Spatial Distribution and Asymmetry of Surface Electromyography on Lumbar Muscles of Soldiers with Chronic Low Back Pain

Alterations in magnitude and spatial distribution of erector spinae muscle activity in cyclists with a recent history of low back pain

PURPOSE

While cycling offers several health benefits, repetitive loading and maintenance of static postures for prolonged periods expose cyclists to low back pain (LBP). Despite high LBP prevalence in cyclists, underlying pathomechanics and specific lumbar region muscle activation patterns during cycling are unclear. Here, we compared lumbar erector spinae (ES) muscles activation and spatial distribution activity in cyclists with and without recent LBP history.

METHODS

Ten cyclists with recent LBP history (LBPG; Oswestry Disability Index score ~ 17.8%) and 11 healthy cyclists (CG) were recruited. After assessing the Functional Threshold Power (FTP), participants underwent an incremental cycling test with 4 × 3 min steps at 70%, 80%, 90%, and 100% of their FTP. High-density surface electromyography (HDsEMG) signals were recorded from both lumbar ES using two 64-channel grids. Information about ES activation levels (root-mean-square, RMS), degree of homogeneity (entropy), and cranio-caudal displacement of muscle activity (Y-axis coordinate of the barycenter of RMS maps) was extracted from each grid separately and then grand-averaged across both grids.

RESULTS

Repeated-measure 2-way ANOVAs showed a significant intensity by group interaction for RMS amplitude (p = 0.003), entropy (p = 0.038), and Y-bar displacement (p = 0.033). LBPG increased RMS amplitude between 70-100% (+ 19%, p = 0.010) and 80-100% FTP (+ 21%, p = 0.004) and decreased entropy between 70-100% FTP (- 8.4%, p = 0.003) and 80-100% FTP (- 8.5%, p = 0.002). Between-group differences emerged only at 100% FTP (+ 9.6%, p = 0.049) for RMS amplitude.

CONCLUSION

Our findings suggest that cyclists with recent LBP history exhibit higher ES muscles activation and less homogeneous activity compared to healthy controls, suggesting potential inefficient muscle recruitment strategy.

TRIAL REGISTRATION NUMBER

HEC-DSB/09-2023.

The effect of trunk position and pain location on lumbar extensor muscle recruitment strategies

The aim of this study was to investigate the effect of trunk position and experimental lumbar pain location on lumbar extensor muscle recruitment strategies. Nineteen healthy participants (10 men and 9 women), aged 25.3 ± 4.7 yr, performed isometric back extension contractions in three positions (neutral, 45°, and 90° trunk flexion) and under three conditions (no pain, caudal pain, and cranial pain). Lumbar muscle activation strategies were recorded using high-density surface electromyography. The effect of position and pain condition on muscle activity amplitude and spatial redistributions was assessed. Muscle activity amplitude was 43% higher in 45° trunk flexion than in neutral position on both sides (P < 0.05). In the 90° trunk flexion, participants showed a more lateral spatial distribution than in the 45° trunk flexion on the left side (P < 0.01, 5.4 mm difference) and the neutral position on both sides (P < 0.05, 8.2 mm difference). In the 45° trunk flexion, participants exhibited a more lateral spatial distribution compared with the neutral position on the right side (P < 0.05, 3.7 mm difference). A lateral spatial redistribution of muscle activity was observed in the caudal pain condition compared with the no pain condition on the right side (P < 0.05, 3.0 mm difference). Individual responses to pain varied across all variables. Different trunk positions result in different distributions of activation within the lumbar extensor muscles, possibly based on regional mechanical advantage. No clear indication of location-specific pain adaptation and no effect of task-dependent pain adaptation were found, whereas individual-specific adaptations were observed.NEW & NOTEWORTHY Changes in muscle activity amplitude and spatial redistribution of lumbar extensor muscles were observed in different trunk positions, potentially due to changes in their mechanical advantage. The results complement the current pain-adaptation theory by illustrating individual spatial redistributions of activation within lumbar extensor muscles during pain. The study found no clear indication of location-specific pain adaptation and no effect of task-dependent pain adaptation.

