| ObjectiveBased on the perspective of exercise intensity, this paper studied the effects oftraining, exercise mode (cycling and running) and gender on the fat oxidationkinetics，the exercise intensity eliciting maximal fat oxidation (Fatmax) and themaximum fat oxidation rate (MFO)；on the basis of this research, the characteristicof fatty oxidation kinetics during exercise for a long time at Fatmaxwas studied fromthe perspective of exercise duration in order to look for the turning point of fatoxidation rate increased dramatically；from perspective of exercise mode, furtherresearch on the energy consumption，fat metabolism and metabolic hormones duringcontinuous exercise and intermittent exercise at Fatmax，and discussed the mechanismof exercise and maximum fat oxidation.Methods124female college students (12trained and12untrained) and21male collegestudents (9trained and12untrained) performed their incremental treadmill exercisetest and incremental bicycle exercise test respectively, and the gas metabolism wasmeasured. The gas metabolism date in the last30seconds of each load was used tocalculate fat oxidation rate，and use a3rd polynomial fitting curve to determine fatoxidation kinetics, Fatmaxand MFO in order to study the effects of long-term trainingon fat oxidation kinetics, Fatmaxand MFO, at the same time, blood samples weretaken from9trained men’s finger in the last30seconds of each load to measure bloodlactate levels, to investigate the consistency of Fatmaxand blood lactate accumulationpoint.212female college students performed an incremental treadmill exercise test andan incremental bicycle exercise test respectively, and the gas metabolism wasmeasured. The gas metabolism date in the last30seconds of each load was used tocalculate fat oxidation rate，and use a3rd polynomial fitting curve to determine fatoxidation kinetics, Fatmaxand MFO in order to study the effects of exercisemode(cycling and running) on fat oxidation kinetics, Fatmaxand MFO.311male college students and12female college students performed an incrementaltreadmill exercise test, and the gas metabolism was measured. The gas metabolismdate in the last30seconds of each load was used to calculate fat oxidation rate，anduse a3rd polynomial fitting curve to determine fat oxidation kinetics, Fatmaxand MFOin order to study the effects of gender on fat oxidation kinetics, Fatmaxand MFO.416college students（8male and8female）performed an incremental treadmillexercise test, and the gas metabolism was measured. The gas metabolism date in thelast30seconds of each load was used to calculate fat oxidation rate，and use a3rdpolynomial fitting curve to determine fat oxidation kinetics and Fatmax, then running60min at Fatmax. The gas metabolism was measured during exercise for60min, andthe gas metabolism date was used to calculate fat oxidation rate, carbohydrateoxidation rate and energy consumption in order to study the fat oxidation kinetics andturning point of fat oxidation rate increased dramatically in duration exercise atFatmax.57female college students performed an incremental treadmill exercise test, andthe gas metabolism was measured. The gas metabolism date in the last30seconds ofeach load was used to calculate fat oxidation rate，and use a3rd polynomial fittingcurve to determine fat oxidation kinetics and Fatmax, then everyone performed two exercise tests at Fatmax:1)a single bout of60min running and60min rest.2)three boutsof20min running and60min rest, separated by a10-min rest between running bouts,the gas metabolism was measured during exercise, and the gas metabolism date wasused to calculate fat oxidation rate, carbohydrate oxidation rate and energyconsumption, at the same time, blood samples were drawn from elbow vein atdifferent time points in order to measure Glucose(GLU), free fatty acid(FFA),epinephrine(EPI), norepinephrine(NE) and insulin(INS), and to study the energyconsumption，fat metabolism and metabolic hormones during continuous exercise andintermittent exercise at Fatmax，and discussed the mechanism of exercise andmaximum fat oxidation.Results1(1) As exercise intensity increased，fat oxidation rate presents first increased andthen decreased trend. During running, the fat oxidation rates in60-70%VO2max showrelatively high level（12.20-12.84mg/min/kg）in trained women，and the fat oxidationrates in50-65%VO2max stage has a relative high level（6.36-6.67mg/min/kg）inuntrained women. During cycling, the fat oxidation rates in50-55%VO2max