Rising up from a chair (sit-to-stand; STS) and stair climbing are both activities of daily living (ADLs) done throughout our lives. The ability to complete ADLs is crucial for independent living. The goal of this thesis was to research how two ADLs interact with each other and affect postural control. It was hypothesized that an increased number of flights of stairs climbed would lead to a decline in postural control during/after a STS in older more than younger adults. Fourteen older adults and fourteen young adults were tested by completing three STSs before and after climbing 1, 3 and 5 flights of stairs, chosen at random. Movements of the center of pressure (COP) for each STS were obtained from a force platform. Only an age effect was found for COP velocity (left-right and anterior-posterior directions) during the momentum transfer phase, during stabilization and after stabilization. Therefore, contrary to our hypothesis, stair climbing did not lead to significant changes in COP movements during and following a STS.

Inledning: Det är vida diskuterat om träning på instabilt underlag har någon effekt på idrottslig prestation. En del studier visar att instabil träning utmanar nervsystemet i högre grad än vad stabil träning gör och kan därav förbättra muskelkoordination och muskelsynnergier. Annan forskning rapporterar minskad kraftutveckling vid träning på instabila underlag, vilket ses som en begränsning för idrottslig prestation. Syfte: Syftet med denna studie var att undersöka vilken effekt hängande frivändningar, på stabilt kontra instabilt underlag har, sett till explosivitet och postural kontroll. Metod: Experimentell kvantitativ randomiserad pilotstudie. Under en träningsperiod på fem veckor genomförde fem manliga deltagare hängande frivändningar tre gånger i veckan. Deltagarna delades in i två grupper, grupp 1 (n=2) utförde frivändningarna på stabilt underlag och grupp 2 (n=3) på instabilt underlag. Innan och efter mättes posturalt svaj och explosivitet i stillastående en minut med slutna ögon på stabilt respektive instabilt underlag samt upphopp på kraftplatta. Resultat: Grupp 2 förbättrade samtliga parametrar av posturalt svaj vid quiet stance på instabilt underlag. Framför allt sågs en minskad svajarea (23 %), en minskning som även sågs på stabilt underlag (16 %). Grupp 1 påvisade en ökning i svajarea på båda underlagen medan förbättring sågs i övriga parametrar på instabilt underlag. Stora individuella variationer gällande explosivitetsförändring vid squat jump sågs i båda grupperna. Konklusion: Denna pilotstudie indikerar att frivändningsträning på instabilt underlag kan ha positiva effekter på den posturala kontrollen. Resultaten behöver verifieras i en framtida större studie grundad på samma metod med längre träningsintervention.