The Application of Surface Electromyography Technology in Evaluating Paraspinal Muscle Function

Surface electromyography (sEMG) has emerged as a valuable tool for assessing muscle activity in various clinical and research settings. This review focuses on the application of sEMG specifically in the context of paraspinal muscles. The paraspinal muscles play a critical role in providing stability and facilitating movement of the spine. Dysfunctions or alterations in paraspinal muscle activity can lead to various musculoskeletal disorders and spinal pathologies. Therefore, understanding and quantifying paraspinal muscle activity is crucial for accurate diagnosis, treatment planning, and monitoring therapeutic interventions. This review discusses the clinical applications of sEMG in paraspinal muscles, including the assessment of low back pain, spinal disorders, and rehabilitation interventions. It explores how sEMG can aid in diagnosing the potential causes of low back pain and monitoring the effectiveness of physical therapy, spinal manipulative therapy, and exercise protocols. It also discusses emerging technologies and advancements in sEMG techniques that aim to enhance the accuracy and reliability of paraspinal muscle assessment. In summary, the application of sEMG in paraspinal muscles provides valuable insights into muscle function, dysfunction, and therapeutic interventions. By examining the literature on sEMG in paraspinal muscles, this review offers a comprehensive understanding of the current state of research, identifies knowledge gaps, and suggests future directions for optimizing the use of sEMG in assessing paraspinal muscle activity.

Time-Resolved Noncontrast Magnetic Resonance Perfusion Imaging of Paraspinal Muscles

BACKGROUND

While evaluation of blood perfusion in lumbar paraspinal muscles is of interest in low back pain, it has not been performed using noncontrast magnetic resonance (MR) techniques.

PURPOSE

To introduce a novel application of a time-resolved, noncontrast MR perfusion technique for paraspinal muscles and demonstrate effect of exercise on perfusion parameters.

STUDY TYPE

Longitudinal.

SUBJECTS

Six healthy subjects (27-48 years old, two females) and two subjects with acute low back pain (46 and 65 years old females, one with diabetes/obesity).

FIELD STRENGTH/SEQUENCE

3-T, MR perfusion sequence.

ASSESSMENT

Lumbar spines of healthy subjects were imaged axially at L3 level with a tag-on and tag-off alternating inversion recovery arterial spin labeling technique that suppresses background signal and acquires signal increase ratio (SIR) from the in-flow blood at varying inversion times (TI) from 0.12 seconds to 3.5 seconds. SIR vs. TI data were fit to determine the perfusion metrics of peak height (PH), time to peak (TTP), mean transit time, apparent muscle blood volume (MBV), and apparent muscle blood flow (MBF) in iliocostal, longissimus, and multifidus. Imaging was repeated immediately after healthy subjects performed a 20-minute walk, to determine the effect of exercise.

STATISTICAL TESTS

Repeated measures analysis of variance.

RESULTS

SIR vs. TI data showed well-defined leading and trailing edges, with sharply increasing SIR to TI of approximately 500 msec subsiding quickly to near zero around TI of 1500 msec. After exercise, the mean SIR at every TI increased markedly, resulting in significantly higher PH, MBV, and MBF (each P < 0.001 and F > 28.9), and a lower TTP (P < 0.05, F = 4.5), regardless of the muscle. MBF increased 2- to 2.5-fold after exercise, similar to the expected increase in cardiac output, given the intensity of the exercise.

DATA CONCLUSIONS

Feasibility of an MR perfusion technique for muscle perfusion imaging was demonstrated, successfully detecting significantly increased perfusion after exercise.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 1.

Associations between Deformation of the Thoracolumbar Fascia and Activation of the Erector Spinae and Multifidus Muscle in Patients with Acute Low Back Pain and Healthy Controls: A Matched Pair Case-Control Study

Background: The thoracolumbar fascia (TLF) is thought to play a role in the development of LBP, but it is not yet clear which factor of TLF changes is a cause and which is an effect. Therefore, some studies used the cross-correlation function (CCR) to reveal time-dependent relationships between biomechanical and neuromotor factors. Methods: Ten patients with acute low back pain (aLBP) were matched to healthy controls. Simultaneous recording of surface electromyography (sEMG) of the erector spinae and multifidus muscle (ESM) and dynamic ultrasound (US) images of TLF deformation were performed during trunk extension. CCR functions and Granger causality (GC) were used to describe the relationship between the two measures. Results: CCR time lags were significant higher in the aLBP group (p = 0.04). GC showed a direct effect of TLF deformation on ESM activation only in the aLBP group (p < 0.03). Conclusions: The results suggest that in aLBP, ESM activity is significantly affected by TLF, whereas this relationship is completely random in healthy subjects studied with CCR and GC comparisons of dynamic US imaging and sEMG data signals. Fascia-related disturbances in neuromotor control, particularly due to altered muscle spindle functions, are suspected as a possible mechanism behind this.