showrelatively high level（12.20-12.84mg/min/kg）in trained men and untrained men,respectively9.29-9.40mg/min/kg and4.91-4.99mg/min/kg;(2) In the same relativeintensity, the fat oxidation rate was higher in trained than that in untrained，and Fatmaxand MFO were higher in trained than those in untrained. Trained and untrained inFatmaxand MFO were63.95±3.16vs56.51±2.50%VO2max (p<0.001) and13.04±1.82vs6.71±1.15mg/min/kg (p<0.001) in running, trained and untrained inMFO were9.51±1.46mg/min/kg and5.09±1.21mg/min/kg（p<0.001）in cycling;(3)The fat oxidation rate were more than95%MFO for trained in57.14-69.86%VO2maxand for untrained in48.21-65.41%VO2max in running. the fat oxidation rate weremore than95%MFO for trained in42.26-59.11%VO2max and for untrained in47.11-56.52%VO2max in cycling;(4) At the same oxygen uptake level (VO2), fatoxidation rate is higher in trained than those in untrained;(5) There are certainpositive correlation between the maximal fat oxidation rate，Fatmaxand maximaloxygen uptake;(6) The Fatmaxand blood lactate accumulation point exists aconsistency.2(1) As exercise intensity increased，fat oxidation rate presents first increased andthen decreased trend. For trained women, the fat oxidation rates in50-60%VO2maxshow relatively high level （4.48-4.68mg/min/kg） in cycling, and which in50-65%VO2max stage has a relative high level（6.36-6.67mg/min/kg）in running.(2)At the same exercise intensity, fat oxidation rate of running is higher than that ofcycling, and the Fatmaxand MFO were also higher than that of cycling, respectively56.51±2.50%VO2max vs53.18±3.25%VO2max (p<0.05) and6.71±1.15mg/min/kgvs4.74±1.67mg/min/kg (p<0.001).3(1) As exercise intensity increased，fat oxidation rate presents first increased andthen decreased trend for men and women. The fat oxidation rates in60-65%VO2maxshow relatively high level （4.48-4.68mg/min/kg） in running, respectively10.76-10.80mg/min/kg for men and11.72-11.82mg/min/kg for women, andrespectively12.41-12.49mg/min/kg FFM for men and15.94-16.07mg/min/kg FFMfor women.(2) At the same intensity (%VO2max), fat oxidation rates of women washigher than that of men, and fat oxidation rate of women was higher than that of maleat the same level of oxygen uptake. MFO was higher in women than in men, were 12.04±3.14vs10.96±2.40mg/min/kg and16.37±4.15vs12.62±2.87mg/min/kgFFM. There was no significant difference in Fatmaxbetween men and women, were64.38±4.09%VO2max and63.63±3.09%VO2max.(3) The fat oxidation rate weremore than95%MFO in57.27-69.04%VO2max for man and in57.39-70.68%VO2maxfor women in running, which is no significant difference.4(1) In the exercise for60min at Fatmax, carbohydrate oxidation rate decreasedgradually with time prolonging. The men began to decrease after20min of exercise,the women began to decrease obviously after30min of exercise.(2) The fat oxidationrate increases with time gradually increased for exercise, the men after20minutes,the women after30minutes, the fat oxidation rate increases obviously, fat oxidationrate was significantly higher than that of the previous stage (P<0.05).(3) The energyconsumption level is relatively stable for men in whole period of exercise, but whichbegan to increase after exercise for50minutes. The energy consumption increased forwomen in front of the20min for60min exercise, then decreased gradually to a stablelevel, and keep to the end of the exercise.5(1) The fat oxidation rate of the last20min in continuous running for60min atFatmaxis higher than that in the first20min and second20min, and carbohydrateoxidation rate decreased, but the energy consumption level basically stable. The fatoxidation rate in the intermittent running at Fatmaxis gradually increasing with boutincreasing, and carbohydrate oxidation rate gradually decreased with increase in bout,but the energy consumption level were lower in the second bout and third bout thanthe first bout. The energy consumption of the middle20min and last20min for60mincontinuous running were higher than that of the second bout and third bout forintermittent running.(2) The fat oxidation rate, carbohydrate oxidation rate and totalenergy consumption were gradually decreased with the recovery time prolong ofcontinuous60min running, however the fat oxidation rate did not significantlydecreased with the recovery time prolong of intermittent60min running. Thecarbohydrate oxidation and energy consumption of the first30min recovery stage ofcontinuous running was lower than that of3recovery interval of intermittent running,but the fat oxidation of the first30min recovery stage of continuous running washigher than that of3recovery interval of intermittent running. There was nosignificant difference was found about the fat oxidation rate, carbohydrate oxidationrate and total energy consumption of the end30min recovery period between the twoexercise modes.