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Changes in spinal kinematic variability have been observed in people with chronic non-specific LBP (CNSLBP) during the performance of various repetitive functional tasks. However, the direction of these changes (i.e., less or more kinematic variability) is not consistent. This study aimed to assess differences in kinematic variability of the 3D angular displacement of thoracic and lumbar spinal segments in people with CNSLBP compared to asymptomatic individuals during a repetitive lifting task. Eleven people with CNSLBP and 11 asymptomatic volunteers performed 10 cycles of multi-planar lifting movements while spinal kinematics were recorded. For the three planes of motion, point-by-point standard deviations (SDs) were computed across all cycles of lifting and the average was calculated as a measure of kinematic variability for both segments. People with CNSLBP displayed higher thoracic (F = 8.00, p = 0.010, ηp2 = 0.286) and lumbar kinematic variability (F = 5.48, p = 0.030, ηp2 = 0.215) in the sagittal plane. Moreover, group differences were observed in the transversal plane for thoracic (F = 7.62, p = 0.012, ηp2 = 0.276) and lumbar kinematic variability (F = 5.402, p = 0.031, ηp2 = 0.213), as well as in the frontal plane for thoracic (F = 7.27, p = 0.014, ηp2 = 0.267) and lumbar kinematic variability (F = 6.11, p = 0.022, ηp2 = 0.234), all showing higher variability in those with CNSLBP. A significant main effect of group was not detected (p > 0.05) for spinal range of motion (ROM). Thus, people with CNSLBP completed the lifting task with the same ROM in all three planes of motion as observed for asymptomatic individuals, yet they performed the lifting task with higher spinal kinematic cycle-to-cycle variation. [ABSTRACT FROM AUTHOR]

The trunk represents almost 50% of the total mass of a person [1] and, because it comprises multiple segments, has a large range of motion [2]. Trunk posture and movement are important in the execution of activities of daily living (ADL), especially for those related with arm function [3]. However, in movement analysis, the trunk is usually defined as a single rigid, cylindrical segment between the shoulders and pelvis. This oversimplification ignores the large movement potential the trunk has [2], and therefore does not enable a complete evaluation of trunk movement. Does a single segment trunk model adequately reveal trunk movements for a simple reaching and grasping movement? The University Ethics Committee (ref:47565) approved the project. Eleven people (7 male; (mean ±SD) age: 27.82 ±3.18years, height: 1.74 ±0.11 m; weight: 75.0 ±12.7 kg) participated after signing the consent form. An upper-body marker-set was used: left/right acromion, iliac-crest, ASIS; manubrium, S1; five inverted "L" clusters of 3 markers: two 2.5 cm lateral of C7, T3, T7, T11 and L3, with the third marker on the long end of the "L" with the length adjusted based on the participant' s size. These defined a single-segment-trunk (acromia to iliac-crests), and upper-, mid- and lower-thoracic, and upper- and lower-lumbar segments (multi-segment-trunk). Participants were asked to stand from a hight-adjustable bench, walk to a low table and lean to collect a mug before returning to the bench. Motion capture data were recorded (100 Hz), tracked, and processed. Segmental angles (in relation to the absolute coordinate system) were estimated for the "leaning to collect" section of each trial. The total displacement in each plane and a combined 3D movement (sum of the three planes) of the single-segment-trunk and of the multi-segment-trunk compared with a paired sample t-test. Table 1 shows the difference in the combined 3D movement for the single-segment-trunk when compared to the multi-segment-trunk (t = 27.95, p<.01) and for each of the planes of movement (t = 18.21, 11.19, 14.15, p<.01, for sagittal, frontal and horizontal). The standardised mean difference was considered very large (8.07 ±8.06). [Display omitted] This simplified approach identified the scale of additional information that could be gained from a multi-segment-trunk. Further exploration should focus on understanding if the amount of movement in a multi-segment-trunk vs single-segment-trunk is of a very different magnitude; it should also look specifically at where are the more important differences. Additional development might focus on understanding the best representation of the trunk movement when assessing ADL in clinical populations. I would say this phrasing is better, calling your approach very simple is an insult to your work, calling it simplified indicates that you're just presenting in a simple way for them. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the spatial distribution and redistribution of lumbar erector spinae (ES) activity during a lumbar extension endurance task in pain‐free participants and how this is modified in people with low back pain (LBP). High density surface electromyography (HDEMG) was recorded using 13 × 5 electrode grids placed over the lumbar ES in 13 LBP and 13 control participants while completing an Ito test to task failure. The root mean square of the HDEMG signals was computed, a topographical map of the EMG amplitude generated and the centre of the activity (centroid) determined throughout the task. The centroid of the EMG amplitude map was systematically more cranial (F = 6.09, P = 0.022) for the LBP participants compared with the control subjects. Regression analysis showed that the extent of redistribution of ES activity was associated with longer endurance. These results show that LBP participants utilised a different motor strategy to perform the endurance task, characterised by greater activation of more cranial regions of the ES and less redistribution of ES activity throughout the task. This study provides new insight into the functional activation of the lumbar ES and how it is modified when people have pain. [ABSTRACT FROM AUTHOR]

