Relationships Between Muscle Activation and Thoraco-Lumbar Kinematics in Direction-Specific Low Back Pain Subgroups During Everyday Tasks
1
School of Healthcare Sciences, Cardiff University, Cardiff CF14 4XN, UK
2
AECC School of Chiropractic, Health Sciences University, Bournemouth BH5 2DF, UK
3
School of Health Sciences, University of Southampton, Southampton SO17 1BJ, UK
*
Author to whom correspondence should be addressed.
Biomechanics 2025, 5(2), 42; https://doi.org/10.3390/biomechanics5020042
Submission received: 2 April 2025
/
Revised: 20 May 2025
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Accepted: 11 June 2025
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Published: 19 June 2025
(This article belongs to the Section Injury Biomechanics and Rehabilitation)
Abstract
:Background/Objectives: The assessment of relationships between trunk muscle activity and thoraco-lumbar movements during sagittal bending has demonstrated that low back pain (LBP) subgroups (flexion pattern and active extension pattern motor control impairment) reveal distinct relationships that differentiate these subgroups from control groups. The study objective was to establish whether such relationships exist during various daily activities. Methods: Fifty participants with non-specific chronic low back pain (NSCLBP) (27 flexion pattern (FP), 23 active extension pattern (AEP)) and 28 healthy controls were recruited. Spinal kinematics were analysed using 3D motion analysis (Vicon™, Oxford, UK) and the muscle activity recorded via surface electromyography during a range of activities (box lift, box replace, reach up, step up, step down, stand-to-sit, and sit-to-stand). The mean sagittal angles for upper and lower thoracic and lumbar regions were correlated with normalised mean amplitude electromyography of bilateral transversus abdominis/internal oblique (IO), external oblique (EO), superficial lumbar multifidus (LM), and erector spinae (ES). Relationships were assessed via Pearson correlations (significance p < 0.01). Results: In the AEP group, increased spinal extension was associated with altered LM activity during box-replace, reach-up, step-up, and step-down tasks. In the FP group, increased lower lumbar spinal flexion was associated with reduced muscle activation, while increased lower thoracic flexion was associated with increased muscle activation. The control group elicited no significant associations. Correlations ranged between −0.812 and 0.754. Conclusions: Differential relationships between muscle activity and spinal kinematics exist in AEP, FP, and pain-free control groups, reinforcing previous observations that flexion or extension-related LBP involves distinct motor control strategies during different activities. These insights could inform targeted intervention approaches, such as movement-based interventions and wearable technologies, for these groups.
1. Introduction
Chronic low back pain (LBP) is a significant global issue, affecting approximately 10% of the world’s population. This has substantial global economic implications, including financial and societal costs and increased pressures on healthcare systems [1,2]. Despite this there have been few advances in understanding the biomechanical underpinning of LBP disorders. This may be attributable in part to the heterogeneity of LBP and the complex interactions between the biopsychosocial domains of the disorder. Additionally, the specificity of the measurement tools used to understand LBP mechanisms (especially biomechanically) has limitations.
There have, however, been some interesting recent observations regarding the biomechanics of LBP. A promising area for further work is the incorporation of multiple co-dependent spinal regions in a biomechanically focused investigation. While people with LBP exhibit a reduced lumbar spine range of motion [3], altered thoracic spine kinematics have been identified in several studies as a potential compensatory mechanism in this population [4,5,6]. Further, the identification of direction-specific subgroups of LBP patients has opened new avenues to explore the interactions between biomechanical variables in subgroups of the wider LBP population, for whom biomechanical factors may be a primary contributory factor to pain persistence.
Differential spinal kinematics have been consistently observed in non-specific chronic low back pain (NSCLBP) movement-based subgroups [7,8,9,10]. Hemming et al. [5] showed that there were significant differences in the regional spinal kinematics between NSCLBP subgroups (flexion pattern (FP) and active extension pattern (AEP) [7]) and healthy control groups during everyday functional tasks. Similarly, reduced movement of the upper lumbar region in FP individuals has been demonstrated during sagittal and coronal tasks [11]. There have also been numerous studies suggesting that muscle activation differs in these subgrouped populations [12,13], suggesting that potential differences in both kinematic and muscular behaviours in symptomatic populations and pain-free individuals warrant further exploration.
Despite this emerging evidence, there remains a critical gap in understanding how spinal kinematics and muscle activation interact during dynamic functional tasks in NSCLBP subgroups. While some studies have evaluated these domains independently, few have simultaneously examined their interplay, and existing work has focused on isolated or simplistic movements, such as forward bending [11]. The integration of muscle activity and kinematic analysis across a broader range of functional activities—particularly in regions such as the thoracic spine, which has been comparatively under-explored—is necessary to enhance our understanding of the biomechanical adaptations underlying chronic LBP.
Interactions between spine kinematics and muscle activity during dynamic spinal movements are crucial to inform specific rehabilitation strategies for people with LBP and may also inform preventative strategies, and physical conditioning approaches, to avoid LBP chronicity. Indeed, it has been suggested that rehabilitation in such populations would be enhanced with the use of more targeted movement-based interventions for subgroups [4,14], the effectiveness of which has been demonstrated by aspects of cognitive functional therapy approaches [15,16]. There is also potential value in further exploring biomechanical adaptations and interactions in the thoracic region, as regional insights may provide an understanding of the development and subsequent management of chronic LBP [3,5,11]. An initial investigation into the relationships between muscle activity and regional spinal kinematics demonstrated distinct variations between NSCLBP subgroups during a simple bending task in the sagittal plane [11]. As potential mechanical biomarkers, there is a clear need to establish if these associations are evident during additional tasks of daily living.
Therefore, the present study aimed to explore the relationship between trunk muscle activation and regional thoracic and lumbar kinematics across two clinically defined NSCLBP subgroups—AEP and FP—and healthy controls during a series of functionally relevant tasks. By addressing the current gap in the literature regarding the dynamic interaction of spinal motion and neuromuscular control, this study seeks to inform more nuanced and effective therapeutic strategies for individuals with NSCLBP.
2. Materials and Methods
The study received ethical approval from The Research Ethics Committee 3 Wales (10/MRE09/28). Data were collected at the Research Centre for Clinical Kinesiology, School of Healthcare Sciences, Cardiff University. Fifty patients (aged 18–65 years) with NSCLBP (27 FP, 23 AEP) were recruited via Cardiff and Vale University Health Board (Cardiff, UK) routine physiotherapy waiting lists. Twenty-eight healthy participants (aged 18–65 years) from the local community, who responded to the study adverts, were recruited as a control group. This group included Cardiff University staff and students. Calculation of sample size is reported elsewhere [5].
2.1. Inclusion and Exclusion Criteria
Exclusion criteria for all participants were: vestibular, visual or neurological dysfunction affecting balance, pregnancy or breastfeeding, or history of spinal surgery, fracture or malignancy. NSCLBP participants were additionally excluded if they had current radiating symptoms, and/or neurological deficit, below the level of the buttock crease [7] or displayed any red flags [17,18,19]. Healthy participants were additionally excluded if they had a history of LBP in the previous 2 years or had had any previous LBP with radiating symptoms below the level of the buttock crease. For NSCLBP participants the inclusion criteria was: current LBP (>12 weeks) and pain in the lumbar region which did not radiate below the level of the buttock crease, a clear mechanical basis of the disorder aligned with specific aggravating and easing postures and movements as described by O’Sullivan [7] and a clinical diagnosis of specific motor control impairment—either AEP or FP [20]. Classification assessment procedures, as confirmed by two clinicians, is detailed elsewhere [5].
2.2. Data Collection
2.3. Motion Analysis
The sagittal angles of the 4 sub-divided spinal regions (i.e., upper thoracic (UTx), lower thoracic (LTx), upper lumbar (ULx) and lower lumbar (LLx) were measured using an 8-camera Vicon 3D motion analysis system, using a sampling frequency of 100 Hz. Retro-reflective spinal markers were attached at the levels of C7, T2, T4, T6, T8, T10, T12, L2, and L4, and over the anterior superior iliac spine (ASIS), posterior superior iliac spine (PSIS) and iliac crest bilaterally. In addition, markers were also placed at the manubrium sterni (superior border); acromioclavicular joints; ulna styloid processes; a point 10 cm lateral of T12 (bilaterally), the lateral knee joint lines; and on the lateral malleoli. Within-subject consistency and variability, using this novel spinal marker set in healthy subjects, has shown substantial to excellent reliability (ICC 0.746 to 0.977), with errors not exceeding 5.8° [22].
