Assessment of Spinal and Pelvic Kinematics Using Inertial Measurement Units in Clinical Subgroups of Persistent Non-Specific Low Back Pain.

Inertial measurement units (IMUs) offer a portable and quantitative solution for clinical movement analysis. However, their application in non-specific low back pain (NSLBP) remains underexplored. This study compared the spine and pelvis kinematics obtained from IMUs between individuals with and without NSLBP and across clinical subgroups of NSLBP. A total of 81 participants with NSLBP with flexion (FP; n = 38) and extension (EP; n = 43) motor control impairment and 26 controls (No-NSLBP) completed 10 repetitions of spine movements (flexion, extension, lateral flexion). IMUs were placed on the sacrum, fourth and second lumbar vertebrae, and seventh cervical vertebra to measure inclination at the pelvis, lower (LLx) and upper (ULx) lumbar spine, and lower cervical spine (LCx), respectively. At each location, the range of movement (ROM) was quantified as the range of IMU orientation in the primary plane of movement. The ROM was compared between NSLBP and No-NSLBP using unpaired t-tests and across FP-NSLBP, EP-NSLBP, and No-NSLBP subgroups using one-way ANOVA. Individuals with NSLBP exhibited a smaller ROM at the ULx (p = 0.005), LLx (p = 0.003) and LCx (p = 0.01) during forward flexion, smaller ROM at the LLx during extension (p = 0.03), and a smaller ROM at the pelvis during lateral flexion (p = 0.003). Those in the EP-NSLBP group had smaller ROM than those in the No-NSLBP group at LLx during forward flexion (Bonferroni-corrected p = 0.005), extension (p = 0.013), and lateral flexion (p = 0.038), and a smaller ROM at the pelvis during lateral flexion (p = 0.005). Those in the FP-NSLBP subgroup had smaller ROM than those in the No-NSLBP group at the ULx during forward flexion (p = 0.024). IMUs detected variations in kinematics at the trunk, lumbar spine, and pelvis among individuals with and without NSLBP and across clinical NSLBP subgroups during flexion, extension, and lateral flexion. These findings consistently point to reduced ROM in NSLBP. The identified subgroup differences highlight the potential of IMU for assessing spinal and pelvic kinematics in these clinically verified subgroups of NSLBP.

Relationships between trunk muscle activation and thoraco-lumbar kinematics in non-specific chronic low back pain subgroups during a forward bending task.

BACKGROUND: Trunk muscle activity and thoraco-lumbar kinematics can discriminate between non-specific chronic low back pain (NSCLBP) subgroups and healthy controls. However, research commonly focuses on lumbar kinematics, with limited understanding of relationships between kinematics and muscle activity across clinical subgroups. Similarly, the thoracic spine, whilst intuitively associated with NSCLBP, has received less attention and potential relationships between spinal regions and muscle activity requires exploration. RESEARCH QUESTION: Is there a relationship between trunk muscle activation and regional thoracic and lumbar kinematics in NSCLBP subgroups during a forward bending task? METHODS: Observational, case-control study. Fifty subgrouped NSCLBP motor control impairment participants (27 Flexion Pattern (FP-MCI), 23 Active Extension Pattern (AEP-MCI)) and 28 pain-free controls were evaluated using 3D motion analysis (Vicon™) and surface electromyography during a forward bending and return to upright task. Mean sagittal angles for the upper-thoracic (UTx), lower-thoracic (LTx), upper-lumbar (ULx) and lower-lumbar (LLx) regions were compared with normalised (% sub-maximal voluntary contraction) mean amplitude electromyography of bilateral transversus abdominis/internal oblique, external oblique, superficial lumbar multifidus and erector spinae (longissimus thoracis) muscles between groups. Pearson correlations were computed to assess relationships (significance p < 0.01). RESULTS: AEP-MCI individuals demonstrated statistically significant relationships between superficial lumbar multifidus and ULx and LLx kinematics (-.812 to.659). FP-MCI individuals exhibited statistically significant relationships between erector spinae and superficial lumbar multifidus and LLx and LTx kinematics (-.686 to.664) in both task phases, and between external oblique and LTx during forward bending) (-.459 to.572). Correlations were moderate to strong for all significant relationships (-.812 to .664). SIGNIFICANCE: Relationships between muscle activity and regional spinal kinematics varied between NSCLBP subgroups, suggesting that those with flexion- or extension-related LBP adopt different motor control strategies when performing a bending task. As effectively mechanical biomarkers, these findings may inform treatment by improving understanding of varied motor strategies in subgroups.