Background Context: Chronic spinal pain is one the most common musculoskeletal disorders. Previous studies have observed microscopic structural changes in the spinal extensor muscles in people with chronic spinal pain. This systematic review synthesizes and analyzes all the existing evidence of muscle microscopic changes in people with chronic spinal pain.Purpose: To assess the microscopy of spinal extensor muscles including the fiber type composition, the area occupied by fiber types, fiber size/cross sectional area (CSA), and narrow diameter (ND) in people with and without chronic spinal pain. Further, to compare these outcome measures across different regions of the spine in people with chronic neck, thoracic and low back pain.Study Design: Systematic review with meta-analysis.Methods: MEDLINE (Ovid Interface), Embase, PubMed, CINAHL Plus, and Web of Science were searched from inception to October 2020. Key journals, conference proceedings, grey literature and hand searching of reference lists from eligible studies were also searched. Two independent reviewers were involved in the selection process. Only studies examining the muscle microscopy of the spinal extensor muscles (erector spinae [ES] and/or multifidus [MF]) between people with and without chronic spinal pain were selected. The risk of bias from the studies was assessed using modified Newcastle Ottawa Scale and the level of evidence was established using the GRADE approach. Data were synthesized based on homogeneity on the methodology and outcome measures of the studies for ES and MF muscles and only four studies were eligible for analysis.Results: All the five studies included were related to chronic low back pain (CLBP). Meta-analysis (inverse variance method for random effect to calculate mean difference and 95% CI) was performed for the ES fiber type composition by numbers for both type I and type II fibers (I2=43% and 0% respectively indicating homogeneity of studies) and showed no difference between the people with and without CLBP with an overall effect estimate Z= 1.49 (p=.14) and Z=1.06 (p=.29) respectively. Meta-analysis was performed for ES fiber CSA for both type I and type II fibers (I2=0 for both) and showed no difference between people with and without CLBP with an overall effect estimate Z=0.08 (p=.43) and Z=0.75 (p=.45) respectively. Analysis was not performed for ES area occupied by fiber types and ND due to heterogeneity of studies and lack of evidence respectively. Similarly, meta-analysis was not performed for MF fiber type composition by numbers due to heterogeneity of studies. MF analysis for area occupied by fiber type, fiber CSA and ND did not yield sufficient evidence.Conclusions: For the ES muscle, there was no difference in fiber type composition and fiber CSA between people with and without CLBP and no conclusions could be drawn for ND for the ES. For the MF, no conclusions could be drawn for any of the muscle microscopy outcome measures. Overall, the quality of evidence is very low and there is very low evidence that there are no differences in microscopic muscle features between people with and without CLBP. [ABSTRACT FROM AUTHOR]

Background: Eumenorrheic women experience cyclic variations in sex hormones attributed to the menstrual cycle (MC) which can impact anterior cruciate ligament (ACL) properties, knee laxity, and neuromuscular function. This systematic review aimed to examine the effects of the MC on ACL neuromuscular and biomechanical injury risk surrogates during dynamic tasks, to establish whether a particular MC phase predisposes women to greater ACL injury risk. Methods: PubMed, Medline, SPORTDiscus, and Web of Science were searched (May-July 2021) for studies that investigated the effects of the MC on ACL neuromuscular and biomechanical injury risk surrogates. Inclusion criteria were: 1) injury-free women (18–40 years); 2) verified MC phases via biochemical analysis and/or ovulation kits; 3) examined neuromuscular and/or biomechanical injury risk surrogates during dynamic tasks; 4) compared ≥1 outcome measure across ≥2 defined MC phases. Results: Seven of 418 articles were included. Four studies reported no significant differences in ACL injury risk surrogates between MC phases. Two studies showed evidence the mid-luteal phase may predispose women to greater risk of non-contact ACL injury. Three studies reported knee laxity fluctuated across the MC; two of which demonstrated MC attributed changes in knee laxity were associated with changes in knee joint loading (KJL). Study quality (Modified Downs and Black Checklist score: 7–9) and quality of evidence were low to very low (Grading of Recommendations Assessment Development and Evaluation: very low). Conclusion: It is inconclusive whether a particular MC phase predisposes women to greater non-contact ACL injury risk based on neuromuscular and biomechanical surrogates. Practitioners should be cautious manipulating their physical preparation, injury mitigation, and screening practises based on current evidence. Although variable (i.e., magnitude and direction), MC attributed changes in knee laxity were associated with changes in potentially hazardous KJLs. Monitoring knee laxity could therefore be a viable strategy to infer possible ACL injury risk. [ABSTRACT FROM AUTHOR]

