Abstract Background context Alterations of the neuromuscular control of the lumbar spine have been reported in patients with chronic low back pain (LBP). During trunk flexion and extension tasks, the ...reduced myoelectric activity of the low back extensor musculature observed during full trunk flexion is typically absent in patients with chronic LBP. Purpose To determine whether pain expectations could modulate neuromuscular responses to experimental LBP to a higher extent in patients with chronic LBP compared with controls. Study design A cross-sectional, case-control study. Patient sample Twenty-two patients with nonspecific chronic LBP and 22 age- and sex-matched control participants. Methods Trunk flexion-extension tasks were performed under three experimental conditions: innocuous heat, noxious stimulation with low pain expectation, and noxious stimulation with high pain expectation. Noxious stimulations were delivered using a contact heat thermode applied on the skin of the lumbar region (L4–L5), whereas low or high pain expectations were induced by verbal and visual instructions. Outcome measures Surface electromyography of erector spinae at L2–L3 and L4–L5, as well as lumbopelvic kinematic variables were collected during the tasks. Pain was evaluated using a numerical rating scale. Pain catastrophizing, disability, anxiety, and fear-avoidance beliefs were measured using validated questionnaires. Results Two-way mixed analysis of variance revealed that pain was significantly different among the three experimental conditions (F2,84=317.5; p<.001). Increased myoelectric activity of the low back extensor musculature during full trunk flexion was observed in the high compared with low pain expectations condition at the L2–L3 level (F2,84=9.5; p<.001) and at the L4–L5 level (F2,84=3.7; p=.030). At the L4–L5 level, this effect was significantly more pronounced for the control participants compared with patients with chronic LBP (F2,84=3.4; p=.045). Pearson correlation analysis revealed that increased lumbar muscle activity in full flexion induced by expectations was associated with higher pain catastrophizing in patients with chronic LBP (r=0.54; p=.012). Conclusions Repeated exposure to pain appears to generate rigid and less variable patterns of muscle activation in patients with chronic LBP, which attenuate their response to pain expectations. Patients with high levels of pain catastrophizing show higher myoelectric activity of lumbar muscles in full flexion and exhibit greater neuromechanical changes when expecting strong pain.
Abstract Objective Whole-body vibration (WBV) exercise is progressively adopted as an alternative therapeutic modality for enhancing muscle force and muscle activity via neurogenic potentiation. So ...far, possible changes in the recruitment patterns of the trunk musculature after WBV remain undetermined. The main objective of this study was to evaluate the short-term effects of a single WBV session on trunk neuromuscular responses in patients with chronic low back pain (cLBP) and healthy participants. Methods Twenty patients with cLBP and 21 healthy participants performed 10 trunk flexion-extensions before and after a single WBV session consisting of five 1-minute vibration sets. Surface electromyography (EMG) of erector spinae at L2-L3 and L4-L5 and lumbopelvic kinematic variables were collected during the trials. Data were analyzed using 2-way mixed analysis of variance models. Results The WBV session led to increased lumbar EMG activity during the flexion and extension phases but yielded no change in the quiet standing and fully flexed phases. Kinematic data showed a decreased contribution to the movement of the lumbar region in the second extension quartile. These effects were not different between patients with cLBP and healthy participants. Conclusions Increased lumbar EMG activity after a single WBV session most probably results from potentiation effects of WBV on lumbar muscles reflex responses. Decreased EMG activity in full trunk flexion, usually observed in healthy individuals, was still present after WBV, suggesting that the ability of the spine stabilizing mechanisms to transfer the extension torque from muscles to passive structures was not affected.
Purpose
The lumbar region offers various muscle recruitment strategies to achieve a task goal under varying conditions. For instance, trunk movement control can be reorganized under the influence of ...low back pain. How such task-modulation is obtained is not fully understood. The objective of this study was to characterize superficial lumbar muscle recruitment strategies under the influence of delayed-onset muscle soreness (DOMS) during unexpected trunk perturbations.