A permanência em pé por um determinado período de tempo exige que os indivíduos produzam periodicamente mudanças posturais, que podem favorecer a adoção de posturas mais assimétricas. Diante da deterioração do sistema de controle postural, é possível que idosos tenham uma dificuldade em permanecerem assimétricos em atividades do cotidiano. Em adição, variações no padrão de ativação muscular podem aumentar o gasto energético e levar os idosos a fadiga, o que resulta em sérias consequências como aumento no risco de quedas. Acredita-se que mudanças posturais durante a postura relaxada ocorram distintamente em adultos jovens e idosos, podem exigir esforços musculares variados e assim influenciar no gasto energético. O presente estudo investigou as assimetrias posturais, ativações musculares e gasto energético em adultos jovens e idosos saudáveis na postura ereta. Cinquenta e três jovens e 16 idosos permaneceram em diferentes posturas enquanto registrou-se as assimetrias na distribuição de peso ao longo do tempo (ADPm). Todos os idosos e 12 jovens submeteram-se ao registro eletromiográfico para análise dos padrões de ativação muscular de músculos da coxa e perna, e 7 indivíduos de cada grupo foram submetidos ao registro de gases para análise do gasto energético, consumo de oxigênio (VO2), quociente respiratório (R) e medida de frequência cardíaca. Os idosos apresentaram dificuldade na transferência de peso em posturas mais assimétricas e ambos os grupos apresentaram ligeira assimetria na postura ereta quieta (em torno de 5±4% de ADPm). Na postura relaxada a maior parte do tempo os indivíduos permaneceram em faixas de pequenas assimetrias, seguido de um tempo menor em posturas significativamente assimétricas. Em geral, as ativações musculares foram maiores em idosos, porém eles foram capazes de recrutar músculos de modo similar aos jovens. O aumento da atividade do músculo gastrocnêmio foi proporcional às posturas mais assimétricas em ambos os grupos. O gasto energético não sofreu grandes variações em condições de simetria ou assimetria posturais em jovens e idosos, porém parece que o aumento do gasto energético nos idosos está relacionado com o aumento da atividade muscular, o que poderia justificar a adoção de posturas menos assimétricas por parte desses indivíduos. Os resultados do presente estudo levantam a questão da possibilidade de haver maior gasto energético, principalmente em idosos, e abre novas possibilidades para que futuros estudos possam compreender a demanda metabólica envolvida na manutenção da postura ereta / To remain standing for a certain period of time we periodically produce postural changes, which may favouring the adoption of more asymmetric postures. In face of the postural control system deterioration, it is possible that older people find it difficult to adopt more asymmetrical postures during daily life activities. In addition, changes in muscle activation pattern may increase energy cost to stand in asymmetric posture, which would lead to muscle fatigue and as consequence increase in fall risk in this population. Thus, postural changes during relaxed postures and the muscular demand necessary to perform such changes may differ among young and older adults, resulting in different energy cost. The present study investigated body weight asymmetries, muscle activations and energy cost in healthy young and elderly adults during sanding tasks with different constrains. Fifty-three young and sixteen elderly subjects remained at different positions while we recorded the body weight asymmetry over time (ADPm). All the elderly participants and twelve young adults undergone to electromyographic record of the thigh and leg muscles, and 7 subjects in each group to gas record in order to quantify the energy cost, oxygen consumption (VO2) and respiratory quotient (R) and registered heart rate. During quiet standing task, both age groups showed a slight and similar WDA (mean values around 5%). However, the elderly had difficulty in maintaining more asymmetric postures - they were less asymmetrical than young in tasks that required great WDA. In the relaxed position, most of the time the subjects remained in small asymmetry ranges, followed by a shorter period in more asymmetric postures. In general, muscle activation level was higher in the elderly, but they were able to recruit muscle in a similar way to young subjects. In addition, gastrocnemius activity increased proportionally to body weight support in both age groups - it was greater in the supportive limb in the most asymmetric postures. Although in this study the energy cost was not significantly affected by the asymmetry in body weight distribution in young and old individuals, it seems that the increased energy cost in the elderly is associated with an increase in muscle activity, which might explain the adoption of less asymmetric postures by these individuals. The results of this study raise the question of the possibility of higher energy expenditure in more asymmetric postures, especially in the elderly, and opens new possibilities for future studies to understand the metabolic demands during upright standing

