Editing Running (section)

===Upper extremity function===
[[file:Police running in North Point lockdown area 20210128.gif|thumb|upright=1.1|Video of man running]]
The upper extremity function serves mainly in providing balance in conjunction with the opposing side of the lower extremity.<ref name="Nicola 2012 187–201"/> The movement of each leg is paired with the opposite arm, which serves to counterbalance the body, particularly during the stance phase.<ref name="Hammer 2010 2709–16"/> The arms move most effectively (as seen in elite athletes) with the elbow joint at approximately 90 degrees or less, the hands swinging from the hips up to mid-chest level with the opposite leg, the Humerus moving from being parallel with the trunk to approximately 45 degrees shoulder extension (never passing the trunk in flexion) and with as little movement in the transverse plane as possible.<ref name="Cavanagh 1990">{{cite book|last=Cavanagh|first=P.R.|title=Biomechanics of Distance Running|year=1990|publisher=Human Kinetics Books|location=Champaign, I.L}}</ref> The trunk also rotates in conjunction with arm swing. It mainly serves as a balance point from which the limbs are anchored.  Thus trunk motion should remain mostly stable with little motion except for slight rotation, as excessive movement would contribute to transverse motion and wasted energy.