Understanding Joint Retirement.

Evidence from different sources shows that spouses' retirement decisions are correlated. Retirement policies affecting individuals in couples are therefore also likely to affect behavior of their spouses. It is therefore important to account for joint features in modeling retirement.

The metabolic cost of constant muscle force production at zero net mechanical work.

The metabolic cost per unit force is generally thought to increase with the mechanical work done by the muscle fibres. It is currently unclear how the metabolic cost of doing alternating positive and negative muscle fibre mechanical work relates to the metabolic cost of doing zero muscle fibre mechanical work at similar muscle force. The current study aimed to investigate this issue by comparing metabolic power between a dynamic and an isometric near-constant force production task.

The effect of retirement on healthcare utilization: Evidence from China.

We examine the effect of retirement on healthcare utilization in China using longitudinal data. We use a nonparametric fuzzy regression discontinuity design, exploiting the statutory retirement age in urban China as a source of exogenous variation in retirement. In contrast to previous results for developed countries, we find that in China retirement increases healthcare utilization.

Inverse dynamics of mechanical multibody systems: An improved algorithm that ensures consistency between kinematics and external forces.

Inverse dynamics is a technique in which measured kinematics and, possibly, external forces are used to calculate net joint torques in a rigid body linked segment model. However, kinematics and forces are usually not consistent due to incorrect modelling assumptions and measurement errors. This is commonly resolved by introducing 'residual forces and torques' which compensate for this problem, but do not exist in reality.

Relationships between infant mortality, birth spacing and fertility in Matlab, Bangladesh.

Although research on the fertility response to childhood mortality is widespread in demographic literature, very few studies focused on the two-way causal relationships between infant mortality and fertility. Understanding the nature of such relationships is important in order to design effective policies to reduce child mortality and improve family planning. In this study, we use dynamic panel data techniques to analyse the causal effects of infant mortality on birth intervals and fertility, as well as the causal effects of birth intervals on mortality in rural Bangladesh, accounting for unobserved heterogeneity and reverse causality.

What they say and what they do: comparing physical activity across the USA, England and the Netherlands.

Background: Physical activity (PA) is important for maintaining health, but there are fundamental unanswered questions on how best it should be measured.

Methods: We measured PA in the Netherlands (n=748), the USA (n=540) and England (n=254), both by a 7 day wrist-worn accelerometer and by self-reports. The self-reports included a global self-report on PA and a report on the frequency of vigorous, moderate and mild activity.

Informal Caregiving, Employment Status and Work Hours of the 50+ Population in Europe.

Using panel data on the age group 50-70 in 15 European countries, we analyze the effects of providing informal care to parents, parents-in-law, stepparents, and grandparents on employment status and work hours. We account for fixed individual effects and test for endogeneity of caregiving using moments exploiting standard instruments (e.g.

Optimizing the Distribution of Leg Muscles for Vertical Jumping.

A goal of biomechanics and motor control is to understand the design of the human musculoskeletal system. Here we investigated human functional morphology by making predictions about the muscle volume distribution that is optimal for a specific motor task. We examined a well-studied and relatively simple human movement, vertical jumping.

The Relationship between Pedal Force and Crank Angular Velocity in Sprint Cycling.

Purpose: Relationships between tangential pedal force and crank angular velocity in sprint cycling tend to be linear. We set out to understand why they are not hyperbolic, like the intrinsic force-velocity relationship of muscles.

Methods: We simulated isokinetic sprint cycling at crank angular velocities ranging from 30 to 150 rpm with a forward dynamic model of the human musculoskeletal system actuated by eight lower extremity muscle groups.

Cause-specific neonatal deaths in rural Bangladesh, 1987-2005: levels, trends, and determinants.

This paper reports on an analysis of neonatal mortality from communicable and non-communicable diseases in Bangladesh. The competing-risks model employed incorporated both observed and unobserved heterogeneity and allowed the two heterogeneity terms to be correlated. The data used came from the Health and Demographic Surveillance System, Matlab.

Contraceptive use, birth spacing, and child survival in Matlab, Bangladesh.

To reduce infant mortality through improved family planning, a better understanding of the factors driving contraceptive use and how this decision affects infant survival is needed. Using dynamic panel-data models of infant deaths, birth intervals, and contraceptive use, this study analyzes the causal effects of birth spacing on subsequent infant mortality and of infant mortality on the use of contraceptives and the length of the next birth interval. Data are drawn from the Health and Demographic Surveillance System in Matlab, Bangladesh, where almost 32,000 births have been observed from 1982 to 2005.

Control of position and movement is simplified by combined muscle spindle and Golgi tendon organ feedback.

