无氧阈是运动过程中有氧运动和无氧运动的过渡，确定无氧阈可用于指导运动训练和参赛工作。在确定无氧阈的主要方法中，通气阈法虽由于其无创性开始代替乳酸阈法，但存在无法实现就地实时测量的问题。可调谐激光吸收光谱技术可以较好地解决如上问题，其可以满足在气体分析中实时性和高灵敏度等要求，这正是体育科学研究和运动实践所需要的。本文应用可调谐激光吸收光谱技术对呼气中均匀呼吸、深呼吸和快速呼吸三种状态检测进行了研究，具体工作如下：
      第一，重点阐述可调谐激光吸收光谱技术在人体呼出气体分析领域应用的研究现状，指出测量人体呼出气体研究中的主要工作目标和突破点为测量实时性、数据准确性和结构紧凑性。
      第二，梳理了呼吸气体检测方法。简要介绍比尔朗伯定律、直接吸收法和波长调制法以及高斯、洛伦兹和福伊特三种线型函数，并在现有实验室条件下基于HITRAN 数据库选取出O₂的目标吸收谱线波数分别为13142.583 cm^-1和13145.580 cm^-1，CO₂的最佳吸收谱线波数为4989.971 cm^-1。
      第三，在常温常压条件下，搭建并评价了基于波长调制法的呼吸气体检测装置。该装置对人体呼吸气体中的O₂和CO₂实现同步测量。通过高斯拟合得到氧气测量系统和二氧化碳测量系统的数据波动标准方差为0.6826%和0.1828%。通过Allan偏差分析得到氧气测量系统的检测限为7781 ppm，最佳积分时间为169 s和最佳检测限为720 ppm。通过Allan偏差分析二氧化碳检测系统的检测限为1495 ppm，最佳积分时间和最佳检测限为86.9 s和87 ppm。无论是长时间内数据稳定性还是检测精度和检测限，二氧化碳检测系统皆优于氧气检测系统。从整体来看，两个系统都满足对人体呼出气体检测的需要。
      第四，对比了深呼吸和均匀呼吸中二氧化碳浓度随时间的变化，前者的上升沿、下降沿和整个周期的时间都长于后者。通过分析深呼吸阶段中氧气和二氧化碳浓度动态变化序列符合预期，且变化趋势实现同步测量，系统没有延后性。

        Anaerobic threshold is the transition between aerobic exercise and anaerobic exercise during exercise. Determining anaerobic threshold can be used to guide sports training and competition. In the main method of determining anaerobic threshold, although the ventilation threshold method began to replace the lactic acid threshold method due to its non-invasiveness, there is a problem that it cannot realize real-time measurement in situ. Tunable laser absorption spectroscopy technology can better solve the above problems, which can meet the requirements of real-time and high sensitivity in gas analysis. This is what sports science research and sports practice need. In this paper, tunable laser absorption spectroscopy is used to detect the three states of uniform respiration, deep respiration and rapid respiration. The specific work is as follows :
        Firstly, the research status of tunable laser absorption spectroscopy in the field of human exhaled gas analysis is expounded. It is pointed out that the main objectives and breakthrough points in the measurement of human exhaled gas are real-time measurement, data accuracy and structural compactness.
        Second, the respiratory gas detection method is combed. This paper briefly introduces Lambert-Beer’s law, direct absorption method and wavelength modulation method as well as Gauss, Lorenz and Ford three linear functions. Under the existing laboratory conditions, based on HITRAN database, the target absorption lines of O₂ are selected as 13142.583 cm^-1 and 13145.580 cm^-1, respectively. The optimal absorption line wave number of CO₂ is 4989.971 cm^-1.
        Thirdly, under normal temperature and pressure, a breathing gas detection device based on wavelength modulation method was built and evaluated. The device can simultaneously measure O₂ and CO₂ in human respiratory gases. The standard deviation of data fluctuation of oxygen measurement system and carbon dioxide measurement system is 0.6826 % and 0.1828 % by Gaussian fitting. Through Allan deviation analysis, the detection limit of oxygen measurement system is 7781 ppm, the optimal integration time is 169 s and the optimal detection limit is 720 ppm. Through Allan deviation analysis, the detection limit of carbon dioxide detection system is 1495 ppm, the best integration time and the best detection limit are 86.9 s and 87 ppm. Regardless of the long-term data stability, detection accuracy and detection limit, the carbon dioxide detection system is superior to the oxygen detection system. Overall, the two systems meet the needs of human exhaled gas detection.
        Fourthly, the variations of CO₂ concentration over time in deep and uniform respiration were compared. The rising edge, falling edge and the whole cycle of the former were longer than those of the latter. By analyzing the dynamic change sequence of oxygen and carbon dioxide concentration in deep breathing stage, it is expected that the change trend is synchronized, and the system has no delay.