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Objective To explore the effects of different weeks of high intensity interval training (HIIT) and moderate intensity aerobic exercise on maximal oxygen uptake (VO2max) and the expression of the skeletal muscle oxidative capacity related factor AMP-activated protein kinase (AMPK) and peroxisome proliferators γactivated receptor coativator-1-α (PGC-1α),so as to provide the basis for the choice of effective load intensity.Methods One hundred and twenty 6-week-old SPF male Wistar rats were equally randomized into 3 groups according to their body weight:a sedentary control group (not receiving any exercise),a moderate-intensity exercise group (undergoing 50-min continuous running at an intensity of 60％-70％ VO2max) and a HIIT group (conducting 3-min running at 90％ VO2max interspersed with 3-min recovery periods at 50％ VO2max and repeating that process 6 times,with a 7-min warm-up and cool-down period at 70％ VO2max).All rats except those in the control group exercised five days a week and 50min per day.All rats were measured their weight at 8:00-9:00am every Sunday.Soleus was taken from ten randomly chosen rats of each group at 2nd,4th,6th and 10th week after the onset of the intervention.The VO2max test was done before taking muscles.Western blotting was used to detect the protein expression of AMPK and PGC-1α.Results (1) Both the exercise duration and mode had a significant impact on rats' body weight,and they had interaction with each other (P＜0.01).(2) The average PGC-1α expression in the skeletal muscle of 10-week HIIT group were significantly higher than those in the control group (P＜0.05),and the average VO2max at the same time was also significantly higher than the other two groups.(3) In the HIIT group,the average VO2max at the 10th week was significantly higher than that at the 2nd,4th and 6th week (P＜ 0.05).The average protein expression of AMPK in the skeletal muscle at the 4th week in the moderate-intensity exercise group was significantly higher than that at the 2nd and 6th week of the same group,and that at the 2nd week of the control group (P＜0.05).The average protein expression of PGC-1α in the HIIT group from the 2nd to the 10th week was significantly higher than the control group at the 2nd week (P＜0.05).(4)The protein expression of PGC-1α was significantly correlated with temporal variation of VO2max in the HIIT group (P＜0.05).Conclusion Ten-week HIIT can effectively promote the expression of AMPK and PGC-1α in skeletal muscles and the maximal oxygen uptake.It plays a more quick and effective role in improving oxidant capacity and cardiorespiratory endurance of skeletal muscles than traditional moderate-intensity exercises.
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Objective To explore the effectiveness of 12-week exercises with different intensities on cardiorespiratory fitness(CRF)of rats,so as to provide theoretical evidences for evaluating effective exercise loads.Methods Forty male Wistar rats were randomly divided into a low intensity group(50％ VO2max),a moderate intensity group(65％VO2max),a high intensity group(80％VO2max)and a sedentary group,each of 10.All rats were measured the VO2max after three-day adaptive training,then they were repeated the VO2max test every two weeks on the non-training days and the load of the next two weeks was adjusted according to the test result.The treadmill speed was controlled to maintain the specific exercise intensity of each group in the training period.The rats in the exercise groups were trained 5 days per week and 60 minutes per day.After 12 weeks of exercise intervention,the ultrasonic cardiogram tests were conducted.Results After 12 weeks of exercise,compared with the sedentary group,the average weight of the low and high intensity groups decreased significantly(P＜0.05,P＜0.01).After the 12-week exercise intervention,the average VO2max of the three exercise groups were significantly higher than the sedentary group (P＜0.01).The average CRF of the moderate and high intensity group improved faster,with their peak value at the 6th and 8th week respectively.However,in the low intensity group significant improvement in the average CRF was observed from the 10th week,with the peak value appearing at the 12th week.The average left ventricular internal dimension systole of the high intensity group was lower than the low intensity group(P＜0.05),while the ejection fraction and left ventricular shortening fraction increased significantly (P＜0.05).Conclusions Exercises with different intensity can improve the CRF.However,compared with moderate and high intensity exercise,it requires longer time to improve CRF with low intensity exercise.Only exercise with 80％VO2max can significantly improve the cardiac pumping function.
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Objective To explore the optimal exercise way of improving the risk indicators of electrocardiogram (ECG) during exercise.Methods Twenty-four healthy male subjects aged between 40 and 49 years old were divided randomly into a control group (n=9),a low amount exercise group of 1200 kcal/wk (n=7) and a high amount exercise group of 2000 kcal/wk (n=8).The intensity of the exercise groups was 65％～ 80％VO2max training in the standard 400 m track for 12 weeks.The accelerometer and polar watch were worn to monitor the exercise process.During the exercise,the exercise amount was controlled using the distance and duration while the intensity was controlled using target heart rate.The subjects took part in the graded exercise test before and after the exercise intervention.Twelve lead electrocardiograms were used to measure the indicators of ST segment depression and corrected QT interval dispersion (QTcd) during the exercise.Results The exercise intervention did not result in significant change in ST segment depression,while the QTcd indicator in both the exercise groups decreased significantly after the intervention (P＜0.05).Moreover,the decrease of QTcd indicator in the low amount exercise group was significantly higher than that of the control group (P＜0.05),while the decrease of QTcd indicator in high volume group was higher than that of the control group (P＜0.01).No significant differences were found in the ST segment depression among the 3 different groups.Conclusion The Twelve-weeks exercise interventions with intensity of 65％ ～ 80％ VO2max and exercise amount of 1200 kcal/wk and 2000 kcal/wk have no effect on the ST segment depression during the exercise.However,they can result in significant decrease in the QTcd of ECG during exercise,reducing the risk of exercise-induced myocardial ischemia.