Moving Forward: Understanding Correlates of Physical Activity and Sedentary Behaviour during COVID-19 in Children and Adolescents-An Integrative Review and Socioecological Approach.

Novel coronavirus disease 2019 (COVID-19) pandemic restrictions have negatively impacted physical activity (PA) and sedentary time/behaviour. This integrative review systematically explored the socioecological factors that impacted and influenced these movement behaviours in children and adolescents during the pandemic. Five electronic databases were systematically searched in January 2021, with data extracted from 16 articles (n = 18,352; 5-17 years; 12 countries). Risk-of-bias was assessed using the Mixed Methods Assessment Tool (MMAT), with correlates identified, coded, and themed via thematic analysis. A socioecological model of during-pandemic PA and sedentary time/behaviour was conceptualised and mapped to the Capability, Opportunity, Motivation, and Behaviour (COM-B) model of behaviour-change mechanisms, illustrating influences over five levels: Individual (biological)-age and sex; Individual (psychological)-mental health, and cognition, motivation, and behaviour; Social-family factors, and structured support; Environmental-area of residence and resources; and Policy-COVID-19-related rules. For sedentary time/behaviour, individual-(age and sex), social-(family factors) and policy-(COVID-19-related rules) level factors may be important correlates. There were no age or sex associations with PA levels, though there was some indication that sedentary time/behaviour increased with age. Interventions seeking to enhance young people's movement behaviours during periods of enforced restrictions should focus on enhancing opportunities on a social and environmental level.

Characterisation of motor cortex organisation in patients with different presentations of persistent low back pain.

Persistence of low back pain is thought to be associated with different underlying pain mechanisms, including ongoing nociceptive input and central sensitisation. We hypothesised that primary motor cortex (M1) representations of back muscles (a measure of motor system adaptation) would differ between pain mechanisms, with more consistent observations in individuals presumed to have an ongoing contribution of nociceptive input consistently related to movement/posture. We tested 28 participants with low back pain sub-grouped by the presumed underlying pain mechanisms: nociceptive pain, nociplastic pain and a mixed group with features consistent with both. Transcranial magnetic stimulation was used to study M1 organisation of back muscles. M1 maps of multifidus (deep and superficial) and longissimus erector spinae were recorded with fine-wire electromyography and thoracic erector spinae with surface electromyography. The nociplastic pain group had greater variability in M1 map location (centre of gravity) than other groups (p < .01), which may suggest less consistency, and perhaps relevance, of motor cortex adaptation for that group. The mixed group had greater overlap of M1 representations between deep/superficial muscles than nociceptive pain (deep multifidus/longissimus: p = .001, deep multifidus/thoracic erector spinae: p = .008) and nociplastic pain (deep multifidus/longissimus: p = .02, deep multifidus/thoracic erector spinae: p = .02) groups. This study provides preliminary evidence of differences in M1 organisation in subgroups of low back pain classified by likely underlying pain mechanisms. Despite the sample size, differences in cortical re-organisation between subgroups were detected. Differences in M1 organisation in subgroups of low back pain supports tailoring of treatment based on pain mechanism and motor adaptation.

Impact of the COVID-19 Pandemic on Sedentary Time and Behaviour in Children and Adults: A Systematic Review and Meta-Analysis.

The aim of this meta-analysis was to quantify the change in sedentary time during the COVID-19 pandemic and its effect on health outcomes in the general population. One thousand six hundred and one articles published after 2019 were retrieved from five databases, of which 64 and 40 were included in the systematic review and meta-analysis, respectively. Studies were grouped according to population: children (<18 years), adults (18-64 years) and older adults (>65 years). Average sedentary time was calculated, with sub-analyses performed by country, behaviour type and health outcomes. Children were most affected, increasing their sedentary time by 159.5 ± 142.6 min day-1, followed by adults (+126.9 ± 42.2 min day-1) and older adults (+46.9 ± 22.0 min day-1). There were no sex differences in any age group. Screen time was the only consistently measured behaviour and accounted for 46.8% and 57.2% of total sedentary time in children and adults, respectively. Increases in sedentary time were negatively correlated with global mental health, depression, anxiety and quality of life, irrespective of age. Whilst lockdown negatively affected all age groups, children were more negatively affected than adults or older adults, highlighting this population as a key intervention target. As lockdowns ease worldwide, strategies should be employed to reduce time spent sedentary. Trial registration: PROSPERO (CRD42020208909).

