Is postural control during unstable sitting a proxy measure for determinants associated with lumbar stability?

Validation of proprioception measures of the lumbar spine

BACKGROUND

To better personalize treatment and monitor recovery of individuals with low back pain, objective tests of sensorimotor functions, such as lumbar proprioception, must be selected based on their reliability and validity. The primary objective of this study was to test the concurrent validity of three measures of lumbar proprioception.

METHODS

Thirty-one participants performed three lumbar proprioception tests (motion perception threshold, active and passive joint positioning sense), a whole-body mobility and balance (time up-and-go) and two trunk-specific postural control (threshold of stability and sensor-based sway measures) tests.

RESULTS

Only the motion perception threshold proprioception test showed some validity, correlating with the trunk-specific postural control tests [r range (positive values): 0.37 to 0.60]. The three lumbar proprioception measures were not correlated to each other. The threshold of stability measure was correlated with the time up-and-go (r = 0.37) and trunk-specific (sensor-based sway measures) postural control [r range (positive values): 0.48 to 0.77] tests.

CONCLUSION

The present study generated three original findings. Only the motion perception threshold proprioception test demonstrated its concurrent validity. In fact, the three lumbar proprioception tests performed in the present study were not correlated to each other, thus assessing different constructs. Finally, the threshold of stability protocol was validated against other tests. These findings will help in selecting the most appropriate lumbar proprioception measures to study the effects of exercise treatments in patients with back pain.

Trunk postural control during unstable sitting among individuals with and without low back pain: A systematic review with an individual participant data meta-analysis

INTRODUCTION

Sitting on an unstable surface is a common paradigm to investigate trunk postural control among individuals with low back pain (LBP), by minimizing the influence lower extremities on balance control. Outcomes of many small studies are inconsistent (e.g., some find differences between groups while others do not), potentially due to confounding factors such as age, sex, body mass index [BMI], or clinical presentations. We conducted a systematic review with an individual participant data (IPD) meta-analysis to investigate whether trunk postural control differs between those with and without LBP, and whether the difference between groups is impacted by vision and potential confounding factors.

METHODS

We completed this review according to PRISMA-IPD guidelines. The literature was screened (up to 7th September 2023) from five electronic databases: MEDLINE, CINAHL, Embase, Scopus, and Web of Science Core Collection. Outcome measures were extracted that describe unstable seat movements, specifically centre of pressure or seat angle. Our main analyses included: 1) a two-stage IPD meta-analysis to assess the difference between groups and their interaction with age, sex, BMI, and vision on trunk postural control; 2) and a two-stage IPD meta-regression to determine the effects of LBP clinical features (pain intensity, disability, pain catastrophizing, and fear-avoidance beliefs) on trunk postural control.

RESULTS

Forty studies (1,821 participants) were included for the descriptive analysis and 24 studies (1,050 participants) were included for the IPD analysis. IPD meta-analyses revealed three main findings: (a) trunk postural control was worse (higher root mean square displacement [RMSdispl], range, and long-term diffusion; lower mean power frequency) among individuals with than without LBP; (b) trunk postural control deteriorated more (higher RMSdispl, short- and long-term diffusion) among individuals with than without LBP when vision was removed; and (c) older age and higher BMI had greater adverse impacts on trunk postural control (higher short-term diffusion; longer time and distance coordinates of the critical point) among individuals with than without LBP. IPD meta-regressions indicated no associations between the limited LBP clinical features that could be considered and trunk postural control.

CONCLUSION

Trunk postural control appears to be inferior among individuals with LBP, which was indicated by increased seat movements and some evidence of trunk stiffening. These findings are likely explained by delayed or less accurate corrective responses.

SYSTEMATIC REVIEW REGISTRATION

This review has been registered in PROSPERO (registration number: CRD42021124658).

