The Effect of 12-week Circuit Training on Insulin Sensitivity and Endothelial Function in Women With Insulin Resistance

Overview

During the last 10 years many studies concerning the impact of physical training on whole-body insulin sensitivity have been published, but there is a lack of an extended investigation on the potential clinical benefits of novel circuit training-based on strength and endurance exercises-relating to the optimization of insulin sensitivity and vascular endothelial function. It is of interest to precisely determine the physiological and biochemical effects of circuit training. An important aspect of the planned research will be the analysis of the effects of physical training on the released during muscle contraction myokines capable of modulating various metabolic processes. We hypothesized that in studied participants 12 weeks of the novel form of training would result in improving insulin sensitivity and vascular endothelial function mainly via myokines released by contracting skeletal muscles. The following questions will be asked: (1) whether the 12-week circuit training (combined strength and endurance exercises) performed by women with insulin resistance, improves insulin sensitivity, carbohydrate and lipid metabolism and promotes the efficiency of endothelial defense mechanisms? (2) whether the 12-week circuit training (combined of strength and endurance exercises) changes the concentrations of transcription factors regulating lipid and carbohydrate metabolism or the synthesis and/or secretion of myokines and adipokines in women with insulin resistance? (3) whether the 12-week strength training, interspersed with bouts of endurance exercise has a positive effect on cytokine profile? (4) whether there is a relationship between changes in body composition, HOMA-IR, and the level of myokines caused by physical training? (5) whether the 12-week circuit training reduces low back pain symptoms, plantar stifness and improve functioning of the patient in everyday life? A group of 80 women, aged 25 to 45 years, with diagnosed insulin resistance will participate in the planned study. Participants will be enrolled in the research program based on medical qualification. Before the intervention all women will have venous blood collected to determine fasting glucose, hemoglobin glycosylated (HbA1C) and insulin levels and insulin resistance by the homeostasis model assessment of insulin resistance (HOMA-IR) will be calculated. The inclusion criteria will be as follows: (1) women, age: 25-45 years, menstruating, (2) BMI 18,5-29,9 kg/m2, (3) insulin resistance based on HOMA-IR (cut-off point 2.5), (4) HbA1C ≤ 6.5%, (5) not contraindicated to physical activity. Participants meeting the inclusion criteria will be randomly divided into two groups. The first group of women will undergo circuit training, consisting of exercises performed on 7 machines arranged in a circuit. Thanks to the use of adequate software the machines will automatically adjust their parameters, such as seat height or resistance to the exercising person, and the training progress will be individually monitored. The planned training will last for 3 months, during which the patients will exercise 3 times a week for 30 minutes (2 circuits will be done during each session). The planned duration of the training session will be controlled (one minute for strength exercises, four minutes for endurance exercises and a 30-second break between each exercise). In the training group, one-repetition maximum exercise test (1RM) will be performed to determine the appropriate training load and later after the program to verify the increase in muscle strength. The range of maximum heart rate (HRmax) will also be determined in all exercising women. The second group of women, who will be asked to maintain their current level of physical activity and their diet for a period of 3 months will serve as a control group. Before and after the training program in all participants of the study pulse wave velocity, anthropometric parameters and body composition will be assessed. Concurrently venous blood will be taken to determine biochemical indicators related to carbohydrate and lipid metabolism, insulin resistance, vascular endothelium function, inflammation and adipocytokines and myokines. In both groups of women, the questioners concerning dietary intake and the level of daily physical activity will be administered. Results will be subjected to analysis involving descriptive, and advanced statistic method among them analysis of correlations, regression, variance and cluster analysis. All calculations and statistics will be performed using TIBCO Statistica 13.3 software (TIBCO).