Moving Forward: Understanding Correlates of Physical Activity and Sedentary Behaviour during COVID-19-An Integrative Review and Socioecological Approach.

Population-level physical activity (PA) and sedentary time/behaviour estimates represent a significant public health issue exacerbated by restrictions enforced to control COVID-19. This integrative review interrogated available literature to explore the pandemic's impact on correlates of such behaviours in adults (≥18 years). Five electronic databases were systematically searched in January 2021. Data extracted from 64 articles were assessed for risk-of-bias using the Mixed Methods Assessment Tool, with correlates identified, coded, and themed via thematic analysis. A socioecological model of during-pandemic PA was conceptualized and mapped to the Capability, Opportunity, Motivation, and Behaviour (COM-B) model of behaviour change mechanisms, which illustrates influences over five levels: Individual (biological)-general health; Individual (psychological)-mental health, cognition, motivation, and behaviour; Social-domestic situation, sociodemographic factors, support, and lifestyle choices; Environmental-resources and area of residence; and Policy-COVID-19-related rules. For sedentary time/behaviour, individual level factors, namely general and mental health, may be important correlates. Neither age or sex were clearly correlated with either behaviour. As we transition into a new normal, understanding which behaviour mechanisms could effectively challenge physical inactivity is essential. Targeting capability on a psychological level may facilitate PA and limit sedentary time/behaviour, whereas, on a physical level, maximizing PA opportunities could be crucial.

Identifying non-specific low back pain clinical subgroups from sitting and standing repositioning posture tasks using a novel Cardiff Dempster-Shafer Theory Classifier.

BACKGROUND: Low back pain (LBP) classification systems are used to deliver targeted treatments matched to an individual profile, however, distinguishing between different subsets of LBP remains a clinical challenge. METHODS: A novel application of the Cardiff Dempster-Shafer Theory Classifier was employed to identify clinical subgroups of LBP on the basis of repositioning accuracy for subjects performing a sitting and standing posture task. 87 LBP subjects, clinically subclassified into flexion (n = 50), passive extension (n = 14), and active extension (n = 23) motor control impairment subgroups and 31 subjects with no LBP were recruited. Thoracic, lumbar and pelvic repositioning errors were quantified. The Classifier then transformed the error variables from each subject into a set of three belief values: (i) consistent with no LBP, (ii) consistent with LBP, (iii) indicating either LBP or no LBP. FINDINGS: In discriminating LBP from no LBP the Classifier accuracy was 96.61%. From no-LBP, subsets of flexion LBP, active extension and passive extension achieved 93.83, 98.15% and 97.62% accuracy, respectively. Classification accuracies of 96.8%, 87.7% and 70.27% were found when discriminating flexion from passive extension, flexion from active extension and active from passive extension subsets, respectively. Sitting lumbar error magnitude best discriminated LBP from no LBP (92.4% accuracy) and the flexion subset from no-LBP (90.1% accuracy). Standing lumbar error best discriminated active and passive extension from no LBP (94.4% and 95.2% accuracy, respectively). INTERPRETATION: Using repositioning accuracy, the Cardiff Dempster-Shafer Theory Classifier distinguishes between subsets of LBP and could assist decision making for targeted exercise in LBP management.

Investigating differences in trunk muscle activity in non-specific chronic low back pain subgroups and no-low back pain controls during functional tasks: a case-control study.

