Open water presents challenges you'll never face in a pool. Rougher water and no lane lines are some of the obvious differences; less immediately obvious is the dramatic difference in energy cost.
Consider this: in a pool, turns and push-offs (in other words, pit stops for your arms) occupy about a quarter of the time and distance. In open water, a mile will take at least 10 per cent more time to swim (because push-offs boost your speed) and there are no pit stops.
Meeting these challenges demands better, and different, technique. Pool training encourages habits that might suffice when your arms have frequent 'stroking breaks', but they could sink you like a rock when you're swimming 1500 or more uninterrupted strokes - the minimum it takes most people to swim a mile in open water. So I developed four techniques that can increase your endurance more than any amount of aerobic training.
As a distance swimmer in my teens and twenties, I trained as hard as anyone, but my race times were nothing special. But since turning 55, I've won National Masters Championships, broken age-group records and been the number-one-ranked 55-59 age-group swimmer in open water - mainly by sacrificing speed in the pool.
At Masters workouts, most of my teammates, including triathletes, would out-swim me on short repeats. But during longer swims, they slowed, while I maintained my steady pace. Not because I was fitter, but as a result of my choice to practise longer, more leisurely strokes.
During 25m and 50m repeats, most others sprinted with a high number of strokes - often taking 21 or more strokes per length, while I limited myself to 15 or fewer. I could have sprinted faster by stroking faster, but because my best events aren't pool sprints, I opted to swim as I would in open water. My sprints were slow by pool standards, but perfectly suited for the fastest parts of open-water races.
Though few shared my reluctance to sprint, a study by Jonty Skinner, Performance Science Director for US Swimming, suggested I'd stumbled upon the best way to train - in the pool - for open water.
Skinner and others had noted that many top short-course swimmers swam far slower in longer events. When he compared video footage of short-course and long-course specialists, Skinner discovered that the best long-course freestylers tended to swim with longer, hip-driven strokes, requiring less turnover.
This style generated a little less speed in short bursts, but was markedly less tiring. Short-course specialists used an urgent, more arm-driven stroke - faster over short bursts, but much harder work.
What explains the difference? In a 25m pool, using the underwater dolphin kick, as Michael Phelps does, you might swim as little as a third of the distance, giving hard-working arms frequent rest breaks. In a 50m pool, you would need to swim at least 70 per cent - but usually more - of the distance, a clear incentive to swim more economically.
I understood immediately that the best style in a 50m pool would become hugely advantageous in open water. But here's the rub: hard-working, naturally competitive athletes, training mostly in 25m pools, will almost inevitably focus on the short-course stroke. But to excel in open water, you'd need to defer immediate gratification (short-term speed) for long-term gain. If that's your goal, here are four open-water techniques to practise in the pool - and use next time you're racing.
1. Hug the surface
Most swimmers instinctively lift or swing their head in rougher water. This increases drag and gives the waves a bigger target. Waves occur above the surface, but it's relatively calm below, so concentrate on knifing through choppy water, not climbing over it. To practise, relax your head until it feels weightless, then visualise a laser projecting from the top of your head. Point that laser where you want to go. This also helps your hips and legs ride higher and lighter, saving further energy by reducing drag and your need to kick.
2. Swim taller
The simplest way to lengthen your stroke is to focus on using your arm to extend your body line. You'll still stroke back, but shift your attention to the hand going forward. Practise by focusing on the following: after entry, visualise slipping your hand through the water, as if through a long sleeve. And spend more of each stroke in the front end slightly exaggerating the overlap between strokes. In rougher water, this will also allow time to establish a firmer grip.
3. Swim with wide tracks
Almost all pool swimmers I've seen move their arms to the centre as they reach forward. Elite freestylers extend and stroke on a line directly forward of the shoulder. This helps channel energy in the direction of travel. It also improves stability in waves and churned-up water; your arms function like stabilising outriggers. To practise, visualise a fat tree trunk in front of your head. Keep your arms either side of it the entire time they're forward of your nose.
4. Enter the 'letter box'
A high-swinging, forward-reaching recovery, common among swimmers in open water, places most of the load of propulsion on fatigue-prone arm muscles. When your hand enters closer to your head (on wide tracks) with a steeper arm angle, your hand reaches the 'catch' with your palm facing back, where hand pressure moves you forward. A steep angle of attack also means less fatigue on your arm muscles because you're generating more power from hip rotation. To practise this: visualise a letter box forward of your shoulder; slip your hand and forearm into the slot before sliding through the sleeve; swim silently - a cleaner entry is always quieter; and watch for, and eliminate, bubbles from your stroke.
5. Rewire your brain
These techniques will not come naturally or instinctively. You'll need to practise new stroke thoughts until they become habits. That means never pushing off for the next length without choosing one to focus on. Just as important as new muscle memory will be mental muscle - the ability to focus on a technique in the middle of a churning pack during a race. Try to memorise the drills in the order above.
Terry Laughlin is Head Coach of Total Immersion Swimming. Find out more about his techniques from Total Immersion DVDs or by visiting www.totalimmersion.net.