The effect of resistance training intensity on enzymatic and non-enzymatic markers of liver function in obese men

dissertation for obtaining a doctorate degree (Ph.D)

trend: exercise physiology

background and purpose: normal liver function is of particular importance for metabolism and it may be affected by exercise training. Although many studies have examined the effects of aerobic exercise on liver function, available evidence shows that resistance exercise has been less investigated. On the other hand, it is not clear what intensity of resistance training can improve liver function. Therefore, the purpose of this study was to investigate the effect of eight weeks of resistance training with different intensities on the results of liver function tests in obese men. Materials and methods: According to the criteria for entering the study, 32 obese men were selected and randomly divided into 4 groups of 8 people (control, low-intensity training, moderate-intensity training, and high-intensity training). Blood samples were measured in pre-test, mid-test and post-test (after 12 hours of fasting). Data were analyzed using ANOVA with repeated measures.

Findings:. In the exercise groups, the percentage of body fat, ALT, GGT and AST decreased significantly compared to the control group (P<.05), but no significant changes were observed in non-enzymatic markers (serum albumin and bilirubin). No significant difference was observed between the training groups.

Conclusion: According to the results of this research, it can be said that resistance training improves the enzyme markers of liver function in obese men. Also, training with light intensity and high repetitions can have better benefits.

Key words: obese men, resistance training, resistance training intensity, liver function

1 statement of the problem

The prevalence of obesity and overweight is increasing worldwide. Comparing the data obtained from 1976-80 with the data of 1999-2000 shows that the prevalence of overweight (BMI=29.9-25 kg/m2) and the prevalence of obesity (30 BMI) have doubled. The obesity epidemic is not limited to a specific country but is increasing worldwide. Many diseases are related to obesity, including type 2 diabetes, high blood pressure, increased lipid profile, heart diseases, respiratory diseases, cerebrovascular diseases, fatty liver disease (non-alcoholic fatty liver disease), intestinal-gastric diseases, osteoarthritis, cancer and kidney diseases.  It has been reported that the prevalence of obesity among patients with fatty liver varies from 30-100% (Malnick et al, 2006, 579-565). The prevalence of non-alcoholic fatty liver disease occurs 4.6 times more in obese people (Ballentanie et al, 2000, 112-132). The complications and discomfort caused by this disease are mild in the early stages, and it is possible that obese people have this disease but are unaware of its existence.  In the early stages of the disease, treatment through non-pharmacological strategies such as exercise and physical activity are important. Researches have shown that if there is no treatment, the disease progresses to liver cirrhosis, and in this situation, the patient is at high risk of the collapse of the liver's defense mechanisms and may die due to the disease. Today, there are many pharmaceutical and non-pharmacological strategies to solve this problem, in most researches, weight loss through lifestyle interventions is considered. Lifestyle interventions reduce liver lipid markers and metabolic control, but weight loss is difficult to achieve and it will be difficult to maintain.

Increasing the level of physical activity and physical fitness is related to reducing the risks of metabolic disorders (Leone et al, 2001, 502-515). Exercise has many beneficial effects on liver function and improves its metabolism and antioxidant capacity (Aoi et al, 2004, 3117-3128). Following aerobic exercise, it has been shown that liver enzyme markers in NAFLD patients are significantly reduced and liver function improves (Koshbaten et al, 2013, 112-116-Johnson et al, 2009, 1105-1117-1105-Sreenvasa et al, 2006, 191-198).Beneficial effects of aerobic exercise on liver function have been reported independent of weight loss, however, the strategy of aerobic exercise may be weak for obese people due to the fact that it requires too much cardiorespiratory effort and the possibility of people getting tired early, and the capacity to continue these exercises is low (Hallsworth et al, 2011, 1278-1283).

Resistance exercises by the Faculty of Sports Medicine America (ACSM) and the American Heart Association have been suggested as a complementary component of exercise programs (ACSM, 2009, 678-708) and the recommendations of using resistance exercises for the treatment of obesity and metabolic disorders have recently been proven (Strasser et al, 2011), but the intensity, repetition and duration of these exercises have not been well defined (Cabay et al, 35-41).

Demand resistance exercises Cardio requires less breathing and may have similar metabolic benefits to aerobic exercise (Hallsworth et al, 2011, 1278-1278). Normal liver function is important for metabolism and may be affected by exercise. Common tests available to check liver function include enzymatic (ALT, AST, GGT, ALP) and non-enzymatic (serum bilirubin, international normalized tests and serum albumin) tests (Limdi et al, 2003, 307-312). It has been reported that the levels of ALT, GGT and AST enzymes were low in people who do physical activity (daily work, aerobic and resistance exercises) (Sagi et al, 2008).

1-Rm was 40-50 and 15-20 repetitions and at the end of the research period, which was carried out for 10 weeks and reached 75-85% of 1RM and 8-12 repetitions They examined liver enzymes in people who had metabolic syndrome risk factors and reported that resistance training could not significantly change liver enzymes (Sagi et al, 2008). Similarly, Hallsworth et al. (2011), who investigated the effect of resistance training with an intensity of 50-70% 1-RM for 8 weeks, did not report significant changes in liver enzymes (Hallsworth et al, 2011, 1278-1283). Blood and glycemic control play an important role in mental and physical health. In addition to these risk factors, it has been proven that serum bilirubin is considered as an important biomarker for various chronic diseases. Researches throughout the last two decades have shown that low levels of serum bilirubin are associated with increased risk of cardiovascular diseases, metabolic syndrome, type 2 diabetes, autoimmune diseases, etc. Bilirubin may regulate the risk of these diseases by reducing lipid peroxidation and reducing inflammation (Loprinzi and Abbott, 2014). It has been shown that bilirubin levels increase due to physical activity. In 2008, Dervies and colleagues (Dervies et al, 2008, 2281-2288) reported that there is no relationship between cycling training and bilirubin levels in obese people. However, in 2012, Swift et al. (Swift et al, 2012, 569-574) reported a positive association between six months of aerobic exercise and serum bilirubin levels among insulin-resistant adults, but they did not report an association between serum bilirubin and insulin-sensitive subjects. Recently, in 2013, Tanaka et al (2013) reported that there is no relationship between serum bilirubin levels and physical activity. In a study conducted in 2014 by Loprinzi and Abbott (Loprinzi and Abbott, 2014), the existence of a relationship between physical activity and serum bilirubin among insulin-resistant people has been reported, showing that increasing physical activity increases serum bilirubin levels.

Abstract

Background and Objective(s): Normal liver function is of crucial importance for metabolism and might be affected by exercise training. Although many studies have investigated the effects of aerobic exercises on liver function, available evidence indicates that in this case, resistance training exercises are rare. On the other hand, it is unclear whether the intensity of resistance training can improve liver function. Accordingly, the aim of this study was to investigate the effect of eight weeks of resistance exercises with various intensities on liver function test results in obese males.