BACKGROUND: Trunk muscle dysfunction is often regarded as a key feature of non-specific chronic low back pain (NSCLBP) despite being poorly understood and variable with increases, decreases and no change in muscle activity reported. Differences in thoraco-lumbar kinematics have been observed in motor control impairment NSCLBP subgroups (Flexion Pattern, Active Extension Pattern) during static postures and dynamic activities. However, potential differences in muscle activity during functional tasks has not been established in these subgroups to date. METHODS: A case-control study design recruited 50 NSCLBP subjects (27 Flexion Pattern, 23 Active Extension Pattern) and 28 healthy individuals. Surface electromyography determined muscle activity during functional tasks: reaching upwards, step-down, step-up, lifting and replacing a box, stand-to-sit, sit-to-stand, bending to retrieve (and returning from retrieving) a pen from the floor. Normalised (% sub-maximal voluntary contraction) mean amplitude electromyography of bilateral musculature (transversus abdominis/internal oblique, external oblique, superficial lumbar multifidus and longissimus thoracis) was analysed using Kruskal-Wallis and post-hoc Mann-Whitney U tests. RESULTS: Transversus abdominis/internal oblique activity was significantly increased in the Flexion Pattern group compared to controls during stand-to-sit (p = 0.009) on the left side only. External oblique activity was significantly greater in the Active Extension Pattern group compared to controls during box lift (p = 0.016) on the right side only. Significantly greater activity was identified in the right Superficial lumbar multifidus during step up (p = 0.029), reach up (p = 0.013) and box replace (p = 0.007) in the Active Extension Pattern group compared to controls. However left-sided superficial lumbar multifidus activity was significantly greater in the Flexion Pattern group (compared to controls) only during stand-to-sit (p = 0.009). No significant differences were observed in longissimus thoracis activity bilaterally during any task. No significant differences between NSCLBP subgroups were observed. CONCLUSIONS: Muscle activity in these NSCLBP subgroups appears to be highly variable during functional tasks with no clear pattern of activity identified. The findings reflect inconsistencies and variability in trunk muscle activity previously observed in these NSCLBP subgroups. Further work evaluating ratios of muscle activity and changes in muscle activity throughout task duration is warranted.

Can different seating aids influence a sitting posture in healthy individuals and does gender matter?

This study determined differences in spinal-pelvic kinematics sitting on (i) mat (ii) block and (iii) novel 10º forward inclined wedge (ButtaflyTM) in a same-subject repeated measures cross-over design in 60 healthy individuals (34 females). Repeated measures ANOVA revealed statistically significant differences between sitting conditions and lumbar and pelvic sagittal angles. Both, the inclined wedge and the block seating aids reduced overall flexion, but the inclined wedge had a greater influence in the lumbar region whilst the block induced the greatest change in the pelvis. This may be relevant for seating aid design personalised to posture type. Statistically significant gender differences were identified in all 3 seating conditions with males adopting more flexed lumbar spine and posteriorly tilted pelvis. Females flexed less in thoracic spine when sitting on an inclined wedge and a block. These statistically significant differences between males and females may provide first explorative direction for bespoke seating aids design.

Inertial Measurement Units for Clinical Movement Analysis: Reliability and Concurrent Validity.

The aim of this study was to investigate the reliability and concurrent validity of a commercially available Xsens MVN BIOMECH inertial-sensor-based motion capture system during clinically relevant functional activities. A clinician with no prior experience of motion capture technologies and an experienced clinical movement scientist each assessed 26 healthy participants within each of two sessions using a camera-based motion capture system and the MVN BIOMECH system. Participants performed overground walking, squatting, and jumping. Sessions were separated by 4 ± 3 days. Reliability was evaluated using intraclass correlation coefficient and standard error of measurement, and validity was evaluated using the coefficient of multiple correlation and the linear fit method. Day-to-day reliability was generally fair-to-excellent in all three planes for hip, knee, and ankle joint angles in all three tasks. Within-day (between-rater) reliability was fair-to-excellent in all three planes during walking and squatting, and poor-to-high during jumping. Validity was excellent in the sagittal plane for hip, knee, and ankle joint angles in all three tasks and acceptable in frontal and transverse planes in squat and jump activity across joints. Our results suggest that the MVN BIOMECH system can be used by a clinician to quantify lower-limb joint angles in clinically relevant movements.

Non-specific chronic low back pain: differences in spinal kinematics in subgroups during functional tasks.

