Keep back straight and bend knees.

背要直，只弯两膝。

youdao

Whenever I tried to bend myself in order to appear shorter, he would tell me, "Stand straight and tall, Alisa."

每当我试图弯腰让自己看起来更矮时，他就会告诉我：“挺直腰板，艾丽莎。”

youdao

Bend the front knee, keeping the back leg straight, press the right heel down on the floor.

前腿膝关节弯曲，后腿保持绷直状态，右脚后跟贴紧地面并向下压。

youdao

It's obvious that a sprinter can run faster down a straight than around a bend.

BBC: Can Tyson Gay break Smith's record in Manchester?

When straight "furlongs" were run frequently, it was felt that we could add 0.465 to straight times to find the equivalent mark on a bend.

BBC: Can Tyson Gay break Smith's record in Manchester?