This movement creates air currents that generate lift from both the upstroke and the downstroke.

这一运动产生了气流，上行和下行时产生升力。

Hummingbirds however, turn their wrists during the upstroke, changing their wing's angle to flap in a figure 8 pattern that continually generates lift throughout their wingbeats.

然，蜂鸟上击时动手腕，改变膀的角度，以 8 字形模式拍打，整个拍中不断产生升力。

Their wing joints are also stiffer than those of flying birds, which helps them produce thrust on both the downstroke - like most birds do - and on the upstroke of the wing.

它们的膀关节也比飞鸟的关节更硬，这有助于它们像大多数鸟类一样下击和上击时产生推力。