Study On The Dynamic Characteristics Of Gas Metabolism And Heart Rate Variability During Incremental Load Exercis

Objective:During exercise,with the change of time and intensity,the organ system of human body will produce a series of changes.However,the mechanism of respiration changes during exercise is still not fully understood.The study suggests that the changes of respiration and circulatory system during exercise are regulated by the autonomic nervous system and related to each other,but the specific mechanism is still unclear.Heart rate variability（HRV）quantifies the modulation of sympathetic and parasympathetic input and is widely used to assess autonomic nervous activity.Studies have focused on whether the threshold of heart rate variability can be used to predict ventilation threshold.However,there is no research on the dynamic change law between gas metabolism and HRV during exercise.Therefore,this study aims to explore the dynamic changes of gas exchange and HRV in male college track and field athletes in the process of increasing load to maximum exercise,and reveal the relationship between gas exchange and HRV at different relative intensities and metabolic stages during exercise,so as to realize the complementarity of the two monitoring methods in application.It provides some reference value for the application of gas metabolism and HRV monitoring in the field of public health and sports training.Methods:36 male college student track and field athletes（19.7±0.9 years old,177.3±4.5cm,67.7±6.3kg,training period 5.6±1.0 years）were jointly trained by increasing load running.The Cortex Exercise cardiopulmonary test system and Firstbeat Sports system were used to monitor the dynamic changes of gas exchange and HRV during exercise.The maximum oxygen uptake percentage（%VO₂max）was used to determine the different relative exercise intensity.The first ventilation threshold（VT1）,the second ventilation threshold（VT2）and the maximum oxygen uptake（VO₂max）were used as the dividing points of different metabolic stages.The gas metabolism and HRV indexes of different relative intensities and different metabolic stages were compared and correlated.Results:1.With the increase of relative exercise intensity,while the levels of HFn,VT,VO₂/kg,VO₂,HR and VCO₂ increase progressively,the levels of LF/HF,LFn,DS/VT and VE/VCO₂ decrease progressively;However,VE and RR showed a rapid linear growth trend and then a nonlinear growth trend at 10%-30%VO₂max.Pet CO₂ increased at 10%-80%VO₂max and then decreased.VLF,LF,HF and TP all showed an obvious decreasing trend at 10%-30%VO₂max and then the decreasing range decreased to 100%VO₂max.2.In the increasing process of relative exercise intensity,VLF,LF,HF and TP are significantly correlated with RR,VT,VE,VO₂/kg,VO₂,HR,Pet CO₂,VCO₂,DS/VT,VE/VCO₂,LF/HF and LFn were significantly correlated with VT,VE,VO₂/kg,VO₂,HR,VCO₂,DS/VT,VE/VCO₂.HFn was significantly correlated with VT,VE,VO₂/kg,VO₂,HR,VCO₂,DS/VT,VE/VCO₂.3.From the perspective of metabolic stage,LF,HF,TP,LF/HF,LFn and HFn showed no significant difference between the beginning of exercise and resting period.Compared with resting period and the beginning of exercise period,the other indexes of VT1,VT2 and VO₂max decreased significantly except HFn,and the HFn was significantly higher than that of VT1 and VO₂max.The remaining indicators are significantly below VT1.4.From the perspective of metabolic stage,compared with the resting stage,there was no significant difference in other indexes at the beginning of exercise except for a significant increase in RR.At VT1,VT and Pet CO₂ increased significantly,while VE/VCO₂ and DS/VT decreased significantly.VT still increased significantly at VT2 and DS/VT decreased significantly.There was no significant difference between Pet CO₂ and VE/VCO₂at VT1.Compared with the significant increase of Pet CO₂ at rest and at the beginning of movement,VE/VCO₂ decreased significantly.At VO₂max,VT,DS/VT showed no significant difference with VT2,VT significantly increased and DS/VT significantly decreased compared with resting,beginning of movement and VT1,Pet CO₂ significantly increased compared with resting and beginning of movement,significantly decreased compared with VT1,and no significant change compared with VT2.VE/VCO₂ decreased significantly at rest and at the beginning of exercise,but there was no significant difference with VT1 and VT2.With the progress of exercise,VE,RR,VO₂,VO₂/kg,HR and VCO₂continued to increase until VO₂max.5.In the process of increasing load exercise,the significant correlation coefficient between HRV and respiratory exchange index was the highest in VT1-VT2 stage.Conclusion:1.In the process of increasing the relative intensity of exercise under increasing load,HRV decreased with the increase of lung ventilation,and respiratory exchange was significantly correlated with HRV index,indicating that the autonomic nerve was an important reason for the regulation of respiration and HRV during the process of exercise under increasing load.2.There are different respiratory and circulatory autonomic nervous regulatory mechanisms in different metabolic stages of increasing load exercise.HRV is the most reliable predictor of respiratory exchange index during moderate intensity subextreme aerobic exercise.HRV index should be used carefully to predict respiratory exchange during low intensity aerobic exercise and extreme exercise.