Your comments on my humble attempt at the jump smash

As Obi-Wan said to Luke, don't think about it, just feel the Force and use it.

 

I think most of the points I was going to raise has been made already but a couple more points to help refine your jump a little bit more.

Your shoulders and upper body is not side-on enough. Your shoulders are facing the net too much. It doesn't need to be perfectly 90-deg but as you draw your racquet arm, just pull your racquet shoulder back a touch more. Also it is clear (as has been said) that your kick is not quite right. You should complete your kick just before impact, usually at the peak of your jump so that you contact the shuttle as you begin your descent. It also looks quite wide - in the sense that you open your legs quite a lot - like a star jump.

 

It will come naturally when you contract your core.

 

Yep. If you start the kinetic chain with the hip first, then core, shoulder, etc, all the way to the fingers (ie. proximal to distal transfer), then the kick will occur naturally as a result.

Just think: hip, hit, hooray. And the kick will follow.

 

In this case it means start with your hips

 

From your video above,

Your upper legs should be bent back when you jump to create a reflex action at the waist so you will be able to bend back your upper body at the same time- your upper legs are bending forward/upward in the jump (bend only occur at the knee only mostly) and straightening down after that, so you felt it is pulling you down.

The kick is the resultant action from at the top of the jump when the waist is bending back forward; which comes to a sudden forceful stop naturally which enable you to throw the elbow and forearm high and above for the hit a racket length in front..