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The aim of this study was to investigate the rate of Myostatin (MSTN) and Follistatin (FLST) gene expression in fast and slow twitch muscles in response to 8 weeks of high intensity interval training (HIIT).  To this end, 12 male 8-week old Wistar rats were randomly classified into two groups of exercise (n=6) and control (n=6). Exercise group performed a progressive HIIT protocol, five times weekly for 8 weeks using alternating sprint running for 30 min/session that divided into three 4min bouts (35-50m/min speed, >90% VO2 max) separated by a 2min active recovery period (30-50% VO2 max). Gene expression levels for MSTN and FLST in Soleus (SOL) and Extensor digitorum longus (EDL) muscles were measured by real-time RT-PCR. MSTN mRNA levels has slightly (7%); yet significantly (p<0.001), decreased in SOL muscle, while expression of this gene in EDL muscle decreased (30%) (p<0.001). Moreover, FLST gene expression in SOL muscle increased 31% (p<0.001). Interestingly, level of FLST gene expression in EDL muscle increased 100% compared to control group (p<0.001).The results provide a perspective regarding muscle differentiation in MSTN and FLST and their variation in response to HIIT and suggests that HIIT may be an effective way to decrease adipose tissue by MSTN and FLST regulation in skeletal muscles.
 

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Background and objectives: Evidence suggests that decrease in the serum concentration of myostatin (MSTN) may reduce age-related decrement in muscle mass, especially in older individuals. This study aimed at investigating the effects of 12 weeks of resistance training with and without blood flow restriction on MSTN and muscular strength (MS) of elderly women.
Methods: Thirty elderly women were randomly assigned into three groups of resistance training with blood flow restriction (n=10), resistance training without blood flow restriction (n=10) and control (n=10). The resistance training intervention was carried out three sessions a week for 12 weeks. Body composition, MS and serum concentrations MSTN were assessed at baseline and 48-36 hours after the last training session.
Results: There was a significant time × group difference in MS following 12 weeks of exercise intervention (P=0.001). However, there was no significant group and time × group difference in MSTN concentrations (P=0.2).
Conclusion: Low intensity BFRT does not decrease MSTN concentrations in elderly women. However, low intensity BFRT can increase MS values in these individuals.

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Background and objectives: The role of genetic components in expression of proteins involved in signaling pathways of fat and carbohydrate metabolism has been well-demonstrated. The aim of this study was to determine effects of high intensity interval training (HIIT) on glucose, insulin, and insulin resistance levels as well as IRS1 expression in gastrocnemius muscle of obese Wistar rats.
Methods: The study included 14 male, Wistar rats (aged 10 weeks) weighting 220 ± 20 g. Obesity was induced in all rats via exposure to a high-fat diet for six weeks. Then, the rats were randomly divided into a HIIT group (n=7) and a control group (n=7). The rats in the HIIT group performed treadmill running, five sessions a week, for eight weeks. Levels of fasting glucose, serum insulin, insulin resistance, and IRS1 expression in the gastrocnemius muscle of the rats were measured after the last training session. Data were analyzed by the independent t-test at statistical significance of 0.05.
Results: The HIIT intervention significantly decreased fasting glucose compared with the control group (p<0.0001). It also resulted in a significant decrease in serum insulin levels and insulin resistance compared with the control group (p<0.0001). Moreover, the HIIT training significantly increased IRS1 expression (p=0.030) in the gastrocnemius muscle of rats.
Conclusion: Based on the available evidence, the increase in insulin function and the decrease in insulin resistance can be attributed to increased IRS1 expression in the gastrocnemius muscle following HIIT training.