One Arm Pushup is an iso-lateral bodyweight exercise that places heavy emphasis on the chest, triceps, and core muscles. By removing one of the supporting arms, the body must exert extra strength to maintain balance. For this reason, some consider the one arm pushup as much a core workout as an upper body workout. For best results, ensure that your center of gravity remains directly over the supporting arm. Scale by performing lateral elbow pushups or diamond pushups.