Relationship between Fear-Avoidance Beliefs and Reaction Time Changes Prior to and following Exercise-Induced Muscle Fatigue in Chronic Low Back Pain.

Background: Reaction time is a reliable indicator of the velocity and efficiency of neuromuscular control and may be associated with fear-avoidance beliefs. However, the effect of exercise-induced muscle fatigue on reaction time in chronic low back pain (cLBP) and its relationship with fear-avoidance beliefs remains poorly understood. Objectives: This study aimed to reveal the relationship between fear-avoidance beliefs and reaction time changes before and after exercise-induced muscle fatigue in cLBP. Methods: Twenty-five patients with cLBP were tested by the Biering-Sorensen test (BST) to induce exhaustive muscle fatigue. Total reaction time (TRT), premotor time (PMT), and electromechanical delay (EMD) of dominated deltoid muscle were recorded by surface electromyography during the arm-raising task with visual cues before and after muscle fatigue. The mean difference (MD) of TRT (MDTRT), PMT (MDPMT), and EMD (MDEMD) was calculated from the changes before and after muscle fatigue. Fear-avoidance beliefs questionnaire (FABQ) was applied to evaluate fear-avoidance beliefs before muscle fatigue. In addition, the duration time of BST was recorded for each subject. Results: TRT and PMT of dominated deltoid muscle were prolonged after exercise-induced muscle fatigue (Z = 3.511, p < 0.001; t = 3.431, p = 0.001), while there was no statistical difference in EMD (Z = 1.029, p = 0.304). Correlation analysis showed that both the MDTRT and MDPMT were positively correlated with FABQ (r = 0.418, p = 0.042; r = 0.422, p = 0.040). Conclusions: These findings suggested that we should pay attention to both muscle fatigue-induced reaction time delay in cLBP management and the possible psychological mechanism involved in it. Furthermore, this study implied that FABQ-based psychotherapy might serve as a potential approach for cLBP treatment by improving reaction time delay. This trial is registered with ChiCTR2300074348.

Cerebellar Transcranial Direct Current Stimulation Modulates Anticipatory Postural Adjustments in Healthy Adults.

During forward swinging of the arm, the central nervous system must anticipate the effect of upraising upon the body. Little is known about the cerebellar network that coordinates these anticipatory postural adjustments (APAs). Stimulating different cerebellar regions with transcranial direct current stimulation (tDCS) and with different polarities modulated the APAs. We used surface electromyography (sEMG) to measure muscle activities in a bilateral rapid shoulder flexion task. The onset of APAs was altered after tDCS over the vermis, while the postural stability and the kinematics of arm raising were not affected. To our knowledge, this is the first human cerebellar-tDCS (c-tDCS) study to separate cerebellar involvement in core muscle APAs in bilateral rapid shoulder flexion. These data contribute to our understanding of the cerebellar network supporting APAs in healthy adults. Modulated APAs of the erector spinae by tDCS on the vermis may be related to altered cerebellar brain inhibition (CBI), suggesting the importance of the vermal-cerebral connections in APAs regulation.

Effect of Cognitive Load on Anticipatory Postural Adjustment Latency and its Relationship with Pain-Related Dysfunction in Non-specific Chronic Low Back Pain: A Cross-Sectional Study.