Footwear can affect postural stability in individuals, particularly in elderly people. Aging-related decline in postural stability, particularly in the mediolateral (ML) direction, is a risk factor for falls and fall-related injuries among older adults. This study aimed to investigate the effects of high cushioned and minimal shoes on dynamic postural stability in ML during obstacle crossing in defined older and younger adults. Six healthy older adults (50–60 years old, body weight: 74.8 kg, body height: 168.0 cm) and six healthy younger adults (18–32 years old, body weight: 73.8 kg, body height: 174.8 cm) participated in the study. A Vicon motion analysis system with 10 optical cameras was used to capture the obstacle (20 cm height) crossing motion of the participants at 200 Hz, and ground reaction forces of obstacle crossing were collected at 1000 Hz. Motion data of obstacle crossing were collected at three shoe conditions, namely, minimal shoe, high cushioned shoe and barefoot (control). Data from five trials of obstacle crossing for each shoe condition were processed using Vicon Nexus software 2.11.0 and Matlab R2013b. Displacement and velocity of centre of mass (COM) in the ML direction, COM–centre of pressure (COP) ML separation, step length, step velocity, toe clearance, pre-horizontal distance, hip flexion angle and hip abduction angle during obstacle crossing were examined. One-way ANOVA with pairwise analysis showed that toe clearance was significantly larger in the high cushioned shoe conditions than in the minimal shoe and barefoot conditions in older adults (high cushioned shoes vs. barefoot: p = 0.019; cushioned shoes vs. minimal shoes: p = 0.031) and younger adults (high cushioned shoes vs. barefoot: p = 0.016; high cushioned shoes vs. minimal shoes: p = 0.000). No significant difference in the measures was found between the minimal shoe and barefoot conditions in each group. Compared with older adults, younger adults showed significantly larger step length in barefoot condition (p = 0.000) and minimal shoe (p = 0.016). Independent t-test for examination of the significant difference of the means of each measure when the shoe condition was changed showed that only step length and step velocity were significantly different between older and younger adults. When the shoe condition was changed from minimal shoe or barefoot to high cushioned shoe, older adults showed significantly bigger change in step velocity (10.04 ± 4.39 cm/s for older; 1.87 ± 0.81 cm/s for younger; p = 0.034) and step length (14.26 ± 6.99 cm for older; 2.086 ± 1.13 cm for younger; p = 0.041) than younger adults. This result indicates that older adults had 23% greater total range of step length and 12% greater total range of step velocity compared with younger adults when shoe condition changed. Moreover, older adults showed 16% smaller total range in their maximal COM-COP ML separations than younger adults when shoe condition changed. It is concluded that high cushioned shoes can influence dynamic postural stability in the ML direction during obstacle crossing in younger and older adults. The minimal shoe and barefoot conditions did not show significant influence on postural stability in the ML direction during obstacle crossing in older and younger adults. The minimal shoe on dynamic postural stability in the ML direction is not significant. Age differences in dynamic postural stability in the ML direction during obstacle crossing were found at the same shoe conditions. Moreover, when shoe condition was changed, shoe cushioning conditions affected postural stability to a larger extent in older adults compared with younger adults. The high cushioned shoe led to a more challenged postural stability in adults aged 50 to 60 than younger adults aged 18 to 32.

6 Abstract Title: Postural stability in subjects with anterior cruciate ligament injury. Objectives: The aim of this thesis was to find out if the postural stability is differed in subjects with anterior cruciate ligament injury and in the control group after the "4 steps - one leg stance" test had been performed. Methods: This study compared a group with anterior cruciate ligament injury and a control group on the basis of the "4 steps - one leg stance" test. Methods of comparison and analysis were used. Results: The test and all measurements revealed differences in postural stability between subjects with anterior cruciate ligament injury and the control group while they were standing both on operated and non-operated limb. There were also differences in postural stability concerning the one leg stance on the operated and the non-operated limb. Keywords: postural stability, injury, ACL, posturomed

Acute stretching increases postural stability in nonbalance trained individuals. J Strength Cond Res 26(11): 3095-3100, 2012-Studies into the relationship between acute stretching and maintenance of postural balance have been inconclusive. It was hypothesized that familiarization with the task and subsequent learning might be involved in the conflicting results. Therefore, this study was to designed determine if a regimen of static stretching exercises after a familiarization period would improve a person's ability to maintain a stabilometer in a neutral position and whether stretching had the same effect on individuals with extensive involvement with balancing tasks. Forty-Two college students (21 male, 21 female) and 10 surfers (all male) performed tests on a stabilometer on 2 separate days after 3 days of familiarization. Testing followed either 30 minutes of quiet sitting (nonstretched) or 30 minutes of stretching activities (stretched). Stretching exercises consisted of various assisted and unassisted static stretches of the muscles around the hip, knee, and ankle joints. Improved flexibility after the stretching exercises was demonstrated by significant (p , 0.05) 6.5 6 2.7 cm (mean 6 SD) increase in the sit and reach. Balance time for the students improved significantly by 11.4% (2.0-second increase), but the surfers had no significant change. Thus, stretching improved maintenance of balance perhaps by helping the subjects to eliminate the gross muscle contractions that caused large stabilometer displacements and to replace them with fine muscle contractions that caused little or no stabilometer displacements. However, it appears that experience doing balance tasks supplants any stretching benefit.

