A common symptom of Idiopathic Parkinson’s disease (IPD) is decreased trunk and balance control. These deficits in patients with IPD are not treatable, and their underlying mechanisms are not well understood. Additionally, it is not known to what extent decreased trunk control contributes to postural instability in patients with IPD. Previous work by Martin (1965) observed that patients with post-encephalitatic Parkinson’s disease would fall in the direction of the tilt when perturbed while seated. In order to better understand the underlying causes of these observed trunk deficits and attempt to replicate Martins findings, this study investigated postural corrective movement of the trunk while seated in patients with IPD and age-matched healthy controls. Participants’ range of motion (ROM) was tested actively and passively while lying supine, following which, bilateral electromyography (EMG) (rectus abdominis (RA), external oblique (EO), and erector spinae (EST9, L3)) and 3-D kinematic measures were recorded while participants were seated on a modified chair and received unexpected perturbations, 7° at 40°/sec, in four different directions (forward, backward, left, and right). EMG responses were normalized to participant’s maximum voluntary contractions. We observed patients with IPD to have decreased active and passive ROM only in the frontal plane relative to controls. Patterning of muscle responses to rotational perturbations did not vary between groups in any direction, except backward, and trends toward significantly greater EST9 activity were observed during backward and left tilts in patients with IPD. Despite this both patients with IPD and controls were able to make appropriate trunk corrective movements opposite the direction of the tilt. However, two patients, who were most severely affected, did make incorrect trunk movements in the direction of the tilt during left and right tilting perturbations which, upon visual inspection, appear to be due to improperly modulated and timed muscle responses. Thus, our data counters the findings of Martin, and suggests the trunk is posturally stable in IPD. Therefore, balance instabilities during stance are likely due to improper responses of the lower limbs. However, as disease severity increases, the contributing influence of an improperly responding trunk may add to their postural deficits.

A common symptom of Idiopathic Parkinson’s disease (IPD) is decreased trunk and balance control. These deficits in patients with IPD are not treatable, and their underlying mechanisms are not well understood. Additionally, it is not known to what extent decreased trunk control contributes to postural instability in patients with IPD. Previous work by Martin (1965) observed that patients with post-encephalitatic Parkinson’s disease would fall in the direction of the tilt when perturbed while seated. In order to better understand the underlying causes of these observed trunk deficits and attempt to replicate Martins findings, this study investigated postural corrective movement of the trunk while seated in patients with IPD and age-matched healthy controls. Participants’ range of motion (ROM) was tested actively and passively while lying supine, following which, bilateral electromyography (EMG) (rectus abdominis (RA), external oblique (EO), and erector spinae (EST9, L3)) and 3-D kinematic measures were recorded while participants were seated on a modified chair and received unexpected perturbations, 7° at 40°/sec, in four different directions (forward, backward, left, and right). EMG responses were normalized to participant’s maximum voluntary contractions. We observed patients with IPD to have decreased active and passive ROM only in the frontal plane relative to controls. Patterning of muscle responses to rotational perturbations did not vary between groups in any direction, except backward, and trends toward significantly greater EST9 activity were observed during backward and left tilts in patients with IPD. Despite this both patients with IPD and controls were able to make appropriate trunk corrective movements opposite the direction of the tilt. However, two patients, who were most severely affected, did make incorrect trunk movements in the direction of the tilt during left and right tilting perturbations which, upon visual inspection, appear to be due to improperly modulated and timed muscle responses. Thus, our data counters the findings of Martin, and suggests the trunk is posturally stable in IPD. Therefore, balance instabilities during stance are likely due to improper responses of the lower limbs. However, as disease severity increases, the contributing influence of an improperly responding trunk may add to their postural deficits.