The relationship between clinical examination measures and ultrasound measures of fascia thickness surrounding trunk muscles or lumbar multifidus fatty infiltrations: An exploratory study

Patients with chronic low back pain (CLBP) exhibit remodelling of the lumbar soft tissues such as muscle fatty infiltrations (MFI) and fibrosis of the lumbar multifidus (LuM) muscles, thickness changes of the thoracolumbar fascia (TLF) and perimuscular connective tissues (PMCT) surrounding the abdominal lateral wall muscles. Rehabilitative ultrasound imaging (RUSI) parameters such as thickness and echogenicity are sensitive to this remodelling. This experimental laboratory study aimed to explore whether these RUSI parameters (LuM echogenicity and fascia thicknesses), hereafter called dependent variables (DV) were linked to independent variables (IV) such as (1) other RUSI parameters (trunk muscle thickness and activation) and (2) physical and psychological measures. RUSI measures, as well as a clinical examination comprising physical tests and psychological questionnaires, were collected from 70 participants with LBP. The following RUSI dependent variables (RUSI-DV), measures of passive tissues were performed bilaterally: (1) LuM echogenicity (MFI/fibrosis) at three vertebral levels (L3/L4, L4/L5 and L5/S1); (2) TLF posterior layer thickness, and (3) PMCT thickness of the fasciae between subcutaneous tissue thickness (STT) and external oblique (PMCTSTT/EO ), between external and internal oblique (PMCTEO/IO ), between IO and transversus abdominis (PMCTIO/TrA ) and between TrA and intra-abdominal content (PMCTTrA/IA ). RUSI measures of trunk muscle's function (thickness and activation), also called measures of active muscle tissues, were considered as independent variables (RUSI-IV), along with physical tests related to lumbar stability (n = 6), motor control deficits (n = 7), trunk muscle endurance (n = 4), physical performance (n = 4), lumbar posture (n = 2), and range of motion (ROM) tests (n = 6). Psychosocial measures included pain catastrophizing, fear-avoidance beliefs, psychological distress, illness perceptions and concepts related to adherence to a home-based exercise programme (physical activity level, self-efficacy, social support, outcome expectations). Six multivariate regression models (forward stepwise selection) were generated, using RUSI-DV measures as dependent variables and RUSI-IV/physical/psychosocial measures as independent variables (predictors). The six multivariate models included three to five predictors, explaining 63% of total LuM echogenicity variance, between 41% and 46% of trunk superficial fasciae variance (TLF, PMCTSTT/EO ) and between 28% and 37% of deeper abdominal wall fasciae variance (PMCTEO/IO , PMCTIO/TrA and PMCTTrA/IA ). These variables were from RUSI-IV (LuM thickness at rest, activation of IO and TrA), body composition (percent fat) and clinical physical examination (lumbar and pelvis flexion ROM, aberrant movements, passive and active straight-leg raise, loaded-reach test) from the biological domain, as well as from the lifestyle (physical activity level during sports), psychological (psychological distress-cognitive subscale, fear-avoidance beliefs during physical activities, self-efficacy to exercise) and social (family support to exercise) domains. Biological, psychological, social and lifestyle factors each accounted for substantial variance in RUSI-passive parameters. These findings are in keeping with a conceptual link between tissue remodelling and factors such as local and systemic inflammation. Possible explanations are discussed, in keeping with the hypothesis-generating nature of this study (exploratory). However, to impact clinical practice, further research is needed to determine if the most plausible predictors of trunk fasciae thickness and LuM fatty infiltrations have an effect on these parameters.

