propelling surface meaning in English

推进面

Frame # 7 : the use of the hand / forearm as a propelling surface is clearly demonstrated with the right arm as adduction continues to be the source of force production
画面7 ：画面清晰显示了手/小臂推水面，内收的右臂继续成为动力之源。
Frame # 7 : the use of the hand / forearm as a propelling surface is clearly demonstrated with the right arm as adduction continues to be the source of force production
手和前臂作为划水面在这幅照片可以清楚地展示，右臂继续回收成为动力之源。
Body roll occurs largely to position sets of muscles to move joints to produce longitudinal forward propulsion and coupled with the arm pull produces a more direct propulsive force off the hand / forearm - propelling surface
身体的滚动幅度大会使肌肉群一起运动产生纵向的推进力而且是两倍于手臂划水直接产生的推进力。