Jike Zhang

Yeah yikes it was painful to watch.... I think this has to do with his extreme forward bend at the waist along with the upper body explosiveness which is sometimes out of sync with his lower body when he does his close-table FH power loops that were so lethal back when he was in his prime form. Now I can see why Ma Long's, Wang Liqin's and FZD's form on the FH is much healthier, the arm is relaxed and follows the waist turn naturally (albeit less explosive and slower, not necessarily less powerful). I believe lots of players which rely more on the upper body for the FH powerloop (Timo Boll, Maze come into mind) have all got injuries in their lower backs at some stage.  

ZJK must have realised that mid-match that he was regressing to his old habits, because after that he started taking a step back from the table when moving towards the FH, so that he has a bit more time to play his FH's in a healthier way (use more waist turn with a fuller stroke).