Orientador: José Angelo Barela / Banca: Sergio Tosi Rodrigues / Banca: Renato de Moraes / Banca: Dora Selma Fix Ventura / Banca: Ana Maria Pellegrini / Resumo: A fim de investigar a utilização da informação visual por crianças e adultos jovens diante de alterações das características do estímulo visual durante a manutenção da posição em pé foram realizados dois experimentos. O primeiro experimento investigou a influência da estrutura do fluxo ótico no acoplamento entre informação visual e oscilação corporal em crianças de 4, 8 e 12 anos de idade e adultos jovens. Os participantes permaneceram em pé dentro de uma sala móvel, em diferentes distâncias da parede frontal da sala, e em três condições: fluxo global, frontal, e lateral. Os resultados indicaram que a influência da distância e da estrutura do fluxo ótico no acoplamento entre informação visual e oscilação corporal foram dependentes da idade e a influência da estrutura do fluxo ótico no acoplamento entre informação visual e oscilação corporal foi dependente da distância. Com base nestes resultados, é possível sugerir que diferenças desenvolvimentais no relacionamento entre informação visual e oscilação corporal estão relacionadas ao modo como as crianças utilizam a informação ótica em diferentes estruturas do fluxo ótico. O segundo experimento investigou a influência de características do estímulo visual no acoplamento entre informação visual e oscilação corporal em crianças de 4, 8 e 12 anos de idade e adultos jovens. Os participantes permaneceram em pé dentro de uma sala móvel em três condições experimentais: diâmetro, contraste, e velocidade do estímulo visual. Os resultados indicaram que o relacionamento temporal entre informação visual e oscilação corporal e a variabilidade do acoplamento entre informação visual e oscilação corporal foram dependentes da idade em todas as condições. O diâmetro e o contraste do estímulo visual não influenciaram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In order to investigate how children and adults use different visual stimulus characteristics during maintenance of upright stance two experiments were designed. The first experiment investigated the influence of optic flow structure in the visual information and body sway coupling of 4-, 8-, and 12-year-old participants and young adults. Participants stood upright inside a moving room at different distances from the frontal wall and at three conditions: global; central; and peripheral optic flow. The results showed that the influence of distance and optic flow structure in the visual information and body sway coupling is age and distance dependent. These results suggest that age-related changes observed in the relationship between visual information and body sway are related to how children use optic information in different optic flow structures. The second experiment investigated the influence of visual stimulus characteristics manipulation in the visual information and body sway coupling of 4-, 8-, and 12-year-old participants and young adults. Participants stood upright inside a moving room with reduced optic flow at three conditions: target with different diameter; contrast; and velocity. The results showed that temporal relationship and variability of coupling between visual information and body sway were age dependent in all conditions. Visual stimulus diameter and visual stimulus contrast did not influence this coupling. Visual stimulus velocity influenced the coupling but this influence was not age dependent. Thus, it can be concluded that age-related changes in coupling between visual information and body sway are not related to different use of stimulus characteristics of the target manipulated in the present experiment. Based upon these results, it can be suggested that the differences in postural control between children and adults... (Complete abstract click electronic access below) / Doutor

Recent findings have suggested that the type of postural control seems to change, with certain conditions promoting a more conscious control and others, a more automatic control. It has been proposed that by withdrawing attention from postural control, external focus and cognitive task conditions allow automatic mechanisms to control sway more efficiently. The present dissertation aimed to investigate whether two types of postural control exist and to provide evidence for these two types of postural control in healthy young and older adults. In experiment 1, the effect of attentional focus and cognitive tasks was examined in healthy older adults. It was found that the cognitive task yielded improvements in stability compared to focus conditions, which highlighted the fact that automaticity is possible in this group. In experiment 2, the effect of attentional focus and cognitive tasks was once again observed in older adults, this time by including electromyographic recordings of lower leg muscles to examine if changes were due to stiffening. Although improvements were observed in external focus and cognitive task conditions compared to baseline and internal focus, no change occurred in muscle activity which lends further support to the idea that changes are due to automaticity. Finally, dynamic measures of sway were used to help interpret the changes that occurred in attentional focus and cognitive task conditions in both young and older adults. The wavelet transform revealed a change in sensory contributions to postural control in cognitive task conditions. There was a shift to increased contributions from the cerebellum and the vestibular system, and a decrease in visual contributions, compared to other conditions. Sample entropy revealed changes in complexity of sway, with cognitive tasks presenting more complex, irregular and efficient sway in both groups compared to baseline standing and attentional focus conditions. Finally, the rambling-trembling decomposition highlighted increases in the spinal reflex contributions to sway in external focus and difficult cognitive task conditions in young adults, while no change occurred in older adults. Results of these experiments provide the evidence of two types of postural control; a more automatic type in cognitive task conditions and a more conscious type in baseline and internal focus conditions. The external focus elicited some changes that could have indicated automaticity, but clear differences were still present between this condition and the cognitive tasks, which suggest automaticity of sway should be viewed as a continuum.

