Unsupported Sitting Research Articles

Development of autonomic heart rate modulations during childhood and adolescence

Autonomic control of heart rate is well known in adult subjects, but limited data are available on the development of the heart rate control during childhood and adolescence. Continuous 12-lead electrocardiograms were recorded in 1045 healthy children and adolescents (550 females) aged 4 to 19 years during postural manoeuvres involving repeated 10-min supine, unsupported sitting, and unsupported standing positions. In each position, heart rate was measured, and heart rate variability indices were evaluated (SDNN, RMSSD, and high (HF) and low (LF) frequency components were obtained). Quasi-normalized HF frequency components were defined as qnHF = HF/(HF + LF). These measurements were, among others, related to age using linear regressions. In supine position, heart rate decreases per year of age were significant in both sexes but lower in females than in males. In standing position, these decreases per year of age were substantially lowered. RMSSD and qnHF indices were independent of age in supine position but significantly decreased with age in sitting and standing positions. Correspondingly, LF/HF proportions showed steep increases with age in sitting and standing positions but not in the supine position. The study suggests that baseline supine parasympathetic influence shows little developmental changes during childhood and adolescence but that in young children, sympathetic branch is less responsive to vagal influence. While vagal influences modulate cardiac periods in young and older children equally, they are less able to suppress the sympathetic influence in younger children.

Gender differences in neck muscle activity during near-maximum forward head flexion while using smartphones with varied postures

Women frequently express heightened neck discomfort even though they exhibit smaller neck flexion (NF) during smartphone use. Differences in natural posture while using smartphones may result in varying muscle activation patterns between genders. However, no study focused on this issue. This study investigated the influence of gender on neck muscle activity and NF when using smartphones, ranging from slight (20°) to nearly maximal forward head flexion, across different postures. We analyzed smartphone usage patterns in 16 men and 16 women and examined these behaviors across different scenarios: standing, supported sitting, and unsupported sitting, at 20°, 30°, 40°, and the maximum head angles. During data collection, muscle activity was measured, expressed as a percentage of the maximum voluntary contraction (%MVC), in the cervical erector spinae (CES) and upper trapezius (UTZ), along with NF. Results show significant influences of gender, head angle, and posture on all measures, with notable interactions among these variables. Women displayed higher muscle activities in CES and UTZ, yet exhibited lesser NF, while using smartphones in both standing (12.3%MVC, 10.7% MVC, and 69.0°, respectively) and unsupported sitting (10.8%MVC, 12.3%MVC, and 71.8°, respectively) compared to men (standing: 9.5%MVC, 8.8%MVC, and 76.1°; unsupported sitting: 9.7%MVC, 10.8%MVC, and 76.1°). This study provides a potential rationale for gender-related disparities in injury outcomes, emphasizing that women experience higher neck and shoulder discomfort level, despite their smaller NF during smartphone use, as found in previous research. Additionally, the cervical flexion-relaxation phenomenon may occur when the head angle exceeded 40°. The near-maximum head angle during smartphone use might induce the cervical flexion-relaxation phenomenon, potentially aggravating neck issues. We recommend limiting smartphone usage postures that exceed the near-maximum head angle, as they are commonly adopted by individuals in the daily smartphone activities.

Pain-free bite force in a healthy population: Within-session test-retest reliability in different sitting positions.

