The piston travels down on the intake stroke, up on the compression stroke, down on the power stroke and up on the exhaust stroke.

进气行程，活塞下行；压缩行程，活塞上行；做功行程，活塞下行；排气行程，活塞上行。

youdao

With the down stroke of a wing during flight, the body moves up, but the subsequent upstroke can counter that force.

用飞行翼的上下行程，身体向上移动，但随后的冲程可以对抗这种力量。

youdao

Both the down stroke and the up stroke are highlighted in different colors.

无论是向上和向下中风中风是突出了不同的颜色。

youdao

Conventional four-stroke engines produce power by moving a piston up and down using rapid explosions of fuel and air in a cylindrical chamber.

FORBES: How to get 51mpg from an engine the size of a large turkey.