Motion extrapolation in sport expertise: Representational momentum and representational gravity in volleyball athletes.

When people indicate the vanishing location of a moving target that suddenly disappears, systematic errors forward (in the direction of motion) and downward (in the direction of gravity) emerge. These spatial displacements were coined, respectively, Representational Momentum and Representational Gravity, and are believed to reflect internalized ecologically relevant physical invariants useful for the anticipation of future states of an event. Previous research has shown that sports athletes exhibit increased Representational Momentum, indicating enhanced motion extrapolation and anticipation, albeit it is still not clear up to what degree this effect is specific for the expertise context or if it generalizes to other dynamic events. Furthermore, the influence of expertise on Representational Gravity, particularly in contexts where anticipation of vertically moving objects is crucial, remains understudied. This study aimed to address these gaps by focusing on Volleyball as a context of expertise due to the prevalence of fast vertically moving balls. Volleyball athletes and non-athletes indicated the perceived offset location of a smoothly moving target, which moved at a constant speed or was subjected to acceleration/deceleration, embedded either in a Volleyball or neutral context. Outcomes revealed that for the Volleyball context, athletes, but not non-athletes, revealed a significant trend to misperceive targets moving along the left diagonal to be further displaced forward beyond what would be expected due to Representational Momentum alone. This finding is discussed in relation to the natural statistics of Volleyball games, where crossed ball trajectories, particularly by the outside hitter, are more prevalent, fast, and offensive, requiring better anticipation to be efficiently dealt with.

Biomechanical analysis of sit-to-walk in different Parkinson's disease subtypes.

BACKGROUND: The Parkinson's disease Postural Instability and Gait Difficulty subtype is well-known to exhibit higher levels of gait and postural instability and higher frequency of falls. However, no studies have investigated the impact of Parkinson's disease subtypes when performing a highly-challenging postural task, such as sit-to-walk. This task is often used daily and can highlight balance impairments. Thus, the aim of this study was to compare Tremor Dominant and Postural Instability and Gait Difficulty subtypes during sit-to-walk measured by performance, kinematic and kinetic analyses. METHODS: Twenty-four people with Parkinson's disease participated in this study, and were divided into two groups: Tremor Dominant (n = 14) and Postural Instability and Gait Difficulty subtype (n = 10). They performed the sit-to-walk under a time constraint (to pick up a phone placed 4 meters away in order to answer an urgent call). Sit-to-walk overall performance, kinetic and kinematic data were assessed as outcome measures. FINDINGS: The Postural Instability and Gait Difficulty group demonstrated a slower anteroposterior center-of-mass velocity at seat-off, a longer duration of transitional phase and poorer movement fluidity. Furthermore, the Postural Instability and Gait Difficulty group showed a longer sit-to-walk total time. These results indicate that the Postural Instability and Gait Difficulty group performed the task slowly and split the task into two subtasks (sit-to-stand and walking), rather than performing a single, continuous task. INTERPRETATION: The Postural Instability and Gait Difficulty group is unable to perform the sit-to-walk continuously, which might reflect the clinical impairments observed in this Parkinson's disease subtype.

Motor adjustments during time-constrained sit-to-walk in people with Parkinson's disease.

INTRODUCTION: Sit-to-walk (STW) is a sequential task and a merge of sit-to-stand (STS) and gait initiation that are impaired in people with Parkinson's disease (PD). Performing sequential task under time constraint (e.g., stand up and walk to answer an urgent call) might influence people with PD due to their deficits on internal regulation of continuous, rhythmic and fast movements. It is known the PD behavior during STS and gait initiation tasks are impaired, however, little is known regarding PD behavior on STW. Thus, the aim of this study was to assess the motor behavior of people with PD and healthy older adults during the STW task under time constraint. METHODS: Fourteen people with idiopathic PD and 14 healthy older adults (OA) participated in this study. They performed the STW task under a time constraint. STW performance (STW total duration, duration of each of the 4 phases of the STW, and the drop in the center of mass (COM) momentum, identified as Fluidity Index - FI), kinematics and kinetics outcomes were assessed throughout the task. RESULTS: The PD group showed increased STW total time and lower FI, longer seat-off (Phase 1) time and first step (Phase 4) when compared to the OA group. Furthermore, the PD group showed more motor impairments (kinematics and kinetics) than the OA group throughout the task from seat-off until heel-off. Also, people with PD exhibited larger mediolateral COM displacement in the standing phase (Phase 2) and greater ground reaction force (GRF) in Phases 1 and 3. CONCLUSIONS: We observed that people with PD exhibited more restrictions when compared with healthy older adults on their STW performance, COM and GRF parameters during the STW under time constraint. Some clinical impairments usually observed in people with PD might explain their STW performance such as, motor planning deficits, less automatic motor control and mediolateral balance impairments.

