40 Sanders, Cappaert, and Pease XX Ross H. Sanders is with the Department of Human Movement Studies, Joondalup Campus, Edith Cowan University, Perth, Australia. Jane M. Cappaert is with the International Center for Aquatic Research (ICAR), Colorado Springs, CO. David L. Pease is with the University of Otago, Dunedin, New Zealand. 40 Wave Characteristics of Olympic Breaststroke Swimmers Ross H. Sanders, Jane M. Cappaert, and David L. Pease The purpose of this study was to investigate the wave characteristics of breaststroke swimming. Particular emphasis was accorded the question of whether modern breast- stroke is “flylike” (referring to the butterfly stroke) and whether “waves” travel along the body during the breaststroke cycle. Selected body landmarks and the center of mass (CM) of 8 Olympic breaststroke swimmers were quantified. Fourier analysis was conducted to determine the amplitude, frequency composition, and phase charac- teristics of the vertical undulations of the vertex of the head, shoulders, hips, knees, and ankles. The differences in phase between these landmarks for the first (H1) and second (H2) Fourier frequencies were investigated to establish whether body waves traveled in a caudal direction. While the motion of the upper body was somewhat flylike, the velocity of the H1 wave from the hips to ankles was variable among sub- jects and, for all subjects, was too slow to be propulsive. Contrary to what one would expect, the range of vertical motion of the CM was inversely related to the range of hip vertical motion. The two highest placing subjects, based on preliminary heat times (S1 and S4), were distinguished by a large range of hip vertical motion and a small range of CM vertical motion. Key Words: undulations, hydrodynamics, streamlining, technique, sequencing Since the introduction of the “wave action” technique by Joseph Nagy (Muckenfuss, 1989), major changes have occurred in the technique that breaststroke swimmers use. The wave action technique, otherwise known as the “undulating breaststroke technique,” is distinguished from conventional or “flat” breaststroke by a high shoulder action and for- ward lunge of the upper body across the top of the water during the period between the pull and kick (recovery phase). Persyn (1991) showed that there are considerable differences among breaststroke swimmers in terms of the postures adopted and the range of angles through which the body segments move. Persyn suggested that breaststroke technique is evolving toward more “dolphinlike” styles in which the body undulates. Sanders (1995) showed that when breaststroke swimmers change from a conventional to a wave action technique, there are substantial changes in the frequency composition of the vertical undulations of the body parts and also in the amplitude and phase of the waveforms. The reasons for the success of JOURNAL OF APPLIED BIOMECHANICS, 1998, 14, 40-51 © 1998 by Human Kinetics Publishers, Inc.