Study On The Effect Of High-intensity Interval Exercise At Different Times On Glucose And Lipid Metabolism In Sedentary Young Adults

PurposeThe purpose of this study was to compare the acute glucolipid responses after high intensity interval exercise（HIIT）performed before breakfast and before dinner in healthy young people of different weights,so as to explore the optimal time for HIIT in a day.MethodsA randomized,controlled,crossover design was used.A total of 26 healthy sedentary subjects were enrolled in this study,including 13 normal weight subjects（age:23.1±2.5years,BMI:20.7±1.6kg/m²）and 13 overweight and obese subjects（age:21.7±2.5 years,BMI:26.8（3.9）kg/m²）.During the 3 days before each experiment condition,subjects wore an accelerometer to record their physical activity,as well as filled in a diet and physical activity form.In this study,all subjects completed three experimental conditions:1)exercise before breakfast（MEx）;2)Exercise before dinner（EEx）;3)No exercise（CON）.In both MEx and EEx experiments,subjects completed HIIT on a treadmill,which consisted of 10 alternating combinations of 1 min high-intensity running(100%VO_2max)and 1min interval running(50%VO_2max),as well as 2minutes of warm-up and finishing exercise(50%VO_2max)immediately before and after the exercise.In MEx and EEx,we detected 24h dynamic interstitial glucose after exercise,furthermore,we measured blood glucose（Glu）,insulin（INS）,free fatty acids（FFA）,triglycerides（TG）levels immediately after and 30 min,60 min,120 min after the post-exercise meal.In CON,we measured 24h dynamic interstitial glucose and the same blood indexes as MEx and EEx after breakfast and dinner.The washout period between the three conditions was at least 5-7 days,and the interventions in female subjects were completed during the follicular phase of the menstrual cycle.Results1.Overall,HIIT before breakfast can significantly reduce the 24 h continuous interstitial glucose levels（t AUC was reduced by5%,p=0.036;i AUC was reduced by20%,p=0.028）and blood glucose variability（CONGA-1 was reduced by 6%;p=0.031）after exercise,which was related to the energy consumption of exercise,but not significantly affect the postprandial Glu,INS,FFA and TG level（p>0.05）after post-exercise meal.HIIT before dinner had no significant effect on 24h interstitial glucose level,blood glucose variability,postprandial Glu,INS and insulin sensitivity（p>0.05）,but FFA level was significantly increased after post-exercise meal（t AUC increased by25%,p=0.022;i AUC increased by 151%,p=0.013）,which was not related to exercise energy expenditure（p=0.028）.2.In normal weight people,HIIT before breakfast improved 24h post-exercise continuous interstitial glucose levels（t AUC decreased by 8%,p=0.030;i AUC decreased by 15%,p=0.028）,glucose variability（CONGA-1 decreased by 8%;p=0.042）,which were associated with exercise energy expenditure,and increased FFA levels（t AUC increased by 44%,p=0.047;i ACU increased by 33%,p=0.001）after post-exercise meal.HIIT before dinner had no significant effect on 24h interstitial glucose,blood glucose variability and postprandial Glu（p>0.05）,but improved postprandial TG level after post-exercise meal（t AUC decreased by 5%,p=0.048;i AUC decreased by 85%,p=0.029）,which was related to exercise energy expenditure.3.For overweight and obese people,HIIT before breakfast can significantly reduce 24h post-exercise continuous interstitial glucose level（t AUC decreased by 3%,p=0.007;i AUC decreased by 18%,p=0.007）and blood glucose variability（MAGE decreased by0.5%,p=0.020;CONGA-1 was decreased by 3%,p=0.009）,which were independent of exercise energy expenditure,but had no significant effects on postprandial Glu,INS,insulin sensitivity,FFA and TG（p>0.05）.HIIT before dinner had no significant effects on 24h interstitial glucose level,blood glucose variability after exercise,as well as serum Glu,INS,insulin sensitivity,FFA and TG after post-exercise meal（p>0.05）.Conclusion1.In sedentary young adults,HIIT before breakfast can reduce interstitial glucose levels and blood glucose variability within 24 hours after exercise,while exercise before dinner has no significant effect on blood glucose,and the effect is related to body weight rather than exercise energy consumption.2.HIIT before breakfast or before dinner had no significant effect on blood glucose levels of sedentary young adults;The serum lipid level was significantly affected by exercise energy consumption,but the effect was different for people with different body weight.Only normal weight sedentary young adults showed both a significant increase in serum free fatty acid levels after HIIT exercise before breakfast and a significant decrease in serum triglyceride levels after HIIT exercise before dinner.Only normal weight sedentary young adults showed both a significant increase in serum free fatty acid levels after HIIT exercise before breakfast and a significant decrease in serum triglyceride levels after HIIT exercise before dinner.In conclusion,doing high-intensity intermittent exercise at different periods of the day have different effects on the metabolism of glucose and lipid.HIIT before breakfast is beneficial to the regulation of blood glucose levels throughout the day and the utilization of fat after breakfast;HIIT before dinner was associated with fat use and decreased triglyceride levels after dinner,especially in normal-weight young adults.