درخت حوزه‌های تخصصی

Background: COVID-19 transmission in team sports is common, but it's uncertain if face masks impact handball players' performance. Aim: This study investigated the effects of wearing surgical face masks during handball exercise for four weeks on athletic performance. Materials and Methods: Thirty-four adolescent handball female players and 17 trained females as the control group were selected in this study. Players were divided into two groups: the mask group (n= 17; age: 12.63±0.67 years, BMI: 20.61±1.19 kg/m2) and the unmasked group (n= 17; age: 13.45± 1.03 years, BMI: 21.08±1.46 kg/m2), who underwent 4-week training with and without face masks, respectively. Performance tests were conducted before and after the training program, which include: countermovement jump (CMJ), squat jump (SJ), 10m, 20m, and 30m sprint, medicine ball throw, and Yo-Yo Intermittent Recovery Test Level 1 (Yo-YoIRT1). Results: After four weeks, both mask and unmasked groups showed significant improvements in CMJ, SJ, 10m, 20m, and 30m sprint, medicine ball throw, and Yo-YoIRT1 (P≤ 0.05). Conclusion: This study concludes that adolescent handball players can safely use face masks during physical activity without experiencing negative effects on their athletic performance.

Introduction : Sleep deprivation is one of common phenomena in athletes. The aim of the present study was to investigate the influence of arginine supplementation following sleep deprivation on carbohydrate and fat metabolism, balance and fatigue index in female athletic students. Methods: The study population included all undergraduate female students of Sport Sciences at Imam Khomeini International University (age: 22.2± 2.16 years, BMI: 230.15±2.59 kg/m<sup>2 ) of whom 8 volunteered took part in the research. All experiments were performed in laboratory of university in 2020. Subjects were classified into four groups: Control, Sleep deprivation, Arginine and Arginine-sleep deprivation. Lactometer was used to measure blood lactate. Best Balance device was used to measure balance and GAS Analyzer was used to measure metabolism. Data was analyzed by analysis of covariance (ANCOVA). Results: Sleep deprivation significantly decreased static balance ( P =0.01) and dynamic balance ( P = 0.004) while arginine consumption resulted in improved static balance in sleep deprivation arginine group ( P =0.03). It was also shown that lactic acid levels were lower in the two groups that took arginine than in the groups that did not take arginine ( P ≤0.05). Conclusion: Arginine consumption can improve static and dynamic balance as well as mitigate side effects of sleep deprivation on static balance.

Purpose: The world is getting old. Alzheimer's disease is a progressive disease, which in case of no intervention, this ratio reaches 4 more advanced stages in people over 85 years old. Some methods have shown that they can be effective in preventing and slowing down the course of the disease. The purpose of this study was to investigate the role of aerobic exercise program on the quality and some physiological parameters related to sleep in the elderly with Alzheimer's disease. Method: 22 elderly people with Alzheimer's disease were randomly divided into two groups of 11 people: aerobic exercise and control. The subjects in the aerobic training group practiced three sessions every week for twelve weeks and each session lasted for 45 minutes. The sleep quality of the subjects was evaluated by the Pittsburgh Sleep Quality Questionnaire (PSQI). Physiological variables related to sleep (TG, TC, LDL, HDL) were also measured by blood sampling before and after twelve weeks of aerobic exercise Results: The results showed that the sleep quality of the subjects improved by 31% in the Pied Heroi group, which was statistically significant. In addition, there was a significant improvement in the changes of TG (p=0.034), TC (p=0.017), LDL (p=0.006), and HDL (p=0.016) in the aerobic training group. The results of the independent t test also showed that there was a significant difference in sleep quality between the aerobic training and control groups. However, no relationship was observed between changes in sleep quality and changes in physiological variables related to sleep. Conclusion: It can be concluded that twelve weeks of aerobic exercise improves sleep quality along with some physiological parameters related to sleep in the elderly with Alzheimer's disease and will be useful as a way to treat sleep problems in the elderly.

The purpose of this study was to investigate the effect of organizational justice on the relationship between organizational policy and organizational citizenship behavior of sports experts in Tehran Municipality. The statistical population of the present study was all the experts of 22 districts of Tehran Municipality (N= 1800) and the statistical sample according to Cochran's formula was equal to 317 people. Finally, out of 350 distributed questionnaires, 323 questionnaires were found to be valid. A four-part questionnaire was used to collect the research data. The validity of the questionnaires was confirmed by 5 experts and Cronbach's alpha coefficient was used in the pilot study for assessing the reliability of the research tool. Conducting Pearson correlation test as well as structural equation modeling through SPSS and LISREL software were used to examine the research hypotheses. The results of Pearson test showed a negative and significant relationship between organizational policy and organizational citizenship behavior (-0.51) and regression analysis of the study showed that 32% of changes in citizenship behavior could be predicted by organizational justice and organizational policy variables (32/32). Testing the research model revealed the indirect effect (mediated by perceived organizational justice) and direct effect of perceived organizational policy on organizational citizenship behavior. Moreover, the coefficient of direct impact (-0.183) of perceived policy on organizational citizenship behavior was found to be more than its indirect effect (-0.705).