Due to the development of IT devices, the number of people using smartphones in present days is continuously increasing. The usage rate of smartphones has increased from 27% in 2011 to 78.8% in 2015 (Korea Communications Commission, 2015), and the number of patients with "turtle neck syndrome" is increasing rapidly. According to the Health Insurance Review and Assessment Service (2015), the number of patients with cervical neck disease increased 16.6% from 2,270,000 in 2011 to 2,650,000 in 2015, among which the number of people diagnosed with turtle neck syndrome increased twofold in 4 years from 606 in 2011 to 1,134 in 2015. Based on the result of the survey on the "utilization rate of smartphone by age," people in their 20s took the first place with 96.4% (Health Insurance Review and Assessment Service, 2012), and the average daily usage time of smartphone by Koreans was 3 h per person. People in their 20s had the longest average daily usage time of 4 h per day (Lim, 2016).The turtle neck syndrome is a symptom in which the cervical bone is deformed into "1" or inverted letter "C" shape. Healthy cervical neck bones have the appearance of a well-curved C shape, which could be deformed if an individual's neck is bent forward for a long time (Jeon, 2016).The turtle neck posture appears to be due to physical imbalance from maintaining a wrong posture for a long period (Hwang, 2012). Habits of maintaining wrong posture can cause deformity of the spine that causes pain and difficulty in having a healthy daily life (Im, 2003). In this way, our body parts such as the shoulder, waist, pelvis, and knee center around the vertebrate to maintain left and right symmetry of the whole body. Therefore, failure to maintain proper posture can lead to physical imbalance (Oh, 2016). Physical imbalance due to poor posture such as having the pelvis twisted to one side or the body tilted to one side can break the overall balance of the whole body and cause pain (Kim,