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The purpose of the present study was to investigate the effects of errorless and errorful practice on children’s learning of motor skills: The Role of Reinvestment. The statistical population of the present study consisted of all the male elementary school students in the age range of 7-10 in Mashhad in the academic year of 2017-2018. For this purpose, 48 male students in the city of Mashhad, , were selected through an available sample and randomly based on the levels of reinvestment. This study is an applied research and the type of practice protocol in four groups: errorless with high reinvestment tendency, errorful with low reinvestment tendency, errorful with high reinvestment tendency. Retention, transfer, and dual-task tests were conducted after the acquisition phase at 24-hour intervals. To analyze the data in the acquisition, retention, transfer, and dual-task phases, a mixed model variance analysis (ANOVA) 2 (reinvestment levels: high and low) × 2 (practice protocol: errorless and errorful) and LSD post-hoc test were used, and the data were analyzed using SPSS 24 software. The results of the acquisition test showed that all groups had made progress, but two groups, the errorful with high reinvestment tendency and the errorless with low reinvestment tendency, performed significantly better than the other groups on the retention and transfer tests. The two groups of the defectless with low reinvestment tendency and the defectless with high reinvestment tendency performed significantly better than the other groups under pressure conditions. Therefore, it is recommended that physical educators pay special attention to these psychological variables (reinvestment) when designing exercises and training programs for children’s motor skills.

The aim of this study was to investigate the role of the errorless, errorful and random practice schedules on the acquisition and learning of relative timing in a motor task. 51 male students (age: 22±4 years old) were selected and randomly assigned to four groups (control, errorful, errorless, and random). This study was carried out in five phases: pretest (PRT), acquisition (ACQ), 10-min retention and transfer and 24-hour retention and transfer. In the acquisition phase, a timing task with three different difficulty levels (simple, moderate, and difficult) was practiced in three sessions of 45 trials with feedback by experimental groups. In order to analyze the data, a mixed-design analysis of variance model with repeated measures on each variable was used in the acquisition and retention phases. The one-way analysis of variance (ANOVA) was used in the other phases. The findings of relative timing showed no significant differences among the groups in the pretest (P˃0.05). Additionally, in retention and transfer tests, errorless group had better performance than errorful, random and control groups (P≤0.05). Errorless group performed better than the random and errorful groups in 24-hour transfer test of the secondary task (P≤0.05). These results showed that practice in errorless conditions leads to a better learning of the task and its generalization to new conditions that are consistent with the implicit learning and reinvestment theories

This study aimed at investigating the effect of blocked, incremental systematic and random contextual interferences on acquisition, retention and transfer of volleyball skills based on changes in a generalized motor program. In fact, this study was conducted to answer this question that whether regular increment of contextual interference level is more effective on learning volleyball service skill than blocked or random practice schedules. 30 students (mean age 23±4 yr, 3 groups and each 10 subjects) participated in this study. The groups were different in practices of the three services. Subjects performed simple, overhead and single arm skills from a distance (9 m from the volleyball net) with different practices. Each participant practiced 108 trials of each service, totally 324 trials during 9 sessions (each session 36 trials). The results indicated that incremental practice resulted in a better performance in retention and transfer tests than blocked and random practices (P˂0.05). In general, it was suggested that the practice should be scheduled so that it can start from low interference and gradually and systematically continues towards high interference in order to facilitate learning of several generalized motor skills.

Thermal power plants are one of the main sources of CO2 emissions in the world. On the other hand, increasing carbon dioxide emissions as a greenhouse gas is led to global warming and climate change. In this study, CO2 mitigation strategies for Iran's thermal power plants regarding Intended Nationally Determined Contributions submitted by Iran using modified STIRPAT model examines are presented. In the first step of this research, CO2 emissions from Iran's power sector are predicted with respect to the parameters including, population, GDP, and electricity generation. In the second step of this research, CO2 mitigation strategies including, using the renewable sources and increasing energy saving as well as power generation efficiency during the years of 2020 to 2025 are analyzed using modified STIRPAT model to reduce carbon dioxide emissions in accordance with Iran's INDCs. The prediction of carbon dioxide emissions by 2025 represents an increase of 26.5% in carbon dioxide emissions compared to 2017 while estimating carbon dioxide emissions in accordance with Iran's INDCs allows a maximum increase of 21.4% compared to 2017. In order to reduce carbon dioxide emissions, the average efficiency of power plants by 2025 should be 1.542% higher than in 2017, or 3.086% of the energy savings should be implemented compared to total electricity generation output projected in 2025, or more than 36.22% increment of electricity generation output from renewable energy is expected compared to the projected level in 2025, or a combination of these three solutions. [ABSTRACT FROM AUTHOR]