SEARCH · PubMed Health
Results for “Competitive Behavior”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
K-selection, alpha-selection, effectiveness, and tolerance in competition: density-dependent selection revisited.
In the Drosophila literature, selection for faster development and selection for adapting to high density are often confounded, leading, for example, to the expectation that selection for faster development should also lead to higher competitive ability. At the same time, results from experimental studies on evolution at high density do not agree with many of the predictions from classical density-dependent selection theory. We put together a number of theoretical and empirical results from the literature, and some new experimental results on Drosophila populations successfully subjected to selection for faster development, to argue for a broader interpretation of density-dependent selection. We show that incorporating notions of alpha-selection, and the division of competitive ability into effectiveness and tolerance components, into the concept of density-dependent selection yields a formulation that allows for a better understanding of the empirical results. We also use this broader formulation to predict that selection for faster development in Drosophila should, in fact, lead to the correlated evolution of decreased competitive ability, even though it does lead to the evolution of greater efficiency and higher population growth rates at high density when in monotypic culture.
Beauty is as beauty does: body image and self-esteem of pageant contestants.
Self-esteem, dieting, and body image of 131 female beauty pageant contestants (mean age 26.0 years) from 43 states were examined by an anonymous survey. Most (89.6%) reported being a pageant finalist or winner and 55.2% had competed at the nationa/international level Over one-fourth (26%) of the women had been told or perceived they had an eating disorder which reportedly began at 16.25 years. Almost half (48.5%) reported wanting to be thinner and 57% were trying to lose weight. Higher self-esteem scores were significantly associated with increased level of competition (i.e.: from local to international pageants), but not with the number of times the women were pageant finalists or winners. Future study is warranted to determine how pageant participation influences self-esteem, body image, and the development of eating disorders.
The role of global negative self-evaluations in the influence of body weight on weight and eating concerns.
The aim of this study was to test a model based on the assumption that a social comparison-process of body mass index could lead to weight and eating concerns by lowering self-evaluation. Three hundred and ninety-five girls from five age cohorts (in grades five through nine at the time of data collection) participated in a questionnaire-based study. Support for a model where global negative self-evaluations played a mediating role was found among the oldest girls who perceived slimness norms among their peers. Among girls not perceiving a norm of thinness, and among younger girls perceiving such a norm, the model found no support. The proposed model gives an explanation of how the dynamic process of social norms of thinness, body weight and self-evaluation, can cause some girls to become concerned about their body weight.
[Are competitions an appropriate instrument for youth smoking cessation? A 1-year follow-up of the Germany-wide "Smoke-free 2004" campaign].
BACKGROUND: In 2004, the German Cancer Research Center ("Deutsches Krebsforschungszentrum" [DKFZ]), collaborating with the Federal Center for Health Education (""Bundeszentrale für gesundheitliche Aufklärung" [BZgA]) and supported by the World Health Organization (WHO), carried out a population-related smoking cessation campaign entitled "Rauchfrei 2004" ("Smoke-free 2004"). Using mass-media communication, the campaign was intended to motivate as many smokers as possible to quit smoking for at least 4 weeks, so as to achieve, ideally, complete cessation of tobacco consumption. This prevention campaign explicitly included juvenile smokers. METHODS: Within a 1-year follow-up survey, a 1/3 random sample was taken from a total of 4,358 juvenile participants whose smoking status by the end of the competition and 1 year later was evaluated according to international standards. RESULTS: 42% of juvenile participants named monetary reasons, 33% health-related reasons as their chief motivation for participating in the competition. 61% of young adults questioned stated that they were abstinent at the end of the competition, i.e., at least for 4 weeks. 1 year later, 19% of juvenile participants stated to be nonsmokers. 12% of them stated to have been continuously abstinent for 12 months after the start of the competition. CONCLUSION: This publication is the first scientific evaluation of juvenile participation in a competition-based smoking cessation campaign. Although some methodological restrictions need to be taken into account, abstinence rates determined according to internationally applied WHO evaluation guidelines are significantly higher than the secular trend. Thus, the prevention approach presented here appears to be similarly effective as alternative intervention programs that tend to be more expensive.
[Nurturing fair play in competitive sports. Results from a study on competitively oriented youth soccer].
Apologists of sports praise them as an ideal way to prevent addiction and violence. Sports critics see it rather as a socialization authority on the morals of the fair foul. This contradiction was investigated based on an examination of fairness behaviour and fairness education in youth soccer as well as the question of the connection between sports and violence and the preventive possibilities of sports. Our results point to differences in understanding fairness according to age, sex and primarily performance/success orientation. Teenagers learn al ready at the latest in the C youth that it is important and right in the interest of success to break rules. Thus it applies that the more distinctive the success orientation, the more in formal and formal fair play degenerate into fictitious action morals of competitive sport and make way for morals of the "fair foul". The coaches play an important, even quite obviously the central role as socialization agents. In stead of learning fairness, the opposite is often conveyed to many young people in the organizations. However, our examinations also show that coach es can positively influence both fairness understanding and fairness behaviour of young footballers. Coach es are thus challenged as role models to exemplify fair play by their own actions.
