Doctors say the bump could come from constantly bending the neck at unnatural angles to look at digital devices.

医生表示这一情况可能是由于在看数码设备时，颈部不断以不自然的角度弯曲造成的。

First, you bend the neck like this so the chin is close to the chest.

首先，把颈部像这样转过去，这样下巴就靠近了胸部。