Leg Push vs. Leg Bend

[racquet_jedi]

Are theses parts of the serve equally important or is it more important about how forcefully you push off the ground vs. how much you bend your legs or vice versa that will contribute more to your service speed?

[SystemicAnomaly]

As long as you are incorporating it properly, greater knee bend should yield more leg drive which, in turn, should allow you to generate greater racket head speed.

Note that the leg extension (leg drive) starts as the racket head drops behind your back (shoulder). This means the the legs extend before that racket arm extends. This way you transfer the power of your leg drive to your upper body, arm & racket.

If your arm extends at the same time that your legs do, then you may reach higher but you won't be transferring leg power effectively to your upper body.

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[tricky]

If your arm extends at the same time that your legs do, then your may reach higher but you won't be transferring leg power effectively to your upper body.

Very true. It means the body sequence is off and the kinetic chain is broken. For most serves (esp. those using a continental grip), both the leg drive and racquet drop are initiated from the hip unwinding.