Pain-free bite force (PFBF) is a promising measure to evaluate bite function in temporomandibular disorders (TMDs), yet the reliability of the measure is unknown. Establish the (1) within-session test-retest reliability of PFBF in a healthy population for a single and mean of three trials in supported and unsupported sitting; (2) standard error of measurement (SEM) and minimal detectable change (MDC). Thirty healthy participants (n = 15 female, mean [SD] age = 34.4 [11.0] years) completed two sessions (30-60 min apart) comprising three PFBF trials on each side, in both supported and unsupported sitting, to provide data for 60 (30 participants × two sides) test-retest assessments. Test-retest reliability for the first trial and mean of three trials in each position were determined using intraclass correlation coefficients (ICCs), before calculating the corresponding SEM and MDC for males (M) and females (F) respectively. Within-session reliability was considered excellent for a single trial in supported sitting (ICC = 0.85; SEM M/F = 99/84 N; MDC M/F = 275/232 N) and unsupported sitting (ICC = 0.91; SEM M/F = 72/59 N, MDC M/F = 200/163 N), and for a mean of three trials in supported sitting (ICC = 0.89; SEM M/F = 66/79 N, MDC M/F = 182/220 N) and unsupported sitting (ICC = 0.92; SEM M/F = 64/59 N, MDC M/F = 177/164 N). Single and a mean of three trials in supported and unsupported sitting appear reliable methods to measure PFBF in a healthy population. Testing PFBF using a mean of three trials in unsupported sitting appears superior over other methods though due to higher test-retest reliability, and lower SEM and MDC. Future studies should examine the reliability of PFBF in TMD populations.

Quantifying unsupported sitting posture impairments in humans with cervical spinal cord injury using a head-mounted IMU sensor.

Cross-sectional study. To evaluate unsupported sitting posture impairments and identify postural regulatory strategies in cervical spinal cord injury (cSCI) participants via a head-mounted IMU sensor. A research lab in the United States of America. cSCI participants and controls maintained postural stability during unsupported sitting with eyes either open or closed. The head-mounted IMU sensor recorded accelerometer data to calculate cumulative sway motion. The postural regulatory strategy was analyzed by assessing the normalized power spectral density (PSD) in four frequency bands: 0-0.1 Hz (visual regulation), 0.1-0.5 Hz (vestibular regulation), 0.5-1 Hz (cerebellar regulation), and >1 Hz (proprioception and muscle control). Significant increases in postural sway were observed in cSCI participants compared to controls during unsupported sitting. For cSCI participants, normalized PSD significantly increased in the low-frequency bands (0-0.1 Hz and 0.1-0.5 Hz) but decreased in the high-frequency band (>1 Hz) compared to controls. cSCI participants were more reliant on visual and vestibular systems for sitting balance, while depending less on proprioception and muscle control compared to controls. These findings suggest that the altered postural regulatory strategy is ineffective in maintaining postural stability during unsupported sitting, emphasizing the importance of proprioception and muscle control for seated postural stability in cSCI participants.

Neck and shoulder strains under various head flexing positions while standing and sitting with and without back support for male and female smartphone users

This study recruited 30 young participants (15 men and 15 women) to examine the smartphone usage patterns in three postures (standing, supported sitting, and unsupported sitting) and at five head angle (HA) positions (0°-40°). Cervical erector spinae (CES) and upper trapezius (UTZ) muscle activity, neck flexion (NF), gaze angle (GA), viewing distance (VD), and discomfort scores were collected. Results showed that HA and posture almost affected all responses, while CES muscle activity, NF, and VD differed between sexes. Strain in the neck and shoulder region increased with HA increase. Particularly, when the HA exceeded 20°, the discomfort scores considerably increased. Unsupported sitting should be avoided during smartphone use because of relatively poor responses in all variables. However, both standing and supported sitting have their respective benefits. Sex-related differences were typically observed in the standing position, with women tending to have lower NF but higher CES muscle activity compared with men. Practitioner summary: Although smartphones have become daily necessities, the overall quantitative neck and shoulder strain of using smartphones in different postures is rarely evaluated. We suggest that maintaining the HA within 20° is recommended because of relatively low load on the neck and shoulders. An unsupported sitting should be avoided during smartphone use.

Reliability and validity of the T-shirt test for the assessment of unsupported sitting in manual wheelchair users with spinal cord injury.