2.4. Electromyography
An 8 Channel Bortec EMG system was synchronised with the Vicon® Nexus, to collect surface electromyography (sEMG) data. Electrode placements, as detailed elsewhere [13], were placed bilaterally over longissimus thoracis (ES), superficial lumbar multifidus (LM), external oblique (EO), and transversus abdominis/internal oblique (IO). System parameters were set as follows, Input impedance of 10GOhm, differential pre-amplifiers with fixed gain of 500, and common rejection ratio was 115 dB. A sampling frequency of 10 Hz to 1000 Hz was used. sEMG data was normalised to sub-maximal voluntary contractions (SMVC) as described previously [13]. Three SMVCs were recorded over 3 s with a 30 s rest between trials.
2.5. Task Protocols
Full details of the task procedures are available in Appendix A. The following functional tasks were evaluated:
- Sit-to-stand-to-sit: This was performed from a usual unsupported sitting position on a plinth with feet on the floor.
- Box lift and replace: The subject was instructed to move a box from left to right, on a plinth set at waist height in front of them, with the box starting and finishing facing the same direction.
- Reaching: The subject stood directly in front of the custom-made shelf (height of the ulna styloid process when the shoulder was fully elevated). The subject placed a jar onto the shelf using their right hand.
- Stepping up and down: Subjects stepped onto a 6-inch Reebok® step (Adidas International Trading, Amsterdam, The Netherlands), then stepped down (self-selected leading leg).
Tasks were repeated until three good quality trials were obtained (where all markers and sEMG traces were clearly recorded and viewed within the Vicon System). Tasks were selected to reflect a cross-section of usual activities of daily living whilst also being representative of activities commonly reported as pain provocative. Protocols were carefully considered to allow for natural functional movement, reflective of habitual behaviour (Appendix A).
2.6. Data Processing and Analysis
Full processing and analysis details have been published previously [5,11,13]. Vicon Nexus (Nexus 1.8.2 Vicon Motion Systems, Oxford, UK) was used to perform all data processing.
Kinematics: Midpoint sagittal spinal angles (UTx, LTx, ULx, LLx spinal regions) [5] were calculated as the sum of the angular changes between all markers within each region (e.g., UTx: C7–T6, LTx: T6–T12, ULx: T12–L3, LLx: L3–S2).
Midpoint sagittal spinal angle = (Maximum flexion sagittal spinal angle + Maximum extension sagittal spinal angle)/2
Positive angles are indicative of relative flexion; negative angles are indicative of relative extension.
Surface Electromyography (sEMG): Mean amplitude (%SMVC) of LM, ES, IO and EO muscles from the duration of each task. Raw signals were band pass filtered using zero phase lag and 20 Hz cut-off with full wave rectification. The signal was amplified by a gain of 2000. A 20 Hz high pass filter was applied to suppress movement artefacts.
Normalised amplitude sEMG (%) = (processed sEMG/SMVC) × 100
SPSS (IBM SPSS Statistics 26) was used to conduct statistical analysis according to the normal distribution and homogeneity of variance of the data. Baseline descriptive statistics were calculated [23,24,25]. Pearson correlations established relationships between kinematics (mean regional sagittal angle: UTx, LTx, ULx, LLx) and sEMG (normalised, mean amplitude, % sub-maximal voluntary contraction) of trunk muscles (LM, ES, IO, EO) between groups. Alpha level was 0.01. Correlation coefficients were interpreted as: negligible (0.0–0.1), weak (0.10–0.39), moderate (0.40–0.69), strong (0.70–0.89), very strong (0.9–1.0) [25]. Positive r-values indicate associations between increased flexion and increased muscle activity. Negative r-values indicate inverse associations between muscle activity and spinal kinematics.
3. Results
3.1. Participant Characteristics
Data were collected from 23 AEP, 27 FP and 28 healthy individuals. Participant characteristics are outlined in Table 1. Weight was significantly greater in the FP group compared to the AEP group, and height was significantly greater in the FP group (and compared to both AEP and the control group). Significant differences in gender between groups (males: AEP 17.1%, FP 77.8%) were noted, although these reflect observed clinical subgroup presentations [9,10]. Both FP and AEP groups reported similar locations of LBP (primarily in the lumbar region). No significant between-group differences in VAS scores for pain were noted.
3.2. Relationships Between Spinal Kinematics and Muscle Activity Across Functional Tasks
Example raw data are detailed in Figure 1 to demonstrate marker positioning in the global co-ordinate system, regional spinal kinematics and raw EMG traces for each muscle (bilaterally) for one participant in each group (FP, AEP, control) during a step up and step down task. Full results tables are detailed in Appendix B (Table A2, Table A3 and Table A4). Correlations were moderate to strong, with the strongest negative correlation being r = −0.812 and the strongest positive correlation being r = 0.754. A summary of the correlations between spinal kinematic data with muscle activity are detailed in Table 2.
3.2.1. AEP
In the AEP group, associations between increased extension and altered LM activity were evident in the lumbar (upper or lower regions) during the box-replace, reach-up, step-up and step-down tasks. No associations between spinal kinematics and muscle activity were noted in the box-lift, stand-to-sit or sit-to-stand tasks. No significant associations were observed between spinal kinematics and IO, EO or ES muscle activity.
3.2.2. FP
In the FP group, many associations between spinal kinematics and muscle activity were observed. Overall increased flexion in the LLx region was associated with a reduction in muscle activity across the abdominal (EO, IO) and extensor musculature (ES, LM) across the tasks. Conversely increased flexion in the LTx region was associated with greater muscle activity of the EO, ES and LM musculature across the box-lift, box-replace, step-up, step-down and reach-up tasks. During the sit-to-stand-to-sit task, the only significant interaction observed was an association between increased LLx flexion and a reduction in ES activity.
3.2.3. Control
In the control group, no associations between spinal kinematics and muscle activity were observed in any task.
Table 2 summarises where significant relationships were observed and the direction of these relationships for each group, spinal region and muscle. The FP group demonstrated the greatest number of relationships between kinematics and muscle activity, followed by the AEP group, with no significant relationships observed in the healthy control group. The scatter plots detailed in Figure 2 and Figure 3 provide an example of the opposing directions of the significant relationships observed between different spinal regions (LLx and LTx) and ES during the box-replace task.
4. Discussion
The novel contribution of this study is the identification of distinct patterns of coordination between regional spinal kinematics and muscle activity to perform specific tasks in NSCLBP subgroups which is not observed in pain-free controls.
Participants in the AEP subgroup exhibited a relative increase in upper lumbar (ULx) extension during tasks such as reach up, step up, and step down. This postural strategy in the ULx was consistently associated with heightened activity of the lumbar multifidus (LM) muscle. These kinematic and muscular patterns align with previously reported behaviours observed during sagittal plane-bending tasks (e.g., pen pick up and return) [11]. Similarly, previous work evaluating kinematic data alone within such subgroups established significant differences between AEP and FP groups with AEP demonstrating significantly more extension in the ULx during reach-up, step-up-and-step-down (and pen-pick-up, and pen-replace) tasks [5]. While causality cannot be inferred, the relationships observed may reflect either a compensatory response to maintain spinal stability or an adaptation to limit excessive movement in the lower lumbar spine.
In contrast, participants in the FP subgroup demonstrated a relative increase in flexion of the lower thoracic (LTx) region during tasks including box lift, box replace, step up, and step down. This increased flexion was also associated with elevated LM activity, suggesting a subgroup-specific neuromechanical strategy. These behaviours may represent adaptations to reduce loading or motion in the lower lumbar region, potentially as a protective mechanism against pain provocation. These findings show the presence of subgroup-specific kinematic-muscular interactions in NSCLBP, supporting the need for targeted rehabilitation strategies based on individual movement profiles.
These strategies have been consistently observed previously [5,9,11,12,13]; however, the current study further corroborates these findings in activities beyond the sagittal plane, highlighting the need for more targeted active physical interventions. As mechanical biomarkers, these results could be valuable in guiding treatment for these subgroups.
Interestingly, no associations between regional kinematics and trunk muscle activity were noted in the pain-free controls suggesting that the presence of pain, or fear of pain provocation, is an influencing factor in the findings observed. CLBP individuals have been observed to exhibit differences in kinematic movement variability during the performance of repetitive functional tasks; therefore, it may be hypothesised that the absence of pain-driven motor adaptations may have led to greater movement variability in the control group [26]. Further research is required to test such hypotheses.
No statistically significant differences between symptomatic and asymptomatic groups in the LLx region in terms of either flexion or extension were observed. It could be hypothesised that, in the presence of pain, the lower lumbar region is stabilised to avoid pain provocation, potentially utilizing other spinal regions to compensate. It is pertinent to consider whether current generic rehabilitation strategies continue to re-enforce mal-adaptive patterns. The recent successes of strategies such as cognitive functional therapy [15], are perhaps demonstrating increased efficacy due to encouraging movement in the lower lumbar regions which may be a focus for future research. Focusing on the areas of restriction, or in this case maladaptive movement, may therefore be of importance for optimizing patient outcomes [4].
