Axiomatic Characterization of the Mean Function on Trees

A mean of a sequence π = (x1, x2, . . . , xk) of elements of a finite metric space (X, d) is an element x for which is minimum. The function Mean whose domain is the set of all finite sequences on X and is defined by Mean(π) = { x | x is a mean of π } is called the mean function on X. In this paper the mean function on finite trees is characterized axiomatically

Effects of beta-alanine supplementation on brain homocarnosine/carnosine signal and cognitive function: an exploratory study

Objectives: Two independent studies were conducted to examine the effects of 28 d of beta-alanine supplementation at 6.4 g d-1 on brain homocarnosine/carnosine signal in omnivores and vegetarians (Study 1) and on cognitive function before and after exercise in trained cyclists (Study 2). Methods: In Study 1, seven healthy vegetarians (3 women and 4 men) and seven age- and sex-matched omnivores undertook a brain 1H-MRS exam at baseline and after beta-alanine supplementation. In study 2, nineteen trained male cyclists completed four 20-Km cycling time trials (two pre supplementation and two post supplementation), with a battery of cognitive function tests (Stroop test, Sternberg paradigm, Rapid Visual Information Processing task) being performed before and after exercise on each occasion. Results: In Study 1, there were no within-group effects of beta-alanine supplementation on brain homocarnosine/carnosine signal in either vegetarians (p = 0.99) or omnivores (p = 0.27); nor was there any effect when data from both groups were pooled (p = 0.19). Similarly, there was no group by time interaction for brain homocarnosine/carnosine signal (p = 0.27). In study 2, exercise improved cognitive function across all tests (P0.05) of beta-alanine supplementation on response times or accuracy for the Stroop test, Sternberg paradigm or RVIP task at rest or after exercise. Conclusion: 28 d of beta-alanine supplementation at 6.4g d-1 appeared not to influence brain homocarnosine/ carnosine signal in either omnivores or vegetarians; nor did it influence cognitive function before or after exercise in trained cyclists

The influence of a Healthy Welcoming Environment on participation in club sport by adolescent girls: a longitudinal study

Background: This study investigated the perceived influence of a Healthy Welcoming Environment (HWE) on participation in sports clubs among adolescent girls, and how these perceptions changed longitudinally. HWE was defined in terms of a set of health promotion policies advocated by a health promotion foundation as the basis of sport club health promotion practice to promote structural reform in state sporting organisations and their affiliated associations and clubs. These included sports injury prevention, smoke-free, responsible serving of alcohol, sun protection, healthy eating, and welcoming and inclusive environments. Methods: Year 7 and 11 female students from metropolitan (n = 17) and non-metropolitan secondary schools (n = 14) in Australia were invited to participate in three annual surveys. These surveys collected information about current or past membership of a sports club and the influence of HWEs on their decision to participate (or not) in a sports club. Results: Year 7 (n = 328; 74.5%) and Year 11 (n = 112; 25.5%) female students completed all three waves (19.6% response rate; 82.7 and 74.0% retention rate). Most agreed that characteristics of HWEs were a positive influence on their participation in sports clubs, except those relating to alcohol and Sunsmart. Welcoming factors had consistent high agreement among respondents. Alcohol and friendliness factors of the club were regarded as being positively influential by higher percentages of non-metropolitan than metropolitan respondents. Conclusions: Welcoming factors were the most positive influences on decisions to participate in sports clubs. These factors may be important in reducing barriers to sport participation. Strategies supporting the social environment within sports clubs should be prioritised

Familial and “On-the-Street” Risk Factors Associated with Alcohol Use among Homeless and Runaway Adolescents

