BBC Sport's Michael Johnson compares the different running styles of 100m rivals Justin Gatlin and Usain Bolt.
Four-time Olympic gold-medal winner Johnson says Jamaican Bolt ran without "lateral stability" in Saturday's heats, resulting in "wasted motion" compared to Gatlin's more solid style.
American Gatlin, who has twice served doping suspensions, clocked 9.83 seconds in the sixth heat, as reigning world and Olympic champion Bolt won the seventh heat in 9.96.
Coverage of the men's 100m continues on BBC Two and online on Sunday with the final taking place at 14:15 BST.
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