درخت حوزه‌های تخصصی

Introduction: Since people experience fatigue after anterior cruciate ligament injury during exercises, it is important to understand how fatigue affects the biomechanical movement patterns. Therefore, this study aimed to investigate the effect of fatigue on ground reaction force variables during single-leg landing in athletes with a history of an anterior cruciate ligament sprain. Methods: it was a case-control study conducted in the University Laboratory. The sample consisted of 36 male athletes who were divided into three groups: 12 people with Anterior Cruciate Ligament Reconstruction (ACLR), 12 people with Anterior Cruciate Ligament Deficiency (ACLD), and 12 people as the control group. Fatigue was induced via the repetitive sets of double-leg squats (n=8), which were interspersed with the sets of countermovement jumps (n=2) and single-leg landings (n=3) until squats were no longer possible. A 2×2 repeated-measures multivariate analysis of variance was used to detect the main effects of group (ACLD, ACLR, control) and fatigue state (prefatigue, postfatigue) on the ground reaction forces variables. Results: The results showed a significant decrease in the peak vertical force and internal-external ground reaction force in the ACLD group after fatigue. Regardless of the fatigue state, the peak vertical ground reaction force in ACLD and ACLR groups was significantly lower than that in the control group. Conclusion: The athletes with the ACL injury, regardless of the selective treatment type, use compensatory strategies to reduce the contact forces on the lower extremity, compared with healthy athletes.

Introduction: Training at altitude or in a hypoxic environment has gained attention among athletes, coaches, and scientists to enhance sea-level performance. However, the efficacy of “Living-Low, Training-High, Training-Low” (LLTHTL) strategy to escalate the mechanisms associated with enhancing performance in the human athletes is still unknown. The present study aimed to investigate the effect of the LLTHTL on Hypoxia-Inducible Factor-1 alpha (HIF-1α) and peroxisome Proliferator-activated Receptor-Gamma Coactivator-1alpha (PGC-1α) levels in elite endurance runners.  Methods: The study has a crossover design in University laboratory. Eight elite male runners (Mean±SD age: 24.50±3.96 years; Mean±SD height: 179.75±4.62 cm; Mean±SD body mass: 67.37±3.42 kg; Mean±SD body mass index: 20.85±1.11 kg/m²) took part in the research. After 4 weeks of Living-Low (LL), the athletes performed 4 weeks Training-High (TH) and then, 3 weeks training-low (TL). Main Outcome Measures: Anthropometric parameters, time trial (1500 m), PGC-1α, and HIF-1α levels were measured in four different time points: pre-LL, post-LL, post-TH, and post-TL.  Results: There were no significant differences between the 4 time points for body mass and body mass index (P>0.05). The time trial was improved significantly (p <0.001) at post-TH as well as post-TL compared with the pre-LL and post-LL. TH decreased HIF-1α level but did not affect PGC-1α. Besides, TL increased both HIF-1α and PGC-1α.  Conclusion: Training at altitude reduces HIF-1α and training at sea-level increased PGC-1α and HIF-1α levels. Both types of training induced an improvement in the time trial. Athletes and coaches seek advice on the effective training strategy to enhance performance at different altitudes.

Introduction: To examine the effects of a 6-week hopping exercise program on time to stabilization and perceived stability among athletes with chronic ankle instability. This is a randomized controlled trial.Materials and Methods: A total of 28 basketball players with chronic ankle instability (Mean±SD age; 22.67±2.88 y, Mean±SD weight: 80.47±8.48 kg, Mean±SD height: 186.82±3.09 cm) participated in this study and were randomly divided into two equal groups of 14 people each: 1. Experimental; and 2. Control. The experimental group performed hop exercises 3 times per week for 6 weeks. The control group received no intervention. Time to stabilization for anterior-posterior and medial-lateral components of ground reaction force, as well as ankle joint function assessment tool were found before and immediately after the exercise program. Descriptive statistics, independent t-test, and paired sample t-test were used to analyze the data at the significance level of 95% (α≤0.05).Results: The 6-week hopping exercise program led to a significant decrease in the time to stabilization of medial-lateral and anterior-posterior of ground reaction force and also a significant increase in the score of ankle joint function assessment tool (p <0.05).Conclusion: Given the effectiveness of hopping exercises, postural control deficit, and time to stabilization in sport exercises, it is suggested that these selected exercises be used in training and rehabilitation protocols.

