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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed February 25, 2010). PDF text: 80 p. : ill. ; 206 K. UMI publication number: AAT 3386551. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed February 25, 2010). PDF text: xi, 257 p. : ill. ; 4 Mb. UMI publication number: AAT 3386549. Includes bibliographical references. Also available in microfilm and microfiche formats.

The main objective of this study was to investigate factors on dynamic load-deflection properties of seat foundations and pressure distributions between a human subject and a seat. The study was divided into three major parts: impact loads on seat foundations, factors on dynamic load-deflection properties of seat foundations, and body mass transfer during human subjects’ stand-to-sit movement. Results of this study indicated that the normal sitting-down speed averaged 16.3 cm/s, and hard sitting-down speed varied from 71 to 84 cm/s which can be considered as a free human body drop speed for seat foundations with panel base and foam, flat spring base and foam. Recorded peak sitting forces in terms of participants’ body weights averaged 100% and 247% for normal and hard sitting-down motions, respectively. Sitting ride, seat foundation stiffness and maximum pressure under buttocks were considered as parameters to describe human subjects’ sitting experience. Statistical analysis indicated that body weight and foam stiffness had no significant effect on seat foundation stiffness in most case. In general, the stiffness of seat foundation decreased significantly as foam thickness increased from 5 to 10 cm, but the decrease was not significant as foam thickness increased from 10 to 20 cm. For sitting ride, curved spring seat foundation had significantly highest sitting ride, followed by flat spring base, then webbing base and then panel base. Seat base, foam stiffness, foam thickness and human body weight had significant effect on maximum pressure under buttocks, but significant difference dependent on treatment combination. In sitting-down motion, it could be concluded that hard sitting-down time for seat foundation of CF and FF was longer than normal sitting-down, but for seat foundation of PF and P, hard sitting-down time was shorter than normal sitting-down. There are two main phases in sitting-down motion: propulsive impulse and braking impulse. In normal sitting-down motion, averaging mean force weight percentage (FWP) on seat yielded 3% of body weight while averaging mean FWP on feet yield 97% body weight, which means, in normal sitting-down motion, braking impulse occurred before body touching the seat foundation.

General body discomfort increases over time during prolonged sitting and it is typically accepted that no single posture can be comfortably maintained for long periods. Despite this knowledge, workplace exposure to prolonged sitting is very common. Sedentary occupations that expose workers to prolonged sitting are associated with an increased risk of developing low back pain (LBP), disc degeneration and lumbar disc herniation. Given the prevalence of occupations with a large amount of seated work and the propensity for a dose-response relationship between sitting and LBP, refining our understanding of the biomechanics of the lumbar spine during sitting is important. Sitting imposes a flexed posture that, when held for a prolonged period of time, may cause detrimental effects on the tissues of the spine. While sitting is typically viewed as a sedentary and constrained task, several researchers have identified the importance of investigating movement during prolonged sitting. The studies in this thesis were designed to address the following two global questions: (1) How do the lumbar spine and pelvis move during sitting? (2) Can lumbar spine movement and postures explain LBP and injury associated with prolonged sitting? The first study (Study 1) examined static X-ray images of the lower lumbo-sacral spine in a range of standing and seated postures to measure the intervertebral joint angles that contribute to spine flexion. The main finding was that the lower lumbo-sacral joints approach their total range of motion in seated postures. This suggests that there could be increased loading of the passive tissues surrounding the lower lumbo-sacral intervertebral joints, contributing to low back pain and/or injury from prolonged sitting. Study 2 compared external spine angles measured using accelerometers from L3 to the sacrum with corresponding angles measured from X-ray images. While the external and internal angles did not match, the accelerometers were sensitive to changes in seated lumbar posture and were consistent with measurements made using similar technology in other studies. This study also provided an in-depth analysis of the current methods for data treatment and how these methods affect the outcomes. A further study (Study 3) employed videofluoroscopy to investigate the dynamic rotational kinematics of the intervertebral joints of the lumbo-sacral spine in a seated slouching motion in order to determine a sequence of vertebral motion. The pelvis did not initiate the slouching motion and