The Effects Of High-intensity Interval Exercise And Moderate-intensity Continuous Exercise On Blood Irisin Of Obese Young Women

Nowadays, the incidence of obesity and its related diseases increases dramatically worldwide, mainly as a result of a physically inactive lifestyle and sedentary. Although the molecular mechanisms by which these beneficial effects occur are less well understood,exercise is still the basic measures of prevention and control of obesity. Skeletal muscle has been recently shown to play an active role in the regulation of metabolic homeostasis by communicating with adipose tissue in an endocrine manner. Irisin, a recently identified exercise-induced myokine, has been shown to induce browning of white adipose tissue,enhancing energy expenditure and mediating some of the beneficial effects of exercise,therefore gained interest as a potential new strategy to combat obesity and its associated disorders. In 2012, the way of irisin produced and its role has been reported, but subsequent studies have reported inconsistent results. Not all exercise can make irisin upregulated, which may be related to exercise intensity, exercise time, subjects age, gender, level of physical fitness. Irisin’s respones to different intensity exercise still needs further research to clarify.Purpose: To compare the responses of circulating irisin to acute high-intensity interval exercise and matched mechanical work moderate-intensity continuous exercise in obese young females, and 12 week training effects on the resting circulating irisin as well.Methods: Test One: 40 young obese women(Fat%:33.6±3.7) were randomly assigned into three groups: high-intensity interval training group(HIIT, n=15), moderate-intensity continuous training group(MICT, n=13), and control group(CON, n=12). The HIIT and MICT groups then received exercise training for 12 weeks. HIIT and MICT group performed exercise training on a cycle ergometer at 90% VO2 peak intensity and 60% VO2 peak intensity respectively.HIIT group completed a bout of 4-min cycling followed by an interval rest, and the above unit was repeated until attaining the target mechanical work. The exercise times of both groups were adjusted to keep an equivalent mechanical work(from 200 KJ to 400KJ). All subjects maintained the same caloric intake, dietary habits and physical activity amount with that before training intervention. Fasting blood irisin concentration, body fat mass, and body fat percentage were measured before and after the intervention. Test Two:20 subjects were randomly selected from two exercise groups in Test one. When they comepleted an exercise session in the first week, the fifth week of the beginning and the end of 12 th week(200, 400 and 400 KJ work were done respectively) the blood were drawn 2h after meal at rest,immediately, 30 min and 2h after exercise for testing irisin, glucose and lactate.Result:Test One:Changes in body weight and body fat: Regarding the baseline of body weight, fat mass,fat % and VO2 max, there was no difference among the HIIT, MICT, and CON groups(P>0.05). After the 12-wk intervention, a significant increase in VO2 max and reductions in body weight, fat mass and fat % in relation to the corresponding pre-intervention values were noted in both the HIIT and MICT groups(P<0.01), and no interaction was found regarding the post-pre intervention differences between the two groups(P>0.05). For the CON group, a tiny but significant decrease in VO2 max was found post-intervention(P<0.05), but other variables did not change significantly(P>0.05).Changes in blood indicators: After 12 weeks of exercise training intervention, HIIT,MICT group fasting blood irisin concentrations were significantly elevated(HIIT, 76.7 ± 21.4vs 446.9 ± 260.9 ng.ml-1, MICT, 66.0 ± 13.7 vs 462.0 ± 284.0 ng.ml-1, P <0.01), and the changes of the two groups was not statistically different. There was no significant difference in fasting blood irisin concentration before and after 12 weeks(85.4±37.2 vs 86.7±37.1ng.ml-1,p> 0.05) in CON group.After 12 weeks of exercise training intervention, three groups total cholesterol, high density lipoprotein, low-density lipoprotein were no statistically significant(P> 0.05). HIIT group’s fasting glucose after 12 weeks of exercise training intervention statistically was no significant difference(p> 0.05), and MICT group intervention increases after the exercise training(P <0.05). For the CON group, before and after 12 weeks there was no significant difference(p> 0.05).Test Two:Irisin change: After completing 200 KJ mechanical work, irisin significantly increased immediately after HIIE, MICE exercise, then gradually reduce and recover in 2 hours after exercise to pre-exercise levels. After the completion of the first 400 KJ mechanical work, irisin significantly increased immediately after HIIE, MICE exercise, then continue to rise, attaining peak after 30 min, and did not recover to pre-exercise levels two hours after exercise. After the completion of the second 400 KJ mechanical work, irisin significantly increased immediately after HIIE, MICE exercise, then continue to rise to a peak after 30 min exercise. HIIE recover to pre-exercise levels at 2 hours post-exercise, But MICE has not been restored. After the three exercise test, the effects of the two intensity exercise on irisin had no interaction(p>0.05).Change of serum glucose: Serum glucose decreased significantly after completion of 200 KJ HIIE mechanical work immediately, and recovered after 30 minutes, but the same work MICE did not alter the serum glucose significantly. When the first 400 KJ mechanical work were completed before exercise, neither HIIE nor MICE altered serum glucose significantly.When the second 400 KJ mechanical work were completed before exercise, serum glucose decreased significantly after completion of 200 KJ HIIE mechanical work immediately, and recovered after 30 minutes, after 2 hours exercise continued to decline in both HIIE and MICE groupsChange of serum lactate:Lactate increased significantly after completion of 200 KJ MIIE mechanical work immediately, and recovered after 30 minutes and not recover to pre-exercise levels at 2 hours post-exercise, but the same work HIIE did not alter the serum glucose significantly. When the first 400 KJ mechanical work were completed before exercise, lactate increased immediately, and recovered after 30 minutes and not recover to pre-exercise levels at 2 hours post-exercise in both HIIE and MICE groups.When the second 400 KJ mechanical work were completed before exercise lactate no alternations were found after both exercises.Conclusion:1.Both 12-week high-intensity interval training and moderate intensity continuous training can elevate young obese women fasting blood irisin concentrations, and the effects are same under the same mechanical work.2. Both an acute high-intensity interval exercise and moderate-intensity continuous exercise can elevate irisin concentrations. Irisin has the same response under same mechanical work.3. Obese young women’s blood irisin response is probably related to the volume of exercise, and the larger one is more evident.4. Young obese women blood irisin’s reaction to high intensity interval exercise has certain adaptation after training.