Swimming is perhaps the perfect athletic complement to running because the two sports are so different. "Just about everything about swimming is exactly the opposite from running in terms of stresses on the body," says Joe Friel, a runner-turned-triathlete and the author of The Triathlete's Training Bible (VeloPress, 2004). "Swimming tends to stretch you out, whereas running tends to compress you." Running, of course, is a high-impact, primarily lower-body activity, while swimming is a full-body activity that's both non-impact and non-weight-bearing.
As a less natural and more technique-dependent sport than running, swimming requires a different training approach. "The key for runners who start to swim is to harness technique rather than energy," says Steven Shaw, the author of Master the Art of Swimming (Collins & Brown, 2006). "People often make the mistake of trying to build up their endurance straight away, but they need a technical foundation first because the most efficient swimmers take the fewest strokes. In running, the opposite is true."
There are a number of ways to swim, of course, but unless you're the Olympian Michael Phelps, you'll be swimming freestyle (sometimes called front crawl). While proper freestyle technique is relatively simple compared with the butterfly, almost all beginning triathletes need feedback on their stroke from a knowledgeable observer. Find a friend who is a good swimmer, or a local swimming coach, and ask if they would look at your stroke. One or two tips from a keen observer will save you weeks of struggling on your own.
Experts also advise beginning swimmers to forget about speed. "If you're competing in a triathlon, you can't afford to use your legs too much in the swim because you'll need them for the bike and run," warns Shaw. "Reduce the pace of your kick and drive the stroke with your arms." Instead of trying to cross the pool faster, count your strokes per length and try to reduce the number.
Running involves sustained effort, but the key to efficient swimming is knowing at what point in the stroke to put in effort. "When your arm comes over the top of the stroke, don't throw it at the water as this actually produces a breaking force," explains Shaw. "Instead harness your energy when your arm is under the water and keep your hand relaxed and open." You may have been told as a child that closed fingers will propel you through the water at greater speed but new studies suggest that's not the case, and in fact makes you more likely to injure your shoulders.
Drills can also help you improve your swimming technique because they allow you to break down the freestyle stroke into parts, so you can focus on improving one or two aspects at a time. Shaw recommends practising different breathing positions to give you confidence for open-water swimming. "Extend one arm and kick on the side with your face almost in the water. If you know that you can adapt your breathing to cope with wind and waves, you'll be more confident in the water."