Mortalidade por pneumonia em crianças brasileiras até 4 anos de idade / Pneumonia mortality in Brazilian children aged 4 years and younger

OBJETIVO: Avaliar a tendência de mortalidade por pneumonia em crianças brasileiras até 4 anos de idade no período de 1991 a 2007. MÉTODOS: Foi realizado um estudo retrospectivo baseado em banco de dados do Departamento de Informática do Sistema Único de Saúde (DATASUS), do qual foram extraídos o número de óbitos por pneumonia e a população residente de até 4 anos de idade nas cinco regiões brasileiras e no país como um todo. O coeficiente de mortalidade foi calculado pelo número de óbitos por pneumonia dividido pela população, multiplicando por 1.000 na faixa etária menor de 1 ano e por 10.000 na faixa etária de 1 a 4 anos. Utilizou-se o teste de regressão linear para avaliar a tendência temporal de mortalidade. RESULTADOS: Observou-se um decréscimo significativo de mortalidade por pneumonia no período estudado em ambas as faixas etárias e em todas as regiões do país. No Brasil como um todo, a redução média anual dos coeficientes de mortalidade na população menor de 1 ano e naquela entre 1 e 4 anos foi de 0,12 e 0,07, respectivamente. As Regiões Sul e Sudeste apresentaram as maiores reduções (-0,14 e -0,18 para < 1 ano; -0,07 e -0,09 para 1 a 4 anos). As menores reduções foram nas Regiões Norte e Nordeste (-0,04 e -0,07) nas crianças menores de 1 ano, e nas Regiões Norte e Centro-Oeste (-0,03 e -0,04) na faixa etária entre 1 e 4 anos. CONCLUSÕES: Houve uma redução significativa na mortalidade por pneumonia em crianças até 4 anos de idade em todo o país no período de 1991 a 2007, porém, uma discrepância entre as diferentes regiões permanece em evidência.

OBJECTIVE: To evaluate the trend of pneumonia mortality in Brazilian children aged 4 years and younger from 1991 to 2007. METHODS: We conducted a retrospective study based on the database of the IT Department of the Brazilian Unified Health System (DATASUS), from which we obtained the number of deaths from pneumonia and the population aged 4 years and younger living in the five Brazilian regions and in the whole country. Mortality rate was calculated according to the number of deaths from pneumonia divided by the population, multiplied by 1,000 for the age group under 1 year old and by 10,000 in the age group from 1 to 4 years. The linear regression test was used to evaluate the time trend of mortality. RESULTS: There was a significant decrease in pneumonia mortality rates during the study period in both age groups and all regions of the country. In Brazil, the mean annual reduction in mortality rates in the population under 1 year old and between 1 and 4 years was 0.12 and 0.07, respectively. The South and Southeast regions showed the greatest reductions (-0.14 and -0.18 for < 1 year and -0.07 and -0.09 for 1 to 4 years). The smallest decreases were in the North and Northeast regions (-0.04 and -0.07) in children younger than 1 year, and in the North and Central West (-0.03 and -0.04) in the age group between 1 and 4 years. CONCLUSIONS: There was a significant reduction in pneumonia mortality in children aged 4 years and younger across the country from 1991 to 2007; however, a discrepancy between the different regions remains evident.

Pneumonia mortality in Brazilian children aged 4 years and younger.

OBJECTIVE: To evaluate the trend of pneumonia mortality in Brazilian children aged 4 years and younger from 1991 to 2007. METHODS: We conducted a retrospective study based on the database of the IT Department of the Brazilian Unified Health System (DATASUS), from which we obtained the number of deaths from pneumonia and the population aged 4 years and younger living in the five Brazilian regions and in the whole country. Mortality rate was calculated according to the number of deaths from pneumonia divided by the population, multiplied by 1,000 for the age group under 1 year old and by 10,000 in the age group from 1 to 4 years. The linear regression test was used to evaluate the time trend of mortality. RESULTS: There was a significant decrease in pneumonia mortality rates during the study period in both age groups and all regions of the country. In Brazil, the mean annual reduction in mortality rates in the population under 1 year old and between 1 and 4 years was 0.12 and 0.07, respectively. The South and Southeast regions showed the greatest reductions (-0.14 and -0.18 for < 1 year and -0.07 and -0.09 for 1 to 4 years). The smallest decreases were in the North and Northeast regions (-0.04 and -0.07) in children younger than 1 year, and in the North and Central West (-0.03 and -0.04) in the age group between 1 and 4 years. CONCLUSIONS: There was a significant reduction in pneumonia mortality in children aged 4 years and younger across the country from 1991 to 2007; however, a discrepancy between the different regions remains evident.