Further, during the sit-to-stand task, the only significant association observed was between increased flexion and reduced ES activity in the LLx in the FP group. The lack of significant associations during this activity may be attributable to the lower postural demands of this task with, potentially, end-range spinal flexion or extension activities being avoided.
Limitations and Future Work
It could be argued that due to the number of analyses and p-values reported in this study, there is the potential for type 1 errors. However, the repeatability of the findings throughout the different tasks suggests that the findings are less likely to be because of a type I error. No associations were observed between kinematics and muscle activity within the control group, suggesting that it is the LBP itself, and potential associated maladaptive behaviours, that led to the observed findings. p-values have been set at 0.01 to tighten the associations. However, the authors acknowledge that no corrections for multiple comparisons were conducted which may weaken confidence in the reported associations.
The unequal gender distribution (FP: 77.8% male, AEP: 82.6% female) between the subgroups may be considered a confounding variable; however, proportionally, gender is reflective of typical clinical presentation patterns reported in previous research [9,10]. Since the analysis focused on correlational patterns within each subgroup, and not on mean differences across groups, together with the modest sample size, any additional covariate or sensitivity analyses were not considered appropriate or statistically meaningful.
Surface EMG as a tool to evaluate trunk musculature is limited in its ability to isolate deep musculature such as the multifidus and transversus abdominis. The use of sEMG also poses considerable limitations for interpreting the physiological meaning of EMG activity, especially due to the potential for cross-talk between muscles (e.g., influence of longissimus when recording LM activity). To mitigate against this, rigorous standardisation processes were adhered to, to standardise electrode placement and raw EMG signal processing. Future studies could consider the use of fine wire or high-density EMG to reduce such issues. Submaximal contractions were utilised to normalise EMG data due to potential kinesiophobia in NSCLBP. This is common practice when evaluating these subgroups [27,28]; however, alternative approaches to normalising EMG or comparing raw EMG signals could be considered in future work. Future clinical trials may explore the effect of focusing on functional rehabilitation interventions for each of the clinical subgroups outlined in this study. The potentially maladaptive strategies utilised by AEP and FP may be corrected with specific focus on the restoration of movement in the LLx region.
5. Conclusions
Distinct motor control patterns exist between these two NSCLBP subgroups (FP and AEP) when performing multiple functional tasks. However, it is difficult to establish whether these neuromuscular patterns contribute to pain persistence or arise as compensatory mechanisms in response to pain. The findings further re-enforce previous observations in these NSCLBP subgroups during bending tasks [11] (see Table 3), re-enforcing both the existence of clinical subgroups and previously observed movement patterns in these subgroups which may be of clinical interest. Subgroups may therefore be a target for future therapeutic interventions (such as movement-based interventions and wearable technologies) to improve the effectiveness of NSCLBP management and there is a need for targeted intervention that considers direction-specific pain provocation in NSCLBP.
Author Contributions
Conceptualisation, R.H., A.d.R., L.S. and V.S.; methodology, R.H., A.d.R., L.S. and V.S.; formal analysis, R.H. and A.d.R.; investigation, R.H.; data curation, R.H. and A.d.R.; writing—original draft preparation, R.H., A.d.R., L.S. and V.S.; writing—review and editing, R.H., A.d.R., L.S. and V.S.; supervision, L.S. and V.S.; project administration, R.H.; funding acquisition V.S. All authors have read and agreed to the published version of the manuscript.
Funding
Funding was received from Arthritis Research UK (18461) and Versus Arthritis (formerly Arthritis Research UK) (20781) as part of the Biomechanics and Bioengineering Research Centre Versus Arthritis, Cardiff University. R.H. also received funding via a President’s Scholarship Award, Cardiff University.
Institutional Review Board Statement
The study was conducted in accordance with the Declaration of Helsinki and approved by the Research Ethics Committee 3 Wales (10/MRE09/28) within the Arthritis Research UK Biomechanics and Bioengineering Centre, Cardiff University, UK.
Informed Consent Statement
Informed consent was obtained from all subjects involved in the study. Written informed consent has been obtained from the patient(s) to publish this paper.
Data Availability Statement
The datasets generated and/or analysed during the current study are not publicly available due to ethics restrictions but are available from the corresponding author on reasonable request.
Acknowledgments
We acknowledge the late Robert van Deursen for his significant contributions to this research. His insights were instrumental in the completion of this work through his involvement in supervision, conceptualisation and analysis. van Deursen authored the MATLAB (2024a) code to analyse kinematic and electromyography data. Support for the study is also acknowledged from Health and Care Research Wales (formerly National Institute of Social, Health and Care (NISCHR) Wales) who provided research officers to support data collection.
Conflicts of Interest
The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
Abbreviations
The following abbreviations are used in this manuscript:
| AEP | Active extension pattern |
| ASIS | Anterior superior iliac spine |
| BMI | Body mass index |
| EMG | Electromyography |
| EO | External oblique |
| ES | Erector spinae (longissimus thoracis) |
| FP | Flexion pattern |
| IO | Transversus abdominis/internal oblique |
| LBP | Low back pain |
| LM | Lumbar multifidus |
| LLx | Lower lumbar |
| LTx | Lower thoracic |
| MVC | Maximal voluntary contraction |
| NISCHR | National Institute for Social Care and Health Research |
| NSCLBP | Non-specific chronic low back pain |
| PSIS | Posterior superior iliac spine |
| ROM | Range of movement |
| SD | Standard deviation |
| sEMG | Surface electromyography |
| SMVC | Sub-maximal voluntary contraction |
| ULx | Upper lumbar |
| UTx | Upper thoracic |
| VAS | Visual analogue scale |
Appendix A
Appendix A.1. Functional Task Protocols
Appendix A.1.1. Box
Task Objective: To lift and move a weighted box (2.5 kg) from left to right on a plinth.
Set-up/Standardisation: To achieve a standardised box position, tape was positioned at a set distance from the midline of the plinth (distance = 70% of the total upper limb length as measured (in cm) from the acromion process (apex) to the distal middle phalanx bilaterally). The plinth height was set to align with the participants’ greater trochanter (in standing). A box (weighing 2.5 kg) was placed over the marked tape to the left side of the plinth.
Posture Standards: Each participant was instructed to adopt a comfortable standing position and ensure their feet remained stationary for the duration of the task. On completion of the task, the subject returned to their original, habitual standing position.
Movement Rhythm: Participants were instructed to stand facing the plinth and move the box from left to right (to a position over the marked tape to the right of the plinth). Participants were instructed to start and finish the motion with the box facing the same direction. No specific instructions on the lifting approach or technique were provided.
Number of Repetitions: 3
Appendix A.1.2. Reaching
Task Objective: Place a jar onto an elevated shelf.
Set-up/Standardisation: A custom-designed shelf was set to the height of the ulna styloid process (right upper limb) with the shoulder fully elevated (full flexion).
Posture Standards: Habitual standing. Feet remained stationary throughout the duration of the task with the participant instructed to always maintain heel contact with the floor. The participant kept hold of the jar throughout the task.
Movement Rhythm: Participants were instructed to stand directly facing the shelf, with the shelf base aligned with the midline of their trunk (frontal plane). Participants placed a jar onto the shelf using their right hand, allowed the jar to rest on the shelf for 2 s, and then returned the jar back to the original position.
Number of Repetitions: 3
Appendix A.1.3. Sit-to-Stand-to-Sit
Task Objective: Move from a sitting to a standing position and return to sitting from the edge of a plinth.
Set-up/Standardisation: The plinth was set to a height where the participants’ hips and knees rested comfortably at 90 degrees. Knee and hip angles were determined using a goniometer (Lafayette Instrument Co. Ltd., Lafayette, IN, USA).
Posture standards: Habitual sitting starting position. Participants sat with their thighs well supported on the plinth.
Movement Rhythm: The participant was instructed to adopt their usual (unsupported) sitting position on the plinth, stand (waiting for 2 s), then return to their original sitting position.
Number of Repetitions: 3
Appendix A.1.4. Stepping Up and Down
Task Objective: Step up onto a step and then step down off the step.
Set-up/Standardisation: Participants stood facing a 6-inch Reebok® step (Adidas International Trading, Amsterdam, The Netherlands).
Posture Standards: Habitual standing starting position. The participant was required to ensure that their self-selected leading leg remained consistent throughout each trial.
