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This review article elucidates the structure and critiques the effects of social loafing in the team sport of volleyball. Drawing upon existing theories, opinions, and research, this review addresses the conceptual framework and factors influencing individual and group behaviors in sports environments, particularly volleyball. These factors include team cohesion, leadership styles, communication, interdependent tasks, and individual motivation. An examination of the research methodologies and article formulations, as well as meta-analyses in academic databases like PubMed, Google Scholar, and PsycINFO, indicates that the predominant approach in studies on this phenomenon is deductive, with survey strategies employed through observational studies and interviews with players and coaches using questionnaires. The findings of this review, on one hand, present and analyze theories and models explaining social loafing behaviors in sports environments and teams, including the processes and dimensions of the emergence (and growth) of social loafing and its impact on individual aspects and team performance in volleyball. On the other hand, it highlights key points and related solutions for future research directions in volleyball, including strategies and interventions (by coaches and team leadership) aimed at reducing social loafing, enhancing cohesion, and improving group dynamics in volleyball teams, ultimately leading to improved team performance.

Background and purpose: Physical activity is effective on the serum level of the monoamine neurotransmitter dopamine and also reduces psychological disorders such as depression. The aim of this study was to investigate the effect of eight weeks of walking on plasma levels of dopamine and the level of depression in elderly women with Alzheimer's disease. Method: In this semi-experimental study, 20 women with Alzheimer's disease with an average age of 73.5 ± 7.72 years who were suffering from moderate to severe depression according to the Beck questionnaire with the opinion of a psychiatrist in a targeted manner and the sample available for were selected to participate in the research. The subjects were randomly divided into two equal groups of 10 people, including the experimental group (walking) and the control group (without regular physical activity). The subjects in the walking group exercised on the treadmill for eight weeks three sessions per week and each session lasted 30-45 minutes with an intensity of 60-75% of the maximum heart rate. Before and after the exercise intervention, blood samples were taken from the cubital vein of all participants in a 12-hour fasting state. Serotonin and dopamine levels were evaluated by ELISA method. The results were extracted using the paired t test and covariance at a significance level of 0.5. Findings: 8 weeks of walking led to a significant increase in dopamine levels (p=0.005) and a significant decrease in depression (p=0.001) in the experimental group compared to the control group. Conclusion: It seems that walking can have positive effects on some neurotransmitters and reduce the level of depression in elderly women with Alzheimer's disease.

Purpose: Delayed onset muscle soreness (DOMS) is pain and stiffness that occurs several hours to several days after unusual or intense exercise. It is thought that this exercise causes small damage (micro trauma) to muscle fibers. The aim of the present study was to compare the effects of high-intensity resistance training and resistance retraining on serum levels of some indices of muscle damage in inactive young girls. Method: Twenty-four healthy inactive young girls voluntarily participated in the present study. They then randomly divided into two groups of 10. The muscle injury protocol included five stations of biceps and shoulder presses with a barbell, squats, chest press, and leg press. Each movement consisted of three sets of 8 to 12 repetitions, with an intensity of 75% of one repetition maximum. Serum levels of creatine kinase, lactate dehydrogenase, and aspartate aminotransferase enzymes were measured before the activity and at intervals of 1, 26, and 48 hours after it. Analysis of variance with repeated measures and independent t-test were used to analyze the data at a significance level of p≥0.05. Results: there was no significant difference in the changes in creatine kinase, lactate dehydrogenase, and aspartate aminotransferase between the two groups at different stages of measurement after retraining (p<0.05). Conclusion: According to the results of the present study, it can be concluded that resistance training cannot be a significant influencing variable on the amount of muscle damage. However, more research in this field is needed.