<p>Syfte</p><p>Studien syftade till att undersöka om långvarig ihållande submaximal aktivering av Transversus Abdominis (TrA) påverkar dess anticipatoriska aktivering vid snabba viljemässigt utförda armrörelser.</p><p>Metod</p><p>I stående position utförde nio fysiskt aktiva kvinnor fem st snabba bilaterala armlyft från 0º till 90º axelflexion före och efter cirka 10 minuters ihållande submaximal aktivet i TrA samt efter 5 minuters vila. Elektromyografisk aktivitet (EMG) registrerades via två intramuskulära trådelektroder, placerade i höger TrA och två ytelektroder placerade på höger Deltoideus anterior. Buktrycket tros tillsammans med TrA stabilisera ryggraden vilket registrerades genom att en tryckgivare placerades i magsäcken.</p><p>Resultat</p><p>TrA aktiverades före Deltoideus både före och efter den långvariga aktiveringen. Initieringen av EMG-signalen i höger TrA hade oförändrat förhållande till initieringen av EMG-signalen i Deltoideus före och efter ihållande aktivitet samt efter 5 minuters vila. EMG amplituden i TrA var oförändrad både i baslinjefasen (600 ms före till 250 ms före deltoideus aktivering) och i den anticipatoriska fasen (100 ms före till 50 ms efter Deltoideus aktivering). Även buktrycksvärdet förblev oförändrat såväl vid baslinjen som i den anticipatoriska fasen.</p><p>Slutsats</p><p>Denna studie visade att centrala nervsystemet påbörjar aktiveringen av de innersta bukmusklerna före initieringen av armrörelserna och att detta förhållande ej påverkas av 10 minuters ihållande submaximal aktivering av TrA. Det finns inga tillgängliga metoder för direkt mätning av TrA:s mekaniska effekt, men eftersom buktrycket förblev oförändrad är det rimligt att tro att TrA:s kontraktilitet inte försämrats av den submaximala aktiveringen.</p> / <p>Aim</p><p>The aim of the study was to investigate whether prolonged sustained sub maximal activation of Transversu Abdominis (TrA) influences its anticipitatory activation associated with fast voluntary shoulder flexion.</p><p>Method</p><p>In a standing position nine physically active female subjects (mean age of 26 ± 3 y) performed five rapid bilateral shoulder flexion from 0° to 90° shoulder flexion, before and after approximately 10 minutes of sustained submaximal activity in TrA as well as after 5 minutes rest. Electromyographic activity (EMG) was recorded using two intramuscular fine-wire electrodes placed in the right TrA and two surface electrodes placed over the Deltoideus anterior. Intra-abdominal pressure (IAP) was recorded intra-gastrically.</p><p>Results</p><p>TrA was activated prior to Deltoideus, before as well as after the sustained activation. The onset of TrA muscle activation relative to the onset of Deltoideus activation was not significantly different between before, directly after, or 5 minutes after the end of the sustained activity. The root mean square of the TrA EMG was unchanged both before arm lifts (baseline) and within the anticipatory window (100 ms before until 50 ms after Deltoideus onset). The IAP-value was unaffected in the baseline as well as in the anticipatory phase.</p><p>Conclusion</p><p>This study shows that the central nervous system begins activating the TrA slightly before initiating arm movements and that this behaviour is unaffected by a 10 min. sustained submaximal activation of TrA. There are no methods available for direct measurement of the mechanical output from TrA activation, but since IAP was unaffected it appears reasonable to conclude that the contractility of TrA is not deteriorated by the submaximal activation of TrA.</p>