Movement Rhythm: They were instructed to step up onto the step (self-selecting their preferred leading leg), wait in a double-stance position on the step (2 s), and then step down (self-selecting their preferred leading leg). To facilitate MATLAB data processing procedures, participants were required to wait in their usual standing position (following step down) for 2 s to assist with defining the end of the task.
Number of Repetitions: 3
Appendix A.2. Data Processing of Functional Tasks
Four tasks were collected during data collection (box lift rotate and replace, reaching, sit-to-stand-to-sit and step up and down). These were sub-divided into seven separate tasks within the MATLAB programme as detailed in Table A1.
Table A1.
Table to show subdivision of the original data collection task into functional tasks used for analysis.
Table A1.
Table to show subdivision of the original data collection task into functional tasks used for analysis.
| Original Task | Functional Task for Analysis |
|---|---|
| Box lift, rotate and replace * | Box lift |
| Box replace | |
| Reaching | Reach up |
| Reach down ** | |
| Sit-to-stand-to-sit | Sit-to-stand |
| Stand-to-sit | |
| Step up and down | Step up |
| Step down |
* Box-lift, rotate and replace task—only the ‘lifting’ and ‘replacing’ components of the task were analysed. ** Reach-down task—data not included in analysis
Appendix B
Table A2.
Overview of the Mean Regional Spinal Kinematics (Degrees), Muscle Activity (%SMVC) and Pearson Correlations (Including Significant Results) for the AEP Group.
Table A2.
Overview of the Mean Regional Spinal Kinematics (Degrees), Muscle Activity (%SMVC) and Pearson Correlations (Including Significant Results) for the AEP Group.
| Spinal Region | Regional Spinal Angle (Degrees) Mean (SD) | Muscle | Muscle Activity (%SMVC) Mean (SD) | Correlations | ||
|---|---|---|---|---|---|---|
| r | p | |||||
| Box Lift | UTx | 23.3 (9.9) | EO | 56.6 (26.1) | −0.176 | 0.471 |
| IO | 64.0 (32.3) | −0.325 | 0.14 | |||
| ES | 26.5 (12.5) | 0.022 | 0.937 | |||
| LM | 27.1 (15.0) | 0.212 | 0.399 | |||
| LTx | 14.1 (9.8) | EO | 56.6 (26.1) | −0.257 | 0.289 | |
| IO | 64.0 (32.3) | 0.129 | 0.568 | |||
| ES | 26.5 (12.5) | −0.143 | 0.611 | |||
| LM | 27.1 (15.0) | −0.124 | 0.623 | |||
| ULx | −11.6 (9.4) | EO | 56.6 (26.1) | −0.563 | 0.012 | |
| IO | 64.0 (32.3) | −0.022 | 0.922 | |||
| ES | 26.5 (12.5) | −0.218 | 0.436 | |||
| LM | 27.1 (15.0) | −0.379 | 0.12 | |||
| LLx | −14.8 (16.7) | EO | 56.6 (26.1) | −0.08 | 0.745 | |
| IO | 64.0 (32.3) | −0.217 | 0.333 | |||
| ES | 26.5 (12.5) | 0.17 | 0.544 | |||
| LM | 27.1 (15.0) | 0.415 | 0.086 | |||
| Box Replace | UTx | 26.8 (8.5) | EO | 54.8 (25.9) | −0.193 | 0.427 |
| IO | 63.1 (32.6) | −0.155 | 0.49 | |||
| ES | 26.6 (14.0) | 0.03 | 0.914 | |||
| LM | 27.3 (15.5) | 0.214 | 0.393 | |||
| LTx | 13.0 (10.0) | EO | 54.8 (25.9) | −0.261 | 0.28 | |
| IO | 63.1 (32.6) | 0.193 | 0.39 | |||
| ES | 26.6 (14.0) | −0.138 | 0.625 | |||
| LM | 27.3 (15.5) | −0.125 | 0.622 | |||
| ULx | −13.8 (10.9) | EO | 54.8 (25.9) | −0.502 | 0.029 | |
| IO | 63.1 (32.6) | 0.085 | 0.707 | |||
| ES | 26.6 (14.0) | −0.307 | 0.266 | |||
| LM | 27.3 (15.5) | −0.524 | 0.026 | |||
| LLx | −20.5 (17.3) | EO | 54.8 (25.9) | −0.095 | 0.698 | |
| IO | 63.1 (32.6) | −0.31 | 0.161 | |||
| ES | 26.6 (14.0) | 0.253 | 0.363 | |||
| LM | 27.3 (15.5) | 0.599 | 0.009 * | |||
| Reach Up | UTx | 27.2 (8.2) | EO | 49.9 (25.3) | −0.159 | 0.515 |
| IO | 59.9 (37.0) | −0.202 | 0.366 | |||
| ES | 25.7 (14.4) | 0.076 | 0.779 | |||
| LM | 22.3 (16.7) | 0.345 | 0.148 | |||
| LTx | 4.4 (13.1) | EO | 49.9 (25.3) | −0.298 | 0.215 | |
| IO | 59.9 (37.0) | 0.237 | 0.288 | |||
| ES | 25.7 (14.4) | −0.002 | 0.994 | |||
| LM | 22.3 (16.7) | 0.032 | 0.897 | |||
| ULx | −19.2 (12.0) | EO | 49.9 (25.3) | −0.205 | 0.4 | |
| IO | 59.9 (37.0) | 0.15 | 0.505 | |||
| ES | 25.7 (14.4) | −0.315 | 0.235 | |||
| LM | 22.3 (16.7) | −0.684 | 0.001 * | |||
| LLx | −23.3 (19.8) | EO | 49.9 (25.3) | −0.127 | 0.603 | |
| IO | 59.9 (37.0) | −0.31 | 0.16 | |||
| ES | 25.7 (14.4) | 0.307 | 0.248 | |||
| LM | 22.3 (16.7) | 0.474 | 0.04 | |||
| Step Up | UTx | 33.1 (7.5) | EO | 56.7 (27.5) | −0.087 | 0.722 |
| IO | 67.2 (39.5) | −0.2 | 0.385 | |||
| ES | 22.6 (8.9) | −0.036 | 0.903 | |||
| LM | 26.6 (23.3) | 0.368 | 0.121 | |||
| LTx | 10.0 (12.5) | EO | 56.7 (27.5) | 0.01 | 0.968 | |
| IO | 67.2 (39.5) | 0.312 | 0.168 | |||
| ES | 22.6 (8.9) | −0.472 | 0.089 | |||
| LM | 26.6 (23.3) | 0.147 | 0.548 | |||
| ULx | −17.0 (11.2) | EO | 56.7 (27.5) | −0.038 | 0.879 | |
| IO | 67.2 (39.5) | 0.198 | 0.389 | |||
| ES | 22.6 (8.9) | −0.436 | 0.119 | |||
| LM | 26.6 (23.3) | −0.613 | 0.005 * | |||
| LLx | −19.0 (19.6) | EO | 56.7 (27.5) | −0.186 | 0.446 | |
| IO | 67.2 (39.5) | −0.378 | 0.091 | |||
| ES | 22.6 (8.9) | 0.421 | 0.134 | |||
| LM | 26.6 (23.3) | 0.232 | 0.34 | |||
| Step Down | UTx | 34.5 (8.2) | EO | 56.9 (29.6) | −0.186 | 0.445 |
| IO | 68.1 (37.9) | −0.317 | 0.161 | |||
| ES | 21.9 (9.5) | −0.095 | 0.747 | |||
| LM | 26.0 (21.6) | 0.465 | 0.045 | |||
| LTx | 9.5 (13.2) | EO | 56.9 (29.6) | −0.099 | 0.688 | |
| IO | 68.1 (37.9) | 0.292 | 0.199 | |||
| ES | 21.9 (9.5) | −0.33 | 0.249 | |||
| LM | 26.0 (21.6) | 0.119 | 0.628 | |||
| ULx | −18.0 (11.8) | EO | 56.9 (29.6) | −0.101 | 0.681 | |
| IO | 68.1 (37.9) | 0.147 | 0.524 | |||
| ES | 21.9 (9.5) | −0.446 | 0.11 | |||
| LM | 26.0 (21.6) | −0.695 | 0.001 * | |||
| LLx | −21.1 (20.8) | EO | 56.9 (29.6) | −0.01 | 0.968 | |
| IO | 68.1 (37.9) | −0.317 | 0.162 | |||
