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

The aim of this study was to test whether determinants associated with lumbar stability can predict performance during unstable sitting (trunk postural control - TPC). If confirmed, unstable sitting could be viewed as a proxy measure for these determinants. Wobbling chair motion was measured in 58 subjects with an inertial sensor, and six outcomes were computed (mean frequency and velocity, frequency dispersion, two variables from the sway density analysis and Lyapunov exponent - short interval) to represent TPC performance. Subjects also performed five other trunk neuromuscular tests to quantify the thickness of back and abdominal muscles and connective tissues, lumbar proprioception, lumbar stiffness, feedforward and feedback control mechanisms, and trunk/muscle coordination. Four to five predictors explained between 36 and 47% of TPC outcomes variance, as determined with multivariate analyses. These predictors were mainly related to (1) angular kinematic parameters of the pelvis or lumbar spine following rapid arm movement, (2) lumbar intrinsic stiffness, (3) thickness of perimuscular connective tissues surrounding specific abdominal muscles, (4) activation onsets of specific trunk muscles (IO/TrA and iliocostalis lumborum) before rapid arm movement, and (5) percent thickness change of internal oblique (IO) and transversus abdominis (TrA) muscles. Lumbar proprioception and reflex responses were not predictive, possibly due to the lack of appropriate measurements. These findings support the use of TPC in unstable sitting as a proxy measure for determinants associated with lumbar stability. This might be useful in research and clinical settings, considering time and equipment constraints associated with measuring these determinants individually.

Larivière C ，Preuss R ，Ludvig D ，Henry SM ... -  《-》

Center of pressure trajectories, trunk kinematics and trunk muscle activation during unstable sitting in low back pain patients.

Trunk motor behavior has been reported to be altered in low-back pain. This may be associated with impaired lumbar proprioception, which could be compensated by trunk stiffening. We assessed trunk control by measuring center-of-pressure, lumbar kinematics and trunk muscle electromyography in 20 low-back pain patients and 11 healthy individuals during a seated balancing task, in conditions with and without disturbance of lumbar proprioception and occlusion of vision. We hypothesized that low-back pain patients show larger postural sway, but smaller thoraco-lumbar movements than healthy individuals. Repeated measures analyses of variance indicated that the effects of proprioception disturbance and vision occlusion were similar between groups. Interestingly, low-back pain patients grabbed the safety rail more often, while differences between groups in sway measures were rather subtle. This suggests that low-back pain patients were more cautious. Furthermore, low-back pain patients had an about 20 degrees less flexed lumbar posture than healthy individuals, and, in contrast to our hypothesis, made larger thoraco-lumbar movements in the sagittal plane, as indicated by higher SDs of thoraco-lumbar flexion and lower (more negative) correlations between pelvis and thorax movements. Activation of the intersegmental longissimus relative to the iliocostalis muscle, which spans all lumbar segments, was lower in low-back pain patients compared to healthy individuals. This difference in muscle activation may be causal for larger thoraco-lumbar movements, and may be causative of reduced control over segmental lumbar movement, but may also reflect the need for larger corrective movements to compensate balance impairments.

Willigenburg NW ，Kingma I ，van Dieën JH 《-》

Trunk postural control in unstable sitting: Effect of sex and low back pain status.

Adequate neuromuscular control of the lumbar spine is required to prevent lumbar injuries. A trunk postural control test protocol, controlling for the influence of body size on performance, was implemented to carry out between-subject comparisons. The aim of this study was to assess the effect of sex and low back pain status with the use of two measures of trunk postural control, the first based on chair motion, and the second based on trunk motion. Thirty-six subjects (with and without low back pain) performed three 60-s trunk postural control trials with their eyes closed while seated on an instrumented wobble chair, following a calibration procedure. Chair and trunk angular kinematics were measured with an optoelectronic system. A chair-based stabilogram and a trunk-based (lumbar spine) stabilogram were created using the angular motions produced in the sagittal and frontal planes. Twenty body-sway measures were computed for each stabilogram. The calibration task efficiently controlled for the influence of body size. Several sex effects were detected, with most of them originating from the trunk-based measures. Subjects with low back pain and healthy controls showed comparable trunk postural control. Sex differences were substantiated for the first time, but almost only with the trunk-based stabilogram, showing that the kinematic information captured on the trunk segments is quite different from what is captured on the wobble chair. Contrary to previous studies, pain status was not related to lowered trunk postural control, which can be attributed to the patients recruited or measurement reliability issues.

Larivière C ，Gagnon DH ，Mecheri H 《-》

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.

Larivière C ，Preuss R ，Gagnon DH ，Mecheri H ，Driscoll M ，Henry SM ... -  《-》

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.

Larivière C ，Henry SM ，Preuss R 《-》