Effects of combined anodal transcranial direct current stimulation and motor control exercise on cortical topography and muscle activation in individuals with chronic low back pain: A randomized controlled study.

BACKGROUND: Aberrant movement in chronic low back pain (CLBP) is associated with a deficit in the lumbar multifidus (LM) and changes in cortical topography. Anodal transcranial direct current stimulation (a-tDCS) can be used to enhance cortical excitability by priming the neuromuscular system for motor control exercise (MCE), thereby enhancing LM activation and movement control. This study aimed to determine the effects of a 6-week MCE program combined with a-tDCS on cortical topography, LM activation, movement patterns, and clinical outcomes in individuals with CLBP. METHODS: Twenty-two individuals with CLBP were randomly allocated to the a-tDCS group (a-tDCS; n = 12) or sham-tDCS group (s-tDCS; n = 10). Both groups received 20 min of tDCS followed by 30 min of MCE. The LM and erector spinae (ES) cortical topography, LM activation, movement control battery tests, and clinical outcomes (disability and quality of life) were measured pre- and post-intervention. RESULTS: Significant interaction (group × time; p < 0.01) was found in the distance between LM and ES cortical locations. The a-tDCS group demonstrated significantly fewer discrete peaks (p < 0.05) in both ES and LM and significant improvements (p < 0.05) in clinical outcomes post-intervention. The s-tDCS group demonstrated a significant increase (p < 0.05) in the number of discrete peaks in the LM cortical topography. No significant changes (p > 0.05) in LM activation were observed in either group; however, both groups demonstrated improved movement patterns. DISCUSSION: Our findings suggest that combined a-tDCS with MCE can separate LM and ES locations over time while s-tDCS (MCE alone) reduces the distance. Our study did not find superior benefits of adding a-tDCS before MCE for LM activation, movement patterns, or clinical outcomes.

Cortical excitability and multifidus activation responses to transcranial direct current stimulation in patients with chronic low back pain during remission.

Evidence indicates that patients with chronic low back pain (CLBP) have lumbar multifidus muscle (LM) activation deficit which might be caused by changes in cortical excitability. Anodal transcranial direct current stimulation (a-tDCS) can be used to restore cortical excitability. This study aimed to (1) determine the immediate effects of a-tDCS on the cortical excitability and LM activation and (2) explore the relationship between cortical excitability and LM activation. Thirteen participants with CLBP during remission and 11 healthy participants were recruited. Cortical excitability (peak-to-peak motor evoked potential amplitude; P2P and cortical silent period; CSP) and LM activation were measured at pre- and post-intervention. We found significant difference (P < 0.05) in P2P between groups. However, no significant differences (P > 0.05) in P2P, CSP and LM activation were found between pre- and post-intervention in CLBP. The CLBP group demonstrated significant correlation (P = 0.05) between P2P and LM activation. Although our finding demonstrates change in P2P in the CLBP group, one-session of a-tDCS cannot induce changes in cortical excitability and LM activation. However, moderate to strong correlation between P2P and LM activation suggests the involvement of cortical level in LM activation deficit. Therefore, non-significant changes could have been due to inadequate dose of a-tDCS.

The role of an active muscular subsystem in prone instability test during rest and leg raise conditions.

BACKGROUND: Clinicians commonly used prone instability test (PIT) by assessing the posterior-to-anterior (PA) displacement to identify lumbar instability. Most studies focusing on passive subsystem found greater mobility in lower lumbar (L4-L5) than upper lumbar (L1-L3) spine. However, there is still a lack of evidence to demonstrate the role of active subsystem. Additionally, it is unclear whether sex affects PA displacements. AIM: To determine differences in displacement among five lumbar segments, between two testing positions (rest and leg raise), and between male and female during PIT in individuals with chronic non-specific low back pain (CNLBP). DESIGN: A cross-sectional study design. SETTING: Spine biomechanics laboratory. POPULATION: Individuals with CNLBP. METHODS: An electromagnetic tracking system was used to measure PA displacement with sensors attached at T12, S2 and a hand-held dynamometer. Participants were asked to perform PIT, while a 100N force was applied to each lumbar segment during resting and leg raise positions. RESULTS: Significantly less PA displacement (P<0.05) was seen in lower compared to upper lumbar spine and in leg raise compared to rest at L1 to L4. No significant interaction of sex with different lumbar levels and conditions (P>0.05) during PIT was found. CONCLUSIONS: Although previous studies have reported that the lower lumbar spine had greater mobility, the lower amount of displacement during the rest position suggests the role of an active subsystem contributing to lumbar stability regardless of sex. CLINICAL REHABILTATION IMPACT: A reduction in displacement during the leg raise position across L1 to L4 suggesting an interaction of stabilizing subsystems of the spine to provide lumbar stability.

