Fumimoto Kanaru, Okada Shima, Tsuji Ryohei, Sakaue Yusuke, Shiozawa Naruhiro, Jeong Hieyong, Makikawa Masaaki
Graduate School of Science and Engineering, Ritsumeikan University, Shiga, Japan.
Department of Robotics, Faculty of Science and Engineering, Ritsumeikan University, Shiga, Japan.
Front Digit Health. 2025 Mar 5;7:1536492. doi: 10.3389/fdgth.2025.1536492. eCollection 2025.
Autonomic nervous system activity (ANSA) plays a crucial role in the physical condition experienced during exercise and prolonged physical activity. In other words, ANSA is related to exercise performance and physical condition. Therefore, it is important to continuously monitor ANSA during high-intensity and sustained exercise. To this end, an uncomplicated and noncontact measurement system is preferable. Hence, in this study, we propose a method for the noncontact measurement of capillary contraction and dilation state, representative of ANSA, using a common commercial camera.
Specifically, we focused on alterations in the green value of facial video images, from which we derived the green-to-blue (G/B) ratio as an indicator of blood vessel dilation and contraction, and to facilitate assessment of their activity. We performed a validation experiment involving exercise tasks using an ergometer in 10 healthy adults (23 ± 1.6 years old). The G/B ratio shows the state of contraction and expansion of facial capillaries, and it was evaluated using heart rate as ground truth data of the fluctuation of autonomic nerve activity.
We observed an increase in heart rate with decreased G/B ratio during exercise in all subjects. Postexercise, the heart rate decreased but the G/B ratio increased.
During exercise, characterized by dominant sympathetic NSA, the G/B ratio decreased, and recovered after exercise when parasympathetic NSA was dominant. In this way, noncontact evaluation of ASNA was achieved by using the G/B ratio. In the future, this measurement system will be applied to functional tests for heat acclimation.
自主神经系统活动（ANSA）在运动及长时间体力活动过程中所经历的身体状况中起着至关重要的作用。换句话说，ANSA与运动表现和身体状况相关。因此，在高强度和持续运动期间持续监测ANSA很重要。为此，一种简单且非接触式的测量系统较为可取。因此，在本研究中，我们提出了一种使用普通商用相机非接触式测量毛细血管收缩和扩张状态的方法，该状态是ANSA的代表。
具体而言，我们关注面部视频图像绿色值的变化，从中得出绿蓝比（G/B）作为血管扩张和收缩的指标，并便于评估其活动。我们对10名健康成年人（23±1.6岁）使用测力计进行运动任务的验证实验。G/B比显示面部毛细血管的收缩和扩张状态，并以心率作为自主神经活动波动的真实数据进行评估。
我们观察到所有受试者在运动期间心率增加而G/B比降低。运动后，心率下降但G/B比增加。
在以交感神经NSA占主导的运动期间，G/B比降低，而在副交感神经NSA占主导的运动后恢复。通过这种方式，利用G/B比实现了对ASNA的非接触式评估。未来，该测量系统将应用于热适应功能测试。