This thesis investigates the differential effects of muscle fatigue on center of pressure (COP) sway and associated central processes (attentional demands and sensory re-weighting) in older compared with young adults. More specifically, we first sought to determine whether the effect of muscle fatigue on unipedal stance was greater during a dual-task in older versus young adults, and second, to determine whether the effect of muscle fatigue on bipedal stance was greater in a condition with less reliable proprioceptive information in older versus young adults. Our main results show that with different muscle groups fatigued (ankle or hip) and postural tasks with varying difficulty (unipedal stance or bipedal stance on compliant surface), young adults increased their COP sway displacement and velocity with muscle fatigue, but not the associated attentional demands. When the central nervous system needed to increase the weight of the vestibular inputs due to sensory information being less reliable at the ankle joints from standing on a compliant surface (peripheral somatosensory information), COP sway displacement and velocity in young adults were greater with ankle muscle fatigue. We also found that healthy older adults were able to compensate for muscle fatigue just as well as young adults when visual information was available during a unipedal stance or when visual information was not available during a bipedal stance on a firm surface. However, when standing on a compliant surface, older adults showed a greater increase in COP sway displacement compared to young adults and increased attentional demands when visual information was not available during a bipedal stance. Our results suggest that healthy young and older adults are able to compensate for ankle muscle fatigue to limit postural control alterations during quiet standing under different conditions, and that the extent of postural control alterations largely depends on the tasks performed. The compensation strategies may be less efficient for older adults with less reliable proprioceptive information and without vision. Thus, a frailer group of older adults, with already reduced proprioception and/or reduced vision could possibly have more difficulty to efficiently use the same compensation strategies, and may be more at risk of falling when fatigued.

Syfte Studien syftade till att undersöka om långvarig ihållande submaximal aktivering av Transversus Abdominis (TrA) påverkar dess anticipatoriska aktivering vid snabba viljemässigt utförda armrörelser. Metod I stående position utförde nio fysiskt aktiva kvinnor fem st snabba bilaterala armlyft från 0º till 90º axelflexion före och efter cirka 10 minuters ihållande submaximal aktivet i TrA samt efter 5 minuters vila. Elektromyografisk aktivitet (EMG) registrerades via två intramuskulära trådelektroder, placerade i höger TrA och två ytelektroder placerade på höger Deltoideus anterior. Buktrycket tros tillsammans med TrA stabilisera ryggraden vilket registrerades genom att en tryckgivare placerades i magsäcken. Resultat TrA aktiverades före Deltoideus både före och efter den långvariga aktiveringen. Initieringen av EMG-signalen i höger TrA hade oförändrat förhållande till initieringen av EMG-signalen i Deltoideus före och efter ihållande aktivitet samt efter 5 minuters vila. EMG amplituden i TrA var oförändrad både i baslinjefasen (600 ms före till 250 ms före deltoideus aktivering) och i den anticipatoriska fasen (100 ms före till 50 ms efter Deltoideus aktivering). Även buktrycksvärdet förblev oförändrat såväl vid baslinjen som i den anticipatoriska fasen. Slutsats Denna studie visade att centrala nervsystemet påbörjar aktiveringen av de innersta bukmusklerna före initieringen av armrörelserna och att detta förhållande ej påverkas av 10 minuters ihållande submaximal aktivering av TrA. Det finns inga tillgängliga metoder för direkt mätning av TrA:s mekaniska effekt, men eftersom buktrycket förblev oförändrad är det rimligt att tro att TrA:s kontraktilitet inte försämrats av den submaximala aktiveringen. / Aim The aim of the study was to investigate whether prolonged sustained sub maximal activation of Transversu Abdominis (TrA) influences its anticipitatory activation associated with fast voluntary shoulder flexion. Method In a standing position nine physically active female subjects (mean age of 26 ± 3 y) performed five rapid bilateral shoulder flexion from 0° to 90° shoulder flexion, before and after approximately 10 minutes of sustained submaximal activity in TrA as well as after 5 minutes rest. Electromyographic activity (EMG) was recorded using two intramuscular fine-wire electrodes placed in the right TrA and two surface electrodes placed over the Deltoideus anterior. Intra-abdominal pressure (IAP) was recorded intra-gastrically. Results TrA was activated prior to Deltoideus, before as well as after the sustained activation. The onset of TrA muscle activation relative to the onset of Deltoideus activation was not significantly different between before, directly after, or 5 minutes after the end of the sustained activity. The root mean square of the TrA EMG was unchanged both before arm lifts (baseline) and within the anticipatory window (100 ms before until 50 ms after Deltoideus onset). The IAP-value was unaffected in the baseline as well as in the anticipatory phase. Conclusion This study shows that the central nervous system begins activating the TrA slightly before initiating arm movements and that this behaviour is unaffected by a 10 min. sustained submaximal activation of TrA. There are no methods available for direct measurement of the mechanical output from TrA activation, but since IAP was unaffected it appears reasonable to conclude that the contractility of TrA is not deteriorated by the submaximal activation of TrA.

