"Luchadores" are traditionally more agile and perform more aerial maneuvers than professional wrestlers in the United States, who more often rely on power and hard strikes to subdue their opponents. The difference in styles is due to the independent evolution of the sport in Mexico beginning in the 1930s and the fact that "luchadores" in the cruiserweight division ("peso semicompleto") are often the most popular wrestlers in Mexican lucha libre. "Luchadores" execute characteristic high flying attacks by using the wrestling ring's ropes to catapult themselves towards their opponents, using intricate combinations in rapid-fire succession, and applying complex submission holds. Rings used in lucha libre generally lack the spring supports added to U.S. and Japanese rings; as a result, lucha libre does not emphasize the "flat back" bumping style of other professional wrestling styles. For this same reason, aerial maneuvers are almost always performed to opponents outside the ring, allowing the luchador to break his fall with an acrobatic tumble.