The significance of best-friend relationships in adolescence

Research is summarized that documents the nature of the best-friend process in adolescence. Similarities and differences between the sexes are detailed. Female relationships are described as more intense, demonstrative, exciusive, and nurturant than male. Females depend heavily on the friend as a confidante with whom to process their mutual experiences and psychological reactions, apparently in an effort to understand and develop their own personalities. While males also confide at an intimate level, male relationships are more likely to be based on enjoyable companionship and similarity in attitudes, with less emphasis on continual analysis of experience. For both sexes, but especially for females, the relationship is important enough to development that lack of a close friend should be viewed as a deficit that responsible adults should help a student to remedy. Resources are cited that may be utilized by school personnel in helping the unfriended to make more effective contact with potential friends.     

Acute cardiovascular responses to interval exercise: A systematic review and meta-analysis

ABSTRACT

Interval exercise training is increasingly recommended to improve health and fitness; however, it is not known if cardiovascular risk is different from continuous exercise protocols. This systematic review with meta-analyses assessed the effect of a single bout of interval exercise on cardiovascular responses that indicate risk of cardiac fibrillation and infarction compared to continuous exercise. Electronic databases Medline, CINAHL, Embase, Scopus and Cochrane were searched. Key inclusion criteria were: (1) intervals of the same intensity and duration followed by a recovery period and (2) reporting at least one of blood pressure, heart rate variability, arterial stiffness or function. Cochrane Risk of Bias tool and GRADE approach were used. Meta-analyses found that systolic blood pressure responses to interval exercise did not differ from responses to continuous exercise immediately (MD 8 mmHg [95% CI ?32, 47], p = 0.71) or at 60 min following exercise (MD 0 mmHg [95% CI ?2, 1], p = 0.79). However, reductions in diastolic blood pressure and flow-mediated dilation with interval exercise were observed 10–15 min post-exercise. The available evidence indicates that interval exercise does not convey higher cardiovascular risk than continuous exercise. Further investigation is required to establish the safety of interval exercise for clinical populations.     

Increasing hip and knee flexion during a drop-jump task reduces tibiofemoral shear and compressive forces: implications for ACL injury prevention training

Although most ACL injury prevention programmes encourage greater hip and knee flexion during landing, it remains unknown how this technique influences tibiofemoral joint forces. We examined whether a landing strategy utilising greater hip and knee flexion decreases tibiofemoral anterior shear and compression. Twelve healthy women (25.9 ± 3.5 years) performed a drop-jump task before and after a training session (10–15 min) that emphasised greater hip and knee flexion. Peak tibiofemoral anterior shear and compressive forces were calculated using an electromyography (EMG)-driven knee model that incorporated joint kinematics, EMG and participant-specific muscle volumes and patella tendon orientation measured using magnetic resonance imaging (MRI). Participants demonstrated a decrease in peak anterior tibial shear forces (11.1 ± 3.3 vs. 9.6 ± 2.7 N · kg^?1; P = 0.008) and peak tibiofemoral compressive forces (68.4 ± 7.6 vs. 62.0 ± 5.5 N · kg^?1; P = 0.015) post-training. The decreased peak anterior tibial shear was accompanied by a decrease in the quadriceps anterior shear force, while the decreased peak compressive force was accompanied by decreased ground reaction force and hamstring forces. Our data provide justification for injury prevention programmes that encourage greater hip and knee flexion during landing to reduce tibiofemoral joint loading.     

Programming Time as a Function of Movement Constraint

Abstract

Although the benefits of exercise are well documented, an international problem of physical inactivity exists. More research, especially theory based, has been recommended. One promising approach for studying exercise behavior is that proposed in the Transtheoretical Model (TTM) of behavior change. This model, however, has received minimal cross-cultural attention and, relative to the current study, measurement instruments have only recently been translated into the Finnish language. The purpose of this study was to assess American and Finnish college students' exercise behaviors on the basis of TTM. Participants were American (n = 169) and Finnish (n = 168) college students who completed language-specific measures of exercise behavior, stage of change, processes of change, decisional balance, self-efficacy, and temptation. The only cultural difference observed was that the American participants rated themselves higher on barrier self-efficacy relative to the Finnish participants. Regardless of nationality or gender, participants classified by their stage of change differed on all the core constructs assessed. These results generally support the utility of TTM for understanding American and Finnish college students' exercise behavior.     

Building Relationships through Communities of Practice: Museums and Indigenous People

Abstract This paper explores the theory of “communities of practice” and how the ideas contained in it could be applied to museums, by demonstrating how a key stakeholder group, Indigenous people, have been involved with and engaged in the work of the Australian Museum, Sydney, over the past 30 years. It is suggested that the processes museums have developed in building relationships with Indigenous people, particularly at the practitioner level, could form a template for how museums make themselves relevant to broader communities through active engagement with multiple communities of practice.     

Expectancies as mediators in the differential-reward conditional discrimination performance of pigeons

In a series of within-subject experiments employing a two-choice delayed conditional discrimination task, pigeons chose correctly more often when kind of correct choice and kind of reinforcer were perfectly correlated than when uncorrelated. Correct choice behavior fell to chance levels when the correlation was reversed or when it was removed by using only one kind of reinforcer. Implications for mediation theories are discussed, with the conclusion being that, although the possibility that instrumental mediators are present in this situation cannot be dismissed, the overall pattern of results indicates that classical mediators are of principal importance in this type of task.     

Endogenous technical advance and the stochastic trend in output: A neoclassical approach

In the recent endogenous growth literature, the trend in output is stochastic, while investment in scientific knowledge is treated as analogous to a capital stock. This paper models both research and development (R&D) and disembodied technical advance using neo-classical equations, which specify the equilibrium stocks as a function of prices and output. The elasticity of R&D in the production function, estimated using factor shares, is time-varying and increasing. Returns to scale are increasing in all factors. The most important aspect of the model is that the equilibrium rate of technical advance is not cyclically invariant, but co-moves with output at business cycle frequencies. This allows the production function to behave as a stochastic trend. Growth accounting demonstrates that long-term variations in the rate of productivity growth have been associated mainly with low-frequency fluctuations in the rate of disembodied technical advance, with secondary effects from the stocks of R&D and physical capital. During the high productivity period 1948–1972, technical advance contributed 1.48 percentage points per year to output, with 0.98 accounted for by R&D. The productivity slowdown of the mid-1970s was accounted by a gradual decline in the effect of R&D, and a more abrupt collapse in disembodied technology. The subsequent productivity revival was associated with two accelerations in disembodied technical advance, the first beginning in the early 1980s, and the second in the mid-1990s. The production function is simulated in a small econometric model. Model simulations find that exogenous shocks to the inflation rate generate significant variations in growth by inducing fluctuations in disembodied technology.