As a swimmer, you can think of your freestyle kick like a turbocharged engine. In a 50-meter sprint, every swimmer needs as much acceleration as possible, maximizing the power of the kick all of the way. However, in events longer than 50 meters, one has to be careful about pushing their legs too hard too soon, in order to conserve energy for the rest of the race. The longer the swim, the more carefully one needs to manage their kick.
Developing a turbocharged freestyle kick is not easy, and it requires developing extraordinary plantar flexibility of the ankle, leg strength for both the down and up kick motions, working both
sides of the leg, and leg fitness. When considering your pulling stroke rate, which may vary between 60 and 100 strokes per minute for any distance over 50 meters, with a six-beat kick, the kicking stroke rate is six times that, or 360-600 kicks per minute. That means that during each stroke cycle, each leg takes three down kicks and three up kicks. This requires a lot of sustained effort and energy, and it is no wonder that many swimmers cannot maintain a turbocharged kick for more than 50 meters without reaching exhaustion.
However, if you want to use your legs in turbocharged mode for any part of the race, they must be extraordinarily fit, even more so than your arms. Once you have developed the capacity for a turbocharged freestyle kick, you must also learn how far down to push the accelerator for each race and when to push the pedal all the way to the metal. Using the turbocharged mode too early or too long will produce too much lactate, which can ultimately shut you down.
To build a better swimming engine with a turbocharged capacity, you must work your legs incessantly, in and out of the water, and develop the right tools for kicking propulsion. Then, plan your longer races carefully, using the first part of the race to get good gas mileage and conserve energy, and saving the turbocharge option for the right time at the end. By doing this, you can finish the race strong, just like elite swimmers Sun Yang or Chris Swanson, and experience the satisfaction of blowing by everyone at the finish.