Objective: This study investigated factors associated with alcohol use among homeless and runaway adolescents, using a risk amplification model.Method: Homeless and runaway adolescents (N = 536, 60% female) were recruited and interviewed by outreach workers directly on the streets, in shelters and in drop-in centers in four Midwestern states. The average age was 16 years; ages ranged from 12 to 22. Results: Parent alcohol problems were indirectly linked to adolescent drinking through familial abuse and its relationship to deviant peers, time on own and risky subsistence behaviors. Parent alcohol problems also predicted offspring alcohol use through parental rejection and its association with deviant peers and with risky subsistence behaviors. The strongest direct effects on alcohol use were hanging out with antisocial friends and participating in deviant behaviors in order to survive on the street. Conclusions: This study sheds light on the nature of alcohol use in a high-risk population. Family background and “on-the-street” (time on own) factors must be taken into consideration when treating alcohol misuse in street youth. The alternative is a vicious cycle whereby homeless youth may become homeless adults

Familial and “On-the-Street” Risk Factors Associated with Alcohol Use among Homeless and Runaway Adolescents

Objective: This study investigated factors associated with alcohol use among homeless and runaway adolescents, using a risk amplification model.Method: Homeless and runaway adolescents (N = 536, 60% female) were recruited and interviewed by outreach workers directly on the streets, in shelters and in drop-in centers in four Midwestern states. The average age was 16 years; ages ranged from 12 to 22. Results: Parent alcohol problems were indirectly linked to adolescent drinking through familial abuse and its relationship to deviant peers, time on own and risky subsistence behaviors. Parent alcohol problems also predicted offspring alcohol use through parental rejection and its association with deviant peers and with risky subsistence behaviors. The strongest direct effects on alcohol use were hanging out with antisocial friends and participating in deviant behaviors in order to survive on the street. Conclusions: This study sheds light on the nature of alcohol use in a high-risk population. Family background and “on-the-street” (time on own) factors must be taken into consideration when treating alcohol misuse in street youth. The alternative is a vicious cycle whereby homeless youth may become homeless adults

Pacing and Decision Making in Sport and Exercise: The Roles of Perception and Action in the Regulation of Exercise Intensity

In pursuit of optimal performance, athletes and physical exercisers alike have to make decisions about how and when to invest their energy. The process of pacing has been associated with the goal-directed regulation of exercise intensity across an exercise bout. The current review explores divergent views on understanding underlying mechanisms of decision making in pacing. Current pacing literature provides a wide range of aspects that might be involved in the determination of an athlete's pacing strategy, but lacks in explaining how perception and action are coupled in establishing behaviour. In contrast, decision-making literature rooted in the understanding that perception and action are coupled provides refreshing perspectives on explaining the mechanisms that underlie natural interactive behaviour. Contrary to the assumption of behaviour that is managed by a higher-order governor that passively constructs internal representations of the world, an ecological approach is considered. According to this approach, knowledge is rooted in the direct experience of meaningful environmental objects and events in individual environmental processes. To assist a neuropsychological explanation of decision making in exercise regulation, the relevance of the affordance competition hypothesis is explored. By considering pacing as a behavioural expression of continuous decision making, new insights on underlying mechanisms in pacing and optimal performance can be developed. © 2014 Springer International Publishing Switzerland

Does the diurnal cycle of cortisol explain the relationship between physical performance and cognitive function in older adults?

Background Regular physical activity is a promising strategy to treat and prevent cognitive decline. The mechanisms that mediate these benefits are not fully clear but physical activity is thought to attenuate the harmful effects of chronic psychological stress and hypercortisolism on cognition. However, the circadian pattern of cortisol secretion is complex and it is not known which aspects are most closely associated with increased cognitive function and better physical performance. This is the first study to simultaneously measure cognitive function, the diurnal cycle of salivary cortisol and physical performance in older adults, without cognitive impairment (n = 30) and with amnestic Mild Cognitive Impairment (aMCI) (n = 30). Results Regression analysis showed that better cognitive function was associated with better physical performance. A greater variance in cortisol levels across the day from morning to evening was associated with better cognitive function and physical performance. Conclusions The results support the idea that a more dynamic cortisol secretion pattern is associated with better cognitive function and physical performance even in the presence of cognitive impairment, but our results could not confirm a mediating role in this relationship

High intensity intermittent games-based activity and adolescents’ cognition: moderating effect of physical fitness

