## 1 Introduction  
In the last decade, the number of Internet users has grown significantly worldwide, increasing from \(\sim\)2.7 billion in 2012 to 5.3 billion in 2022 [1]. In addition, as modern society accesses the Internet via computers and smartphones, the average time spent on such electronic devices has also experienced a correlating increase. When a user uses a computer or smartphone for a long time, the user's head bends forward, which results in a bad posture that induces physical health issues such as neck pain. Overtime, this may progress to the forward head posture (FHP) condition, in which the anterior and posterior curvatures of the lower cervical and upper thoracic spines, respectively, are exaggerated to maintain balance.  
FHP is the most common cervical postural defect found in almost the entire human population regardless of race or age [2]. It is strongly associated with chronic neck pain in modern populations [3], and it also negatively impacts static balance control [2, 4]. According to [PERSON] et al. [5], out of 154 diseases, those related to neck pain had the highest healthcare expenditures in 2016 for the United States alone at approximately USD 134.5 billion. According to [PERSON] et al. [6], the annualized prevalence of neck pain among white collar workers ranged from 42% to 63%, while that of neck diseases only ranged from 17% to 21%. Furthermore, studies have shown that the weight exerted on the spine increases drastically when the head is bent forward due to FHP, where \(\sim\)49 lbs of weight is exerted on the spine due to the forward 45\({}^{\circ}\) head bend, which was indicated in a person in [7]. Therefore, the habituation of bad posture adversely affects the spine, and it is also highly associated with round shoulders, thoracic kybosis, and turtle neck [8].  
To prevent or treat bad postures that can progress to FHP, it is important for people to consciously maintain good posture. Therefore, recognizing one's neck condition in real time in daily life is important [9]. In modern times, the use of computers and smartphones has become a daily routine as people are continually immersed in digital content. However, because it is difficult for people to recognize their bad posture, they are unable to make a conscious effort to maintain a good posture for a long time. Particularly, bad posture has been reported to cause body pain in adolescents who sit and study for a long time, as well as in office workers who use computers in their occupation, thus making both daily life and study difficult [10].  
In this study, we propose a system for real-time posture detection in daily life using an inertial measurement unit (IMU) sensor attached to the human body, which is used to detect bad posture and induce a correct posture for the prevention of diseases caused by FHP. The contributions of this paper are as follows:  
* The identification of optimal location on the body to attach a wearable IMU sensor to accurately detect FHP status.
* The providing of an intuitive visual interface to enables users to easily recognize a bad posture and correct their posture.
* The proposal of a personalized system that can visually display the results of real-time (with a delay of less than 0.5 s) posture-data acquisition and processing, as well as an improvement in the effectiveness of practical correction and prevention of bad postures in daily life.  
This paper is organized as follows: Section 2 introduces the studies related to posture judgment and FHP correction methods; Section 3 describes the proposed system structure and algorithm; Section 4 discusses the location selection for sensor attachment for the purposes of detecting and correcting posture when using a gyro acceleration sensor, as well as details the conducted experiments and result analyses; and Section 5 presents the conclusions of this study.