Thanks for your replies, guys. It seems he has been practicing so much lately (bowling center let him play for free the last three weeks in preparation for the upcoming finals in a national youth tournament) that he has had time to develop a bad habit. When his approach is working well, his body posture goes smoothly from slightly forward bend on the first step to smooth knee bend at the line - and no tracking over the finger holes. When his approach is working badly he looks more like a divebomber and the ball tracks over the finger holes. These problems seem to occur either when he is tired from too many games or when he is not properly warmed up. Longer breaks between his sessions on the lanes and proper stretching exercises seem to help.


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Regards,

jensm