To start with, let’s consider some definitions. Each kicking pattern (2BK, 4BK or 6BK) describes the number of kicks for one arm cycle (i.e. two arm strokes). So what’s wrong with our normal four-beat or six-beat kick? Nothing – if what we want is speed over short distances. Swimmers keen on swimming as fast as they can over, say, 100 metres use 6BK. They want every bit of thrust they can muster including the ten percent given by the kick. But if we want to swim longer distances, the effort expended with using 6BK – or even 4BK – increases energy consumption significantly. Swimming at a moderate speed of 60 seconds for 50 metres, the competent distance swimmer consumes 400 percent more oxygen by kicking compared with swimming with arms alone. Clearly, this would exhaust a distance swimmer with consequences for achieving a good time or distance.
How do we do the 2BK?
Minimise your kicking effort so that your legs draft behind in the slipstream of your torso. Your kick should be a shin and toe ‘flick’ rather than a full leg drive. Synchronise a right foot ‘flick’ with your left arm entry, followed by a left foot ‘flick ‘with your right arm entry
Rather than churn the water with your kick, allow your kick to result from arm extension and torso rotation, rather than working the leg muscles
By timing your kick with your arms (one kick per arm stroke), use the kick to help arm extension and torso rotation.
Non-competitive distance swimmers tend to use a 2BK for their whole swim in order to devote most of their energy consumption to their ‘paddles’- their arms. Competitive distance swimmers will do the same except for the final 200 metres or so when they will usually switch to 6BK in order to get the edge on their competitors.