Methods
Healthy participants experienced a series of 15 sudden external perturbations with and without the influence of low back DOMS. During these perturbations, high-density surface electromyography was used to characterize recruitment strategies of superficial lumbar muscles, while kinematics sensors were used to characterize movements of the trunk. Lumbar muscle recruitment strategies, characterized by the amplitude of muscle activity amplitude, the latencies of the reflex activity and the spatial distribution of muscle activity, were compared across perturbations trials and with and without DOMS.
Results
An attenuation of lumbar muscle activity amplitude was observed across perturbation trials without DOMS, but not with DOMS. The spatial distribution of muscle activity was similar with and without DOMS. No significant changes in reflex activity latency and trunk flexion movement were observed.
Conclusions
Following an unexpected trunk perturbation under DOMS effects, trunk movement are controlled using two different superficial lumbar muscles control strategies: keeping a constant level of their overall muscle activity and using a variable muscle recruitment pattern.
Purpose
This study aimed at identifying the short-term effect of creep deformation on the trunk repositioning sense.
Methods
Twenty healthy participants performed two different trunk-repositioning ...tasks (20° and 30° trunk extension) before and after a prolonged static full trunk flexion of 20 min in order to induce spinal tissue creep. Trunk repositioning error variables, trunk movement time and erector spinae muscle activity were computed and compared between the pre- and post-creep conditions.
Results
During the pre-creep condition, significant increases in trunk repositioning errors, as well as trunk movement time, were observed in 30° trunk extension in comparison to 20°. During the post-creep condition, trunk repositioning errors variables were significantly increased only when performing a 20° trunk extension. Erector spinae muscle activity increased in the post-creep condition, while it remained unchanged between trunk repositioning tasks.
Conclusions
Trunk repositioning sense seems to be altered in the presence of creep deformation, especially in a small range of motion. Reduction of proprioception acuity may increase the risk of spinal instability, which is closely related to the risk of low back pain or injury.
The active control of the lumbar musculature provides a stable platform critical for postures and goal-directed movements. Voluntary and perturbation-evoked motor commands can recruit individual ...lumbar muscles in a task-specific manner according to their presumed biomechanics. Here, we investigated the vestibular control of the deep and superficial lumbar musculature. Ten healthy participants were exposed to noisy electrical vestibular stimulation while balancing upright with their head facing forward, left, or right to characterize the differential modulation in the vestibular-evoked lumbar extensor responses in generating multidirectional whole body motion. We quantified the activation of the lumbar muscles on the right side using indwelling deep multifidus, superficial multifidus, caudal longissimus (L4), and cranial longissimus (L1) and high-density surface recordings. We characterized the vestibular-evoked responses using coherence and peak-to-peak cross-covariance amplitude between the vestibular and electromyographic signals. Participants exhibited responses in all lumbar muscles. The vestibular control of the lumbar musculature exhibited muscle-specific modulations: responses were larger in the longissimus (combined cranio-caudal) compared with the multifidus (combined deep-superficial) when participants faced forward (
< 0.001) and right (
= 0.011) but not when they faced left. The high-density surface recordings partly supported this observation: the location of the responses was more lateral when facing right compared with left (
< 0.001). The vestibular control of muscle subregions within the longissimus or the multifidus was similar. Our results demonstrate muscle-specific vestibular control of the lumbar muscles in response to perturbations of vestibular origin. The lack of differential activation of lumbar muscle subregions suggests the vestibular control of these subregions is co-regulated for standing balance.
We investigated the vestibular control of the deep and superficial lumbar extensor muscles using electrical vestibular stimuli. Vestibular stimuli elicited preferential activation of the longissimus muscle over the multifidus muscle. We did not observe clear regional activation of lumbar muscle subregions in response to the vestibular stimuli. Our findings show that the central nervous system can finely tune the vestibular control of individual lumbar muscles and suggest minimal regional variations in the activation of lumbar muscle subregions.
Purpose
To investigate if the recruitment of different regions within the lumbar extensor muscles in response to unexpected perturbations depends on trunk posture.