PURPOSE: A multidimensional classification approach suggests that motor control impairment subgroups exist in non-specific chronic low back pain (NSCLBP). Differences in sitting lumbar posture have been identified between two such subgroups [flexion pattern (FP) and active extension pattern (AEP)] and healthy individuals; however, functional spinal movement has not been explored. This study will evaluate whether NSCLBP subgroups exhibit regional spinal kinematic differences, compared to healthy individuals, during functional tasks. METHODS: Observational, cross-sectional study design. Spinal kinematics of 50 NSCLBP subjects (27 FP, 23 AEP) and 28 healthy individuals were investigated using 3D motion analysis (Vicon™) during functional tasks [reaching upwards, step down, step up, lifting, and replacing a box, stand-to-sit, sit-to-stand, bending to retrieve (and returning from retrieving) a pen from the floor]. Mean sagittal angle for the total thoracic, total lumbar, upper thoracic, lower thoracic, upper lumbar, and lower lumbar regions between groups was compared. RESULTS: Significant differences were observed in lower thoracic and upper lumbar regions between NSCLBP subgroups during most tasks. Significant differences were observed between the FP and healthy group in the lower thoracic region during stand-to-sit-to-stand tasks and bending (and returning from) to retrieve a pen from the floor. All significant results demonstrated the FP group to operate in comparatively greater flexion. CONCLUSIONS: The thoraco-lumbar spine discriminated between FP and AEP, and FP and healthy groups during functional tasks. FP individuals demonstrated more kyphotic thoraco-lumbar postures, which may be pain provocative. No significant differences were observed between AEP and healthy groups, suggesting that alternative mechanisms may occur in AEP.

Clinical challenges of classification based targeted therapies for non-specific low back pain: What do physiotherapy practitioners and managers think?

BACKGROUND: Classification of non-specific low back pain (NSLBP) was recommended to better target care and so maximise treatment potential. This study investigated physiotherapy practitioners' (PPs) and managers' (PMs) views, experiences and perceptions of barriers and enablers for using classification systems (CSs) to better target treatment for NSLBP in the NHS primary care setting. DESIGN: Qualitative focus group and interviews. METHODS: Data from semi-structured interviews of three PMs and a focus group with five PPs, considered local opinion leaders in physiotherapy, was thematically analysed. RESULTS: Five themes emerged (i) CS knowledge: PPs and PMs were aware of CSs and agreed with its usefulness. PPs were mostly aware of CSs informing specific treatments whilst PMs were aware of prognosis based CSs. (ii) Using CSs: PPs classify by experience and clinical reasoning skills, shifting between multiple CSs. PMs were confident that evidence-based practice takes place but believed CSs may not be always used. (iii) Advantages/disadvantages of CSs: Effective targeting of treatments to patients was perceived as advantageous; but the amount of training required was perceived as disadvantageous. (iv) Barriers: Patients' expectations, clinicians' perceptions, insufficiently complex CSs, lack of training resources. (v) Enablers: Development of sufficiently complex CSs, placed within the clinical reasoning process, mentoring, positive engagement with stakeholders and patients. CONCLUSIONS: PPs and PMs were aware of CSs and agreed with its usefulness. The current classification process was perceived to be largely influenced by individual practitioner knowledge and clinical reasoning skills rather than being based on one CS alone. Barriers and enablers were identified for future research.

Classification-guided versus generalized postural intervention in subgroups of nonspecific chronic low back pain: a pragmatic randomized controlled study.

STUDY DESIGN: Pragmatic randomized controlled single-blinded study. OBJECTIVE: To compare the effects of the classification system guided postural intervention (CSPI) with generalized postural intervention (GPI) in subgroups of nonspecific chronic low back pain (NSCLBP). SUMMARY OF BACKGROUND DATA: Spinal motor control impairments and the associated alterations in spinal postures adopted by patients with NSCLBP are highly variable. Research evaluating the effect of interventions that target the specific movement/posture impairments in NSCLBP subgroups is therefore warranted. METHODS: A total of 49 patients with NSCLBP with a classification of flexion pattern (n = 29) and active extension pattern (n = 20) control impairment were recruited from a large cohort study and randomly assigned into CSPI and GPI. The primary outcome was change in Roland-Morris Disability Questionnaire, secondary outcomes were change in pain visual analogue scale, spinal repositioning sense including thoracic and lumbar absolute error, variable error, constant error, and trunk muscle activity during sitting and standing. The intervention was evaluated at baseline, immediately post one-to-one intervention and post 4-week home-based training. RESULTS: The CSPI produced statistically and clinically significant reduction in disability (4.2 [95% CI, 2.9-5.3]) and pain (2, [95% CI, 1.3-2.6]) compared with minimal change in the GPI disability (0.4, [95% CI, -0.8 to 1.6]) and pain (-0.2, [95% CI, -0.5 to 0.9]). Repeated measures analysis of variance revealed that CSPI significantly reduced absolute error in thoracic (sitting) and lumbar spine (standing) and constant error in lumbar spine (standing) post one-to-one phase, although this was no longer significant at 4 weeks. Neither intervention had an effect on trunk muscle activity. CONCLUSION: Compared with minimal change in the GPI group, the CSPI produced statistically and clinically significant improvements in disability and pain outcomes and short-term improvements in some parameters of spinal repositioning sense in NSCLBP subgroups.