Background: An acute bout of exercise elicits a beneficial effect on subsequent cognitive function in adolescents. The effect of games-based activity, an ecologically valid and attractive exercise model for young people, remains unknown; as does the moderating effect of fitness on the acute exercise-cognition relationship. Therefore, the aim of the present study was to examine the effect of games-based activity on subsequent cognition in adolescents, and the moderating effect of fitness on this relationship. Methods: Following ethical approval, 39 adolescents (12.3 ± 0.7 year) completed an exercise and resting trial in a counterbalanced, randomised crossover design. During familiarisation, participants completed a multi-stage fitness test to predict VO2 peak. The exercise trial consisted of 60-min games-based activity (basketball), during which heart rate was 158 ± 11 beats∙min−1. A battery of cognitive function tests (Stroop test, Sternberg paradigm, trail making and d2 tests) were completed 30-min before, immediately following and 45-min following the basketball. Results: Response times on the complex level of the Stroop test were enhanced both immediately (p = 0.021) and 45-min (p = 0.035) post-exercise, and response times on the five item level of the Sternberg paradigm were enhanced immediately post-exercise (p = 0.023). There were no effects on the time taken to complete the trail making test or any outcome of the d2 test. In particular, response times were enhanced in the fitter adolescents 45-min post-exercise on both levels of the Stroop test (simple, p = 0.005; complex, p = 0.040) and on the three item level of the Sternberg paradigm immediately (p = 0.017) and 45-min (p = 0.008) post-exercise. Conclusions: Games-based activity enhanced executive function and working memory scanning speed in adolescents, an effect particularly evident in fitter adolescents, whilst the high intensity intermittent nature of games-based activity may be too demanding for less fit children

Laying the Foundation for Policy: Measuring Local Prevalence for Autism Spectrum Disorder

Claims have been made that families with children living with autism spectrum disorders (ASD) have been migrating to Alberta because of higher funding available for ASD supports compared to other provinces. The legitimacy of these claims, along with many others about the adequacy or inadequacy of funding for supporting persons living with ASD, has not been evaluated because we simply don’t know how many people in Alberta are living with ASD. Typically in Canada, ASD prevalence is reported in national figures, based on international estimates. Canadian prevalence estimates for ASD are needed. With no national surveillance system in place, national estimates are difficult to determine. In addition, such broad measurements are problematic as they may not adequately inform the service delivery needs for specific jurisdictions. A new study shows that 1,711, or 1 in 94, school age children in the Calgary region have an ASD diagnosis. As this number matches what is often reported for the national prevalence of ASD, it suggests that Alberta’s relatively higher ASD funding is not inducing in-migration of families seeking better support. The data also show that the prevalence is higher in elementary-grade children, with a diagnosis in one of every 86 children. In the senior grades, there are significantly fewer students with ASD diagnoses, specifically within the Calgary Board of Education. There is no evident reason for diagnoses to seemingly dematerialize in the older grades. These students could be dropping out or choosing home-schooling in greater numbers. Possibly there has been an increase in prevalence. These prevalence estimates help to inform the demand for special-needs services within the local school system. In addition, there is growing concern that upon graduation there is a “support cliff” resulting from a less systematized, less generous support system available for adults with neurodevelopmental disability. Families that need support for ASD face enough challenges; it is critical for policy-makers to be aware of the extent of the situation in their own jurisdiction so as to develop the right kinds of supports for these families

Creatine supplementation research fails to support the theoretical basis for an effect on cognition: Evidence from a systematic review

Creatine supplementation has been put forward as a possible aid to cognition, particularly for vegans, vegetarians, the elderly, sleep deprived and hypoxic individuals. However, previous narrative reviews have only provided limited support for these claims. This is despite the fact that research has shown that creatine supplementation can induce increased brain concentrations of creatine, albeit to a limited extent. We carried out a systematic review to examine the current state of affairs. The review supported claims that creatine supplementation can increases brain creatine content but also demonstrated somewhat equivocal results for effects on cognition. It does, however, provide evidence to suggest that more research is required with stressed populations, as supplementation does appear to significantly affect brain content. Issues with research design, especially supplementation regimens, need to be addressed. Future research must include measurements of creatine brain content