فصلنامه المپیک
سال بیستم شماره 3 (پیاپی 59، پاییز 1391)

The purpose of this study was to examine the effect of sodium bicarbonate ingestion on blood lactate levels and interval performance of elite swimmers. Ten elite female swimmers in Foolad Mobarakeh Sepahan club in Isfahan (age: 15.3 ± 1.7 yr, height: 155.4 ± cm, weight: 51.3 ± 3.16 kg, %Fat: 20.3 ± 1.7 and BMI: 21.3±5.4 kg/m2), presented two different days (separated for a minimum of 3 days and maximum of 7 days) in order to perform the tests. They ingested 0.3 g. kg-1 of body weight of NaHCO3 or placebo in each of the experimental procedures. The substances were ingested in seven doses over a 90-min ingestion period. The first dose was administered two hours before the first time trial. The subjects swam 100 m breast Crowley and then participated in passive recovery for 15 minutes and then 100 breast Crowley test was repeated. Blood lactate, was measured from subject's finger tip in 5 steps: before taking placebo or sodium bicarbonate, 3, 6, 15 minutes after the first swim and 3 minutes after the second swim. Analysis of variance (ANOVA) with repeated measures revealed significant decreases in blood lactate levels at 3, 6 and 15th min of recovery in bicarbonate group compared to placebo. Although it was observed an improvement in performance in supplement group but it was not significant versus placebo (p=0.09). The results suggest that sodium bicarbonate ingestion prior to sprint swim performance consisting of short rest intervals between events is an ergogenic procedure for decreasing lactate and improving performance.

The purpose of present study was to compare fat oxidation rate during and after three different exercise intensities. Eight non-athletes male students (aged, 19.7±1.8 yr; height, 174.3±5.1 cm; weight, 64.5±7 kg; VO2max, 40.1±4.4 ml/kg/min) were in this study and exercised at 55, 65, and 75% VO2max on treadmill at three separate days which elapsed by at least one week. Experimental protocol consisted of a 15 min pre-exercise resting, 60 min exercise, and 2-h recovery periods. Fat oxidation was calculated by using an indirect energy measurement method (Indirect calorimetric) was used throughout the experimental protocol] to measure fat oxidation rate. The results of present study showed that absolute fat oxidation rates during and after 75% VO2max and also total absolute fat oxidation rates were significantly higher than other intensities (P≤ 0.05). Relative fat oxidation rate during 55% VO2max was significantly higher than other intensities (P≤ 0.05), but relative fat oxidation rate and total relative fat oxidation rate were not significantly different after three exercise intensities. Absolute CHO oxidation during the three intensities and total absolute CHO oxidation increased with intensity; however, there was no significant difference in this. But, there was a significant difference in relative CHO oxidation during exercise at 55 and 75 % VO2 max (P≤ 0.05). In post exercise recovery period, absolute and relative CHO oxidation decreased with intensity (P≤ 0.05). Energy expenditure during 75% VO2max and total Energy expenditure were significantly higher than other intensities (P≤ 0.05). It was concluded that exercise with 75% VO2 max can be beneficial to reduce and maintenance of the weight.

The purpose of this study was to determine neural adaptations role after short-term plyometric training within soccer practice, in young soccer players. 15 young soccer players (age 14.26 years, weight 40.42 kg, height 153,56, body fat 7.64%) were randomly assigned to training (plyometric and soccer skills training) group (n=8) and control (soccer skills training) group (n=7) that performed 6 weeks training (16 seasons). To assess neural adaptations surface EMG was done on vastus lateralis and vastus medialis muscles, pre and post training program. Hoffmann reflex was also evaluated in soleus muscle. At baseline and after training, performances of players were assessed with the tests: 5-meter sprint, 10-meter sprint, agility test, counter movment jump (CMJ), Bosco5 and 15 seconds. Two way repeated measure ANOVA (2×2, time×group) was used to identify any significant differences and p ≤ 0.05was accepted. As expected, the results show plyometric training was associated with significant decreases in 5-meter sprint (% 5.97), 10-meter sprint (%-4.05) and agility (%-8.99) and significant increases in SEMG vastus lateralis (%36.54), jump height for CMJ (%12.95), Bosco 5 seconds (%14.08) and Bosco 15 seconds (%13.84) that demonstrated the effectiveness of plyometric training. Control group showed only a significant decrease in agility (%-4.72). However, in two groups H-reflex did not show significant variation. Therefore, according to these results it seems that performance adaptations which achieved in result of short-term plyometric training have possibly a neural origin which may be attributable to increased motor unit recruitment and/or faster firing rates, but motor reflex does not seem to play any role in these adaptations. The position of this study is to advise the application of plyometric trainings combined with soccer training rather than soccer training alone to improve the explosive functions of young soccer players.