This study aimed to evaluate the validity and reliability of the T-shirt test (TST) in assessing sitting stability under three thigh support conditions and with timed outcomes derived in six ways among individuals with a spinal cord injury (SCI). The TST was performed five times under three thigh support conditions (85%, 55% and 25% of total thigh length) in two evaluations spaced between 7-14 days. For each thigh condition, six different outcomes were derived (average or best time from 2, 3, and 5 trial). All outcomes derivation showed excellent reliability on test day (intraclass correlation coefficient; ICC ≥ 0.997) and excellent test-retest reliability (ICC ≥ 0.874) for each thigh support condition. The TST showed high inverse correlations with the Spinal Cord Independence Measure III (SCIM)-mobility score for all outcomes and support conditions (ρ≥-0.706), except for Best-5; moderate inverse correlations with total SCIM-total scores for most outcome derivations and support conditions (ρ≥-0.636); and a moderate inverse correlation with confidence and capacity domains of Wheelchair Skills Test-Questionnaire for most outcome derivation and support conditions (ρ≥-0.504). The TST could discriminate cervical from high and low thoracic levels of injuries under minimal thigh support condition. Overall, all the TST-derived outcomes and support conditions showed adequate validity and test-retest reliability, but Best-5 had inconsistency. Under the minimal thigh support condition, all outcome derivations except Best-3 could discriminate cervical from other injury-level groups. Although all outcome derivations and thigh support conditions provided reliable results, we recommend using the average of 3 trials under the maximal thigh support condition.

Walking status and spinopelvic parameters in young children with achondroplasia: 10-year follow-up.

Thoracolumbar kyphosis (TLK) is common in children with achondroplasia and resolves in 90% by 10years of age. Our purpose was to describe the natural progression of TLK in a cohort of pre-walking children with achondroplasia. A single-center, retrospective review identified 62 children (32 male, 30 female) with achondroplasia. Clinical information and sagittal spinopelvic parameters were collected. The children were divided into positive pelvic tilt (PT) and negative PT. All parents were routinely counseled about unsupported sitting. Spontaneous resolution rate was 64.5% at 1-year post-walking, 74.2% at 5years of age, and 88.7% at 10years of age. None of the children required posterior spinal decompression and fusion for progressive deformity or symptomatic spinal stenosis. At 1-year post-walking, the negative PT group had a higher sacral slope (p = 0.006), higher lumbar lordosis (p < 0.001), and lower pelvic incidence (p < 0.001). This relationship remained constant up to 10years of age, and there was no association with TLK. In this largest series to date, spontaneous resolution of TLK in children with achondroplasia was 64.5% at 1-year post-walking, 74.2% at 5years of age, and 88.7% in children followed to 10years of age. With early identification and regular follow-up with patient education, no patient in this series required treatment or developed symptomatic spinal stenosis. While not predictive of resolution of TLK, the dichotomous presentation of PT in young children with achondroplasia persists at 5 and 10years of age and reliably predicts the spinopelvic parameters. III-retrospective comparative study.

Sitting And Standing Balance Assessment Tools In Patients With Spinal Cord Injury: A Systematic Review

Background: The effectiveness of interventions depend on utility of a specific common set of clinical tools that has ability to assess important clinical outcomes.&#x0D; Objective: To identify clinical assessment tools for assessing unsupported sitting and standing balance in SCI population.&#x0D; Methods: PubMed access provided articles with key words “spinal cord injury,” and “balance assessment”. Studies describing measurement of balance in subjects with SCI, were included.&#x0D; Results: After thorough screening 9 articles showed : 3 clinical scales assessed sitting balance and seated postural control, 1 clinical scale assessed standing function, 4 scale assessed functional mobility, static and dynamic walking balance; one scale assessed risk of fall during walking and 3 sensor based tools were identified.&#x0D; Conclusion: It was observed that majority studies showed assessment of standing and walking balance; and both clinical performance based and sensor based tools were used for balance assessment.&#x0D; Key words: balance assessment, spinal cord injury.

Field Study of Postural Characteristics of Standing and Seated Smartphone Use.

