There should be a slight inward curve in your lower back, an outwardcurve in your upper back, and another inward curve at your neck.
这时你下背部应该是一条略微内凹的曲线，上背部是一条略微外凸的曲线，脖子则是另一条内凹的曲线。
2
The quality of plane designing for curve bridge directly affects the structure design, the degree of construction difficulty; engineering cost and outward appearance.