Quantification of the development of trunk control in healthy infants using inertial measurement units

Trunk motor control is essential for the proper functioning of the upper extremities and is an important predictor of gait capacity in children with delayed development. Early diagnosis and intervention could increase the trunk motor capabilities in later life, but current tools used to assess the level of trunk motor control are largely subjective and many lack the sensitivity to accurately monitor development and the effects of therapy. Inertial measurement units could yield an objective quantitative assessment that is inexpensive and easy-to-implement. We hypothesized that root mean square of jerk, a proxy for movement smoothness, could be used to distinguish age and thereby presumed motor development. We attached a sensor to the trunks of six young children with no known developmental deficits. Root mean square of jerk decreases with age, up to 24 months, and is correlated to a more established method, i.e., center-of-pressure velocity, as well as other standard inertial measurement unit outputs. This metric therefore shows potential as a method to differentiate trunk motor control levels.

Cortical activity, kinematics and trunk muscles activity response to pelvis movements during unstable sitting

BACKGROUND

Balance control is a leading component of human motor activities and its impairment is associated with an increased risk of falling, lower back pain due to impaired motor control mechanism. Prolonged sitting position at workplace is one of the risk factors of reduced postural control and lower back pain.

OBJECTIVE

To evaluate theta and alpha waves cortical activity, trunk muscles activity and kinematics in static sitting, dynamic sitting on different platforms: simple wobble board (WB) and wobble board on bearing surface (WBB).

METHODS

The kinematics of body segments, electromyography of five trunk muscles, electroencephalography of 32 scalp electrodes were measured during balance tasks in sitting position for 17 subjects with continuous seated position at workplace.

RESULTS

Cortical power on WBB1 increase in fronto - central (p< 0.05) region while on WBB2 increase in centro - parietal region (p< 0.05). WBB2 increase more muscles compared with WB2. The amplitude of movement of ASIS, Th10 can be seen lower on WBB compared with WB (p< 0.05).

CONCLUSIONS

The study shows that WBB can increase personalized sitting and improve trunk motor control during hours of prolonged sitting.

Structural remodeling of the lumbar multifidus, thoracolumbar fascia and lateral abdominal wall perimuscular connective tissues: Medium-term test-retest reliability of ultrasound measures

INTRODUCTION

Growing interest is being paid to the lumbar multifidus (LM) intramuscular fatty infiltrations and fibrosis that are secondary to low back pain as well to the remodeling of perimuscular connective tissues (fasciae) such as the thoracolumbar fascia and fascia sheets separating the abdominal wall muscles. Magnetic resonance imaging and computed tomography have traditionally been used but rehabilitative ultrasound imaging (RUSI) is much more affordable and practical, which can accelerate research and clinical applications on this topic. The aim of this study was to test the medium-term (8 weeks) test-retest reliability of the corresponding RUSI measures.

METHODS

Thirty-four participants with non-acute LBP and 30 healthy controls performed a RUSI assessment before and after an 8-week time interval. LM echogenicity was quantified to assess fatty infiltrations and fibrosis while fasciae were quantified with thickness measures. Relative and absolute reliability were estimated using the generalizability theory as a framework, allowing to partition the different sources of error.

RESULTS

Overall, the reliability findings were quite acceptable, with negligible systematic effects. Excellent relative reliability was reached in half of the investigated RUSI measures, particularly when averaging measures across trials. However, neither relative, nor absolute reliability results support the use of these RUSI measurements on an individual basis (e.g. clinical applications) but they are useful on a group basis (e.g. research applications).

DISCUSSION

The different sources of error were distributed unequally across RUSI measures, pointing to different measurement strategies to mitigate the underlying errors.

CONCLUSIONS

The use of the generalizability theory allowed identifying the sources of error of the different RUSI measures. For each category of measure, depending of the distribution of errors, it was possible to recommend specific measurement strategies to mitigate them.

