Muscle Activation in World-Champion, World-Class, and National Breaststroke Swimmers.

PURPOSE To investigate the muscle-activation patterns and coactivation with the support of kinematics in some of the world's best breaststrokers and identify performance discriminants related to national elites at maximal effort. METHODS Surface electromyography was collected in 8 muscles from 4 world-class (including 2 world champions) and 4 national elite breaststroke swimmers during a 25-m breaststroke at maximal effort. RESULTS World-class spent less time during the leg recovery (P = .043), began this phase with a smaller knee angle (154.6° vs 161.8°), and had a higher median velocity of 0.18 m/s during the leg glide than national elites. Compared with national elites, world-class swimmers showed a difference in the muscle-activation patterns for all 8 muscles. In the leg-propulsion phase, there was less triceps brachii activation (1 swimmer 6% vs median 23.0% [8.8]). In the leg-glide phase, there was activation in rectus femoris and gastrocnemius during the beginning of this phase (all world-class vs only 1 national elite) and a longer activation in pectoralis major (world champions 71% [0.5] vs 50.0 [4.3]) (propulsive phase of the arms). In the leg-recovery phase, there was more activation in biceps femoris (50.0% [15.0] vs 20.0% [14.0]) and a later and quicker activation in tibialis anterior (40.0% [7.8] vs 52.0% [6.0]). In the stroke cycle, there was no coactivation in tibialis anterior and gastrocnemius for world champions. CONCLUSION These components are important performance discriminants. They can be used to improve muscle-activation patterns and kinematics through the different breaststroke phases. Furthermore, they can be used as focus points for teaching breaststroke to beginners.