Research to improve breaststroke performances with rule changes

Since the seventies, each swimmer, visiting the K.U.Leuven Evaluation Centre, was diagnosed to improve his performances, based on a fi lm or video observation and analysis, using a checklist of faults and a physical profi le chart. Presently, a diagnosis can be made by any expert in any pool, when he disposes of the individual’s video recordings and a specifi c PC-program, in addition to the physical profi le chart. At a number of Congresses of Biomechanics and Medicine in Swimming, since long before the rule change, permitting to dive with the head below the water durface, special attention was paid to body undulation in breaststroke. At the Congress in Brussels (1974), e.g., an Olympic fi nalist in the Games of Munich (1972) was described, who rotated excessively the trunk above the water surface, backward by cambering and forward by launching (as can be observed in dolphins.) This style was assumed to correspond with a more even velocity and more economy (Fig. 1,a) . Another animal-like propulsion concept, below the water surface, was visualised in butterfl y, namely body waving (as observed in eels) (Fig. 1,b). By launching and waving, a breaststroke swimmer risked, however, to dive with the head below the water surface, which was not allowed until ’87. In the Games of Munich, the usual butterfl y-like arm pull, below the body, after start and turns in breaststroke, was often accompanied by a downward butterfl y-like leg kick (to maintain the trunk horizontally). This also was not allowed until recently. Instead, a screwlike, upand downward, more vertical, arm pull was proposed (inspired by penguins) (Fig. 1,c) . Because the amplitude of this pull is wider and propulsion is better directed in the length axis of the body, a higher impulse was generated. However, when swimming at the surface, using this wide, more vertical pull, the swimmer risked also to dive the head below the surface. Research to improve breaststroke performances with rule changes Ulrik Persyn , Véronique Colman , Bart Soons 1 e Antonio Silva 2 (1) Faculty of Kinesiology and Rehabilitation Sciences, KULeuven (Belgium) (2) Universidade de Trás-os-Montes e Alto Douro (Portugal)