曲球於1870年代首次出現，曲球握球時食指與中指握在球的曲球外側縫線處，使球造成旋轉，曲球是曲球相當古老的一種變化球。會使球在進入本壘板前的曲球垂直掉落幅度遠大於快速球。出手時藉著手腕的曲球順時針方向旋轉與手指的向下施力，進而產生垂直向分力，曲球

曲球（Curveball）棒球中的曲球一種球路。加上重力的曲球作用， 參考 Version 1: Candy Cummings was the inventor of the curveball Version 2: Fred Goldsmith: co-inventor of the curveball or 曲球pitcher who gave first recorded demonstration of the curveball? Aerodynamics of a Curveball in Navier-Stokes Flow How to Throw a Curveball – wikiHow page outlining technique 棒球球路