It’s possible that his torso moves forward towards the end of the backswing, rotating the shoulders forward, allowing the arms to go too far backwards, slowing the rturn swing. the first thing to ensure is that the shoulders are relaxed and down and that the torso is held straight. If that doesn’t solve the problem, check to see if he’s pulling the arms back on the backswing. the action should be to pull DOWN from the highest point and the backswing will take care of itself.
Thanks for your reply. I think you have hit the nail on the head. My athlete is a very upright and relaxed runner and does not lift his shoulders even under max effort.
Unfortunately from a very early age we have instilled in him the need to pull backwards with the elbows while attempting to maintain a 90 degree angle as much as possible[as advocated by a well known expert ].
We even have him reinforce this action with a running arm drill as part of his warm up.
It was only after after coming across a post on cfts that likened armswing to the action of beating a drum and comparing the two actions side on by video that seemed to confirm what was causing the problem.
It is a pity that so much incorrect “expert advice” is about and that it is only thru a fluke that we come across info as on this site.
I guess all we can do now is practice the correct action as much as possible and hope that it can be ingrained asap