Spinal position sense and trunk muscle activity during sitting and standing in nonspecific chronic low back pain: classification analysis.

STUDY DESIGN: A cross-sectional study between subgroups of nonspecific chronic low back pain (NSCLBP) and asymptomatic controls. OBJECTIVE: To investigate NSCLBP subgroup differences in spinal position sense and trunk muscle activity when repositioning thoracic and lumbar spine into neutral (midrange) spinal position during sitting and standing. SUMMARY OF BACKGROUND DATA: Patients with NSCLBP report aggravation of symptoms during sitting and standing. Impaired motor control in NSCLBP, associated with sitting and standing postures nearer the end range of spinal motion, may be a contributing factor. Rehabilitation improving neutral (midrange) spinal position control is advocated. Postural and motor control alterations vary in different NSCLBP subgroups, potentially requiring specific postural interventions. There is limited evidence on whether subgroup differences exist when performing neutral spine position tasks. METHODS: Ninety patients with NSCLBP and 35 asymptomatic controls were recruited. Two blinded practitioners classified NSCLBP into subgroups of active extension pattern and flexion pattern. Participants were assisted into neutral spine position and asked to reproduce this position 4 times. Absolute, variable, and constant errors were calculated. Three-dimensional thoracic and lumbar kinematics quantified the repositioning accuracy and surface electromyography assessed back and abdominal muscles activity bilaterally. RESULTS: Irrespective of subclassification, patients with NSCLBP produced significantly greater error magnitude and variability than the asymptomatic controls, but subgroup differences were detected in the error direction. Subgroup differences in the trunk muscle activity were not consistently identified. Although both subgroups produced significantly higher abdominal activity, subclassification revealed difference in superficial multifidus activity during standing, with flexion pattern producing significantly greater activity than the asymptomatic controls. CONCLUSION: Subgroups of NSCLBP had similar neutral spinal position deficits regarding error magnitude and variability, but subclassification revealed clear subgroup differences in the direction of the deficit. The trunk muscle activation was shown to be largely nondiscriminatory between subgroups, with the exception of superficial lumbar multifidus.

Preliminary study: reliability of the spinal wheel. A novel device to measure spinal postures applied to sitting and standing.

Postural re-education is an integral part of physiotherapy management in patients with back pain. Although the link between posture and back pain is largely unknown, postural re-education is performed on the premise of optimizing spinal alignment to minimize stresses on the passive structures of the spine, to facilitate optimal muscular support and thus to prevent possible damage and further pain. A reliable and clinically meaningful measurement of spinal postures to monitor such interventions remains challenging. This study evaluated within-day (intra-tester, inter-tester) and between-day (test-retest) reliability of a novel spinal wheel device measuring thoracic and lumbar postures during sitting and standing. 17 healthy volunteers (age 39.5 +/- 5.4, BMI 25 +/- 9.2; 9 males) were measured three times, by three testers, on two separate occasions (1 week apart). The angular change between C7 and T12 and between T12 and S1 provided thoracic and lumbar curvatures, respectively. Intra-class correlation coefficient (ICC) with 95% confidence intervals and typical error were calculated. Excellent reliability was demonstrated with intra-tester ICCs between 0.947 and 0.980 and typical error between 1.7 degrees and 3.7 degrees and inter-tester ICCs between 0.949 and 0.986 and typical error between 2.0 degrees and 4.7 degrees. Test-retest reliability was high with ICCs 0.719-0.908 and typical error between 4.0 degrees and 7.4 degrees. In conclusion, the spinal wheel demonstrated excellent within-day and high between-day reliability. The device may be used in conjunction with 2D camcorder to provide clinically useful visual evaluation of postures for assessment, intervention monitoring, and feedback during postural re-education.