Purpose: To investigate whether people with chronic low back pain (LBP) show dysfunctional exercise‐induced hypoalgesia (EIH) in response to repeated contractions of their back muscles during a lifting task. Methods: In this cross‐sectional observational study conducted on asymptomatic participants (n = 18) and participants with chronic LBP (n = 21), quantitative sensory testing (QST) was applied extensively over the lumbar region and a remote area before and after a repeated task that involved lifting a 5‐kg box for ~7 minutes. QST included pressure pain thresholds (PPTs), thermal detection, pain thresholds, and measures of temporal summation. Topographical maps of the percentage change in PPT detected at 16 locations over the lumbar region were generated to explore regional differences and compared between groups. Results: Mean (standard deviation) PPTs measured from 16 sites over the lower back changed significantly in asymptomatic participants (+29.78 kPa [41.4]) following task completion, indicative of EIH, whereas no significant change was observed for the low back pain (LBP) group (−14.87 kPa [61.2]). No changes were detected at the remote site for either group. No changes were revealed for the thermal tests. Temporal summation data revealed decreasing pain sensitivity as the test progressed, but the test response did not change after the exercise for either group. Conclusion(s): Unlike asymptomatic individuals, participants with LBP lacked EIH over the lumbar erector spinae muscles following repeated lifting. Although these results should be considered in relation to the study limitations, particularly the absence of a control group, the findings support impaired EIH in patients with LBP. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate differences in passive muscular stiffness between the superficial multifidus (SM) and deep multifidus (DM), and to compare their passive and active stiffness in individuals with low back pain (LBP) and asymptomatic individuals. Fifteen LBP individuals and 15 asymptomatic individuals were recruited. Passive stiffness of the SM and DM was measured bilaterally using shear wave elastography (SWE) with participants lying prone. Active stiffness was measured for the SM during trunk extension, and the contraction ratio was calculated. DM displayed higher passive muscular stiffness than SM in both the asymptomatic and LBP groups (14.41 ± 2.62 and 15.40 ± 2.77 kPa respectively; p < 0.001). Individuals with LBP exhibited higher passive muscular stiffness of SM (LBP: 10.15 ± 4.21, asymptomatic: 6.84 ± 1.69 kPa; p < 0.005) and a lower contraction ratio (LBP: 1.54 ± 0.47, asymptomatic: 2.65 ± 1.36 kPa; p < 0.003) compared to the asymptomatic group. The findings support a differentiation in passive muscular stiffness between SM and DM and provide evidence for an alteration in muscular stiffness at rest in individuals with LBP. The lower increase of muscular stiffness with contraction observed for those with LBP may reflect a deficit in activation of the multifidus. [ABSTRACT FROM AUTHOR]

Recent research using high-density electromyography (HDEMG) has provided a more precise understanding of the behaviour of the paraspinal muscles in people with low back pain (LBP); but so far, HDEMG has not been used to investigate the flexion relaxation phenomenon (FRP). To evaluate this, HDEMG signals were detected with grids of electrodes (13 × 5) placed bilaterally over the lumbar paraspinal muscles in individuals with and without LBP as they performed repetitions of full trunk flexion. The root mean square of the HDEMG signals was computed to generate the average normalized amplitude; and the spatial FRP onset was determined and expressed as percentage of trunk flexion. Smoothing spline analysis of variance models and the contrast cycle difference approach using the Bayesian interpretation were used to determine statistical inference. All pain-free controls and 64.3% of the individuals with LBP exhibited the FRP. Individuals with LBP and the FRP exhibited a delay of its onset compared to pain-free controls (significant mean difference of 13.3% of trunk flexion). They also showed reduced normalized amplitude compared to those without the FRP, but still greater than pain-free controls (significant mean difference of 27.4% and 11.6% respectively). This study provides novel insights into changes in lumbar muscle behavior in individuals with LBP. [ABSTRACT FROM AUTHOR]