The Association between Symmetrical or Asymmetrical High-Arched Feet and Muscle Fatigue in Young Women

The foot arches are responsible for proper foot loading, optimal force distribution, and transmission throughout the soft tissues. Since the foot arch is an elastic structure, able to adapt to forces transmitted by the foot, it was reported that low arch is related to excessive foot pronation, while high arched foot is more rigid and inflexible. Therefore, it is also probable, that foot arch alterations may change the force transmission via myofascial chains. The objective of this study was to evaluate the effect of symmetrical and asymmetrical excessive feet arching on muscle fatigue in the distal body parts such as the lower limbs, trunk, and head. Seventy-seven women (25.15 ± 5.97 years old, 62 ± 10 kg, 167 ± 4 cm) were assigned to three groups according to the foot arch index (Group 1—both feet with normal arch, Group 2—one foot with normal arch and the other high-arched, Group 3—both feet with high-arch). The bioelectrical activity of the right and left hamstrings muscles, erector spine, masseter, and temporalis muscle was recorded by sEMG during the isometric contraction lasting for 60 s. The stable intensity of the muscle isometric contraction was kept for all the time during the measurement. Mean frequency difference (%), slope (Hz), and intercept (Hz) values were calculated for muscle fatigue evaluation. No differences were observed in fatigue variables for all evaluated muscles between the right and left side in women with symmetrical foot arches, but in the group with asymmetric foot arches, the higher muscle fatigue on the normal-arched side compared to the high-arched side was noted. Significantly greater values of the semitendinosus—semimembranosus muscle frequency difference was observed on the normal-arched side compared to the high-arched side (p = 0.04; ES = 0.52; −29.5 ± 9.1% vs. −24.9 ± 8.4%). In the group with asymmetric foot arches, a significantly higher value of lumbar erector spinae muscle frequency slope (p = 0.01; ES = 1.32; −0.20 ± 0.04 Hz vs. −0.14 ± 0.05 Hz) and frequency difference (p = 0.04; ES = 0.92; −7.8 ± 3.1% vs. −4.8 ± 3.4%) were observed on the high-arched foot side compared to the side with normal foot arching. The thoracic erector spine muscle frequency slope was significantly larger in women with asymmetrical arches than in those with both feet high-arched (right side: p = 0.01; ES = 1.25; −0.20 ± 0.08 Hz vs. −0.10 ± 0.08 Hz); (left side: p = 0.005; ES = 1,17; −0.19 ± 0.04 Hz vs. −0.13 ± 0.06 Hz) and compared to those with normal feet arches (right side: p = 0.02; ES = 0.58; −0.20 ± 0.08 Hz vs. −0.15 ± 0.09 Hz); (left side: p = 0.005; ES = 0.87; −0.19 ± 0.04 Hz vs. −0.14 ± 0.07 Hz). In the group with asymmetric foot arches, the frequency difference was significantly higher compared to those with both feet high-arched (right side: p = 0.01; ES = 0.87; −15.4 ± 6.8% vs. 10.4 ± 4.3%); (left side: p = 0.01; ES = 0.96; 16.1 ± 6.5% vs. 11.1 ± 3.4%). In the group with asymmetric foot arches, a significantly higher value of the masseter muscle frequency difference was observed on the high-arched side compared to the normal-arched side (p = 0.01; ES = 0.95; 6.91 ± 4.1% vs. 3.62 ± 2.8%). A little increase in the longitudinal arch of the foot, even though such is often not considered as pathological, may cause visible changes in muscle function, demonstrated as elevated signs of muscles fatigue. This study suggests that the consequences of foot high-arching may be present in distal body parts. Any alterations of the foot arch should be considered as a potential foot defect, and due to preventing muscle overloading, some corrective exercises or/and corrective insoles for shoes should be used. It can potentially reduce both foot overload and distant structures overload, which may diminish musculoskeletal system pain and dysfunctions.