a disordered sequence of vertebral rotation was observed at the initiation of the movement. Individuals performed the slouching movement using a number of different motion strategies that influenced the IVJ angles attained during the slouching motion. From the results of Study 1, it would appear as though the lowest lumbar intervertebral joint (L5/S1) contribute the most to lumbo-sacral flexion in upright sitting, as it is at approximately 60% of its end range in this posture. However, the results from Study 3 suggest that there is no consistent sequence of intervertebral joint rotation when flexing the spine from upright to slouched sitting. When moving from standing to sitting, lumbar spine flexion primarily occurs at the lowest joint (i.e. L5/S1); however, a disordered sequence of vertebral motion the different motion patterns observed may indicate that different joints approach their end range before the completion of the slouching movement. In order to understand the biomechanical factors associated with sitting induced low back pain, Study 4 examined the postural responses and pain scores of low back pain sufferers compared with asymptomatic individuals during prolonged seated work. The distinguishing factor between these two groups was their respective time-varying seated lumbar spine movement patterns. Low back pain sufferers moved more than asymptomatic individuals did during 90 minutes of seated work and they reported increased low back pain over time. Frequent shifts in lumbar spine posture could be a mechanism for redistributing the load to different tissues of the spine, particularly if some tissues are more vulnerable than others. However, increased movement did not completely eliminate pain in individuals with pre-existing LBP. The LBP sufferers’ seated spine movements increased in frequency and amplitude as time passed. It is likely that these movements became more difficult to properly control because LBP patients may lack proper lumbar spine postural control. The results of this study highlight the fact that short duration investigations of seated postures do not accurately represent the biological responses to prolonged exposure. Individuals with sitting-induced low back pain and those without pain differ in how they move during seated work and this will have different impacts on the tissues of the lumbar spine. A tissue-based rational for the detrimental effects on the spinal joint of prolonged sitting was examined in Study 5 using an in vitro spine model and simulated spine motion patterns documented in vivo from Study 4. The static protocol simulated 2 hours of sitting in one posture. The shift protocol simulated infrequent but large changes in posture, similar to the seated movements observed in a group of LBP sufferers. The fidget protocol replicated small, frequent movements about one posture, demonstrated by a group of asymptomatic individuals. Regardless of the amount of spine movement around one posture, all specimens lost a substantial amount of disc height. Furthermore, the passive range of motion of a joint changed substantially after 2 hours of simulated sitting. Specifically, there were step-like regions of reduced stiffness throughout the passive range of motion particularly around the adopted “seated flexion” angle. However, small movements around a posture (i.e. fidgeting) may mitigate the changes in the passive stiffness in around the seated flexion angle. The load transferred through the joint during the 2-hour test was varied either by changing postures (i.e. shifting) or by a potential creep mechanism (i.e. maintaining one static posture). Fidgeting appeared to reduce the variation of load carriage through the joint and may lead to a more uniform increase in stiffness across the entire passive range of motion. These changes in passive joint mechanics could have greater consequences for a low back pain population who may be more susceptible to abnormal muscular control and clinical instability. Nevertheless, the observed disc height loss and changes in joint mechanics may help explain the increased risk of developing disc herniation and degeneration if exposure to sitting is cumulative over many days, months and years. In summary, this work has highlighted that seated postures place the joints of the lumbar spine towards their end range of motion, which is considered to be risky for pain/injury in a number of tissue sources. In-depth analyses of both internal and external measurements of spine postures identified different seated motion patterns and self-selected seated postures that may increase the risk for developing LBP. The model of seated LBP/discomfort development used in this thesis provided evidence that large lumbar spine movements do not reduce pain in individuals with pre-existing LBP. Tissue-based evidence demonstrated that 2 hours of sitting substantially affects IVJ mechanics and may help explain the increased risk of developing disc herniation and degeneration if exposure to sitting is cumulative over many days, months and years. The information obtained from this thesis will help develop and refine interventions in the workplace to help reduce low back pain during seated work.

