美国温特劳市医生在美国《医生联合会杂志》上曾说，靠椅背而向后仰坐时，过分的伸脖或者头向后张，这样的头部动作对年纪大的人尤其危险。医学研究认为，人的年纪大了，颈部血管便变得狭窄，而且有血管经过的骨头，正常情况下非常平滑，年纪大了里边会出现锐缘。当脖颈放到极 Doctor Wentrao, in the United States, said in the magazine “Doctor’s Union,” that when sitting on the back and backwards, excessive stretching or head-back stretching is particularly dangerous for older people . Medical research suggests that when people are older, the blood vessels in the neck become narrower and the blood vessels pass through the bones. Under normal circumstances, they are very smooth and sharp edges appear when they are older. When the neck very