Under normal condition, swimmers should not reduce speed when close to pool edge and should maintain ongoing
momentum so that helpful for completing pike rotation motions; when pike to do rotation, revolve speed can be
accelerated and meanwhile make preparation for subsequent pushoff, after ending pushoff, close two arms together
and move forward, let head clamp between two arms so as to reduce water resistance. Make motions analysis with
breaststroke turn as an example, human state in breaststroke turn important time phase as Fig.6 shows