General body discomfort increases over time during prolonged sitting and it is typically accepted that no single posture can be comfortably maintained for long periods. Despite this knowledge, workplace exposure to prolonged sitting is very common. Sedentary occupations that expose workers to prolonged sitting are associated with an increased risk of developing low back pain (LBP), disc degeneration and lumbar disc herniation. Given the prevalence of occupations with a large amount of seated work and the propensity for a dose-response relationship between sitting and LBP, refining our understanding of the biomechanics of the lumbar spine during sitting is important. Sitting imposes a flexed posture that, when held for a prolonged period of time, may cause detrimental effects on the tissues of the spine. While sitting is typically viewed as a sedentary and constrained task, several researchers have identified the importance of investigating movement during prolonged sitting. The studies in this thesis were designed to address the following two global questions: (1) How do the lumbar spine and pelvis move during sitting? (2) Can lumbar spine movement and postures explain LBP and injury associated with prolonged sitting? The first study (Study 1) examined static X-ray images of the lower lumbo-sacral spine in a range of standing and seated postures to measure the intervertebral joint angles that contribute to spine flexion. The main finding was that the lower lumbo-sacral joints approach their total range of motion in seated postures. This suggests that there could be increased loading of the passive tissues surrounding the lower lumbo-sacral intervertebral joints, contributing to low back pain and/or injury from prolonged sitting. Study 2 compared external spine angles measured using accelerometers from L3 to the sacrum with corresponding angles measured from X-ray images. While the external and internal angles did not match, the accelerometers were sensitive to changes in seated lumbar posture and were consistent with measurements made using similar technology in other studies. This study also provided an in-depth analysis of the current methods for data treatment and how these methods affect the outcomes. A further study (Study 3) employed videofluoroscopy to investigate the dynamic rotational kinematics of the intervertebral joints of the lumbo-sacral spine in a seated slouching motion in order to determine a sequence of vertebral motion. The pelvis did not initiate the slouching motion and a disordered sequence of vertebral rotation was observed at the initiation of the movement. Individuals performed the slouching movement using a number of different motion strategies that influenced the IVJ angles attained during the slouching motion. From the results of Study 1, it would appear as though the lowest lumbar intervertebral joint (L5/S1) contribute the most to lumbo-sacral flexion in upright sitting, as it is at approximately 60% of its end range in this posture. However, the results from Study 3 suggest that there is no consistent sequence of intervertebral joint rotation when flexing the spine from upright to slouched sitting. When moving from standing to sitting, lumbar spine flexion primarily occurs at the lowest joint (i.e. L5/S1); however, a disordered sequence of vertebral motion the different motion patterns observed may indicate that different joints approach their end range before the completion of the slouching movement. In order to understand the biomechanical factors associated with sitting induced low back pain, Study 4 examined the postural responses and pain scores of low back pain sufferers compared with asymptomatic individuals during prolonged seated work. The distinguishing factor between these two groups was their respective time-varying seated lumbar spine movement patterns. Low back pain sufferers moved more than asymptomatic individuals did during 90 minutes of seated work and they reported increased low back pain over time. Frequent shifts in lumbar spine posture could be a mechanism for redistributing the load to different tissues of the spine, particularly if some tissues are more vulnerable than others. However, increased movement did not completely eliminate pain in individuals with pre-existing LBP. The LBP sufferers’ seated spine movements increased in frequency and amplitude as time passed. It is likely that these movements became more difficult to properly control because LBP patients may lack proper lumbar spine postural control. The results of this study highlight the fact that short duration investigations of seated postures do not accurately represent the biological responses to prolonged exposure. Individuals with sitting-induced low back pain and those without pain differ in how they move during seated work and this will have different impacts on the tissues of the lumbar spine. A tissue-based rational for the detrimental effects on the spinal joint of prolonged sitting was examined in Study 5 using an in vitro spine model and simulated spine motion patterns documented in vivo from Study 4. The static protocol simulated 2 hours of sitting in one posture. The shift protocol simulated infrequent but large changes in posture, similar to the seated movements observed in a group of LBP sufferers. The fidget protocol replicated small, frequent movements about one posture, demonstrated by a group of asymptomatic individuals. Regardless of the amount of spine movement around one posture, all specimens lost a substantial amount of disc height. Furthermore, the passive range of motion of a joint changed substantially after 2 hours of simulated sitting. Specifically, there were step-like regions of reduced stiffness throughout the passive range of motion particularly around the adopted “seated flexion” angle. However, small movements around a posture (i.e. fidgeting) may mitigate the changes in the passive stiffness in around the seated flexion angle. The load transferred through the joint during the 2-hour test was varied either by changing postures (i.e. shifting) or by a potential creep mechanism (i.e. maintaining one static posture). Fidgeting appeared to reduce the variation of load carriage through the joint and may lead to a more uniform increase in stiffness across the entire passive range of motion. These changes in passive joint mechanics could have greater consequences for a low back pain population who may be more susceptible to abnormal muscular control and clinical instability. Nevertheless, the observed disc height loss and changes in joint mechanics may help explain the increased risk of developing disc herniation and degeneration if exposure to sitting is cumulative over many days, months and years. In summary, this work has highlighted that seated postures place the joints of the lumbar spine towards their end range of motion, which is considered to be risky for pain/injury in a number of tissue sources. In-depth analyses of both internal and external measurements of spine postures identified different seated motion patterns and self-selected seated postures that may increase the risk for developing LBP. The model of seated LBP/discomfort development used in this thesis provided evidence that large lumbar spine movements do not reduce pain in individuals with pre-existing LBP. Tissue-based evidence demonstrated that 2 hours of sitting substantially affects IVJ mechanics and may help explain the increased risk of developing disc herniation and degeneration if exposure to sitting is cumulative over many days, months and years. The information obtained from this thesis will help develop and refine interventions in the workplace to help reduce low back pain during seated work.

