We can compare this movement to pushing a car: in order to exert force with our arms and body, we have to stand firmly on the ground, and if it’s hard, so much the better. Imagine doing this in the mud. It would be like hitting the wind. more info : deportesoutlet.com
We can also imagine that when we hit a backhand, someone pulls hard on our clumsy arm; this would create more force and direction in the hand making the hit. We can imagine this kick as a lift; to create strength and good stretch in the skillful hand, we can imagine that after throwing the ball upwards, we hold on to a fixed point with our awkward hand and then launch ourselves far upwards (as if we were climbing a wire fence or wall).
Watch the point of impact
Very often when we hit a ball we immediately want to see where it flies, and this usually causes us to ‘cast our eyes forward (and sometimes to the side) along with our head, blurring the technique. Let’s be clear: all shots (except some volleyball shots) involve “preparation (creating force)”, “holding” and “finishing” (helping to give the ball more speed, height, spin, etc.). When we see someone play, we can see with the naked eye that the ball immediately flies out of the strings of the racket; but when we watch the “hitting” in very slow motion, the ball remains stuck in the strings and flies out at the end of the stroke.
In short, if we keep our eyes on the point of impact, the shoulder and arm reaction (“lead”) when hitting the ball will be long and forward; if we don’t, the eye-head-body rotation produces a short lead to the side and down. Ideally, this should be particularly applicable to backhand, serve and smash (the shot where we are most afraid to see where the ball flies; in some cases, when we try to smash too hard and too hastily, we miss the ball because we look down and want to see where our shot was before we see the point of impact)