Players uses different timing on loading their forearm (f.arm supination) before to roll it and drive the r. face for conctact. Seeing videos about shots from baseline, man often starts their forward movement with r. head up and relaxed arm, then loads (..stretch) the forearm during the shoulder rotation in forward swing, and roll it (f.arm pronat.) to snap the r. face to the ball. Many woman starts with r.head pointing back so loads shoulders (trunc) and forearm on the some time, then swing forward and roll. Is it only a difference between "multi-segment" and "unit turn" ? How and when we have to use the one and the other ? Does it depend from speed of incoming ball (example. on first serve return ) ? Does it depend from target of the shot ( winner, approach, drive ..) ? Is it only a player habit ? Many thanks.