A review of postfeeding larval dispersal in blowflies: implications for forensic entomology.
Immature and adult stages of blowflies are one of the primary invertebrate consumers of decomposing animal organic matter. When the food supply is consumed or when the larvae complete their development and migrate prior to the total removal of the larval substrate, they disperse to find adequate places for pupation, a process known as postfeeding larval dispersal. Several important ecological and physiological aspects of this process were studied since the work by Green (Ann Appl Biol 38:475, 1951) 50 years ago. An understanding of postfeeding larval dispersal can be useful for determining the postmortem interval (PMI) of human cadavers in legal medicine, particularly because this interval may be underestimated if older dispersing larvae or those that disperse longer, faster, and deeper are not taken into account. In this article, we review the process of postfeeding larval dispersal and its implications for legal medicine, in particular showing that aspects such as burial behavior and competition among species of blowflies can influence this process and consequently, the estimation of PMI.
[Snowboarding. History--injuries--risks--new materials--tournament on-site services--prevention].
Since the 1998 Olympic Winter Games in Nagano, snowboarding has been established as a popular winter sport for youth and adults. The most frequently affected body region reported in many studies on snowboarding injuries are the wrists accounting for more than 50% of severe injuries, especially in beginners. Wrist braces are effective in protecting snowboarding beginners against wrist injuries. Male snowboarders up to the age of 16 and female snowboarders over the age of 25 have a higher risk of injury. Snowboarders should not use ski boots and should be careful with rented equipment. Systems providing body and limb protection and also snowboard-specific helmets can reduce the injury risk for alpine racers, freestylers, and also freeriders. Snowboard training is important to prevent injuries especially for beginners, and icy slopes should be avoided.
[Is competitive running associated with osteoarthritis of the hip or the knee?].
BACKGROUND: The aim of the study was to find what degenerative changes were present in the hip and knee joints of former elite marathon runners and how these subjects' joints differ from those of control persons. METHODS: Twenty former elite German marathon runners (active careers 1972-86) underwent clinical (FFbH-OA [hip joint] and AKSS [knee joint]) and radiographic (hip and knee joints, Kellgren and Lawrence classification) examination. X-Rays of the hip joints were compared with those of controls matched for age, gender and BMI who did not engage in much sport. RESULTS: In the group of former elite marathon runners, 3 of the 38 knee joints for which comparison with control joints was possible were found to be affected by grade 2 osteoarthritis. In the same group, severe osteoarthritis (Kellgren and Lawrence grade 3) was documented in 1 and moderate osteoarthritis (grade 2) in 6 of the 28 hips for which direct comparison against the controls was possible, as against 1 hip affected by grade 2 osteoarthritis in the entire control group. The clinical evaluation showed high scores in all athletes. CONCLUSIONS: Osteoarthritis of the knee joint is rare in former elite marathon runners. The risk of osteoarthritis of the hip joint seems to be higher than in control subjects who do not engage in much sport.
[Improving performance and promoting health by sports participation].
The 20th century witnessed the globalization of international sporting competitions, most notably in Olympic Competition. Thus whereas fewer than 20 countries competed in the 1900 Olympic Games, close to 200 countries were represented at the 2000 Olympic Games in Sydney. There has also been a progressive improvement in athletic performance during the past century, for reasons that are described in this article. A question that needs to be asked is whether this increased global participation in competitive sport has improved the health of the general population in those countries in which international competitive sports have been promoted. There is little evidence to support this possibility. An important goal of the beginning century must be to globalize sporting participation amongst the general population specifically for health enhancement.
Tryptophan depletion increases aggression in women during the premenstrual phase.
RATIONALE: Reducing serotonin by the method of tryptophan depletion (TD) has led to increased aggression but experimental studies have not used female subjects. OBJECTIVE: To evaluate the effects of TD on aggression in women in the late luteal phase of their menstrual cycle. METHODS: Healthy women were recruited and randomly assigned to an amino acid drink either depleted or with a balanced amount of tryptophan. At 4.5 h later, they competed on the competitive reaction time task. RESULTS: Women who had received the TD drink showed more behavioural aggression in response to provocation. CONCLUSION: Decreased serotonergic neurotransmission increases aggression in women as well as men.
Bacterial competition in activated sludge: theoretical analysis of varying solids retention times on diversity.