A common symptom of Idiopathic Parkinson’s disease (IPD) is decreased trunk and balance control. These deficits in patients with IPD are not treatable, and their underlying mechanisms are not well understood. Additionally, it is not known to what extent decreased trunk control contributes to postural instability in patients with IPD. Previous work by Martin (1965) observed that patients with post-encephalitatic Parkinson’s disease would fall in the direction of the tilt when perturbed while seated. In order to better understand the underlying causes of these observed trunk deficits and attempt to replicate Martins findings, this study investigated postural corrective movement of the trunk while seated in patients with IPD and age-matched healthy controls. Participants’ range of motion (ROM) was tested actively and passively while lying supine, following which, bilateral electromyography (EMG) (rectus abdominis (RA), external oblique (EO), and erector spinae (EST9, L3)) and 3-D kinematic measures were recorded while participants were seated on a modified chair and received unexpected perturbations, 7° at 40°/sec, in four different directions (forward, backward, left, and right). EMG responses were normalized to participant’s maximum voluntary contractions. We observed patients with IPD to have decreased active and passive ROM only in the frontal plane relative to controls. Patterning of muscle responses to rotational perturbations did not vary between groups in any direction, except backward, and trends toward significantly greater EST9 activity were observed during backward and left tilts in patients with IPD. Despite this both patients with IPD and controls were able to make appropriate trunk corrective movements opposite the direction of the tilt. However, two patients, who were most severely affected, did make incorrect trunk movements in the direction of the tilt during left and right tilting perturbations which, upon visual inspection, appear to be due to improperly modulated and timed muscle responses. Thus, our data counters the findings of Martin, and suggests the trunk is posturally stable in IPD. Therefore, balance instabilities during stance are likely due to improper responses of the lower limbs. However, as disease severity increases, the contributing influence of an improperly responding trunk may add to their postural deficits. / Education, Faculty of / Kinesiology, School of / Graduate

Neuromuscular fatigue, even that caused by light submaximal exercise, impairs motor performance and alters motor planning. This impairment is evident in muscle reaction time, force production capacity and joint position sense as well as in more complex tasks such as postural stability. When an individual is fatigued their postural sway increases and they are less able to recover from unexpected postural perturbations. Although a large number of work-related falls are caused by fatigue every year, the mechanisms behind the instability are not well understood. Since postural control does not require a large amount of muscular strength it is unclear whether the post-fatigue changes in posture are due to impairment within the muscle fibers or are a central modification of the motor plan used to execute the movement task. In order to better understand neuromuscular fatigue researchers have labeled fatigue occurring within the muscles ‘peripheral fatigue’ and that occurring within the central nervous system ‘central fatigue’. At the onset of a muscular contraction peripheral and central fatigue develop simultaneously, making it difficult to clearly articulate the role that they each play in the decreased motor performance found post-fatigue. Techniques such as transcranial magnetic and electrical nerve stimulation quantify the contribution of central fatigue to the decreased maximal force production but the impact on motor planning is still not well understood. Therefore, the primary aim of this doctoral dissertation was to isolate central fatigue from peripheral muscle fatigue and to compare the influence that it may have on dynamic postural control to the changes caused by general fatigue of the local postural muscles. This overarching research goal was accomplished through five separate studies. The first study in this dissertation determined that at least seven postural trials needed to be performed to ensure that the participants had fully adapted to the postural task before the fatigue protocol was implemented. Experiment 2 characterized the fatigue produced by bilateral, isometric ankle muscle contractions and examined the recovery of the central and peripheral changes throughout a ten-minute post-fatigue recovery period. The results demonstrated that the alternating maximal ankle plantar and dorsiflexor contractions created central and peripheral fatigue. Central fatigue recovered within the first two minutes post-fatigue while peripheral fatigue lasted throughout the ten-minute post-fatigue period. Experiment 3 analyzed the impact of this ankle muscle fatigue protocol on the postural response to a continual, externally driven, sinusoidal oscillation of the support platform. In this study the fatigued participants were able to stabilize their center of mass displacement using two different anticipatory postural responses to the backwards perturbation whereas all of the participants used the same anticipatory response to the forwards perturbation. All three postural responses became progressively more conservative throughout the ten-minute post-fatigue period, despite the rapid recovery of the ankle force production capacity. The final two studies characterized the fatigue produced during a continuous, isometric forearm contraction and assessed the impact on ankle motor performance (Experiment 4) and on postural control (Experiment 5). Peripheral fatigue created in the forearm muscles during this contraction remained throughout the post-fatigue testing session. Central fatigue and a decreased maximal force production capacity were quantified in both the forearm and ankle plantarflexor muscles immediately after the forearm contraction, indicating that central fatigue created during the forearm exercise crossed over to the distal and unrelated ankle plantarflexor muscles. The influence of the central fatigue created during the forearm contraction affected the anticipatory postural response in a similar way to the fatigue created by the ankle fatigue protocol. The post-fatigue modification of the postural response dissipated as the central fatigue recovered. Taken together, these five studies extend the current understanding of how exercise induced neuromuscular fatigue modifies the central nervous system’s control of complex motor tasks.

