| Purposes:Oxygen uptake is the amount of oxygen ingested by the body per unit time,and during aerobic exercise oxygen uptake reflects energy consumption in response to the stimulation of the body by the load.Therefore,oxygen uptake can be used as an important parameter reflecting aerobic exercise intensity.However,direct monitoring of oxygen uptake is very complicated and needs expensive equipment.By applying incremental submaximal aerobic running on treadmill,the study analyzed correlations between each of the individual variables:respiration rate,heart rate,and heart rate variability and the variable of oxygen uptake.On basis of the correlation analysis,we created a Long Short-term Memory oxygen uptake estimation model,by which to explore the feasibility of indirect oxygen uptake evaluation.Methods:a total of 72 subjects with regular physical training background were randomly attributed into two groups:test group and confirmation group.The test group had 60 subjects and were asked to perform an incremental exhaustive exercise test on treadmill.The confirmation group of 12 subjects did not performed the text,but were later used to test the feasibility of the oxygen uptake estimation model obtained on basis of the results from the test group.For the test group,the subjects were equipped with VE tracker,breathing mask,and Polar heart rate belt which were connected to the CORTEX gas metabolism analyzer,in which data of Respiration Rate,Heart Rate,Heart Rate Variability index,and oxygen uptake were recorded during the test.The obtained data were then analyzed for（1）correlation analysis between each individual variables of Respiration Rate,Heart Rate,and Heart Rate variability index,and the variable of oxygen uptake;（2）Using LSTM to create an oxygen estimation model,and then to test the correlations and analyze the errors between calculations according to the oxygen uptake estimation model,and the actual oxygen uptake measured by gas analyzer of the confirmation group.Results:（1）During the test,the correlation coefficients between oxygen uptake and Respiration Rate,and Heart Rate are r RR-VO2=0.831±0.067,and r HR-VO2=0.949±0.030,respectively.The correlation coefficients of oxygen uptake and Heart Rate Variability are r SDNN-VO2=-0.729±0.072,r RMSSD-VO2=-0.636±0.097,r PNN50-VO2=-0.554±0.097,r VAL-VO2=-0.608±0.137,r VLI-VO2=-0.735±0.070,rn LF-VO2=0.366±0.122,rn HF-VO2=-0.366±0.122;（2）The average error between calculation according to the oxygen uptake model and the actual oxygen uptake is 3.59 ml/kg·min.At different exercise intensities,the average errors varied:3.23 ml/kg·min during low-intensity,3.58 ml/kg·min during medium-intensity,and 4.4 ml/kg·min during high-intensity;（3）The average error of oxygen uptake according to the oxygen uptake estimation model is lower than that according to the ACSM oxygen uptake formula,but is higher during high-intensity exercise.Conclusions:（1）On basis of the results that during the incremental exercise test,Respiratory Rate and Heart Rate had high correlations with oxygen uptake,whereas the correlations between Heart Rate Variability and oxygen uptake varied from low to high,and that at different exercise intensities,the correlations varied:high at low and moderate intensity,but low at high intensity,we concluded that the accuracy of the oxygen uptake estimation model is sensitive to exercise intensity;（3）on basis of the results that the average errors of the model is less than that of the ACSM oxygen uptake formula,the method used in the study in estimating oxygen uptake is feasible. |
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