A mechanistic model for activated sludge sewage treatment was developed to predict exploitative competition of six aerobic heterotrophic bacterial species competing for three essential resources. The central hypothesis of the model is that in a multispecies/limiting resource system the number of coexisting bacterial species, N, exceeds the number of limiting resources, K, available for them. The explanation for this is that for certain species combinations, the dynamics of the competition process generate oscillations in the abundances of species, and these oscillations allow the coexistence of greater number of species than the number of limiting resources ( N > K). This result is a direct contradiction of an existing activated sludge steady state competition theory, "the principle of competitive exclusion," which states that the competition process proceeds to equilibrium, allowing only N </= K species to coexist. The model was used to investigate the effect of varying solids retention times on the diversity of species using the conventional, completely mixed activated sludge configuration. The results of model simulations showed that for a certain range of solids retention times (2.28-5.66 days) the competition of six species for three essential resources produces oscillations within the structure of the bacterial community allowing for the sustained growth of more than three species on three resources.
Year class coexistence or competitive exclusion for strict biennials?
We consider a discrete time model of semelparous biennial population dynamics. Interactions between individuals are modelled with the aid of an "environmental" variable I. The impact on and the sensitivity to the environmental condition is age specific. The main result is that competitive exclusion between the year classes is possible as is their coexistence. For moderate values of the basic reproduction ratio R(0) there is a strict dichotomy: depending on the other parameters we either find competitive exclusion or coexistence. We characterize rather precisely the patterns of age specific impact and sensitivity that lead to either of these outcomes.
Variation in the outcome of population interactions: bifurcations and catastrophes.
The nature of the association between two species may vary depending on population abundances, age or size of individuals, or environmental conditions. Interactions may switch between beneficial and detrimental depending on the net balance of costs and benefits involved for each species. We study the repercussion of the ecological setting on the outcomes of conditional or variable interactions by means of a model that incorporates density-dependent interaction coefficients; that is, interaction alpha-functions. These characterize the responsiveness and sensitivity of the association to changes in partner's abundance, and can take positive and negative values. Variable outcomes - and transitions between them - are categorized as homeo- or allo-environmental, that is, occurring under the same ecological setting, or not, respectively. Bifurcation analyses show that these dynamics are moulded by ecological factors that are: intrinsic to the nature of the association (concerning the sensitivity of the interaction), and extrinsic to the association itself (the quality of the environment referred to each species alone). The influence of these factors may be conflicting; consequently, the dynamics involve catastrophic events. In a facultative variable association, stable coexistence is expected when environmental conditions are adverse; otherwise, the exclusion of one species is the likely outcome. Remarkable situations as the switching of victim-exploiter roles illustrate the theoretical perspective.
Competitive exclusion and coexistence for pathogens in an epidemic model with variable population size.
We study an SIR epidemic model with a variable host population size. We prove that if the model parameters satisfy certain inequalities then competition between n pathogens for a single host leads to exclusion of all pathogens except the one with the largest basic reproduction number. It is shown that a knowledge of the basic reproduction numbers is necessary but not sufficient for determining competitive exclusion. Numerical results illustrate that these inequalities are sufficient but not necessary for competitive exclusion to occur. In addition, an example is given which shows that if such inequalities are not satisfied then coexistence may occur.
Permanence of discrete-time Kolmogorov systems for two species and saturated fixed points.
This paper considers the dynamics of a discrete-time Kolmogorov system for two-species populations. In particular, permanence of the system is considered. Permanence is one of the concepts to describe the species' coexistence. By using the method of an average Liapunov function, we have found a simple sufficient condition for permanence of the system. That is, nonexistence of saturated boundary fixed points is enough for permanence of the system under some appropriate convexity or concavity properties for the population growth rate functions. Numerical investigations show that for the system with population growth rate functions without such properties, the nonexistence of saturated boundary fixed points is not sufficient for permanence, actually a boundary periodic orbit or a chaotic orbit can be attractive despite the existence of a stable coexistence fixed point. This result implies, in particular, that existence of a stable coexistence fixed point is not sufficient for permanence.
Sex ratio evolution through group selection using diffusion approximation.
We consider a haploid, hermaphrodite population subdivided into an infinite number of demes of finite size N. Assuming recurrent mutation, random union of gametes, partial dispersal, genetic drift, and incorporating group competition, a diffusion approximation is used to describe the evolution of sex ratio, corresponding to sex allocation to male versus female functions. The stationary distribution is deduced. In presence of group selection, a female-biased sex ratio in the whole population is found to be optimal in the sense that an allele coding for this sex ratio is always more frequent at equilibrium when segregating with another allele coding for a different sex ratio than for the same sex ratio. Numerical studies are presented to check the validity and accuracy of this prediction.
Intermingled basins in a two species system.
We present simple examples of (competitive) two species systems with complicated dynamic behaviour. From almost all initial conditions one of the two species dies out. But the survivor is unpredictable: The basins of the two chaotic one-species attractors are everywhere dense and intermingled.