12-4  Force Production:  Body leans forward  Base leg extends 180 degrees at take-off  Opposite ( or swing) leg drives forward with knee bent  Arms flexed 90 degrees & pump in opposition to legs  Swing Phase:  Flight phase  After push–off swing leg bends & heel comes close to buttocks to shorten lever & speed time to foot contact  Support Phase:  Heel-to-toe or ball of foot landing
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