Neuromuscular fatigue, even that caused by light submaximal exercise, impairs motor performance and alters motor planning. This impairment is evident in muscle reaction time, force production capacity and joint position sense as well as in more complex tasks such as postural stability. When an individual is fatigued their postural sway increases and they are less able to recover from unexpected postural perturbations. Although a large number of work-related falls are caused by fatigue every year, the mechanisms behind the instability are not well understood. Since postural control does not require a large amount of muscular strength it is unclear whether the post-fatigue changes in posture are due to impairment within the muscle fibers or are a central modification of the motor plan used to execute the movement task. In order to better understand neuromuscular fatigue researchers have labeled fatigue occurring within the muscles ‘peripheral fatigue’ and that occurring within the central nervous system ‘central fatigue’. At the onset of a muscular contraction peripheral and central fatigue develop simultaneously, making it difficult to clearly articulate the role that they each play in the decreased motor performance found post-fatigue. Techniques such as transcranial magnetic and electrical nerve stimulation quantify the contribution of central fatigue to the decreased maximal force production but the impact on motor planning is still not well understood. Therefore, the primary aim of this doctoral dissertation was to isolate central fatigue from peripheral muscle fatigue and to compare the influence that it may have on dynamic postural control to the changes caused by general fatigue of the local postural muscles. This overarching research goal was accomplished through five separate studies. The first study in this dissertation determined that at least seven postural trials needed to be performed to ensure that the participants had fully adapted to the postural task before the fatigue protocol was implemented. Experiment 2 characterized the fatigue produced by bilateral, isometric ankle muscle contractions and examined the recovery of the central and peripheral changes throughout a ten-minute post-fatigue recovery period. The results demonstrated that the alternating maximal ankle plantar and dorsiflexor contractions created central and peripheral fatigue. Central fatigue recovered within the first two minutes post-fatigue while peripheral fatigue lasted throughout the ten-minute post-fatigue period. Experiment 3 analyzed the impact of this ankle muscle fatigue protocol on the postural response to a continual, externally driven, sinusoidal oscillation of the support platform. In this study the fatigued participants were able to stabilize their center of mass displacement using two different anticipatory postural responses to the backwards perturbation whereas all of the participants used the same anticipatory response to the forwards perturbation. All three postural responses became progressively more conservative throughout the ten-minute post-fatigue period, despite the rapid recovery of the ankle force production capacity. The final two studies characterized the fatigue produced during a continuous, isometric forearm contraction and assessed the impact on ankle motor performance (Experiment 4) and on postural control (Experiment 5). Peripheral fatigue created in the forearm muscles during this contraction remained throughout the post-fatigue testing session. Central fatigue and a decreased maximal force production capacity were quantified in both the forearm and ankle plantarflexor muscles immediately after the forearm contraction, indicating that central fatigue created during the forearm exercise crossed over to the distal and unrelated ankle plantarflexor muscles. The influence of the central fatigue created during the forearm contraction affected the anticipatory postural response in a similar way to the fatigue created by the ankle fatigue protocol. The post-fatigue modification of the postural response dissipated as the central fatigue recovered. Taken together, these five studies extend the current understanding of how exercise induced neuromuscular fatigue modifies the central nervous system’s control of complex motor tasks.

No description available.

