فصلنامه علوم زیستی ورزشی
پیاپی 42 (پاییز 1398)

The aim of this study was to investigate the effect 16 weeks of aerobic exercise on serum adropin levels and insulin resistance index in obese sedentary women. 20 obese women (mean ± SD: age: 41.40±4.53 yr; weight: 76.69±6.14 kg) participated in this study. Subjects were randomly divided into two groups: aerobic exercise (EX) and control. The exercise program in EX group consisted of 90 minutes of aerobic exercise and running on a treadmill for 15.18±5.63 minutes, 4 sessions a week for 16 weeks with an intensity of 7 MET. Before and after the intervention, blood samples were collected to measure serum adropin, fasting insulin and glucose. Paired sample t test and independent t test were used to analyze data. BMI, WHR and HOMA-IR showed a significant reduction in EX group compared with the control group. Serum adropin levels increased significantly in EX group compared with the control group. A significant correlation were observed between changes of adropin and changes of BMI, WHR and HOMA-IR (P<0.05). According to the relationship between adropin and insulin resistance and their susceptibility to aerobic exercise, adropin may play a special role in weight control and prevention of type 2 diabetes.

This study aimed at determining the effect of aerobic training on Tumor necrosis factor-alpha (TNF-α) and insulin resistance in males with type 2 diabetes. 30 inactive adult obese men (30≤BMI≤36) with type 2 diabetes were randomly divided into experimental (n=15) and control (n=15) groups. The experimental subjects participated in three months of aerobic training (3 sessions per week) at %60–75 HRmax. Serum levels of TNF-α, glucose and insulin resistance were measured before and 48 hours after the last training session. Independent t test was used to compare variables at baseline. Paired t test was used to determine the effect of training program on variables. Kolmogorov-Smirnov was applied to determine the normal distribution of data. Aerobic intervention significantly decreased glucose (P=0.001) and insulin resistance (P=0.034) and did not change TNF-α (P=0.83). Despite the lack of change in TNF-α, 3 months of aerobic training was accompanied with a significant improvement in glucose and insulin resistance in type 2 diabetes patients. Based on our findings and other available evidence, improvement in glycemic profile and insulin resistance can be attributed to the changes in other hormonal or metabolic mediators that needs more studies in this area.

Previous studies have investigated the effect of continuous aerobic training (CAT) on gene expression of positive regulatory domain-containing protein 16 (PRDM16) in white adipose tissue. However, no study has yet investigated the effect of different models of training especially high intensity interval training (HIIT) on the expression of this gene. Thus, the aim of this study was to investigate the effect of two models of HIIT and two models of CAT on gene expression of PRDM16. 40 rats were divided randomly into five groups: 1) control 2) moderate volume CAT 3) high volume CAT 4) moderate volume HIIT and 5) high volume HIIT. The subjects of training groups underwent two models of HIIT and two models of CAT on a treadmill for 8 weeks, 5 sessions per week. After the last training session, rats were euthanized and subcutaneous adipose tissue were dissected. The Real Time–PCR method was used to measure the relative gene expression of PRDM16. Data showed that the gene expression of PRDM16 had no significant difference in two HIIT and two CAT groups compared with the control group (P>0.05). The results of this study indicated that training exercises including CAT and HIIT do not change the gene expression of PRDM16 in subcutaneous adipose tissue.

There are little data on irisin concentration and regulation under various physiological conditions. 18 rats had a high-fat diet and 6 rats were nourished with a standard diet (non-obese) for 12 weeks. Then, non-obese group and 6 obese rats (baseline obese) were killed. 12 remaining rats were divided into training obese and control obese groups. Training group ran on a treadmill for 14 weeks, 5 days/week with high intensity. Samples were collected 48 hours after last training session. Serum irisin and leptin concentrations in baseline obese group were higher than non-obese group (P≤0.05). Training increased serum irisin and decreased serum leptin (P≤0.05). In the baseline obese group, UCP1 mRNA expression was lower than non-obese group (P≤0.05) while it was more in training group than control group (P≤0.05). There was a positive relationship between irisin and leptin in baseline obese group and a negative relationship in the training group (P≤0.05). There was a negative relationship between leptin and UCP1 in baseline obese group (P≤0.05). Although the obesity was associated with an increase in leptin and irisin, there was a negative significant relationship between leptin and UCP1. However, training led to weight loss of obese rats by leptin decrease and irisin and UCP1 increase.

