This study revealed that re-establishment of posture and balance was a result of the individuals’ ability to rapidly modulate ES with respect to EO activity and that the bi-directional postural responses, although shifted in time and amplitude, retained temporal features in the presence of acute LBP.

Effects of Muscle Fatigue, Creep, and Musculoskeletal Pain on Neuromuscular Responses to Unexpected Perturbation of the Trunk: A Systematic Review

“…Similar observations were found in patients with acute or episodic LBP. On the other hand, studies investigating the effects of acute clinical LBP induced by experimental LBP, consistently reported no change in trunk muscle baseline activity prior to an unexpected perturbation (Gregory et al, 2008; Boudreau et al, 2011; Miller et al, 2013). Despite the overall conflicting observations, results from the meta-analysis showed a moderate effect indicating a longer reflex latency for erector spinae muscles in patients with chronic LBP compared to healthy participants.…”

Association between Cross-sectional Areas of Lumbar Muscles on Magnetic Resonance Imaging and Chronicity of Low Back Pain

“…When there is a sudden and unexpected loading on torso, the body's preparation for minimizing the destabilizing postural disturbance and the mechanical loading of the musculoskeletal system always involves the pretensioning of the erector spinae muscle 20. The ability of reestablishment of the posture and balance after a sudden and unexpected change in the posture depends on the individuals' ability to rapidly and independently modulate erector spinae muscle 21. There are reflex pathways between the erector spinae and lower leg, and the reflexes in erector spinae muscle initiated by the activation of sensory receptors in the foot that provide important information for posture and balance play a role in stabilizing the trunk for maintaining posture and balance 22…”

Effect of exercise-induced fatigue on postural control of the knee

“…Postural perturbations were produced using a computercontrolled movable platform (Andersen and Sinkjaer, 2003;Boudreau et al, 2011). Participants were instructed to step onto the center of the platform and position their feet approximately shoulder-width apart such that they were able to stand comfortably.…”