Reliability And Validity Of Heart Rate Variability Threshold(HRVT) In Evaluating Ventilatory Threshold Of Male College Students

Research purpose:Ventilatory Threshold(VT)is an effective and non-invasive method for evaluating human cardiorespiratory fitness,but the required expensive equipment and the operation process is complicated,so it is not suitable for widely use in the students physical fitness tests.In an incremental load exercise,as the exercise intensity continues to increase,sympathetic nerve activity dominates,parasympathetic nerve activity gradually decreases,resulting in a"withdrawal"phenomenon and an inflection point,which is the heart rate variability threshold(Heart Rate Variability Threshold,HRVT).In recent years,due to the high degree of coincidence between HRVT and VT in sports,researchers has gradually paid attention to sports science.Research on the relationship between HRVT and VT in different groups still lacks relevant data.This paper explores the reliability and validity of HRVT assessment of VT by observing the heart rate variability and gas metabolism of healthy male students from college during an incremental load exercise,and provides a methodological evidence for the application of HRVT to student physical fitness monitoring.Research methods:20 healthy male students from college were recruited through posters and other methods.Among them,5 were lost due to sports injury and data loss.Finally,15 were selected(age:21.1±1.9 years old;height:175.5±3.4cm;weight:64.5±8.3kg;BMI:20.9±2.3kg/m~2;body fat rate:14.4±5.4%)as the research object,without hypertension,diabetes,hyperlipidemia,hypoglycemia and other related diseases,and without any movement disorders.The two exercises are performed at the same time point of the day,and at least three days apart.The Polar RS800cx heart rate telemeter was used to continuously record the R-R interval signal during exercise.The Polar ProTrainer?5.0 software was used to download and eliminate the interference in the signal.Then,the Kubios HRV Premium?3.3.1 software was used to analyze the non-linear index SD1(Poincaréplot,corresponding to the semi-short axis of the Poincaréellipse),according to the inflection point of the index SD1 with the change of exercise time,determine the HRVT in an incremental load exercise of outdoor field and an incremental load exercise of indoor treadmill,and the corresponding heart rates are recorded as HRVT1-HR and HRVT-HR respectively;Cortex Metamax3B gas metabolism analyzer to test the gas metabolism of an incremental load exercise on a treadmill,using the metabolic equivalent method combined with the respiratory quotient equal to"1"to determine the ventilatory threshold(VT),the corresponding heart rate can be recorded as VT-HR.In order to further explore the repeatability of an incremental load exercise of outdoor field to determine the HRVT,14 subjects(age:21.3±1.9 years old;height:176.1±2.9cm;weight:64.6±8.6kg;BMI:20.8±2.4kg/m2;body fat rate:13.0±5.4%)who participate in the first part of the study were selected to complete the second incremental load exercise of outdoor field.The test conditions of this incremental load exercise of outdoor field are basically consistent with those of the outdoor field test conditions in part I of the experiment.The corresponding heart rate at the HRVT of the second exercise judgment was recorded as HRVT2-HR.The data was statistically analyzed by SPSS20.0,the Kolomogorov-Smirnov and Shapiro-Wilk test was used to check the normality of the data distribution,using the Levene test to test the homogeneity of variance,and using ANOVA to compare each group in HRVT1,HRVT,VT corresponding to the difference in heart rate data.Pearson correlation coefficient and Bland-Altman scatter plot method were used to verify the validity of the two test results of each indicator.The intra-class correlation coefficient(ICC)and inter-subject coefficient of variation(CV)were used to test the repeatability of the two test results.The data are expressed as~—X±SD,and P<0.05indicates a significant difference.Research results:(1)There is no significant statistical difference between HRVT1-HR determined by an incremental load exercise of outdoor field and HRVT-HR and VT-HR determined by an incremental load exercise of indoor treadmill.The correlation coefficient of HRVT1-HR and HRVT-HR,HRVT1-HR and VT-HR,and HRVT-HR and VT-HR was 0.708,0.742,and 0.906,respectively,and the Bland-Altman scatter plot shows high consistency.(2)The correlation coefficient of HRVT1-HR and HRVT2-HR obtained in two an incremental load exercise of outdoor field was 0.833,ICC was 0.909,and CV was 4.0%.At the same time,and the Bland-Altman scatter plot shows high consistency between them.Research conclusion:The heart rate variability threshold determined by the analysis of the change in the non-linear index SD1 of the heart rate variability during an incremental load exercise may be an alternative way to assess the ventilation threshold of male students from college.