The only way to build endurance is to endure

Three weeks into our season, I gave the team an endurance challenge heavy on butterfly. Instructions were minimal: “See how far you can go.” This was the set:

Why do a set like this? What if you consider yourself a sprinter? What if you know with absolute certainty that you are never in all your days going to get up and race a 200 fly? What’s the benefit? What’s the point?

The point is that swimming is an endurance sport.

Let me explain.

Water is about 800 times more resistant than air. That means it’s way harder to move through water than it is to move on land. The fastest runners in the world can do a 100 metre sprint in about 10 seconds. In swimming, the men’s 100 metre world record is 46.86. The difference is significant, and here’s why.

Not all physical activity is created equal. While every activity, including sleep, is powered by the same fuel – adenosine triphosphate (ATP ) – sprinting can only harness as much ATP as the body is able to store in your muscles for immediate, explosive use. The trick is, there is only about 6-10 seconds worth of ATP on hand. After 10 or 15 seconds, your body already has to start breaking down the next available energy source, called creatine phosphate (CP), to try to produce more ATP. Altogether, ATP-CP will max out after about 30 seconds.

So you see our dilemma. The shortest, fastest race in swimming is the 50 metre freestyle. Even the fastest swimmers in the world, clocking in under 23 seconds, have exhausted ATP stores and are accessing CP to generate fuel.

And that’s just one race. As we’ve seen, even the fastest 100 metre freestyler in the world has to proceed to metabolize the next available energy source – glycogen, the stored form of glucose – to generate more fuel. When you use up all your glycogen, it feels yuck. But that’s ok because that’s what you need to do to get fit. You get stronger by exhausting all your glycogen stores and then recycling the by-product, called lactic acid, into glucose, which the body can store as glycogen or use to make more ATP. In other words, if you want to get faster, you have to train.

I think swimming is like other endurance sports in that you can’t train until you have baseline endurance. The beginning of the season is always about building your aerobic base. Doing lots of LSD: long slow distance. It has to be done. That’s why when I put a freestyle/butterfly endurance set up on the whiteboard, swimmers may initially protest and complain, but it doesn’t take them long to get right down to it. And swimmers will tell you that swimming endurance is different from running endurance or cycling endurance. Why? Because when you swim, you’re trying to achieve consistent output with limited access to oxygen. When beginners say they feel like they can’t breathe, it’s often not so much a technical issue as it is a basic lack of swimming endurance.