| ES | 21.9 (9.5) | 0.428 | 0.126 | |||
| LM | 26.0 (21.6) | 0.278 | 0.249 | |||
| Stand-to-Sit | UTx | 22.1 (8.8) | EO | 54.3 (28.8) | 0.192 | 0.46 |
| IO | 56.8 (40.0) | −0.213 | 0.397 | |||
| ES | 40.9 (24.4) | 0.233 | 0.444 | |||
| LM | 39.5 (37.3) | 0.022 | 0.927 | |||
| LTx | 8.8 (11.2) | EO | 54.3 (28.8) | −0.121 | 0.643 | |
| IO | 56.8 (40.0) | 0.399 | 0.101 | |||
| ES | 40.9 (24.4) | −0.376 | 0.205 | |||
| LM | 39.5 (37.3) | 0.283 | 0.241 | |||
| ULx | −11.9 (9.7) | EO | 54.3 (28.8) | −0.024 | 0.927 | |
| IO | 56.8 (40.0) | 0.5 | 0.035 | |||
| ES | 40.9 (24.4) | −0.21 | 0.491 | |||
| LM | 39.5 (37.3) | −0.32 | 0.182 | |||
| LLx | −11.6 (15.0) | EO | 54.3 (28.8) | −0.013 | 0.959 | |
| IO | 56.8 (40.0) | −0.444 | 0.065 | |||
| ES | 40.9 (24.4) | 0.605 | 0.028 | |||
| LM | 39.5 (37.3) | 0.01 | 0.966 | |||
| Sit-to-Stand | UTx | 20.4 (8.7) | EO | 50.5 (25.4) | −0.014 | 0.957 |
| IO | 54.5 (36.4) | −0.499 | 0.03 | |||
| ES | 26.2 (14.4) | −0.069 | 0.814 | |||
| LM | 32.0 (43.2) | −0.144 | 0.581 | |||
| LTx | 7.8 (11.0) | EO | 50.5 (25.4) | −0.3 | 0.243 | |
| IO | 54.5 (36.4) | 0.359 | 0.131 | |||
| ES | 26.2 (14.4) | −0.227 | 0.434 | |||
| LM | 32.0 (43.2) | 0.338 | 0.184 | |||
| ULx | −10.6 (8.7) | EO | 50.5 (25.4) | −0.268 | 0.299 | |
| IO | 54.5 (36.4) | 0.264 | 0.275 | |||
| ES | 26.2 (14.4) | −0.262 | 0.366 | |||
| LM | 32.0 (43.2) | −0.328 | 0.198 | |||
| LLx | −11.0 (15.8) | EO | 50.5 (25.4) | −0.121 | 0.644 | |
| IO | 54.5 (36.4) | −0.432 | 0.065 | |||
| ES | 26.2 (14.4) | 0.279 | 0.335 | |||
| LM | 32.0 (43.2) | 0.076 | 0.771 | |||
Key: EO = external obliques, IO = internal obliques, ES = erector spinae (longissimus thoracis), LM = superficial lumbar multifidus, AEP = active extension pattern, FP = flexion pattern, p = p-value, %SMVC = % sub-maximal voluntary contraction, r = r-value (correlation coefficient), SD = standard deviation, ext = extension, flex = flexion, * = significant (p < 0.01), UTx = upper thoracic spine, LTx = lower thoracic spine, ULx = upper lumbar spine, LLx = lower lumbar spine. Note: negative correlations indicate an inverse relationship between muscle activity and spinal movement.
Table A3.
Overview of the Mean Regional Spinal Kinematics (Degrees), Muscle Activity (%SMVC) and Pearson Correlations (Including Significant Results) for the FP Group
Table A3.
Overview of the Mean Regional Spinal Kinematics (Degrees), Muscle Activity (%SMVC) and Pearson Correlations (Including Significant Results) for the FP Group
| Spinal Region | Regional Spinal Angle (Degrees) Mean (SD) | Muscle | Muscle Activity (%SMVC) Mean (SD) | Correlations | ||
|---|---|---|---|---|---|---|
| r | p | |||||
| Box Lift | UTx | 23.9 (7.1) | EO | 50.6 (22.7) | 0.184 | 0.438 |
| IO | 73.2 (42.0) | 0.013 | 0.955 | |||
| ES | 22.5 (16.1) | 0.127 | 0.595 | |||
| LM | 22.6 (19.4) | 0.131 | 0.55 | |||
| LTx | 22.4 (7.9) | EO | 50.6 (22.7) | 0.521 | 0.018 | |
| IO | 73.2 (42.0) | 0.371 | 0.108 | |||
| ES | 22.5 (16.1) | 0.579 | 0.007 * | |||
| LM | 22.6 (19.4) | 0.706 | 0.000 * | |||
| ULx | −2.4 (9.4) | EO | 50.6 (22.7) | 0.333 | 0.151 | |
| IO | 73.2 (42.0) | 0.522 | 0.018 | |||
| ES | 22.5 (16.1) | 0.321 | 0.168 | |||
| LM | 22.6 (19.4) | 0.303 | 0.16 | |||
| LLx | −20.4 (13.7) | EO | 50.6 (22.7) | −0.501 | 0.024 | |
| IO | 73.2 (42.0) | −0.37 | 0.108 | |||
| ES | 22.5 (16.1) | −0.585 | 0.007 * | |||
| LM | 22.6 (19.4) | −0.259 | 0.232 | |||
| Box Replace | UTx | 25.4 (7.2) | EO | 50.4 (23.0) | 0.239 | 0.31 |
| IO | 72.9 (40.3) | 0.216 | 0.36 | |||
| ES | 22.3 (16.9) | 0.22 | 0.351 | |||
| LM | 21.9 (18.6) | 0.227 | 0.298 | |||
| LTx | 21.7 (8.2) | EO | 50.4 (23.0) | 0.512 | 0.021 | |
| IO | 72.9 (40.3) | 0.447 | 0.048 | |||
| ES | 22.3 (16.9) | 0.602 | 0.005 * | |||
| LM | 21.9 (18.6) | 0.66 | <0.001 * | |||
| ULx | −3.8 (8.6) | EO | 50.4 (23.0) | 0.317 | 0.174 | |
| IO | 72.9 (40.3) | 0.444 | 0.05 | |||
| ES | 22.3 (16.9) | 0.266 | 0.257 | |||
| LM | 21.9 (18.6) | 0.293 | 0.175 | |||
| LLx | −24.7 (13.5) | EO | 50.4 (23.0) | −0.586 | 0.007 * | |
| IO | 72.9 (40.3) | −0.418 | 0.066 | |||
| ES | 22.3 (16.9) | −0.636 | 0.003 * | |||
| LM | 21.9 (18.6) | −0.308 | 0.153 | |||
| Reach Up | UTx | 25.3 (7.8) | EO | 50.2 (22.8) | 0.406 | 0.068 |
| IO | 69.0 (36.2) | 0.366 | 0.123 | |||
| ES | 21.0 (16.2) | 0.485 | 0.035 | |||
| LM | 19.7 (19.7) | 0.262 | 0.251 | |||
| LTx | 11.1 (9.2) | EO | 50.2 (22.8) | 0.601 | 0.004 * | |
| IO | 69.0 (36.2) | 0.501 | 0.029 | |||
| ES | 21.0 (16.2) | 0.754 | 0.000 * | |||
| LM | 19.7 (19.7) | 0.684 | 0.001 * | |||
| ULx | −11.0 (10.0) | EO | 50.2 (22.8) | 0.304 | 0.18 | |
| IO | 69.0 (36.2) | 0.384 | 0.104 | |||
| ES | 21.0 (16.2) | 0.277 | 0.25 | |||
| LM | 19.7 (19.7) | 0.223 | 0.331 | |||
| LLx | −29.9 (18.5) | EO | 50.2 (22.8) | −0.511 | 0.018 | |
| IO | 69.0 (36.2) | −0.481 | 0.037 | |||
| ES | 21.0 (16.2) | −0.805 | 0.000 * | |||
| LM | 19.7 (19.7) | −0.376 | 0.093 | |||
| Step Up | UTx | 32.1 (7.4) | EO | 52.5 (22.9) | 0.551 | 0.01 * |
| IO | 72.6 (38.3) | 0.339 | 0.133 | |||
| ES | 24.3 (17.3) | 0.274 | 0.229 | |||
| LM | 22.9 (20.4) | 0.317 | 0.161 | |||
| LTx | 18.0 (9.2) | EO | 52.5 (22.9) | 0.563 | 0.008 * | |
| IO | 72.6 (38.3) | 0.472 | 0.031 | |||
| ES | 24.3 (17.3) | 0.638 | 0.002 * | |||
| LM | 22.9 (20.4) | 0.65 | 0.001 * | |||
| ULx | −7.3 (8.9) | EO | 52.5 (22.9) | 0.293 | 0.198 | |
| IO | 72.6 (38.3) | 0.473 | 0.03 | |||
| ES | 24.3 (17.3) | 0.18 | 0.434 | |||
| LM | 22.9 (20.4) | 0.169 | 0.465 | |||
| LLx | −22.8 (15.7) | EO | 52.5 (22.9) | −0.644 | 0.002 * | |