Lipocalin-2 is a novel adipokine which is secreted from adipose tissues and is closely associated with low inflammation, obesity, insulin resistance and metabolic syndrome. The aim of this study was to investigate the effect of 8 weeks of selected aquatic aerobic training on lipocalin-2, glycemic indices and lipid profile in overweight middle-aged men. 24 overweight men (BMI≥25 Kg/m2, age range of 45 to 55 years old) were selected randomly from 70 volunteers after a public call. After they met necessary requirements, they were divided into experimental (n=12) and control (n=12) groups. Training program included selected aquatic aerobic training with 45-65% of maximum heart rate for 8 weeks. Blood samples were collected before and after training to measure study variables. The comparison of control and experimental groups with independent t test showed a significant difference in lipoprotein-2, insulin resistance index, cholesterol, triglyceride and LDL-C (P<0.05) while changes in glucose, insulin and HDL-C variables were not significant (P>0.05). Results showed that aquatic aerobic training could have positive effects on reducing some cardiovascular risk factors in overweight middle-aged men. Therefore, these types of training can be recommended by sport and health experts for these individuals.

The aim of this study was to investigate the effect of training exercise intensity on left ventricular structure and function in rats with myocardial infarction (MI). Firstly, male Wistar rats were exposed to LAD coronary artery ligation surgery and then echocardiography confirmed creation of MI. 4 weeks after surgery, the rats with MI were divided randomly into 4 groups: low intensity training (LIT), moderate intensity training (MIT), high intensity training (HIT), and sham, plus a healthy control group (Con). Training groups performed training exercise protocols for 6 weeks, 5 sessions per week. The results of one-way ANOVA showed significant differences in ejection fraction (EF), fractional shortening (FS), left ventricular internal diameter end diastole (LVIDd) and end systole (LVIDs) among all groups (P≤0.05). LSD post hoc test results demonstrated that ejection fraction in the 3 training exercise groups and fractional shortening in MIT and HIT groups increased significantly compared with the sham group. However, their values in the MI groups were significantly lower than the Con group (P≤0.05). LVIDd values in the HIT group significantly increased compared with the Con, sham and MIT groups and also in LIT group compared with Con group. Also, LVIDs values in MI groups were significantly higher than Con group (P≤0.05). In conclusion, training exercise, regardless the intensity, improves left ventricular structure and function. However, it seems that higher intensities of training exercise have more drastic effects on left ventricular function in rats with MI.

The elderly often exhibit high levels of co-contraction in lower extremity muscles which may appear to compensate for deteriorations of organs and better motor control. Normal gait depends on both the neuromuscular system and cognitive health and motion automation. Thus, subjects’ attention can be attracted to outer environment by challenging executive resources through rhythmic auditory cueing and thus daily activity such as gait can change to automatic mode. 30 qualified elderly men (age range of 60 to 75 years old) were voluntarily selected and were divided into two control groups (detraining group and walking without auditory cueing) and one experimental group (walking with auditory cueing). The pattern of lower limb muscles activity including soleus, tibialis anterior, vastus medialis, vastus lateralis and biceps femoris during 90s walking at preferred speed was investigated in pretest and posttest to evaluate muscle co-contraction. This program was performed for 6 weeks, 3 sessions per week and 20 minutes each session. Data were analyzed using ANCOVA and nonparametric Bootstrap test at the significance level of 0.05. The results showed an increase in co-contraction in the synergic muscles but a reduction in agonist–antagonist muscles after 18 sessions of program, but these findings were not statistically significant (P˃0.05). These results indicated that auditory cueing during gait could not influence muscle co-contraction in early aging which is probably due to the lack of evident cognitive changes.

Glucose is the major substrate of the lung tissue under physiological conditions. However, the glucose transfer in the lung tissue during training has not received enough attention. The aim of the present study was to determine the effect of HIIT on GLUT-1 and PDK1 expressions at mRNA level in lung tissue.  14 Wistar male rats (age: 4 weeks old, weight: 68±9 g) were randomly assigned to training and control groups. The training program included 9 weeks of HIIT which started with the speed of 25 m/min. and ended with the speed of 70 m/min. Following tissue sampling, RNA was extracted and cDNA was synthesized, and the expressions of genes were determined by real time RT-PCR technique. GLUT-1 gene expression decreased following 9 weeks of interval training compared with the control group and this change was not significant. Also, PDK1 expression increased following the training program and showed a significant difference with the control group during the 9 weeks (P≤0.05). According to the current results, it is likely that other substrates other than glucose are involved in metabolic pathways of the lung tissue during training.