There are a couple of kinds of kick in triathlon training and racing. The first kind of kick is in the swim. The kick is necessary but needs to be managed in the swim. The kick is also in the run in the last section toward the finish line. These two kinds of kick are needed to truly go faster in triathlon. Both of these kicks have to be managed in order to utilize them to the fullest extent.
The kick in the swim is a technique that is truly difficult for one to master. The question always arises when preparing to swim in a triathlon of "how much should I kick in the swim?" I have read and observed several different answers to this question. I think the dividing line comes whenever you discover if that individual has been on a swim team previously. If they have been on a swim team there is usually a propensity to kick more than those who weren't. I was not on a swim team and find that I struggle to know exactly how much to kick. I have adopted the total immersion swimming format for my swim which minimizes the kick as more to balance and propel the swim and not to be the motorboat plowing through the water behind. I have found that on longer swims such as half ironman distance (1.2 miles) or full Ironman distance (2.4 miles) when minimizing leg kick throughout the swim you need to speed up the kick in the last 100-200 yard toward the finish of the swim to "activate" your legs or you will fall over when you come out of the water. I think that minimizing the leg kick is good but don't just drag them behind you. I have been working on making my kick effective in the water by utilizing the techniques of kicking from the hip and not the knee, keeping the foot in the right position to propel, and making my kick forceful as possible. I tend to kick once for every stroke and this tends to help move me through the water. I certainly know that kicking harder will make me go faster, but also will use up my legs too fast before getting into the rest of the race. Remember, you cannot win the race in the swim but you can lose it by exerting too much energy. I try to remind myself to use up my arms as much as possible in the swim because the rest of the day they don't do a whole lot.
Kick in the Run
The kick in the run is what you save up for in the last portion of the run. Do you have anything left in the tank at the end of a triathlon race? I think this kick is something you train for. I try to finish every run that I have in training with a kick at the end to push me to finish, then in a race, it is natural to do this. I try to push the last 1/2 mile at least to up my pace considerably. I want to end the race with nothing left in the tank and on a high note. In my last race, I passed 3-4 people in the last mile or two because I had a kick at the end. You never know how much you might need at the end, but certainly, train yourself to have that kick so that you finish strong.
These two types of Kick in triathlon are both necessary to gain success in triathlon training or racing.