INTRODUCTION: This study aimed to investigate the effect of cognitive load on anticipatory postural adjustment (APA) latency in patients with non-specific chronic low back pain (NCLBP) and its relationship with pain-related functional changes. METHODS: A cross-sectional study was conducted from December 15, 2022 to January 25, 2023. Participants were divided into a healthy control group (n = 29) and an NCLBP group (n = 29). Each group was assigned a single task of rapid arm raising and a dual task of rapid arm raising combined with a cognitive load. The cognitive load task was conducted using visual conflict. The APA latency for bilateral trunk muscles was observed using electromyography. The duration of electromyography recording in each task cycle was 28 s. Pain related-functional changes were evaluated using Roland-Morris Disability Questionnaire (RMDQ) before all tasks. RESULTS: The APA latency for the right multifidus was significantly delayed in the NCLBP group [25.38, 95% confidence interval (CI) 13.41-37.35] than in the healthy control group (- 5.80, 95% CI - 19.28 to 7.68) during dual task (p = 0.0416). The APA latency for the right multifidus (25.38, 95% CI 13.41-37.35) and transverse abdominis/internal oblique (29.15, 95% CI 18.81-39.50) were significantly delayed compared with on the left side in the NCLBP group during dual task (- 3.03, 95% CI - 15.18-9.13, p = 0.0220; 3.69, 95% CI - 6.81 to 14.18, p = 0.0363). The latency delay of the right and left multifidus APA in the NCLBP group under the dual-task was positively correlated with RMDQ scores (r = 0.5560, p = 0.0017; r = 0.4010, p = 0.0311). CONCLUSIONS: Cognitive load could induce APA delay in the right trunk muscles and co-activation pattern changes in bilateral trunk muscle APA in patients with NCLBP. The APA onset delay in multifidus is positively related to pain-related daily dysfunction. Trial Registration ChiCTR2300068580 (retrospectively registered in February 23, 2023).

Postural Control of Patients with Low Back Pain Under Dual-Task Conditions.

Low back pain is a major global public health problem, but the current intervention effect is not ideal. A large body of previous literature suggests that patients with chronic low back pain may have abnormal postural control, which is more evident in the dual task situation. In recent years, research on postural control in patients with low back pain under dual-task conditions has gradually become a hot topic. However, the results obtained from these studies were not entirely consistent. In this review, we summarized relevant studies on the performance of postural control in patients with low back pain under dual-task conditions, analyze it from the perspective of the theoretical model of dual-task interaction, the specific research paradigm of dual task, the performance of postural control, and the related factors affecting postural control performance, etc. It was reasonable to assume that patients with low back pain might have a certain degree of abnormal postural control, and this abnormality was affected by comprehensive factors such as age, cognitive resource capacity, attention needs, complex sensorimotor integration, external environment, etc. Furthermore, postural control performance in low back pain patients under dual-task conditions was further influenced by the nature and complexity of the different tasks. In general, the more attention resources were needed, the external environmental conditions were worse, and the age-related functions were degenerate, etc., the weaker posture control ability was. In short, a deeper understanding of postural control in patients with low back pain under dual-task conditions may shed light on more references for the rehabilitation and management of low back pain, as well as some new ideas for scientific research on cognition and postural control.

Physical exercise modulates the astrocytes polarization, promotes myelin debris clearance and remyelination in chronic cerebral hypoperfusion rats.

AIMS: White matter damage is the main pathological feature of chronic cerebral hypoperfusion (CCH) and glial activation is crucial in this process. Physical exercise has protective effects on CCH, but the mechanism is unclear. Therefore, this study focuses on investigating the influence of physical exercise on activated astrocytes polarization and its role in CCH. MAIN METHODS: Rats were given wheel running 48 h after 2VO (2 vessel occlusion) surgery. The cognitive function was evaluated by Morris water maze and novel object recognition test. Inflammatory cytokines expressions were detected by ELISA. Astrocytes polarization was analyzed by immunofluorescence. Myelin debris clearance and remyelination were detected by immunofluorescence and transmission electron microscopy. KEY FINDINGS: Astrocytes were activated and mainly switched to A1 phenotype in rats 2 and 3 months after 2VO. Myelin debris deposition and limited remyelination can be observed at the corresponding time. Whereas physical exercise can improve the cognitive function of 2VO rats, downregulate the expression of inflammatory factors IL-1α, C1q and TNF, upregulate the release of TGFß, and promote activated astrocytes transformation from A1 to A2 phenotype. In addition, it can also enhance myelin debris removal and remyelination. SIGNIFICANCE: These findings suggest that the benefits of physical exercise on white matter repair and cognition improvement may be related to its regulation of astrocytes polarization, which contributes to myelin debris clearance and effective remyelination in CCH.

C-C chemokine receptor type 2-overexpressing exosomes alleviated experimental post-stroke cognitive impairment by enhancing microglia/macrophage M2 polarization.