名古屋大学博士学位論文 学位の種類:博士(リハビリテーション療法学) (課程) 学位授与年月日　平成22年9月30日

Made available in DSpace on 2014-06-11T19:28:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-28Bitstream added on 2014-06-13T19:37:40Z : No. of bitstreams: 1 santos_rm_me_bauru.pdf: 830347 bytes, checksum: e0bae54e1790df70aaa93108fa369c07 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A postura sentada promovo diversas alterações nas estruturas músculo-esquelética, na circulação dos membros inferiores e no conforto dos membros superiores. Tais alterações produzem consequencias no processo de ensino-aprendizagem no âmbito escolar. Esta pesquisa buscou investigar os efeitos do procedimento de Reforço de Verbalização (RV) e Treino de Correspondência (TC) sobre a postura sentada em escolares e sobre seus relatos acerca dos posicionamentos dos pés, coluna lombar, coluna cervical e antebraços em três sequencias (Dizer-Fazer, Fazer-Dizer e Dizer-Fazer-Dizer). Participaram do estudo 9 alunos do 4º ano do ensino fundamental de uma escola pública do estado de São Paulo, com alturas semelhantes, que foram divididos em três grupos: Dizer-Fazer, (DF), Fazer-Dizer, (FD) e Dizer-Fazer-Dizer (DFD) com três alunos em cada grupo. O procedimento experimental compreendeu 4 condições experimentais: Linha de Base 1, Reforço de Verbalização (as respostas verbais corretas emitidas pelos participantes eram consequenciadas positivamente pela pesquisadora), Treino de Correspondência (a emissão das respostas verbais e dos posicionamentos corretos dos participantes eram consequenciados positivamente) e Linha de Base 2. Para verificar a correspondência entre o comportamento verbal e o não-verbal foi analisada a frequencia das respostas verbais corretas apresentadas pelos alunos em relação aos registros dos posicionamentos apresentados em relação a cada segmento corporal selecionado. Durante a Fase RV a frequencia da verbalização correta aumentou para todos os participantes dos três grupos, e os posicionamentos dos segmentos corporais pés e coluna lombar aumentaram para os participantes dos grupos DF e FD. / The sitting posture promotes several changes in the musculoskeletal structures, the movement of the lower limbs and in the comfort of the upper limbs. These effects have consequences in the teaching and learning in schools. This research investigates the effects of the procedure Boost Verbosity (VR) training and correspondence (TC) on sitting posture in children and about his statement regarding the positions of the feet, spine, cervical spine and forearm in three sequences (say-Do, Do-say and Do-Say-Say). Study participants were nine students in the 4th grade of elementary education at a public school in the state of Sao Paulo, with similar heights, which were divided into three groups: Say-Do, (DF), Do-Tell (FD) and Say-Do-Telling (DFD) with three students in each group. The experimental prodedure consisted of four experimental conditions: baseline 1, Strengthening of verbalization (the correct verbal responses issued by the participants were positive consequences for the researcher), Correspondence Training (the emission of verbal responses and the correct positioning of the participants were positive consequences) and Baseline 2. To verify the correspondence between the verbal and nonverbal analyzed the frequency of correct verbal responses made by students in relation to records of the positions presented in relation to each body segment selected. During Phase RV verbalization correct frequency increased for all three groups of participants, and positions of body segments, Iegs and lumbar spine increased for participants in the FD groups. In Phase CT correct verbalization was maintained by all participants of all groups and increased the correct position all body segments and hence the correspondence between the verbal and nonverbal behavior. In LB2 correct verbalization was maintained in all groups and there was a small decrease in matching segments of the cervical spine for all groups and for groups of forearms and DF DFD.

