Neuromechanical response to spinal manipulation therapy: effects of a constant rate of force application

Abstract

BackgroundNeuromechanical responses to spinal manipulation therapy (SMT) have been shown to be modulated through the variation of SMT biomechanical parameters: peak force, time to peak force, and preload force. Although rate of force application was modulated by the variation of these parameters, the assumption that neuromuscular responses are modulated by the rate of force application remains to be confirmed. Therefore, the purpose of the present study was to evaluate the effect of a constant rate of force application in neuromechanical responses to SMT in healthy adults.MethodsFour SMT force-time profiles presenting different time to peak force and peak force, but with a constant rate of force application were applied on 25 healthy participants’ T7 transverse processes. Muscular responses were recorded through surface electromyography electrodes (T6 and T8 levels), while vertebral displacements were assessed through pasted kinematic markers on T6 to T8 spinous processes. Effects of SMT force-time profiles on neuromechanical responses were assessed using repeated-measures ANOVAs.ResultsThere was no main effect of SMT force-time profile modulation on muscular responses (ps > .05) except for the left T8 (F (3, 72) = 3.23, p = .03) and left T6 (F (3, 72) = 2.94, p = .04). Muscular responses were significantly lower for the lowest peak force condition than the highest (for T8) or second highest (for T6). Analysis showed that increasing the SMT peak force (and concomitantly time to peak force) led to a significant vertebral displacement increase for the contacted vertebra (FT7 (1, 17) = 354.80, p < .001) and both adjacent vertebras (FT6(1, 12) = 104.71, p < .001 and FT8 (1, 19) = 468.68, p < .001).ConclusionThis study showed that peak force modulation using constant rate of force application leads to similar neuromuscular responses. Coupled with previous investigations of SMT peak force and duration effects, the results suggest that neuromuscular responses to SMT are mostly influenced by the rate of force application, while peak force modulation yields changes in the vertebral displacement. Rate of force application should therefore be defined in future studies. Clinical implications of various SMT dosages in patients with spine related pain should also be investigated.Trial registrationClinicalTrials.gov NCT02550132. Registered 8 September 2015

Assessing forces during spinal manipulation and mobilization: factors influencing the difference between forces at the patient-table and clinician-patient interfaces

“…For instance, the muscular response amplitude seems to increase with higher total peak force [ 12 , 23 , 24 ]. When thrust duration and total peak force were modulated while keeping a constant rate of force application, there was no difference observed in muscular response amplitude [ 25 ]. In animal studies, muscle spindle activity was amplified by either shorter thrust duration or higher total peak force during SMT [ 26 – 31 ].…”

Influence of Spinal Manipulative Therapy Force Magnitude and Application Site on Spinal Tissue Loading: A Biomechanical Robotic Serial Dissection Study in Porcine Motion Segments

“…Although several prior studies have investigated the effects of various SMT parameters on biomechanical and neurophysiological responses, 8,9,15,16,27,28 this is the first study to quantify the effect of changing SMT application parameters on spinal tissue response. In the intact specimen, although differences in spinal forces were identified when SMT was applied with 100 N, 300 N, and 500 N, this was only present in specific axes of movement and when a 100-N force magnitude was compared with 500 N. For these structures, the comparison between 100 N with 300 N and 300 N with 500 N force magnitudes did not reveal any significant difference in experienced loads.…”

The effect of a single spinal manipulation on cardiovascular autonomic activity and the relationship to pressure pain threshold: a randomized, cross-over, sham-controlled trial

“…The mechanical parameters of the interventions (e.g. preload force, peak force, and time to peak force) and thus the resulting rate of force application during the thrust might have an impact on some outcomes, as shown on the immediate neuromuscular response following HVLA manipulation [7][8][9]. We did not record force profiles of the interventions during the trial.…”

“…For instance, the effects of spinal manipulative techniques have been explored using biomechanical [5,6] and neurophysiological outcomes, in the latter case studying e.g. neuromuscular response [7][8][9], pain sensitivity [10,11], or autonomic mediated physiology [12][13][14].…”