While at first glance it may seem like you’ll need to save your legs for the bike and run, there are several other factors to consider.
Firstly, your legs (the biggest muscle group in your body) use between 60-80% of your total oxygen, and even very light kicking can stimulate this use.
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Admittedly kick is relatively inefficient for propulsion, adding 30% drive in the best-case scenario and 5% at worst, but this should give you every reason to do more kicking and improve efficiency, in the same way you would seek small gains on the bike and run.
Perfecting your kick will provide added propulsion, but poor technique could actually create resistance. Ensuring that toes are pointed, knees are straight and your kick is being propelled from the hips are all very important factors to consider; otherwise you’re just wasting energy.
Secondly, a solid kicking technique allows you to stretch your hip flexors out. Being tucked in on a bike (or sat down at work), and then overusing your hip flexors when running can create huge amounts of strain and tightness through the hip area. Being able to kick with long, relaxed legs will help you stretch out, and ultimately benefit your entire training regime overall.
Finally, in a race situation you want your legs warmed up when you get on the bike. If you kept your legs still throughout the swim, they would potentially be stiff and cold when you start the bike. No doubt your legs would also drift from side to side and create more resistance during your swim; all the more reason why this shouldn’t be an option to you.
So how much should you do? As a top-level competitive swimmer covering up to 75km a week in the pool, I was told by my old coach that I had to do 30-40% of my training as kick, as were the 1,500m swimmers.
As a triathlon coach, I would suggest 10% of your swimming training should be kick. This means you would do 200m of kick in a 2,000m session, which really isn’t a great deal – and that doesn’t even have to be done all in one go. It could be incorporated into a warm-up, cool-down or as part of your main set.
Whatever you do, make sure it’s done well; whether you kick on your front, back or side focus on kicking from the hips and pointing your toes. Then regardless of how fast or how hard you kick, to some extent you will increase efficiency and propulsion and your kick will help rather than hinder you.
For lots more swimming advice and drills, head to our Training section