The aim of this study was to determine the effect of combined Regular exercise treadmill running and plant extracts on functional consist to creatinine and Blood urea nitrogen(BUN) and structural (glomerular sclerosis) indicators of kidney in chronic hypertension. For this purpose, thirty male Wistar rats were randomly divided into 4 groups (Basline, Sham-operate, L-NAME and combination of exercise and supplement groups. For the hypertension, L-NAME is administrated with 10 mg/kg dosage, intraperitoneally (i.p), for 8 weeks and 6 sessions a week in L-NAME and exercise and supplement groups. Training protocol was performed 15 to 22 m/min for 25 to 64 minutes, 5 times a week for 8 weeks on treadmill. Ferula gummosa was administered with 90 mg/kg per day dosage for 8 weeks using gavage. The sham group received saline solution with the same conditions. Baseline group also did not participate in any intervention. ANOVA showed, administration of L-NAME led to hypertension (It was found that increased activity of angiotensin-converting enzyme or ACE) As well as significant increases in blood urea nitrogen (BUN) and creatinine compared with baseline and sham groups. Results showed that combined aerobic exercise and plant Ferula gummosa extracts reduced the ACE and reduced levels of function indicators of kidney compared with L-NAME groups. The glomerular sclerosis was observed in L-NAME group but was not observed Ferula gummosa + exercise group. The findings of this study can be using approaches such as regular running exercise along with Ferula gummosa plant as a plant antioxidant with inhibiting hypertension can have positive effects on function and structural of kidney in hypertensive patients.

The aim of this research was to examine the impacts of ZMA and CHO supplementations during six weeks resistance training on testosterone and IGF-1 hormones and CK and LDH enzymes in untrained males. 27 untrained young male students (mean of age 21.3 years, and BMI 21.6 kg/ m2) were voluntarily participated and randomly divided in three groups including ZMA group (n=10), ZMA-CHO group (n=9) and placebo group (n=8). All three groups carried out the resistance exercise protocol consisted of three sessions per week, with 70-85 % one repetition maximum. Blood samples were drawn, before and at the end of six weeks of training, following 12 h overnight fasting. For data analysis, Two Way Repeated Measure and Bonferroni post hoc test were used. Results showed, despite the relative increase in anabolic hormones in the groups receiving supplements, there were no significant differences between the three groups in serum testosterone and IGF-1 levels. However, ZMA supplementation with resistance training resulted in a significant reduction in the amount of lactate dehydrogenase (25.5 and 22.5% in the groups receiving the supplement), whereas no effect on enzyme activity of creatine kinase. In addition, significant increases were seen in bench press maximum strength in all three groups. These results suggested that ZMA Supplementation coupled with resistance training may increase the secretion of anabolic hormones and reduced the cellular damage; however, resistance training alone was enough to increase the strength in subjects.