This thesis investigates the differential effects of muscle fatigue on center of pressure (COP) sway and associated central processes (attentional demands and sensory re-weighting) in older compared with young adults. More specifically, we first sought to determine whether the effect of muscle fatigue on unipedal stance was greater during a dual-task in older versus young adults, and second, to determine whether the effect of muscle fatigue on bipedal stance was greater in a condition with less reliable proprioceptive information in older versus young adults. Our main results show that with different muscle groups fatigued (ankle or hip) and postural tasks with varying difficulty (unipedal stance or bipedal stance on compliant surface), young adults increased their COP sway displacement and velocity with muscle fatigue, but not the associated attentional demands. When the central nervous system needed to increase the weight of the vestibular inputs due to sensory information being less reliable at the ankle joints from standing on a compliant surface (peripheral somatosensory information), COP sway displacement and velocity in young adults were greater with ankle muscle fatigue. We also found that healthy older adults were able to compensate for muscle fatigue just as well as young adults when visual information was available during a unipedal stance or when visual information was not available during a bipedal stance on a firm surface. However, when standing on a compliant surface, older adults showed a greater increase in COP sway displacement compared to young adults and increased attentional demands when visual information was not available during a bipedal stance. Our results suggest that healthy young and older adults are able to compensate for ankle muscle fatigue to limit postural control alterations during quiet standing under different conditions, and that the extent of postural control alterations largely depends on the tasks performed. The compensation strategies may be less efficient for older adults with less reliable proprioceptive information and without vision. Thus, a frailer group of older adults, with already reduced proprioception and/or reduced vision could possibly have more difficulty to efficiently use the same compensation strategies, and may be more at risk of falling when fatigued.

Low back pain (LBP) affects many individuals worldwide. The established association between LBP and spine motor control has led to the development of many control assessment techniques. To understand the association between motor control and LBP, it is essential to understand the relationship between separate assessment techniques. Systems identification (SI) and local dynamic stability (LDS) are two methods commonly used to quantify spine control. SI provides a detailed description of control but uses linear assumptions, whereas LDS provides a “black box” non-linear assessment and can be quantified during dynamic movements. Although both SI and LDS techniques aim to measure the control of the spine, each employs different experimental setups and data processing strategies. Therefore, the purpose of this thesis was to compare the motor behaviour outcomes of SI and LDS quantification techniques. To do this, 15 participants completed two tasks (SI and LDS) in a random order. For the SI task, participants were seated and ventrally perturbed at the level of the 10th thoracic vertebrae (T10). They completed this task under instructions to resist the perturbations (resist condition) or relax and remain upright (relax condition). Admittance was represented using frequency response functions, and a validated neuromuscular control model quantified lumbar stiffness, damping and muscle spindle feedback gains. The LDS task involved participants completing three repetitive movement blocks consisting of flexion/extension, axial rotation, and complex movements. In each block, the maximum finite-time Lyapunov exponent (λmax) was estimated. A stepwise linear regression determined that λmax during the rotation task was best predicted by SI outcomes in the relax condition (adjusted R square = 0.65). Many conditions demonstrated no significant relationship between λmax and SI outcomes. These findings outline the importance of a consistent framework for the assessment of spine control. This could improve clinical assessment efficiency as well as the understanding of the association between LBP and motor control.

