An extended trans-contextual model of motivation for health-related physical activity was tested in samples from four nations. The model proposes a motivational sequence in which perceived autonomy support from teachers in a physical education (PE) context and from peers and parents in a leisure-time physical activity context predict autonomous motivation, intentions and physical activity behaviour in a leisure-time context. A three-wave prospective correlational design was employed. High-school pupils from Britain, Estonia, Finland and Hungary completed measures of perceived autonomy support from PE teachers, autonomous motivation in both contexts, perceived autonomy support from peers and parents, attitudes, subjective norms, perceived behavioural control and intentions from the Theory of Planned Behaviour (TPB), and measures of behaviour and past behaviour in a leisure-time context. Path-analyses controlling for past behaviour supported trans-contextual model hypotheses across all samples. Effects of perceived autonomy support from peers and parents on leisure-time autonomous motivation were small and inconsistent, while effects on TPB variables were stronger. There was a unique effect of perceived autonomy support from PE teachers on leisure-time autonomous motivation. Findings support the model, which provides an explanation of the processes by which perceived autonomy support from different sources affects health-related physical activity motivation across these contexts.
In social insects, colony-level complexity may emerge from simple individual-level behaviors and interactions. Emergent global properties such as colony size, which can be viewed as a consequence of life history traits, may inf luence individual-level behaviors themselves. The effects of colony size on productivity, body size, behavioral f lexibility, and colony organization are examined here by considering colony size as an independent variable. Large colony size commonly corresponds with complex colony-level performance, small body size, and lower per capita productivity. Analyzing the construction behavior of various wasp societies reveals that complexity of individual behavior is inversely related to colony size. Parallel processing by specialists in large colonies provides f lexible and efficient colony-level functioning. On the other hand, individual behavioral f lexibility of jack-of-all trades workers ensures success of the small and early societies.Evolutionary biology recently has developed new interest in explanations of how autonomous units can cooperate to form more complex systems (1). Parallel-processing systems poised at the boundary between chaos and order are well able to adapt and evolve (2). Parallel processing requires the existence of several agents or units, plus mechanisms that ensure the specialization and organization of these units into a complex efficient system. An intriguing and simple system organized in this way can be found in social insects, where the colony conducts all of its operations concurrently instead of sequentially. Reliability theory posits that redundancy at the subunit level is more efficient than redundancy at the system level (3). In relation to insect colonies, a system of redundant components (labor is divided by task, the separate tasks are concatenated to form a complete sequence) is preferred to several separate systems (wherein each individual performs the entire sequence independently of other individuals
The aim of the present study was to investigate the effects of a short-term in-season plyometric training program on power, agility and knee extensor strength. Male soccer players from a third league team were assigned into an experimental and a control group. The experimental group, beside its regular soccer training sessions, performed a periodized plyometric training program for six weeks. The program included two training sessions per week, and maximal intensity unilateral and bilateral plyometric exercises (total of 40 – 100 foot contacts/session) were executed. Controls participated only in the same soccer training routine, and did not perform plyometrics. Depth vertical jump height, agility (Illinois Agility Test, T Agility Test) and maximal voluntary isometric torque in knee extensors using Multicont II dynamometer were evaluated before and after the experiment. In the experimental group small but significant improvements were found in both agility tests, while depth jump height and isometric torque increments were greater. The control group did not improve in any of the measures. Results of the study indicate that plyometric training consisting of high impact unilateral and bilateral exercises induced remarkable improvements in lower extremity power and maximal knee extensor strength, and smaller improvements in soccer-specific agility. Therefore, it is concluded that short-term plyometric training should be incorporated in the in-season preparation of lower level players to improve specific performance in soccer.
The present study tested the cross-cultural generalizability of the measurement and structural parameters of the theory of planned behavior (TPB) among youth in a physical activity context. Pupils from five cultural groups completed measures of attitudes, subjective norms, perceived behavioral control (PBC), and intentions for physical activity. Five weeks later, participants completed self-report measures of physical activity behavior. Confirmatory factor analyses and multisample structural equation models revealed well-fitting models within each sample with minimal variations in the measurement parameters across cultures. There were a few significant cross-cultural differences in the structural relations among the TPB constructs. Attitudes predicted intentions in all samples (β range = .300 to .550), whereas the effect of the subjective norms on intention was nonsignificant in all but the Hungarian sample (β = .243). Conversely, the effect of PBC on intentions was significant (β range = .302 to .573) in all but the Hungarian sample. Findings support the generalizability of the measures and pattern of effects for the TPB among young people in a physical activity context.
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