Prior investigations have been primarily conducted in a laboratory to examine the effects of the smartphone use on the neck and head positions, whether these results are applicable to actual conditions is still unknown. This field survey thus analyzed the neck flexion (NF), head flexion (HF), gaze angle (GA), and viewing distance (VD) of smartphone users in public areas in Taipei, Taiwan. Six hundred smartphone users (300 men and 300 women) were photographed sagittally in standing, supported sitting, or unsupported sitting postures while using a smartphone. Results showed that women had significantly less NF and HF and shorter VDs than male users. Regardless of gender, higher NF was observed for standing than for sitting. Women had similar NF and HF while sitting supported and unsupported, but both were significantly lower than those while standing. By contrast, male users had higher NF and HF during unsupported sitting than during supported sitting. The NF (45°–50°) was much greater than the recommended maximum safe NF of 15°. Women may be at higher risk of visual strain because of shorter VD.

Quadriceps muscle strength in patients with knee osteoarthritis

Osteoarthritis is degenerative disease mainly affects weight bearing joints. Usually patients with knee osteoarthritis have pain, stiffness and functional limitation. This functional limitation might be caused by muscle weakness specially in quadriceps muscle. The hand held dynamometer is widely used in the clinical setting as a valid and reliable outcome measure, which used in this study to measure quadriceps muscle strength during supported and unsupported sitting. It can be concluded that subjects produce greater force in supported sitting than in unsupported sitting.

Influences of continuous sitting and psychosocial stress on low back kinematics, kinetics, discomfort, and localized muscle fatigue during unsupported sitting activities

Continuous seated postures may increase the risk of adverse health outcomes such as low-back pain, and this risk may be influenced by several modifying factors. In the present study, we aimed to quantify the effects of continuous sitting and psychosocial stress under an unsupported sitting condition. Fourteen participants completed continuous, 40 min. periods of computer-based tasks, involving both low and higher levels of psychosocial stress, while using a laptop computer without a desk. Continuous sitting significantly increased perceived discomfort (particularly in the upper and lower back), trunk flexion and metrics of localized muscle fatigue. A higher level of psychosocial stress increased estimated lumbosacral compression forces (by ∼12%). Only weak correlations were found between subjective and objective measures, while various fatigue metrics showed a good level of correspondence with each other. These results could support the future evaluation or design of diverse seated work configurations.Practitioner Summary: Continuous, 40 min. periods of unsupported sitting had broad impacts on subjective and objective outcomes, including discomfort, postures, spine loads and localized muscle fatigue, while psychosocial stress only had a substantial influence on lumbosacral compression. These results extend our understanding of sitting behaviors and provide information for designing future sitting environments.

Energy expenditure and muscle activity during lying, sitting, standing, and walking in people with motor-incomplete spinal cord injury.

Cross-sectional exploratory study. To determine oxygen uptake (VO2), energy expenditure (EE), and muscle activity (MA) during lying (rest), sitting, standing, and walking among ambulatory individuals with spinal cord Injury (SCI) and to compare VO2, EE, and MA between individuals with different levels of ambulation. Rehabilitation institution with a spinal cord injury unit. A total of 22 adults with motor-incomplete SCI, ten in a low-ambulation group (non-functional or household walker) and 12 in a high-ambulation group (community or normal walker). VO2 was measured using indirect calorimetry. EE was expressed in metabolic equivalent of task (MET). MA was measured using a wireless surface electromyography device. Mean VO2 was 3.19 ml/kg/min. During lying and sitting, EE was below 1.5 METs for all participants. During standing, three participants of the low-ambulation group and none in the high-ambulation group showed MET values of >1.5. In the walking condition, all participants showed MET values above 1.5. MA during stance was higher compared to the sitting condition and significantly higher in the low-ambulation group compared to the high-ambulation group. Lying, supported- and unsupported sitting, without moving, appear to be sedentary behaviors for ambulatory individuals with a motor-incomplete SCI (MET values of <1.5 and a lack of MA). Walking, but not standing, is a moderate physical activity (>1.5 METs), which can be used by all individuals with motor-incomplete SCI to interrupt sedentary behavior.

Impact of patient position on coronal Cobb angle measurement in non-ambulatory myelodysplastic patients.