| IO | 72.6 (38.3) | −0.554 | 0.009 * | |||
| ES | 24.3 (17.3) | −0.762 | 0.000 * | |||
| LM | 22.9 (20.4) | −0.562 | 0.008 * | |||
| Step Down | UTx | 33.8 (7.9) | EO | 51.9 (21.5) | 0.435 | 0.049 |
| IO | 69.4 (35.9) | 0.312 | 0.168 | |||
| ES | 24.5 (16.6) | 0.325 | 0.15 | |||
| LM | 22.8 (18.9) | 0.299 | 0.189 | |||
| LTx | 18.4 (9.1) | EO | 51.9 (21.5) | 0.528 | 0.014 | |
| IO | 69.4 (35.9) | 0.504 | 0.02 | |||
| ES | 24.5 (16.6) | 0.583 | 0.006 * | |||
| LM | 22.8 (18.9) | 0.635 | 0.002 * | |||
| ULx | −8.1 (9.5) | EO | 51.9 (21.5) | 0.31 | 0.171 | |
| IO | 69.4 (35.9) | 0.511 | 0.018 | |||
| ES | 24.5 (16.6) | 0.158 | 0.494 | |||
| LM | 22.8 (18.9) | 0.13 | 0.573 | |||
| LLx | −23.7 (16.1) | EO | 51.9 (21.5) | −0.604 | 0.004 * | |
| IO | 69.4 (35.9) | −0.587 | 0.005 * | |||
| ES | 24.5 (16.6) | −0.739 | 0.000 * | |||
| LM | 22.8 (18.9) | −0.499 | 0.021 | |||
| Stand-to-Sit | UTx | 20.5 (6.7) | EO | 50.7 (22.6) | 0.248 | 0.307 |
| IO | 70.7 (49.6) | 0.304 | 0.22 | |||
| ES | 32.9 (18.9) | −0.406 | 0.068 | |||
| LM | 30.5 (17.8) | −0.007 | 0.975 | |||
| LTx | 18.1 (8.5) | EO | 50.7 (22.6) | 0.43 | 0.066 | |
| IO | 70.7 (49.6) | 0.374 | 0.126 | |||
| ES | 32.9 (18.9) | 0.266 | 0.244 | |||
| LM | 30.5 (17.8) | 0.45 | 0.046 | |||
| ULx | −0.8 (8.5) | EO | 50.7 (22.6) | 0.277 | 0.251 | |
| IO | 70.7 (49.6) | 0.36 | 0.142 | |||
| ES | 32.9 (18.9) | 0.074 | 0.75 | |||
| LM | 30.5 (17.8) | −0.088 | 0.711 | |||
| LLx | −12.0 (11.6) | EO | 50.7 (22.6) | −0.489 | 0.033 | |
| IO | 70.7 (49.6) | −0.48 | 0.044 | |||
| ES | 32.9 (18.9) | −0.239 | 0.297 | |||
| LM | 30.5 (17.8) | −0.158 | 0.505 | |||
| Sit-to-Stand | UTx | 18.8 (6.2) | EO | 49.2 (22.0) | 0.093 | 0.705 |
| IO | 57.7 (39.3) | 0.05 | 0.845 | |||
| ES | 23.0 (15.6) | −0.171 | 0.458 | |||
| LM | 22.2 (20.6) | −0.075 | 0.753 | |||
| LTx | 17.6 (8.1) | EO | 49.2 (22.0) | 0.372 | 0.117 | |
| IO | 57.7 (39.3) | 0.509 | 0.031 | |||
| ES | 23.0 (15.6) | 0.342 | 0.129 | |||
| LM | 22.2 (20.6) | 0.31 | 0.184 | |||
| ULx | −0.6 (8.3) | EO | 49.2 (22.0) | 0.147 | 0.547 | |
| IO | 57.7 (39.3) | 0.111 | 0.66 | |||
| ES | 23.0 (15.6) | −0.232 | 0.312 | |||
| LM | 22.2 (20.6) | −0.414 | 0.07 | |||
| LLx | −11.3 (12.0) | EO | 49.2 (22.0) | −0.551 | 0.014 | |
| IO | 57.7 (39.3) | −0.543 | 0.02 | |||
| ES | 23.0 (15.6) | −0.643 | 0.002 * | |||
| LM | 22.2 (20.6) | −0.226 | 0.339 | |||
Key: EO = external obliques, IO = internal obliques, ES = erector spinae (longissimus thoracis), LM = superficial lumbar multifidus, AEP = active extension pattern, FP = flexion pattern, p = p-value, %SMVC = % sub-maximal voluntary contraction, r = r-value (correlation coefficient), SD = standard deviation, ext = extension, flex = flexion, * = significant (p < 0.01), UTx = upper thoracic spine, LTx = lower thoracic spine, ULx = upper lumbar spine, LLx = lower lumbar spine. Note: negative correlations indicate an inverse relationship between muscle activity and spinal movement.
Table A4.
Overview of the Mean Regional Spinal Kinematics (Degrees), Muscle Activity (%SMVC) and Pearson Correlations (Including Significant Results) for the Control Group.
Table A4.
Overview of the Mean Regional Spinal Kinematics (Degrees), Muscle Activity (%SMVC) and Pearson Correlations (Including Significant Results) for the Control Group.
| Spinal Region | Regional Spinal Angle (Degrees) Mean (SD) | Muscle | Muscle Activity (%SMVC) Mean (SD) | Correlations | ||
|---|---|---|---|---|---|---|
| r | p | |||||
| Box Lift | UTx | 24.0 (8.5) | EO | 42.6 (17.8) | 0.116 | 0.625 |
| IO | 63.7 (46.1) | 0.396 | 0.062 | |||
| ES | 22.7 (10.1) | −0.3 | 0.154 | |||
| LM | 16.4 (8.5) | −0.348 | 0.096 | |||
| LTx | 16.7 (10.2) | EO | 42.6 (17.8) | 0.322 | 0.166 | |
| IO | 63.7 (46.1) | −0.171 | 0.436 | |||
| ES | 22.7 (10.1) | −0.251 | 0.236 | |||
| LM | 16.4 (8.5) | 0.32 | 0.128 | |||
| ULx | −7.5 (7.5) | EO | 42.6 (17.8) | −0.035 | 0.884 | |
| IO | 63.7 (46.1) | −0.107 | 0.629 | |||
| ES | 22.7 (10.1) | −0.197 | 0.357 | |||
| LM | 16.4 (8.5) | 0.154 | 0.474 | |||
| LLx | −15.0 (9.7) | EO | 42.6 (17.8) | −0.387 | 0.092 | |
| IO | 63.7 (46.1) | 0.097 | 0.66 | |||
| ES | 22.7 (10.1) | 0.202 | 0.343 | |||
| LM | 16.4 (8.5) | −0.156 | 0.466 | |||
| Box Replace | UTx | 26.6 (7.7) | EO | 42.8 (17.6) | 0.138 | 0.562 |
| IO | 63.3 (46.9) | 0.259 | 0.222 | |||
| ES | 22.2 (10.6) | −0.23 | 0.279 | |||
| LM | 15.7 (8.7) | −0.256 | 0.227 | |||
| LTx | 15.5 (11.0) | EO | 42.8 (17.6) | 0.346 | 0.135 | |
| IO | 63.3 (46.9) | −0.136 | 0.526 | |||
| ES | 22.2 (10.6) | −0.248 | 0.242 | |||
| LM | 15.7 (8.7) | 0.373 | 0.073 | |||
| ULx | −10.1 (7.4) | EO | 42.8 (17.6) | 0.039 | 0.871 | |
| IO | 63.3 (46.9) | −0.13 | 0.545 | |||
| ES | 22.2 (10.6) | −0.283 | 0.18 | |||
| LM | 15.7 (8.7) | 0.04 | 0.851 | |||
| LLx | −18.9 (10.1) | EO | 42.8 (17.6) | −0.319 | 0.171 | |
| IO | 63.3 (46.9) | 0.07 | 0.747 | |||
| ES | 22.2 (10.6) | 0.115 | 0.593 | |||
| LM | 15.7 (8.7) | −0.199 | 0.35 | |||
| Reach Up | UTx | 27.1 (7.6) | EO | 42.2 (18.3) | 0.052 | 0.828 |
| IO | 55.5 (40.8) | 0.482 | 0.023 | |||
| ES | 20.9 (11.4) | −0.148 | 0.482 | |||
| LM | 13.0 (7.6) | −0.209 | 0.317 | |||
| LTx | 6.4 (11.4) | EO | 42.2 (18.3) | 0.363 | 0.115 | |
| IO | 55.5 (40.8) | 0.004 | 0.987 | |||
| ES | 20.9 (11.4) | −0.298 | 0.147 | |||
| LM | 13.0 (7.6) | 0.257 | 0.215 | |||
| ULx | −17.4 (8.0) | EO | 42.2 (18.3) | 0.121 | 0.611 | |
| IO | 55.5 (40.8) | −0.099 | 0.662 | |||
| ES | 20.9 (11.4) | −0.257 | 0.215 | |||
| LM | 13.0 (7.6) | −0.09 | 0.67 | |||