Whereas muscle spindles play a prominent role in current theories of human motor control, Golgi tendon organs (GTO) and their associated tendons are often neglected. This is surprising since there is ample evidence that both tendons and GTOs contribute importantly to neuromusculoskeletal dynamics. Using detailed musculoskeletal models, we provide evidence that simple feedback using muscle spindles alone results in very poor control of joint position and movement since muscle spindles cannot sense changes in tendon length that occur with changes in muscle force.

Satisfaction with Social Contacts of Older Europeans.

This paper analyses the determinants of an important component of well-being among individuals aged 50 years or older in eleven European countries: satisfaction with social contacts. We use data from the Survey of Health, Ageing and Retirement in Europe and anchoring vignettes to correct for potential differences in responses scales across countries and socio-demographic groups. On average, older Europeans report being satisfied with their social contacts, but there exist substantial differences across countries: respondents from Northern countries tend to be more satisfied than individuals from Central or Mediterranean countries.

Do we use a priori knowledge of gravity when making elbow rotations?

In this study, we aim to investigate whether motor commands, emanating from movement planning, are customized to movement orientation relative to gravity from the first trial on. Participants made fast point-to-point elbow flexions and extensions in the transverse plane. We compared movements that had been practiced in reclined orientation either against or with gravity with the same movement relative to the body axis made in the upright orientation (neutral compared to gravity).

Infant death clustering in families: magnitude, causes, and the influence of better health services, Bangladesh 1982-2005.

This analysis of infant mortality in Bangladesh focuses on explaining death clustering within families, using prospective data from a rural region in Bangladesh, split into areas with and without extensive health services (the area covered by the International Centre for Diarrhoeal Disease Research and the comparison area, respectively). The modelling framework distinguishes between two explanations of death clustering: (observed and unobserved) heterogeneity across families and a causal 'scarring' effect of the death of one infant on the survival chances of the next to be born. Keeping observed and unobserved characteristics constant, we find scarring in the comparison area only.

Validating the Use of Anchoring Vignettes for the Correction of Response Scale Differences in Subjctive Questions.

Comparing self-assessed indicators of subjective outcomes such as health, work disability, political efficacy, job satisfaction, etc. across countries or socio-economic groups is often hampered by the fact that different groups use different response scales. This paper develops an integrated framework in which objective measurements are used to validate vignette-based corrections.

The puzzle of Muslim advantage in child survival in India.

The socioeconomic status of Indian Muslims is, on average, considerably lower than that of upper-caste Hindus. Muslims nevertheless exhibit substantially higher child survival rates, and have done for decades. This paper analyses this seeming puzzle.

Gross efficiency during rowing is not affected by stroke rate.

Purpose: It has been suggested that the optimal stroke rate in rowing is partly determined by the stroke-rate dependence of internal power losses. This should be reflected in a stroke-rate dependency of gross efficiency (e(gross)). The purpose of this study was to investigate if e(gross) is affected by stroke rate.

Intertemporal consumption with directly measured welfare functions and subjective expectations.

Euler equation estimation of intertemporal consumption models requires many, often unverifiable assumptions. These include assumptions on expectations and preferences. We aim at reducing some of these requirements by using direct subjective information on respondents' preferences and expectations.

Health and wealth of elderly couples: causality tests using dynamic panel data models.

A positive relationship between socio-economic status (SES) and health, the "health-wealth gradient", is repeatedly found in many industrialized countries. This study analyzes competing explanations for this gradient: causal effects from health to wealth (health causation) and causal effects from wealth to health (wealth or social causation). Using six biennial waves of couples aged 51-61 in 1992 from the US Health and Retirement Study, we test for causality in panel data models incorporating unobserved heterogeneity and a lag structure supported by specification tests.

Dynamics of work disability and pain.

This paper investigates the role of pain dynamics in subsequently affecting dynamics in self-reported work disability and the dynamics of employment patterns of older workers in the US. Not only is pain prevalence quite high, there also are many transitions in and out of pain at these ages. We investigate pain and its relationship to health (work disability) and work in a dynamic panel data model, using six biennial waves from the Health and Retirement Study.

A Test for Anchoring and Yea-Saying in Experimental Consumption Data.

We analyze experimental survey data, with a random split into respondents who get an open-ended question on the amount of total family consumption (with follow-up unfolding brackets of the form "Is consumption $X or more?" for those who answer "don't know" or "refuse") and respondents who are immediately directed to unfolding brackets. In both cases, the entry point of the unfolding bracket sequence is randomized. Allowing for any type of selection into answering the open-ended or bracket questions, a nonparametric test is developed for errors in the answers to the first bracket question that are different from the usual reporting errors that will also affect open-ended answers.