Multi-age-grouping paradigm for young swimmers.

The purpose of this study was to examine the adequacy of "multi-age" classification systems in youth sports with a specific focus on the unisex multi-age-groupings used by USA Swimming. In addition, we offer an analytical rationale for the multi-age-groupings and potential alternatives. We examined the top 100 US swim performances for three years (2005, 2006, and 2007) for girls and boys in 15 age-groups (7 to 20 years and a singular group of 21 years and older). Data for each age and sex were pooled over the three years and means were calculated for each of seven competitive swim events. Swim times differed among each age up to the 14-year age-group in girls (F (14,30885) = 183.9, P < 0.01, Cohen's d = 1.19-3.72, large effect) and 16-year age-group in boys (F (14,30885) = 308.7, P < 0.01, Cohen's d = 0.81-3.64, large effect) for all events. Age-related differences in swim times continued later in boys than girls likely due to differences between the sexes in timing of growth and maturation. Because of the differences in swim performance in contemporary multi-age-groups, stratifying swimmers by a single age is the best means to ensure competitive fairness and equality, although there is no rationale for swimmers under the age of 8 years to compete in separate unisex competitive groups.

Contemporary work characteristics, stress, and ill health.

This study investigates the relationship between work and ill health resulting from stressors originating in the work environment. The association between work and health has been well-documented. Factors in the work environment leading to ill health have included generalized psychological stress and/or specific physical environmental characteristics. Data for this study come from a 1998 telephone survey, the Indiana Survey of Work in a Polarized Economy, under the auspices of the Center for Survey Research at Indiana University. The dependent variable is an index that measures ill health among workers; control variables include sociodemographic and lifestyle characteristics of these workers as well as their job characteristics; and the four key independent variables are occupational status, organizational disruption, layoff experience, and educational discordance of the workers. Multiple regression analysis on the entire sample (n = 919) demonstrates that occupational status is negatively associated with ill health, while organizational disruption, layoff experience, and educational discordance are positively associated with it. Separate analyses for male (n = 474) and female (n = 445) respondents find significant sex differences in the effects of the key variables: for males, organizational disruption is positively related to ill health while for women occupational status is negatively related and layoff experience and educational discordance are positively related to ill health. The findings from the present research provide insight into the interrelationship of occupational environment and health within the framework of evolutionary medicine.

Are all grandmothers equal? A review and a preliminary test of the "grandmother hypothesis" in Tokugawa Japan.

An unresolved question arising from human evolutionary research relates to the function of the postreproductive period in human females. If menopause is not merely an artifact resulting from the benefits of civilization, there must be an adaptive mechanism favoring the offspring of women who continue to thrive well past the time of their last ovulation. The "grandmother hypothesis" was developed on the basis of the original suggestion by Williams (1957 Evolution 11:32-39) that "stopping early" would benefit already-born children. This idea, combined with the concepts of kin selection (Hamilton 1964 J Theor Biol 7:1-52) and parental investment (Trivers 1972 Sexual Selection and the Descent of Man, Chicago: Aldine, p. 136-179), was expanded to suggest that postreproductive women (in contrast to males) contribute to their inclusive fitness by extending support to their grandchildren. We used discrete time event history analysis (Allison [1984] Event History Analysis, Newbury Park: Sage; Allison [1995] Survival Analysis, Cary, NC: SAS Institute) and logistic regression on data provided in population registers (Shumon Aratame Cho, or SAC) from a village in central Japan, covering the period from 1671-1871, in a preliminary investigation of the effects of household grandparental presence on the probability of a child's death. We found that after accounting for the presence of other household members, the only grandparent whose presence exerted a consistent negative effect on the likelihood of a child's death was the mother's mother. Due to the small sample size of households that contained maternal grandmothers, these results failed to achieve statistical significance. Their importance, however, is in what they suggest about future research, i.e., census data from preindustrial societies can provide a basis for testing evolutionary proposals, including the "grandmother hypothesis."

New perspectives on the face in fetal alcohol syndrome: what anthropometry tells us.

Fetal alcohol syndrome (FAS) refers to the adverse effects to the fetus from prenatal exposure to alcohol. Originally, the diagnosis of FAS was given only to those individuals that were the most severely affected. Since that time, it has become apparent that the effects of prenatal alcohol exposure are broad-based, and those individuals diagnosed with FAS represent the severe end of the continuum in their phenotypic expression. This study utilized 21 craniofacial anthropometric measurements on 100 prenatally exposed individuals to quantify the elements of the FAS facial phenotype and to extend the quantitative phenotype to individuals who exhibited less severe or incomplete manifestations of prenatal alcohol exposure.