| LLx | −22.6 (13.9) | EO | 42.2 (18.3) | −0.395 | 0.085 | |
| IO | 55.5 (40.8) | −0.122 | 0.588 | |||
| ES | 20.9 (11.4) | 0.015 | 0.943 | |||
| LM | 13.0 (7.6) | 0 | 1 | |||
| Step Up | UTx | 34.1 (6.9) | EO | 42.7 (19.1) | 0.007 | 0.975 |
| IO | 63.8 (39.8) | 0.154 | 0.473 | |||
| ES | 21.7 (11.6) | −0.217 | 0.296 | |||
| LM | 13.4 (7.6) | −0.215 | 0.314 | |||
| LTx | 11.8 (10.3) | EO | 42.7 (19.1) | 0.429 | 0.059 | |
| IO | 63.8 (39.8) | −0.31 | 0.14 | |||
| ES | 21.7 (11.6) | −0.146 | 0.486 | |||
| LM | 13.4 (7.6) | 0.43 | 0.036 | |||
| ULx | −14.1 (7.8) | EO | 42.7 (19.1) | −0.038 | 0.872 | |
| IO | 63.8 (39.8) | −0.195 | 0.362 | |||
| ES | 21.7 (11.6) | −0.233 | 0.263 | |||
| LM | 13.4 (7.6) | 0.04 | 0.851 | |||
| LLx | −17.4 (9.9) | EO | 42.7 (19.1) | −0.288 | 0.217 | |
| IO | 63.8 (39.8) | 0.189 | 0.377 | |||
| ES | 21.7 (11.6) | 0.103 | 0.624 | |||
| LM | 13.4 (7.6) | −0.197 | 0.356 | |||
| Step Down | UTx | 35.2 (6.9) | EO | 45.0 (20.3) | 0.078 | 0.743 |
| IO | 65.5 (37.7) | 0.316 | 0.133 | |||
| ES | 22.8 (10.9) | −0.168 | 0.422 | |||
| LM | 14.7 (8.3) | −0.129 | 0.548 | |||
| LTx | 12.6 (10.3) | EO | 45.0 (20.3) | 0.351 | 0.129 | |
| IO | 65.5 (37.7) | −0.346 | 0.098 | |||
| ES | 22.8 (10.9) | −0.123 | 0.558 | |||
| LM | 14.7 (8.3) | 0.411 | 0.046 | |||
| ULx | −15.1 (8.4) | EO | 45.0 (20.3) | −0.022 | 0.925 | |
| IO | 65.5 (37.7) | −0.288 | 0.172 | |||
| ES | 22.8 (10.9) | −0.26 | 0.209 | |||
| LM | 14.7 (8.3) | −0.133 | 0.536 | |||
| LLx | −20.2 (9.9) | EO | 45.0 (20.3) | −0.373 | 0.105 | |
| IO | 65.5 (37.7) | 0.276 | 0.192 | |||
| ES | 22.8 (10.9) | −0.172 | 0.41 | |||
| LM | 14.7 (8.3) | −0.254 | 0.231 | |||
| Stand-to-Sit | UTx | 22.5 (7.8) | EO | 41.8 (19.7) | −0.075 | 0.761 |
| IO | 40.9 (23.1) | −0.298 | 0.178 | |||
| ES | 35.2 (25.1) | −0.376 | 0.077 | |||
| LM | 17.2 (14.4) | −0.282 | 0.204 | |||
| LTx | 10.7 (10.9) | EO | 41.8 (19.7) | 0.442 | 0.058 | |
| IO | 40.9 (23.1) | 0.21 | 0.349 | |||
| ES | 35.2 (25.1) | −0.298 | 0.168 | |||
| LM | 17.2 (14.4) | 0.068 | 0.765 | |||
| ULx | −6.3 (7.3) | EO | 41.8 (19.7) | −0.081 | 0.742 | |
| IO | 40.9 (23.1) | −0.049 | 0.828 | |||
| ES | 35.2 (25.1) | −0.309 | 0.151 | |||
| LM | 17.2 (14.4) | −0.047 | 0.837 | |||
| LLx | −9.7 (9.4) | EO | 41.8 (19.7) | −0.502 | 0.029 | |
| IO | 40.9 (23.1) | −0.288 | 0.194 | |||
| ES | 35.2 (25.1) | −0.365 | 0.087 | |||
| LM | 17.2 (14.4) | −0.346 | 0.114 | |||
| Sit-to-Stand | UTx | 20.6 (7.4) | EO | 40.8 (19.0) | −0.09 | 0.714 |
| IO | 38.8 (23.0) | −0.156 | 0.488 | |||
| ES | 26.1 (14.0) | −0.069 | 0.755 | |||
| LM | 12.4 (6.9) | −0.214 | 0.339 | |||
| LTx | 9.9 (11.2) | EO | 40.8 (19.0) | 0.426 | 0.069 | |
| IO | 38.8 (23.0) | 0.247 | 0.268 | |||
| ES | 26.1 (14.0) | −0.164 | 0.456 | |||
| LM | 12.4 (6.9) | 0.162 | 0.47 | |||
| ULx | −5.4 (7.6) | EO | 40.8 (19.0) | 0.04 | 0.87 | |
| IO | 38.8 (23.0) | −0.028 | 0.902 | |||
| ES | 26.1 (14.0) | −0.1 | 0.649 | |||
| LM | 12.4 (6.9) | 0.15 | 0.505 | |||
| LLx | −9.0 (8.9) | EO | 40.8 (19.0) | −0.503 | 0.028 | |
| IO | 38.8 (23.0) | −0.348 | 0.112 | |||
| ES | 26.1 (14.0) | −0.203 | 0.353 | |||
| LM | 12.4 (6.9) | −0.402 | 0.064 | |||
Key: EO = external obliques, IO = internal obliques, ES = erector spinae (longissimus thoracis), LM = superficial lumbar multifidus, AEP = active extension pattern, FP = flexion pattern, p = p-value, %SMVC = % sub-maximal voluntary contraction, r = r-value (correlation coefficient), SD = standard deviation, ext = extension, flex = flexion, ↑ = increased, UTx = upper thoracic spine, LTx = lower thoracic spine, ULx = upper lumbar spine, LLx = lower lumbar spine. Note: negative correlations indicate an inverse relationship between muscle activity and spinal movement.
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Figure 1.
Example raw data during a step up and down task showing (a) kinematic marker position in global co-ordinate system, (b) regional spinal kinematics throughout the task and (c) raw EMG traces for each muscle (bilaterally) for one participant in each group (FP, AEP, control). Key: high thoracic = upper thoracic (UTx), low thoracic = lower thoracic (LTx), high lumbar = upper lumbar (ULx), low lumbar = lower lumbar (LLx), mm = millimetres, Transverse Abd/Int Oblique = transversus abdominis/internal oblique (IO), Ext Oblique = external oblique (EO), Lumb Multifidus = lumbar multifidus (LM), Thor Erector Spinae = thoracic erector spinae (ES). NB: dashed vertical lines indicate the defined start and end points of each task phase, as outlined in Appendix A (Table A1). A green line indicates the start of the task phase. A black line indicates the end of the task phase.
Figure 1.
Example raw data during a step up and down task showing (a) kinematic marker position in global co-ordinate system, (b) regional spinal kinematics throughout the task and (c) raw EMG traces for each muscle (bilaterally) for one participant in each group (FP, AEP, control). Key: high thoracic = upper thoracic (UTx), low thoracic = lower thoracic (LTx), high lumbar = upper lumbar (ULx), low lumbar = lower lumbar (LLx), mm = millimetres, Transverse Abd/Int Oblique = transversus abdominis/internal oblique (IO), Ext Oblique = external oblique (EO), Lumb Multifidus = lumbar multifidus (LM), Thor Erector Spinae = thoracic erector spinae (ES). NB: dashed vertical lines indicate the defined start and end points of each task phase, as outlined in Appendix A (Table A1). A green line indicates the start of the task phase. A black line indicates the end of the task phase.
Figure 2.
