Hence “lots” of rotational training. Don’t forget to add all the “gymnastic” iso holds, tightening/activating of the MAJOR deep muscles of the core etc. Which carries over.
Where is the power generated?. Core.
Awesome core strength/speed of core rotation has too have the biggest impact, surely. Look at the position/direction of his body/bellybutton as he releases the javelin. Its almost straight left. There is a lot of of torque there in that part of the body.
Go back & do standing Russian twists with a 25lb-50lb plate. 4-5 sets x 20-30 reps.
Come back & tell me that hasn’t increased rotational speed (given you a even badder back :D) & generating more speed in your golf swing, club & clubhead speed.
<<< 1 handicap golfer here (when I was playing competitively) :).
Barbell twists? You boys are crazy. Probably damn heavy too.