If you’re going to hit the ball back over the net, you need somewhere to swing from and the previous full body turn makes a full take back of the racket head possible.
In addition to the turn, Guga has clicked the hand into a backhand grip on the racket handle – can you see it? – as soon as he knows the ball is coming to his backhand side.
If your one handed backhand is weaker than your forehand, you can be doubly prepared by awaiting each shot from your opponent with your racket backhand gripped – you’ll find it easier than fumbling around at the last moment for an as-yet unfamiliar backhand grip.
The term ‘trigger back’ is another mantra from my coaching days. Here’s another of my favourite on-handed Stroke Models and in these frames Cedric Pioline puts some distance between his racket head and ball, over which he can build up racket head speed and power it through to a perfect contact.
Obviously, there are physical limits to how far you can get the racket back-and-away from the ball.
But the theory is this:- the greater the distance the racket head travels (before contact), the greater is your potential for racket head speed.
In frames 3 & 4 you can see Cedric’s shoulder has been pulled round so much that it is now under his chin, and it is barely possible for him to get the racket head further into a backswing.
Cedric’s triggered-up and ready to rumble.