Going back to the video of Asafa Powell I noticed that at toe off his heal makes a definite outward movement away from the midline and perhaps this is what causes the judder at the ankle joint immediately after the foot clears the ground . This is very noticeable in seconds 10-15 during a short slow motion video section . For me the question is what causes this and what is its significance ?

Gerry

Ps A pop up blocks the view of the left foot in the video so you need to cancel this as soon as it appears .