The purpose of this research was to examine the effect of carrying backpacks with different weights on electromyography activity of rectus abdominis (RA) and lumbar erector spine (ES) muscles in male elementary schools students. Twenty and two Subjects (9.1±1.5 years) were randomly selected, voluntarily. Electromyography activity of these muscles was recorded, bilaterally by an 8-channel EMG recorder System during one minute of direct standing, immediately after 15 minutes of carrying backpacks with 9.5, 11, 12.5 and 14% of body weight on a treadmill at 1.1 m/s. Analysis of data by repeated-measures ANOVA and Tokey tests revealed that carrying backpacks equal to 12.5 and 14% of body weight, induced significant decrease (P<0.003) of ES activity, significant increase (P<0.001) of RA activity and asymmetrical activity (P<0.01) of right and left parts of RA muscle, but carrying backpacks equal to 9.5 and 11 % of body weight not induced significant changes in EMG activity in both of muscles (P>0.05). Also, it is symmetric the ES EMG activity between right and left parts during carrying backpacks with different weights (P>0.05). Thus, according to the results of present study, the loads equal to 9.5 and 11% of body weight recommend for elementary schools students as optimal weight and maximum allowable weight of backpack, respectively.

Kicking and cutting skills in soccer are clearly unilateral, require asymmetrical motor patterns and lead to the development of asymmetrical adaptations in the musculoskeletal function of the lower limbs. So, the purpose of this study was to compare isometric strength of knee muscles between the preferred and non-preferred leg in youth men professional soccer players. In total 36 young men soccer players (Mean ±SD; age: 18.7 ± 1.6 y, weight: 73.1±6.4 kg, height: 181.3±5.5 cm) with at least 5 years soccer experience from two professional clubs volunteered to participate in this study. The isometric quadriceps and hamstring torques measured at 30°, 60° and 90° of knee extension and flexion by Biodex System 3. T-test and one way ANOVA was used for analysing the data. Results of this study showed that preferred leg had significantly higher peak torque in knee flexors than non-preferred leg torque at 3 angels (P<0.05). Although non-preferred leg had more peak torque in knee extensors than preferred leg but the differences between them was not significant at three angles. There were significance differences in the peak torque of quadriceps muscles of preferred leg in three angles (P<0.05). The non-preferred leg knee extensors peak torque increased significantly as angles degree increased (P<0.05). With increasing degree of knee angles from 30 to 90 in preferred leg hamstring strength also decreased (P<0.05). Level of peak torque of hamstring in non-preferred similar to preferred leg at 30 degree was highest and at 90 degree was lowest (P<0.05). About 88.9% of soccer players had significance musculoskeletal deficits. It can be concluded that playing soccer and use more of one side of body led to musculoskeletal asymmetry. Therefore, it is suggested that soccer players use of training to strengthening both sides of the body.

The aim of this research was to optimize of resistance training volume for improvement maximal strength with the help of artificial neural network. For this purpose, 12 different combines of sets and repetitions has considered, then 94 untrained male selected as available sample between all boy students of Hakim Sabzevari University (age: 22±1.2 years, height: 173±7 cm, body mass: 66±10.7 kg) that had registered physical education, and were randomly assigned to 8 training groups (3×3 RM, 3×4 RM, 3×6 RM, 4×4 RM, 4×6 RM, 5×3 RM, 5×5 RM and 5×6 RM), and 4 remained groups (3×5 RM, 4×3 RM, 4×5 RM and 5×4 RM) eliminated from proposed sets and repetitions domain because with the help of artificial neural network can be predicted results of this groups. Subjects in each training groups performed bench press, leg press, rowing and lying leg adduction exercises, 2 days per week, for 8 weeks. Before beginning and after ending of training period, lean body mass, body fat percentage, and 1 repetition maximum (1RM) values for leg press and bench press was measured. In this research artificial neural network model, designed with 2 input variables and one output variable. At the end, the results of experimental and predicted groups, that they have stated in percentage, was compared with each other, and following results gained: the 5×6 RM group achieved greater increase in leg press 1RM and lean body mass and greater decrease in body fat percentage, whereas 4×4 RM group achieved greater increase in bench press 1RM. According to these results, people who are interested to gain greater maximal strength in lower body muscles, lean body mass and decrease in body fat percentage, in above-mentioned of domain of sets and repetitions, high volumes training protocol, is superior to other protocols; whereas increasing of maximal strength in upper body muscles by use of lower volume protocols, will be achieved too.