A scatterplot, with regression lines, to show relationships between mean amplitude EMG (%SMVC) for erector spinae and lower thoracic spinal angles during the box-replace task between groups (NB: significant positive correlation observed in the FP group only). Key: ES = erector spine, %SMVC = Percentage of sub-maximal voluntary contraction, LTx = lower thoracic spine, AEP = active extension Pattern, FP = flexion pattern.
Figure 2.
A scatterplot, with regression lines, to show relationships between mean amplitude EMG (%SMVC) for erector spinae and lower thoracic spinal angles during the box-replace task between groups (NB: significant positive correlation observed in the FP group only). Key: ES = erector spine, %SMVC = Percentage of sub-maximal voluntary contraction, LTx = lower thoracic spine, AEP = active extension Pattern, FP = flexion pattern.
Figure 3.
A scatterplot, with regression lines, to show relationships between mean amplitude EMG (%SMVC) for erector spinae and lower thoracic spinal angles during the box-replace task between groups. (NB: significant negative correlation observed in the FP group only). Key: ES = erector spine, %SMVC = Percentage of sub-maximal voluntary contraction, LTx = lower lumbar spine, AEP = active extension pattern, FP = flexion pattern.
Figure 3.
A scatterplot, with regression lines, to show relationships between mean amplitude EMG (%SMVC) for erector spinae and lower thoracic spinal angles during the box-replace task between groups. (NB: significant negative correlation observed in the FP group only). Key: ES = erector spine, %SMVC = Percentage of sub-maximal voluntary contraction, LTx = lower lumbar spine, AEP = active extension pattern, FP = flexion pattern.
Table 1.
Participant baseline characteristics across groups. (Note: Values are mean (SD) unless otherwise stated).
Table 1.
Participant baseline characteristics across groups. (Note: Values are mean (SD) unless otherwise stated).
| Variable | AEP | FP | Healthy | Significance | |
|---|---|---|---|---|---|
| (n = 23) | (n = 27) | (n = 28) | |||
| Gender | Male | 4 (17.4%) | 21 (77.8%) | 12 (42.9%) | p < 0.001 * |
| Female | 19 (82.6%) | 6 (22.2%) | 16 (57.1%) | ||
| Age (years) | 43.7 (11.2) | 41.0 (10.0) | 38.5 (11.2) | p = 0.238 | |
| Mass (kg) | 68.9 (18.0) | 82.5 (14.6) | 72.9 (15.2) | p = 0.005 * (AEP vs. FP) | |
| Height (cm) | 164.9 (10.2) | 175.9 (8.7) | 169.4 (7.3) | p < 0.001 * (AEP vs. FP/FP vs. H) | |
| BMI (kg/m2) | 20.8 (4.9) | 23.4 (3.5) | 21.5 (4.1) | p = 0.127 | |
| Site of back pain N (%) | Right | 8 (34.8%) | 5 (18.5%) | - | - |
| Left | 2 (8.7%) | 3 (11.1%) | |||
| Central | 13 (56.4%) | 19 (70.4%) | |||
| Time since pain onset N (%) | 3–6 months | 2 (8.7%) | 8 (29.6%) | - | - |
| 6–12 months | 7 (30.4%) | 2 (7.4%) | - | - | |
| >1 year | 14 (60.9%) | 17 (63.0%) | |||
| Pain score (VAS) | 4.6 (1.4) | 4.5 (1.4) | - | p = 0.986 | |
Key: FP = flexion pattern motor control impairment, AEP = active extension pattern motor control impairment, H = healthy, BMI = body mass index (mass (kg)/height (m)2), kg = kilogrammes, cm = centimetres, * significant difference (p < 0.05), VAS = visual analogue scale, SD = standard deviation, N = number of participants.
Table 2.
Summary of all significant relationships (p < 0.01) observed across the three groups (AEP, FP and healthy control) during a series of functional tasks.
Table 2.
Summary of all significant relationships (p < 0.01) observed across the three groups (AEP, FP and healthy control) during a series of functional tasks.
| Spinal Region | Muscle | AEP | FP | Control | |
|---|---|---|---|---|---|
| Box Lift | LTx | ES | ↑flex = ↑ES activity | ||
| LM | ↑flex = ↑LM activity | ||||
| LLx | ES | ↑flex = ↓ES activity | |||
| Box Replace | LTx | ES | ↑flex = ↑ES activity | ||
| LM | ↑flex = ↑LM activity | ||||
| LLx | EO | ↑flex = ↓EO activity | |||
| ES | ↑flex = ↓ES activity | ||||
| LM | ↑ext = ↓LM activity | ||||
| Reach Up | UTx | ES | ↑flex = ↑ES activity | ||
| LTx | EO | ↑flex = ↑EO activity | |||
| ES | ↑flex = ↑ES activity | ||||
| LM | ↑flex = ↑LM activity | ||||
| ULx | LM | ↑ext = ↑LM activity | |||
| LLx | ES | ↑flex = ↓ES activity | |||
| Step Up | UTx | EO | ↑flex = ↑EO activity | ||
| LTx | EO | ↑flex = ↑EO activity | |||
| ES | ↑flex = ↑ES activity | ||||
| LM | ↑flex = ↑LM activity | ||||
| ULx | LM | ↑ext = ↑LM activity | |||
| LLx | EO | ↑flex = ↓EO activity | |||
| IO | ↑flex = ↓IO activity | ||||
| ES | ↑flex = ↓ES activity | ||||
| LM | ↑flex = ↓LM activity | ||||
| Step Down | LTx | ES | ↑flex = ↑ES activity | ||
| LM | ↑flex = ↑LM activity | ||||
| ULx | LM | ↑ext = ↑LM activity | |||
| LLx | EO | ↑flex = ↓EO activity | |||
| IO | ↑flex = ↓IO activity | ||||
| ES | ↑flex = ↓ES activity | ||||
| Sit-to-Stand | LLx | ES | ↑flex = ↓ES activity |
Key: EO = external obliques, IO = transversus abdominis/internal obliques, ES = erector spinae (longissimus thoracis), LM = superficial lumbar multifidus, AEP = active extension pattern, FP = flexion pattern, ext = extension, flex = flexion, ↑ = increased, ↓ = decreased, UTx = upper thoracic spine, LTx = lower thoracic spine, ULx = upper lumbar spine, LLx = lower lumbar spine. NB: No significant differences were observed during stand-to-sit in any group.
Table 3.
Highlights’ summary: Common relationships observed in different NSCLBP subgroups.
| Tasks | Subgroup | Region | Relationship |
|---|---|---|---|
| Reach up, step up, step down. Note: also Pick up pen, and pick up pen return from Hemming et al., (2024) [11] | AEP | ULx | ↑ext = ↑LM activity |
| Box lift, box replace, reach up, step up, step down. Note: also pick up pen, and pick up pen return from Hemming et al., (2024) [11] | FP | LTx | ↑flex = ↑LM activity |
| Box lift, box replace, reach up, step up, step down, sit to stand. Note: also pick up pen, and pick up pen return from Hemming et al., (2024) [11] | FP | LLx | ↑flex = ↓ES activity |
Key: ES = erector spinae (longissimus thoracis), LM = superficial lumbar multifidus, AEP = active extension pattern, FP = flexion pattern, ext = extension, flex = flexion, ↑ = increased, ↓ = decreased, LTx = lower thoracic spine, ULx = upper lumbar spine, LLx = lower lumbar spine.
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Hemming, R.; du Rose, A.; Sheeran, L.; Sparkes, V. Relationships Between Muscle Activation and Thoraco-Lumbar Kinematics in Direction-Specific Low Back Pain Subgroups During Everyday Tasks. Biomechanics 2025, 5, 42. https://doi.org/10.3390/biomechanics5020042
AMA Style
Hemming R, du Rose A, Sheeran L, Sparkes V. Relationships Between Muscle Activation and Thoraco-Lumbar Kinematics in Direction-Specific Low Back Pain Subgroups During Everyday Tasks. Biomechanics. 2025; 5(2):42. https://doi.org/10.3390/biomechanics5020042
Chicago/Turabian StyleHemming, Rebecca, Alister du Rose, Liba Sheeran, and Valerie Sparkes. 2025. "Relationships Between Muscle Activation and Thoraco-Lumbar Kinematics in Direction-Specific Low Back Pain Subgroups During Everyday Tasks" Biomechanics 5, no. 2: 42. https://doi.org/10.3390/biomechanics5020042
APA StyleHemming, R., du Rose, A., Sheeran, L., & Sparkes, V. (2025). Relationships Between Muscle Activation and Thoraco-Lumbar Kinematics in Direction-Specific Low Back Pain Subgroups During Everyday Tasks. Biomechanics, 5(2), 42. https://doi.org/10.3390/biomechanics5020042