The purpose of this study was to assess the impact of patient position on the magnitude of the coronal Cobb angle measurements in relation to the change of position using plain radiograph on non-ambulatory children with myelodysplasia. Whole-spine radiographs with the patient sitting generally are preferred for the diagnosis and monitoring of progression of scoliosis in neuromuscular patients. Supine, supine traction, and sitting push-up positions have been used as substitutes, although there is no general consensus validating if these positions correlate with the sitting position. The magnitude of the Cobb angles in neuromuscular scoliosis may vary greatly depending on the position of the patient. Radiographs of 39 myelodysplastic, non-ambulatory children were evaluated to assess the impact of change in positions (unsupported sitting, sitting push-up, supine, and supine traction) on coronal Cobb angle measurement using plain whole-spine radiographs. The mean difference in thoracic Cobb angle measurements between sitting and all other positions ranged from 6° to 12°. At the lumbar level, the Cobb angles ranged from 12° to 16°. Statistically significant differences in the Cobb angle measurements were identified between plain radiographs of the whole spine with the patient in the unsupported sitting position compared to sitting push-up, supine, and supine traction positions. The data support that the magnitude of the Cobb angles in neuromuscular scoliosis varies greatly depending on the position of the patient. III.

Effect of voluntary teeth clenching and sitting posture on maximal static force of limb muscles.

People clench their teeth to activate facial, neck and abdominal muscles when they need to generate heavy muscle force against large resistance like lifting heavy objects, in order to gain possible ergogenic advantage. These are termed as remote voluntary contractions. Aim of this study was to evaluate the effect of voluntary teeth clenching on maximal voluntary contraction of extensors and flexors of the knee, shoulder and elbow joints of the dominant side during slouch and unsupported upright sitting. One hundred healthy young male adults (mean age 23.3 years) participated in this study. Maximal voluntary contraction was measured using a hand-held dynamometer. Jaw clenching caused different ergogenic effect during slouch versus unsupported sitting postures. The data revealed that during unsupported upright sitting, the effect of jaw clenching consistently results in larger maximal voluntary contraction of both extensor and flexor muscles of all the three studied joints. However, during slouch sitting, only the maximal voluntary contraction of extensors of elbow and flexors of knee were larger with clenched teeth position. Jaw clenching can affect the maximal voluntary contraction of limb muscles which is sitting posture dependent. Jaw clenching can consistently facilitate certain muscles of the upper and lower limbs to generate greater force production during upright sitting.

Clinical Instruments for Measuring Unsupported Sitting Balance in Subjects with Spinal Cord Injury: A Systematic Review.

Background: Evidence of intervention effectiveness depends on, among other things, the use of a common set of valid and reliable measures that are responsive to change and reflect clinically important outcomes. Objective: To identify clinical assessment instruments with properties for measuring unsupported sitting balance in subjects with spinal cord injury (SCI). Methods: Bibliographic databases (PubMed, Science Direct, CINAHL, and Central) were searched for articles with the key words "spinal cord injury," "unsupported sitting," and "outcome assessment" in combination with a specific methodological search filter for each database. Studies describing the application of any assessment instrument for measuring unsupported sitting balance in subjects with SCI, which had the evaluation of any measurement property, were included in the review. Publication details, measure's name, setting, summary statistics, measurement properties (reliability, validity, responsiveness), and statistical significance (p values) were extracted. Results: Eight hundred forty publications were identified; 8 articles were included in the systematic review. Twelve instruments were identified and analyzed, showing limited and incomplete measurement properties. Among them, 10 addressed activity, 1 addressed structures/body functions, and 1 addressed both activity and structures/body functions domains of the International Classification of Functioning, Disability and Health (ICF). Conclusion: Based mainly on the measurement properties and the development of the instruments analyzed in this review, the Sitting Balance Measure, the Trunk Control Test, and the Set of Assessment Tools for Measuring Unsupported Sitting seem to be the most appropriate and recommended measures to assess unsupported sitting in subjects with SCI.