(3) The energy consumption in the exercise period of continuousexercise is higher than that of intermittent exercise, the energy consumption in therecovery period of continuous exercise is lower than that of intermittent exercise, butthe total energy consumption for exercise period and recovery period were nosignificant differences between the two exercise modes. In the recovery period, the fatoxidation of continuous running is higher than that of intermittent running, thecarbohydrate oxidation and energy consumption of continuous running is lower thanthat of intermittent running. The total fat oxidation for exercise period and recoveryperiod in continuous exercise seems to been higher than that in intermittent exercise,but the total carbohydrate oxidation seems to been lower than that in intermittentexercise.6(1) the blood GLU and FFA are no significant difference between continuousrunning and intermittent running at Fatmaxduring exercise period and recovery period,and the change trends of blood GLU and FFA are same between continuous runningand intermittent running. In the beginning of exercise, GLU concentration decreasedand FFA increased, then they gradually restore.(2) Compared with before the exercise,plasma NE and INS levels had a small change in continuous exercise and intermittent exercise at Fatmax, but the EPI levels have no significant change. INS appeared adecrease in40min for continuous running, and returned to the pre-exercise level in60min after exercise. INS appeared a decrease in60min for intermittent running, andhad not been returned to the pre-exercise level by recovery for60min. Plasma NElevels were higher than those before exercise in continuous running and intermittentrunning period, and recovery quickly. On the entire exercise period and recoveryperiod, no significant differences in hormone levels of the same point in time betweenthe two exercise modes was found.Conclusion1From the training background, at the same intensity (%VO2max), the fat oxidationrate is higher in trained than that in untrained，the Fatmaxand MFO are also higher intrained man than those in untrained man, suggest that long-term endurance trainingcan enhance the fat mobilization and oxidation capacity. From the exercise mode, atthe same intensity, the fat oxidation rate is higher in running than in cycling，theFatmaxand MFO are also higher in running than those in cycling, suggest that runningmay be better than cycling in the intervention of obesity, diabetes and other associatedwith fat metabolism disorders. In addition, the fat oxidation rate can reach more than95%MFO in running at the range of50-65%VO2max for untrained young women,and the fat oxidation rate can reach more than95%MFO in running at the range of60-70%VO2max for trained young women2The fat oxidation rate is higher in women than in men at the same intensity, and theMFO of women is also higher than that of men, but the Fatmaxand the range ofintensity that induce high fat oxidation rate are similar in men and women.3In prolonged running at Fatmax, the fat oxidation rate increase rapidly after exercisefor about20min in men, and after exercise for about30min in women.4In the exercise period, the energy consumption of the continuous running is higherthan that of the intermittent running. In the recovery period, the energy consumptionof the continuous running is lower than that of the intermittent running. But the totalenergy consumption of exercise period and recovery period are similar in the twoexercise mode. In the recovery period, the fat oxidation of continuous running ishigher than that of intermittent running, and the carbohydrate oxidation of continuousrunning is lower than that of intermittent running. In addition, compared with beforethe exercise, the plasma norepinephrine and insulin hormone levels only slightlychange, and epinephrine had no significant change in continuous running andintermittent running at Fatmax, suggest the high fat oxidation rate at Fatmaxmay be theresult of other mechanisms. |
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