Introduction: This study aimed to investigate the onset time and the electromyographic activity level of the selected lower limb muscles in the active and inactive old women.Materials and Methods: In this case-control study, 28 old women with a Mean±SD age of 61.07±0.88 years were selected in the inactive (15 people) and active (13 people) groups. The electrical activity of the selected muscles of the lower limbs was collected by the EMG device in a stair down movement. Results: The onset time of tibialis anterior, vastus lateralis, and biceps femoris muscles are faster in the active group (p <0.05). Besides, the activity level of the rectus femoris muscle in the interval of 100 ms before the initial contact and the ratio of the vastus medialis muscle to the biceps femoris muscle was significantly lower (p <0.05) in the active group.Conclusion: It seems that the muscles of the lower limbs in the group of women with regular physical activity are activated faster than the inactive group and the decrease in the activity of the rectus femoris muscle and the ratio of the vastus medialis to the biceps femoris muscle in the active women may be accompanied by fatigue and reduced intra-articular forces. Therefore, it is recommended that old women participate in regular and active exercise programs to improve their onset times of muscle activity.

Background and Purpose: Increasing participation in sports activities has increased the incidence of sports injuries. Considering the short and long term complications of sports injuries, the need to prevent them is one of the most important goals. The purpose of this study was to evaluate the effects of ankle bracing on the ankle plantar flexor muscles activity in different foot position during drop landing with and without fatigue. Method: Fourteen female college athletes participated in this study. Five models of 5 and 10 degrees medial, lateral and normal wedged insoles were used to simulate the position of the feet on the ground at the wrong landing technique. The Medial Gastrocnemius (MG) and Peroneus Longus (PL) muscles activity 100 ms before and 100ms after landing in different foot position before and after muscles fatigue with and without ankle bracing was recorded with surface electromyography. Repeated measures ANOVA was used for statistical analysis (p≤0.05). Results: The results showed that the effect of time on the activity of MG and PL muscles in landing with brace was significant, so that the MG muscle before landing and PL muscle after landing had a higher activity in both times before and after fatigue (p≤0.001). The activity of this muscles was not significant when using the ankle brace during landing in different positions (p˃0.05). Conclusions: According to the results of this study, lace-up brace can help to increase muscles activity when they were fatigue, while the using of brace does not affect muscle activity when landing perform in different positions without fatigue. According to the results, In the case of a suggestion to use brace for athletes, all aspects of using this equipment should be considered.

Purpose: The purpose of this study was to investigate the dimensions of brand impact on sports, economic and professional experts, managers and experts in Kermanshah province. Method: This is a descriptive-survey research. The statistical population consisted of 120 experts, managers and experts in sport and economic in Kermanshah province who were selected by random sampling. In this study, 87 experts including experts, managers and experts in two fields of sport and economics completed a researcher-made questionnaire assessing the dimensions of sport brand effectiveness. The measurement tool was a questionnaire of sport brand management whose reliability and validity were tested for this research. The Cronbach's alpha value for all factors is 7 or higher, indicating the appropriateness of the questions posed to assess each of the dimensions affecting sport brand management. SPSS software version 20 was used for data analysis. The results of the tests showed that all four sectors (managerial, economic, cultural and social) influenced sport brand management. Results: Finally, the overall summary of the tests shows that social media management brand with a mean of 3.09 and cultural management factor with a mean of 1.82 have the highest and lowest priority in influencing sport brand, respectively. Conclusions: The research results show that the social sector of the brand has a higher priority and microeconomic and macroeconomic indicators should be recognized.

Purpose: The purpose of this study was to analyze the public relations status of Sports and Youth Organization in Kohgilouyeh and Boyer Ahmad province. The present research was applied and study was a consecutive hybrid exploratory strategy and is implemented by qualitative content analysis and questionnaire quantitative survey. Method: Statistical society in qualitative section, ten people in Kohgiluyeh and Boyer Ahmad provincial authority of sports and youth, and in quantitative personnel in public relations department and 46 provincial active board and sports reporters in the province in total there were 150 people. Data collection tool was a face-to-face interview and a researcher-made questionnaire. Based on the findings of the qualitative section, a questionnaire was designed and its face and content validity was evaluated by several experts in the field of public relations and sport management and its construct validity was done by confirmatory factor analysis and its reliability was Cronbach's alpha coefficient of 0/94. Results: The qualitative data were analyzed by qualitative data encoding method and in quantitative part of descriptive statistics, frequency table was included and in the inferential part Friedman test was used. Conclusions: The results showed that the public relations status of Sports and Youth Organization in this province was below average, and Friedman's test showed that the importance, rank, and status of public relations were totally different.