Orientador: Maria Regina Cavalcante / Banca: Luis Carlos Paschoarelli / Banca: Jair Lopes Junior / Resumo: A postura sentada promovo diversas alterações nas estruturas músculo-esquelética, na circulação dos membros inferiores e no conforto dos membros superiores. Tais alterações produzem consequencias no processo de ensino-aprendizagem no âmbito escolar. Esta pesquisa buscou investigar os efeitos do procedimento de Reforço de Verbalização (RV) e Treino de Correspondência (TC) sobre a postura sentada em escolares e sobre seus relatos acerca dos posicionamentos dos pés, coluna lombar, coluna cervical e antebraços em três sequencias (Dizer-Fazer, Fazer-Dizer e Dizer-Fazer-Dizer). Participaram do estudo 9 alunos do 4º ano do ensino fundamental de uma escola pública do estado de São Paulo, com alturas semelhantes, que foram divididos em três grupos: Dizer-Fazer, (DF), Fazer-Dizer, (FD) e Dizer-Fazer-Dizer (DFD) com três alunos em cada grupo. O procedimento experimental compreendeu 4 condições experimentais: Linha de Base 1, Reforço de Verbalização (as respostas verbais corretas emitidas pelos participantes eram consequenciadas positivamente pela pesquisadora), Treino de Correspondência (a emissão das respostas verbais e dos posicionamentos corretos dos participantes eram consequenciados positivamente) e Linha de Base 2. Para verificar a correspondência entre o comportamento verbal e o não-verbal foi analisada a frequencia das respostas verbais corretas apresentadas pelos alunos em relação aos registros dos posicionamentos apresentados em relação a cada segmento corporal selecionado. Durante a Fase RV a frequencia da verbalização correta aumentou para todos os participantes dos três grupos, e os posicionamentos dos segmentos corporais pés e coluna lombar aumentaram para os participantes dos grupos DF e FD. / Abstract: The sitting posture promotes several changes in the musculoskeletal structures, the movement of the lower limbs and in the comfort of the upper limbs. These effects have consequences in the teaching and learning in schools. This research investigates the effects of the procedure Boost Verbosity (VR) training and correspondence (TC) on sitting posture in children and about his statement regarding the positions of the feet, spine, cervical spine and forearm in three sequences (say-Do, Do-say and Do-Say-Say). Study participants were nine students in the 4th grade of elementary education at a public school in the state of Sao Paulo, with similar heights, which were divided into three groups: Say-Do, (DF), Do-Tell (FD) and Say-Do-Telling (DFD) with three students in each group. The experimental prodedure consisted of four experimental conditions: baseline 1, Strengthening of verbalization (the correct verbal responses issued by the participants were positive consequences for the researcher), Correspondence Training (the emission of verbal responses and the correct positioning of the participants were positive consequences) and Baseline 2. To verify the correspondence between the verbal and nonverbal analyzed the frequency of correct verbal responses made by students in relation to records of the positions presented in relation to each body segment selected. During Phase RV verbalization correct frequency increased for all three groups of participants, and positions of body segments, Iegs and lumbar spine increased for participants in the FD groups. In Phase CT correct verbalization was maintained by all participants of all groups and increased the correct position all body segments and hence the correspondence between the verbal and nonverbal behavior. In LB2 correct verbalization was maintained in all groups and there was a small decrease in matching segments of the cervical spine for all groups and for groups of forearms and DF DFD. / Mestre

This dissertation aimed to investigate the relationship between posture and reaching in both healthy and pathological conditions, approaching the trunk as a multi-segmented structure. For this purpose, neuromuscular and kinematic profiles were recorded from trunk and arm during seated reaches providing mid-rib vs pelvic levels of trunk support. Healthy adults with mature postural and reaching abilities displayed invariant arm kinematics during the reach. However, participants displayed increased anticipatory control and earlier activation of cervical muscles with mid-rib support. Participants also presented increased compensatory responses of paraspinal muscles when responding to the increased trunk balance demands with pelvic support. Children with moderate/severe cerebral palsy (CP) cannot maintain an upright sitting position and thus cannot create a stable postural frame around which upper limb movements are planned and executed. A second set of studies examined postural and reaching characteristics in these children, while applying axillae, mid-rib or pelvic levels of support. Participants were classified according to their intrinsic level of trunk control as mild, moderate and severe. With higher levels of support children with moderate to severe impairments in trunk control showed improvements of head and trunk control along with enhanced reaching performance. Participants with mild trunk dysfunction were able to sit independently and thus did not demonstrate significant changes in postural and reaching proficiency across levels of external trunk support. Electromyographic profiles were more variable depending on the severity of intrinsic trunk control. Overall, participants in the mild group presented more refined timing mechanisms for both anticipatory (closer to reaching onset) and compensatory (reduced latency) postural adjustments during the reach across all levels of support. Participants in the moderate group displayed earlier muscle onsets and more efficient arm/trunk muscle amplitudes with higher levels of support. Participants in the severe group showed very limited capability of anticipatory control of paraspinal muscles, delayed muscle onsets and variable muscle amplitudes across levels of support. These results emphasize the complex neuro-anatomical nature of trunk control during reaching. Also, they highlight that inefficient postural control while sitting significantly impacts children with CP and trunk dysfunction. This dissertation includes previously unpublished co-authored material.