Postural control is the skill developed allowing body equilibrium and orientation, allowing for an efficient interaction with the environment. This skill is developed from birth; the first major landmark is the maintenance of an upright stance of a child, followed by the skill to walk freely (Shumway-Cook & Woollacott, 1985). A second important development occurs between the ages of 7-10 years-old when children start to demonstrate adult-like postural control (Riach & Hayes, 1987). While adults and older adults have shown increased automaticity in postural control in a dual-task (DT) (Potvin-Desrochers, Richer, & Lajoie, 2017), children have not yet been studied. The purpose of this experiment was to determine if children aged 6-7, 8-9, and 10-11 years old would demonstrate better postural stability, and greater postural automaticity in a DT condition than in a postural task (PT). To verify this, children were asked to stand still on a force platform in a PT or in a DT condition (PT with concurrent cognitive task). Results showed that older children had better postural stability, as demonstrated by a smaller sway area (7.20 cm2), reduced sway variability (0.60 cm), and a slower MV of sway (4.70 cm/s) than younger children (12.37 cm2, 0.78 cm, 6.60 cm/s). Older children also had a higher MPF in the PT (0.24 Hz) than in the DT (0.16 Hz). A wavelet transformation revealed a greater contribution of the ultra-low frequency band in the PT (49.9%) than in the DT (46.8%) across all children. These results demonstrated that older children were more stable than younger children. The smaller contribution to the ultra-low band in the DT may be an indication that children rely less heavily on their visual system in the DT. This research shows that children do not demonstrate automaticity of postural control between the ages of 6-11 years.

Made available in DSpace on 2014-06-11T19:30:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-09-25Bitstream added on 2014-06-13T18:41:03Z : No. of bitstreams: 1 godoi_d_dr_rcla.pdf: 658902 bytes, checksum: 2d229c902dd493b974d6e1f791ddc202 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A fim de investigar a utilização da informação visual por crianças e adultos jovens diante de alterações das características do estímulo visual durante a manutenção da posição em pé foram realizados dois experimentos. O primeiro experimento investigou a influência da estrutura do fluxo ótico no acoplamento entre informação visual e oscilação corporal em crianças de 4, 8 e 12 anos de idade e adultos jovens. Os participantes permaneceram em pé dentro de uma sala móvel, em diferentes distâncias da parede frontal da sala, e em três condições: fluxo global, frontal, e lateral. Os resultados indicaram que a influência da distância e da estrutura do fluxo ótico no acoplamento entre informação visual e oscilação corporal foram dependentes da idade e a influência da estrutura do fluxo ótico no acoplamento entre informação visual e oscilação corporal foi dependente da distância. Com base nestes resultados, é possível sugerir que diferenças desenvolvimentais no relacionamento entre informação visual e oscilação corporal estão relacionadas ao modo como as crianças utilizam a informação ótica em diferentes estruturas do fluxo ótico. O segundo experimento investigou a influência de características do estímulo visual no acoplamento entre informação visual e oscilação corporal em crianças de 4, 8 e 12 anos de idade e adultos jovens. Os participantes permaneceram em pé dentro de uma sala móvel em três condições experimentais: diâmetro, contraste, e velocidade do estímulo visual. Os resultados indicaram que o relacionamento temporal entre informação visual e oscilação corporal e a variabilidade do acoplamento entre informação visual e oscilação corporal foram dependentes da idade em todas as condições. O diâmetro e o contraste do estímulo visual não influenciaram... / In order to investigate how children and adults use different visual stimulus characteristics during maintenance of upright stance two experiments were designed. The first experiment investigated the influence of optic flow structure in the visual information and body sway coupling of 4-, 8-, and 12-year-old participants and young adults. Participants stood upright inside a moving room at different distances from the frontal wall and at three conditions: global; central; and peripheral optic flow. The results showed that the influence of distance and optic flow structure in the visual information and body sway coupling is age and distance dependent. These results suggest that age-related changes observed in the relationship between visual information and body sway are related to how children use optic information in different optic flow structures. The second experiment investigated the influence of visual stimulus characteristics manipulation in the visual information and body sway coupling of 4-, 8-, and 12-year-old participants and young adults. Participants stood upright inside a moving room with reduced optic flow at three conditions: target with different diameter; contrast; and velocity. The results showed that temporal relationship and variability of coupling between visual information and body sway were age dependent in all conditions. Visual stimulus diameter and visual stimulus contrast did not influence this coupling. Visual stimulus velocity influenced the coupling but this influence was not age dependent. Thus, it can be concluded that age-related changes in coupling between visual information and body sway are not related to different use of stimulus characteristics of the target manipulated in the present experiment. Based upon these results, it can be suggested that the differences in postural control between children and adults... (Complete abstract click electronic access below)