Background: Postural instability is a prevalent and deleterious consequence of aging. It is unclear how the occurrence of chronic pain augments balance issues as age progresses. Research question: We investigated how postural stability is influenced by aging and chronic pain. Methods: Fifty-five participants with and without recent chronic pain balanced on one foot while performing three tasks, a standard balancing task with no challenge, a mental task in which participants answered arithmetic questions while balancing on one foot, and a knot-tying task in which participants tied knots in a ribbon while balancing on one foot. General linear models were used to assess the relationship between age, sex, BMI, and pain category for the three different balancing tasks. In addition, a multivariate analysis of variance was used to test the effect of age and pain category on Hurst exponents from all of three different balancing tasks. Results: Our results show that aging changes the control strategy of balancing from less persistent to more repetitive. The strong feedback elements intrinsic to healthy stability ensure quick reactions and strong capacity to compensate for balance checks; this reactive state changes into a less reactive and more predictable balance strategy with age while balancing on one foot. Mental tasks during balancing also decreased the feedback in balancing strategy. Balance strategy during the knot-tying task was correlated with age, but unaffected by chronic pain. Overall, the chronic pain group had a worse balance strategy while performing the mental task in comparison with healthy people, but were not differentiable from controls in the standard or knot-tying tasks. Significance: Scores from balancing while engaging in cognitive tasks may provide evidence of health decline, and contribute to our knowledge about how pain affects feedback mechanisms.

Objective: We quantified, via complexity analysis, the postural stability of healthy people from a wide age range. Approach: Thirty-five healthy people aged 18-72 performed three tasks while balancing on one foot on a force plate: standard balancing task, mental task (balancing while answering basic arithmetic questions), and knot-tying task (balancing while tying two knots in a piece of ribbon). Mediolateral force trajectories were analyzed to determine control strategy via Hurst exponents, Lyapunov exponents, Kolmogorov complexity, root mean square, and phase-space plots. Main results: We found increased pattern repetition in balancing with increased age, as evidenced by the emergence of a double attractor pattern in phase-space plots and the increase of Hurst exponents with age from approximately 0.3 to 0.8. Significance: As people age, they tend to develop strong feed-forward control strategies for balancing, and lose the complexity of micro movements intrinsic to young age. There is an open-loop control strategy for balancing that emerges in older adulthood, and there are attractors inherent to balancing which begin to develop in middle age.

No description available.

Chronic ankle instability (CAI), a pathological condition characterized by repetitive bouts of the ankle giving way, commonly develops following a lateral ankle sprain injury. Individuals with CAI have been shown to exhibit deficits in postural control and alterations in movement dynamics, which have been suggested to be contributing factors to the recurrent injury paradigm. The purpose of this investigation was to conduct a comprehensive biomechanical analyses to examine the influence of CAI on postural control and movement dynamics during a single leg squat, side-cut task, and single leg landing on an inverted surface. Fifteen participants with CAI and fifteen participants without CAI completed the study following a between-subjects design, with limb serving as the repeated measure during the single leg squat. Each participant completed a single leg squat, side-cut task, and unexpected and expected single leg landings on a tilted surface. Results from the single leg squat and single leg landings on the tilted surface were analyzed using a 2 x 2 mixed-model ANOVA, while results from the side-cut task were analyzed using an independent samples t-test. Statistical significance was considered for all dependent variables when p < 0.05. Individuals with CAI demonstrated impaired postural control, as indicated by reduced time-to-boundary, during the single leg squat compared to controls. Altered ankle joint kinetics and increased sagittal plane hip joint stiffness were observed in the CAI group compared to controls. With regards to the single leg landings on the inverted surface, during the unexpected landing condition the CAI group displayed altered neuromuscular control and ankle kinematics. However, when the landing on the inverted surface as expected, the CAI group exhibited similar motor control strategies to the control group. Findings from this study indicate CAI alters postural control and movement dynamics during functional and dynamic movements, which may be used by researchers and clinicians to develop rehabilitation protocols to restore maladaptive movement patterns in individuals that develop CAI.