Type and Timing of Rehabilitation Following Acute and Subacute Spinal Cord Injury: A Systematic Review.

Objectives:The objective of this study was to conduct a systematic review of the literature to address the following clinical questions: In adult patients with acute and subacute complete or incomplete traumatic SCI, (1) does the time interval between injury and commencing rehabilitation affect outcome?; (2) what is the comparative effectiveness of different rehabilitation strategies, including different intensities and durations of treatment?; (3) are there patient or injury characteristics that affect the efficacy of rehabilitation?; and (4) what is the cost-effectiveness of various rehabilitation strategies?Methods:A systematic search was conducted for literature published through March 31, 2015 that evaluated rehabilitation strategies in adults with acute or subacute traumatic SCI at any level. Studies were critically appraised individually and the overall strength of evidence was evaluated using methods proposed by the GRADE (Grades of Recommendation Assessment, Development and Evaluation) working group.Results:The search strategy yielded 384 articles, 19 of which met our inclusion criteria. Based on our results, there was no difference between body weight–supported treadmill training and conventional rehabilitation with respect to improvements in Functional Independence Measure (FIM) Locomotor score, Lower Extremity Motor Scores, the distance walked in 6 minutes or gait velocity over 15.2 m. Functional electrical therapy resulted in slightly better FIM Motor, FIM Self-Care, and Spinal Cord Independence Measure Self-Care subscores compared with conventional occupational therapy. Comparisons using the Toronto Rehabilitation Institute Hand Function Test demonstrated no differences between groups in 7 of 9 domains. There were no clinically important differences in Maximal Lean Test, Maximal Sidewards Reach Test, T-shirt Test, or the Canadian Occupational Performance Measure between unsupported sitting training and standard in-patient rehabilitation.Conclusion:The current evidence base for rehabilitation following acute and subacute spinal cord injury is limited. Methodological challenges have contributed to this and further research is still needed.

Postural regulatory strategies during quiet sitting are affected in individuals with thoracic spinal cord injury

Thoracic spinal cord injury (SCI) can have significant negative consequences, which can affect the ability to maintain unsupported sitting. The objectives of this study were to compare postural control of individuals with high- and low-thoracic SCI to able-bodied people and evaluate the effects of upper-limb support on postural control during quiet sitting. Twenty-five individuals were recruited into: (a) high-thoracic SCI; (b) low-thoracic SCI; and (c) able-body subgroups. Participants were seated and asked to maintain a steady balance in the following postures: (1) both hands resting on thighs; (2) both arms crossed over the chest; and (3) both arms extended. Center of pressure (COP) fluctuations were evaluated to compare postural performance between groups and different postures. Results showed that individuals with high- and low-thoracic SCI swayed more compared to the able-bodied group regardless of upper-limb support. No differences between the two SCI groups were observed, but the neurological level of injury was correlated to postural performance implying that those with higher injuries swayed more and faster. Unsupported sitting was more unstable in comparison to supported sitting posture, especially in the anterior-posterior direction. The velocity of postural sway was not different between groups, but the results suggest that postural regulation had unique effect during different postures in different groups. These results imply reduced postural stability after thoracic SCI. Overall, the way individuals with high-thoracic SCI achieved stability was different from that of individuals with low-thoracic SCI, suggesting different postural regulation strategies.

Increased energy expenditure during posture maintenance and exercise in early Parkinson disease.

BackgroundEvidence for the effects of Parkinson disease on energy expenditure is incomplete and contradictory. A number of studies showed increased resting energy expenditure among patients with Parkinson disease whereas others did not. It was hypothesized that energy expenditure increases during exercise, based on findings in patients with a variable regime of anti‐parkinsonian therapies and at different stages of the disease. However, energy expenditure during posture maintenance has been neglected. To better understand these issues, we studied energy expenditure in a homogenous population of Parkinson patients in an early stage of the disease and different states of activity.MethodsOxygen consumption was assessed in a group of 10 males with early Parkinson disease without dopaminergic treatment and controls matched for age and body composition. Oxygen consumption was measured at rest, during trunk unsupported sitting, and during exercise at different intensities (unloaded and loaded cycling).ResultsResting energy expenditure was similar between groups. Higher energy consumption was observed during maintenance of trunk posture at rest and during light intensity aerobic exercise (P < .05 for all conditions). The increment in energy expenditure associated with increased physical demand tended to be steeper in Parkinson disease.ConclusionResting energy expenditure is normal in Parkinson disease. However, energy expenditure increases during physical activity and even during the maintenance of unsupported posture among patients with Parkinson disease.