Methods
In a semi-seated posture, ...healthy adult participants experienced unexpected posterior-anterior trunk perturbations in three different postures: neutral, trunk flexion and left trunk rotation. High-density surface electromyography was used to identify the regional distribution of activation within the lumbar erector spinae muscles. The effect of posture and side (left vs right) on muscle activity and centroid coordinates was investigated at baseline and in response to perturbations.
Results
Higher muscle activity was observed in trunk flexion compared to neutral and rotation postures at baseline (multiple
p
< 0.001) and in response to the perturbation (multiple
p
< 0.01). At baseline, the centroid of the electromyographic amplitude distribution was localized more medially in trunk flexion compared to trunk neutral posture (
p
= 0.003), while activation was localized more laterally in response to the perturbation (multiple
p
< 0.05). When the trunk was rotated, the electromyographic amplitude distribution was localized more cranially on the left than the right side, both at baseline (
p
= 0.001) and in response to the perturbation (
p
= 0.001). Finally, a more lateral location of the centroid on the left side in rotation compared to neutral posture was observed in response to the perturbation (multiple
p
< 0.001).
Conclusions
Regional differences in the distribution of electromyographic amplitude indicate that different muscle regions were recruited in different trunk postures and in response to perturbations, possibly based on regional mechanical advantage of the erector spinae muscle fibers.
This study aims to identify how spatial distribution of lumbar muscle activity is modulated by different fatigue tasks. Twenty healthy adults performed two different isometric trunk extension ...endurance tasks (the modified Sorensen test and the inverted modified Sorensen test) until exhaustion. During these tasks, bilateral superficial lumbar muscle activity was recorded using high-density electromyography. The spatial distribution of activation within these muscles was obtained using the centroid coordinates in the medio-lateral and cranio-caudal directions. The effects of task and endurance time (left and right sides) were investigated using repeated measures ANOVA. Results revealed a significant lateral shift of the centroid throughout the fatigue tasks on both sides and no difference between tasks. Significant task × time interaction effects were found for the cranio-caudal direction on both sides showing a significantly more caudal location of the centroid in the modified Sorensen test compared to the inverted test at the beginning of the tasks. Our findings suggest that spatial distribution of lumbar muscle activity is task-dependent in a pre-fatigue stage while an alternative but similar muscle recruitment strategy is used in both tasks to maintain performance in the later stages of muscle fatigue.
Similar impact on proprioception has been observed in participants with lumbar delayed-onset muscle soreness (DOMS) and chronic low back pain (LBP), raising questions about the relevance of lumbar ...DOMS as a suitable pain model for LBP when assessing back pain-related postural stability changes.
Does lumbar DOMS impact postural stability?
Twenty healthy adults participated in this experimental study and underwent a posturographic examination before and 24 to 36 h after a protocol designed to induce lumbar DOMS. Posturographic examination was assessed during quiet standing on both feet with eyes opened (EO), with eyes closed (EC), and on one-leg (OL) standing with eyes opened. Postural stability was assessed through center of pressure (COP) parameters (COP area, velocity, root mean square, mean power frequency) which were compared using repeated measure ANOVA. Moreover, pain, soreness and pressure pain threshold (PPT) on specific muscles were assessed.
There was a significant main effect of the postural condition on all COP variables investigated. More specifically, each COP variable reached a significantly higher value in the OL stance condition than in both EO and EC bipedal conditions (all with p < 0.001). In addition, the COP velocity and the mean power frequency along the anteroposterior direction both reached a significantly higher value in EC than in EO (p < 0.001). In contrast, there was no significant main effect of the DOMS nor significant DOMS X postural condition interaction on any of the COP variables. There was a significant decrease in the PPT value for both the left and right erector spinae muscles, as well as the left biceps femoris.
Lumbar DOMS had no impact on postural stability, which contrasts findings in participants with clinical LBP. Although DOMS induces similar trunk sensorimotor adaptations to clinical LBP, it does not appear to trigger similar postural stability adaptations.
•Lumbar delayed onset muscle soreness (DOMS) does not affect postural stability.•Differences between lumbar DOMS and clinical low back pain (LBP).•Lumbar DOMS as a suitable pain model for clinical LBP remains to be studied.
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