Correct

挺胸

/ tǐng xiōng /
Strokes

Example

As a Verb

square/straighten one's shoulders

1
Táitóu
抬头
tǐngxiōng
挺胸
  

Raise your head and square your shoulders.

2
Shōu
收腹
tǐngxiōng
挺胸

suck in/pull in one's stomach and puff out one's chest