Effects of wearing different facial masks on respiratory symptoms, oxygen saturation, and functional capacity during six-minute walk test in healthy subjects.

Background: During the current COVID-19 pandemic and increased air pollution levels, wearing a facial mask has been recommended. This study aimed to compare the impact of wearing different masks when performing a submaximal functional activity (six-minute walk test; 6MWT) on respiratory symptoms, oxygen saturation, and functional capacity. Methods: Twenty-nine subjects (10 men, 19 women; age 22 ± 1 yr.; FEV1/FVC 0.90 ± 0.01) performed four rounds of 6MWT wearing different masks (surgical (Medima SK, Thailand), handmade cloth, and N95 (3M AuraTM 1870+, USA)) and while not wearing a mask. Respiratory symptoms (dyspnea and breathing effort), oxygen saturation, and other physiological parameters were assessed before and after each walking trial. Results: Six-minute walking distances were comparable between walking trials (P = 0.59). At the end of minute 6, a significant difference between groups was found on dyspnea (P = 0.02) and breathing effort (P < 0.001). Post hoc tests showed that wearing a cloth mask significantly increased dyspnea (P = 0.004) compared to wearing a surgical mask. Wearing a cloth mask also significantly increased breathing effort compared to wearing a surgical mask (P < 0.001) and not wearing a mask (P < 0.001). Likewise, while wearing an N95 mask, breathing effort significantly increased compared to wearing a surgical mask (P = 0.007) and not wearing a mask (P = 0.002). Conclusions: Wearing different masks while performing submaximal functional activity results in no differences in functional performance, oxygen saturation, heart rate, or blood pressure. However, wearing cloth masks and N95 masks results in higher respiratory symptoms.

Multifidus Muscle Contractility Deficit Was Not Specific to the Painful Side in Patients with Chronic Low Back Pain During Remission: A Cross-Sectional Study.

Purpose: Morphology studies demonstrated that patients with chronic low back pain (CLBP) have bilateral multifidus muscle (LM) atrophy. This atrophy should result in LM contractility deficit bilaterally. Additionally, a recent study showed the effect of sex on LM thickness. Researchers proposed percentage LM contractility (LMCONT) as standardization to enable the comparison across participants. This study aimed to determine side-to-side difference in LMCONT and to determine the difference in LMCONT between males and females. Patients and Methods: Twenty-five healthy individuals (NoLBP group; 10 males and 15 females) and 35 with CLBP (CLBP group; 16 males and 19 females; 23 unilateral pain and 12 bilateral pain) were recruited. Ultrasound imaging was used to measure LM thickness at rest, during maximum voluntary isometric contraction, and during combined maximum voluntary isometric contraction with electrical stimulation. These data were used to calculate LMCONT. For unilateral CLBP, right and left LMCON were renamed to painful and non-painful sides. Results: Data demonstrated no significant difference (p > 0.05) between right (87.3 ± 13.7%) and left (87.2 ± 14.0%) in NoLBP, right (71.2 ± 15.7%) and left (76.5 ± 19.7%) in bilateral CLBP, and painful (70.3 ± 17.5%) and non-painful (77.7 ± 18.4%) in unilateral CLBP. No difference (p > 0.05) was found between males and females in both NoLBP (male 84.8 ± 6.5%, female 88.9 ± 15.4%) and CLBP groups (male 76.3 ± 15.5%, female 71.9 ± 14.0%). Conclusion: The findings suggested that LM contractility deficit in CLBP is not specific to painful side. No effect was found of sex on LM contractility. Therefore, we can use averaged LM activation across painful and non-painful sides and across males and females to compare between NoLBP and CLBP groups.