Each lesson has a duration of 40 minutes, including the first five minutes of warm-up, 30 minutes of manual therapy and the last five minutes of cool-down.

Each lesson has a duration of 40 minutes, including the first five minutes of warm-up, 30 minutes of Tai Chi and the last five minutes of cool-down.

Each lesson has a duration of 40 minutes, including the first five minutes of warm-up, 15-min Tai Chi exercise and 15-min manual therapy, with the order of intervention being Tai Chi exercise first and then manual therapy, and the last five minutes of cool-down.

The therapist checks the range of motion of the cervical joints and gives manual treatment to the restricted joints. Throughout the examination, the subject lied in a supine position on a professional rehabilitation bed with the seventh cervical vertebra (C7) on the edge of the bed and the other the body above the C7 were placed off the bed. The therapist held the subject's occipital bone with one hand and the radial aspect of the second metacarpophalangeal joint of the other hand to grip the spinous process of the sixth cervical vertebra and slowly pushed the occiput downward to check the joint mobility of the fifth cervical vertebra and the sixth cervical vertebra. After the examination, the restricted joint was accurately located and treated with targeted manual therapy. For example, stretching was performed with the right side of C4-C5 flexed, closing only the right side of the subject's C4-C5 as much as possible to increase joint mobility on the right side of C4-C5.

Participants' cranial vertebral angles before and after the intervention will be measured using photogrammetry to assess the change in cranial vertebral angle at 3 months compared to baseline.

Participants' cervical range of motion before and after the intervention will be measured using universal goniometer to assess the change in cranial vertebral angle at 3 months compared to baseline.