Structural remodeling of the lumbar multifidus, thoracolumbar fascia and lateral abdominal wall perimuscular connective tissues: A search for its potential determinants

Recently remodeling of lumbar soft tissues has received increased research attention. However, the major determinants that influence remodeling need to be elucidated in order to understand the impact of different rehabilitation modalities on tissue remodeling. The main aim of this study was to explore the between-subject variance of different measures of lumbar soft tissues quantified with rehabilitative ultrasound imaging (RUSI). RUSI measures (n = 8) were collected from 30 subjects without and 34 patients with LBP: (1) lumbar multifidus (LM) echogenicity (fatty infiltration/fibrosis) at three vertebral levels (L3/L4, L4/L5 and L5/S1) (n = 3); (2) posterior layer thickness of the thoracolumbar fascia (n = 1); and (3) thickness of the fasciae surrounding the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) (n = 4). Forward stepwise multivariate regression modeling was conducted with these RUSI measures as dependent variables, using the following independent variables as potential determinants: age, sex, the presence of LBP, body size/composition characteristics (height, weight, trunk length, subcutaneous tissue thickness over the abdominal, and LM muscles), trunk muscle function (or activation) as determined with the percent thickness change of LM, EO, IO, and TrA muscles during a standardized effort (RUSI measures), and physical activity level during sport and leisure activities as estimated with a self-report questionnaire. Two or three statistically significant predictors (or determinants) were selected in the regression model of each RUSI measure (n = 8 models), accounting for 26-64% of their total variance. The subcutaneous tissue thickness on the back accounted for 15-30% variance of LM echogenicity measures and thoracolumbar fascia thickness while the subcutaneous tissue thickness over the abdominals accounted for up to 42% variance of the fascia separating the subcutaneous adipose tissues and the EO muscle. The thickness of IO at rest accounted for 13-21% variance of all investigated abdominal fasciae except the fascia separating the subcutaneous adipose tissue and EO. Pain status accounted for 13-18% variance of the anterior and posterior fasciae of the TrA. Age accounted for 11-14% variance of LM echogenicity at all investigated vertebral levels while sex accounted for 15-21% variance of LM echogenicity at L3/L4 and fascia separating subcutaneous adipose tissue and EO muscle. The function (or activation) of EO and LM at L3/L4 accounted for 8-11% variance of the thoracolumbar fascia and fascia separating TrA and intra-abdominal content (TrA posterior fascia), respectively. Finally, the physical activity level during sport activities accounted for 7% variance of the fascia separating the subcutaneous adipose tissues and the EO muscle. These findings suggest that determinants other than body size characteristics may impact the remodeling of lumbar soft tissues, more importantly the subcutaneous adipose tissue deposits (thickness RUSI measures), which are associated with ectopic fat deposition in the LM and in the fasciae that are more closely positioned to the surface. While age, sex, and pain status explain some variability, modifiable factors such as physical activity level as well as trunk muscle thickness and function were involved. Overall, these results suggest that rehabilitation can potentially impact tissue remodeling, particularly in terms of intramuscular and perimuscular adipose tissues.

The immediate effect of two lumbar stabilization methods on postural control parameters and their reliability during two balance tasks

Background: Lumbosacral orthosis (LSO) and/or the isolated contraction of the transversus abdominis muscle by the abdominal drawing-in maneuver (ADIM) can increase lumbar stiffness, consequently influencing postural control. The purpose of this study was to compare the effects of LSO and ADIM on postural control during two balance tasks and determine their reliability.Methods: Twenty participants (50% men) randomly performed three experimental conditions: 1) without lumbar stabilization, 2) with LSO), and 3) with ADIM. Each experimental condition was tested in two postural tasks: semi-tandem and one-legged stance on a force platform for 30 seconds, while the Center of pressure postural (COP) parameters were computed.Results: The two methods of lumbar stabilization were comparable and did not significantly reduce the COP values across time, even though a few individuals presented a change in their COP data above the levels of measurement errors. The reliability of these measurements was generally acceptable and sometimes excellent (≥ 0.90 and ≤10% error measurement).Conclusions: Both LSO and isolated contraction of the transversus abdominis muscle by ADIM do not change postural control in one-legged stance and in semi-tandem tasks. These results have implications for use or not these methods for postural control on a rehabilitation perspective.