BACKGROUND: Human-derived mesenchymal stromal cells have been shown to improve cognitive function following experimental stroke. The activity of exosomes has been verified to be comparable to the therapeutic effects of mesenchymal stromal cells. However, the effects of exosomes derived from human umbilical cord mesenchymal stem cells (HUC-MSCs) (ExoCtrl) on post-stroke cognitive impairment (PSCI) have rarely been reported. Moreover, whether exosomes derived from C-C chemokine receptor type 2 (CCR2)-overexpressing HUC-MSCs (ExoCCR2) can enhance the therapeutic effects on PSCI and the possible underlying mechanisms have not been studied. AIM: To investigate the effects of ExoCtrl on PSCI and whether ExoCCR2 can enhance therapeutic effects on PSCI. METHODS: Transmission electron microscopy, qNano® particles analyzer, and Western blotting were employed to determine the morphology and CCR2 expression of ExoCtrl or ExoCCR2. ELISA was used to study the binding capacity of exosomes to CC chemokine ligand 2 (CCL2) in vivo. After the intravenous injection of ExoCtrl or ExoCCR2 into experimental rats, the effect of ExoCtrl and ExoCCR2 on PSCI was assessed by Morris water maze. Remyelination and oligodendrogenesis were analyzed by Western blotting and immunofluorescence microscopy. QRT-PCR and immunofluorescence microscopy were conducted to compare the microglia/macrophage polarization. The infiltration and activation of hematogenous macrophages were analyzed by Western blotting and transwell migration analysis. RESULTS: CCR2-overexpressing HUC-MSCs loaded the CCR2 receptor into their exosomes. The morphology and diameter distribution between ExoCtrl and ExoCCR2 showed no significant difference. ExoCCR2 bound significantly to CCL2 but ExoCtrl showed little CCL2 binding. Although both ExoCCR2 and ExoCtrl showed beneficial effects on PSCI, oligodendrogenesis, remyelination, and microglia/macrophage polarization, ExoCCR2 exhibited a significantly superior beneficial effect. We also found that ExoCCR2 could suppress the CCL2-induced macrophage migration and activation in vivo and in vitro, compared with ExoCtrl treated group. CONCLUSION: CCR2 over-expression enhanced the therapeutic effects of exosomes on the experimental PSCI by promoting M2 microglia/macrophage polarization, enhancing oligodendrogenesis and remyelination. These therapeutic effects are likely through suppressing the CCL2-induced hematogenous macrophage migration and activation.

An Animal Trial on the Optimal Time and Intensity of Exercise after Stroke.

INTRODUCTION: Although exercise is a safe, cost-effective, and therapeutic poststroke therapy, the proper time window and dosage of exercise are still unknown. We aim to determine the optimal combination of time window and intensity of exercise by assessing infarct volume, neurological recovery, and underlying mechanisms in middle cerebral artery occlusion rats. METHODS: The study contains two parts: the time-window and the dosage experiments. The time-window experiment assessed the effects of moderate-intensity exercise that was initiated at 24, 48, 72, 96 h and the control. In the dosage experiment, moderate and another two intensity exercise groups (low, high) were assessed. Forced wheel running was the exercise technique used. Infarct volume and neurological function (modified neurological severity scores [mNSS]) were measured. Inflammatory cytokines, cell death, and proliferation were further detected in the ischemic penumbra. RESULTS: The time window part revealed that neither infarct volume nor mNSS was reduced in the exercise group initiated at 24 h. The other three groups with exercise initiated after 24 h had reduced infarct volume and reduced mNSS but those outcomes do not differ from each other. In the dosage part, the low- and moderate-intensity groups with exercise initiated at 48 h were both better than the high-intensity group in terms of infarct volume and mNSS at 14 d; however, there was no statistical difference between these low and moderate groups. Exercise initiated at 24 h or high-intensity promoted proinflammatory cytokines and cell death. CONCLUSIONS: Exercise at 24 h is harmful. Low- and moderate-intensity exercise initiated at 48 h poststroke appears to be the optimal combination for maximal functional recovery.