Orientador: Eliane Mauerberg de Castro / Banca: Cynthia Yukiko Hiraga / Banca: Renato de Moraes / Resumo: O controle postural está relacionado com os ajustes corporais necessários à manutenção ou à busca da postura desejável, de acordo com a meta da tarefa. Mesmo um comportamento cotidiano como permanecer em pé, pode ser considerado uma tarefa complexa que envolve um estreito relacionamento entre informação sensorial e atividade motora. Barela (2000) afirma que as forças atuantes nos segmentos corporais não são constantes, pois, mesmo que a pessoa se mantenha o mais estável possível, o corpo nunca está totalmente imóvel. Por isso, a postura em pé é chamada de "quase-estável". Algumas populações têm maior predisposição a apresentar problemas de ordem postural, como por exemplo, obesos, idosos ou pessoas com deficiência intelectual - DI. As pessoas obesas ou com sobrepeso, por apresentarem maior acúmulo de gordura na região abdominal, estão mais propensas à perda de equilíbrio ou eventuais quedas, pois o centro de massa está deslocado para frente. Uma população bastante exposta à obesidade é aquela com deficiência intelectual, quer seja por característica genética, por maus hábitos alimentares ou estilo de vida sedentário. A fim de verificar a associação da obesidade com a deficiência intelectual quanto ao controle postural em tarefa do tipo estática em pé, foram recrutados 40 participantes. A tarefa consistiu em permanecer em pé sobre uma plataforma de força e foram realizadas sete tentativas: uma chamada de controle na qual os pés permaneciam paralelos e os olhos abertos, três tentativas com os pés em posição semi-tandem - ST - e os olhos abertos e outras três tentativas com os pés em posição ST e os olhos fechados. As variáveis dependentes analisadas foram: amplitude média de oscilação e amplitude média da velocidade de oscilação, em ambas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Postural control is related to the adjustments needed to maintain body or the search of desirable posture, according to the goal of the task. Even an everyday behavior such as standing, can be considered a complex task that involves a close relationship between sensory information and motor activity. According to Barela (2000) the forces acting on the body segments are not constant, so even if the person remains as stable as possible, the body is never completely still. Therefore, the standing posture is called "quasi-static." Some populations are more likely to present postural problems, for example, obese, elderly or people with intellectual disabilities - ID. People who are obese or overweight, had higher accumulation of abdominal fat are more prone to loss of balance or falls, as the center of mass is moved forward. A population exposed for the obese is that with intellectual disabilities, whether by genetic feature, poor eating habits or sedentary lifestyle. In order to verify the association of obesity with intellectual disabilities on the postural control tasktype static standing, 40 participants were recruited. The task was to stand on a force platform and seven attempts were made: one call control in which the feet parallel and the eyes remained open, three attempts with their feet in a semi-tandem - ST - and open eyes and three more attempts with his feet in position ST and eyes closed. The dependent variables were analyzed: amplitude of oscillation and amplitude of the oscillation velocity in both ML and AP directions. The results showed that all participants had changed postural control in changing the position of the feet as in the occlusion of vision. The groups non-obese without ID and obese with ID were different for both variables, supporting the hypothesis that obesity affects postural control and... (Complete abstract click electronic access below) / Mestre

This thesis investigates the differential effects of muscle fatigue on center of pressure (COP) sway and associated central processes (attentional demands and sensory re-weighting) in older compared with young adults. More specifically, we first sought to determine whether the effect of muscle fatigue on unipedal stance was greater during a dual-task in older versus young adults, and second, to determine whether the effect of muscle fatigue on bipedal stance was greater in a condition with less reliable proprioceptive information in older versus young adults. Our main results show that with different muscle groups fatigued (ankle or hip) and postural tasks with varying difficulty (unipedal stance or bipedal stance on compliant surface), young adults increased their COP sway displacement and velocity with muscle fatigue, but not the associated attentional demands. When the central nervous system needed to increase the weight of the vestibular inputs due to sensory information being less reliable at the ankle joints from standing on a compliant surface (peripheral somatosensory information), COP sway displacement and velocity in young adults were greater with ankle muscle fatigue. We also found that healthy older adults were able to compensate for muscle fatigue just as well as young adults when visual information was available during a unipedal stance or when visual information was not available during a bipedal stance on a firm surface. However, when standing on a compliant surface, older adults showed a greater increase in COP sway displacement compared to young adults and increased attentional demands when visual information was not available during a bipedal stance. Our results suggest that healthy young and older adults are able to compensate for ankle muscle fatigue to limit postural control alterations during quiet standing under different conditions, and that the extent of postural control alterations largely depends on the tasks performed. The compensation strategies may be less efficient for older adults with less reliable proprioceptive information and without vision. Thus, a frailer group of older adults, with already reduced proprioception and/or reduced vision could possibly have more difficulty to efficiently use the same compensation strategies, and may be more at risk of falling when fatigued.

No description available.

No description available.

No description available.