Postural Cueing to Increase Lumbar Lordosis Increases Lumbar Multifidus Activation During Trunk Stabilization Exercises: Electromyographic Assessment Using Intramuscular Electrodes.

Controlled laboratory study, repeated-measures design. Diminished multifidus activation and cross-sectional area are frequent findings in persons with low back pain. Increasing lumbar lordosis has been shown to increase activation of the multifidus with a minimal increase in activation of the long global extensors during unsupported sitting. To examine the influence of postural cueing to increase lumbar lordosis on lumbar extensor activation during trunk stabilization exercises. Thirteen asymptomatic participants (9 male, 4 female) were instructed to perform 6 trunk stabilization exercises using a neutral position and increasing lumbar lordosis. Electrical activity of the deep multifidus and longissimus thoracis was recorded using fine-wire intramuscular electrodes. The mean root-mean-square of the electromyography (EMG) signal obtained during each exercise was normalized to a maximum voluntary isometric contraction (MVIC). A 2-way, repeated-measures analysis of variance (posture by exercise) was performed for each muscle. When averaged across the 6 exercises, postural cueing to increase lumbar lordosis resulted in greater multifidus EMG activity compared to performing the exercises in a neutral posture (35.3% ± 15.1% versus 29.5% ± 11.2% MVIC). No significant increase in longissimus thoracis EMG activity was observed when exercising with cueing to increase lumbar lordosis. This study suggests that postural cueing to increase lumbar lordosis during trunk stabilization exercises may better promote multifidus activation than traditional stabilization exercises alone. Future studies are needed to determine whether increasing lumbar lordosis improves multifidus activation in persons with low back pain.

15. Comparison of EMG activity during stable and unstable standing and sitting in patients with primary orthostatic tremor

Background Primary orthostatic tremor (OT) is characterised by 14–16 Hz leg and truncal tremor when standing, accompanied by an intense sense of unsteadiness. Both are relieved by sitting or walking. Methods To evaluate whether OT pathogenesis is related to stance or isometric muscle contraction, and whether normal subjects develop OT when feeling unsteady, we recorded electromyographic (EMG) activity in leg and paraspinal muscles of 9 OT and 8 controls during 5 conditions: quiet standing; unsteady standing; supported standing; supported sitting; and unsupported sitting. A handheld potentiometer was used to indicate levels of subjective unsteadiness. Spectral analysis was used to quantify OTP (OT Power, mean EMG power between 13–18 Hz) and OTPR (ratio between OT power and mean EMG between 2–25 Hz). Results OTP was significantly higher in patients compared with controls during quiet and unsteady standing. In patients, OTP was attentuated during supported standing without significant changes in OTPR. During unsupported sitting, 33% of patients developed typical OT EMG activity, 22% demonstrated poorly formed OT bursting and in the remaining 45% there was not tremor. No controls developed OT. Comparing supported standing with unsupported sitting in patients, OTP was similar during both, but OPTR was significantly higher during supported standing versus unsupported sitting, suggesting a disproportionate increase in mean non-tremor locked EMG during unsupported sitting. Conclusion OT is primarily elicited by standing rather than isometric contraction. OTPR remains similar when the requirement of balance maintenance was alleviated. OT was seen in only some patients during non-standing posture maintenance requiring isometric contraction. Only one control developed poorly formed OT isolated to the leg muscles during Unsteady Standing, arguing against OT being a physiological response to unsteadiness.