This is taken from an email exchange with Steve Eldred, one of the most determined athletes I’ve met. A fall from a balcony 20 years ago left Steve with a disabled left arm, yet he completed the Lake Placid Ironman in 2008 and is now preparing for his second. In 2008, he struggled to finish the 2.4-mile swim, emerging from Mirror Lake in 2 hrs 20 min as the last swimmer in. He felt ill much of the rest of the race because of how exhausting the swim was. Almost miraculously he passed quite a few people and did complete the race, becoming an inspiration to many.
Over the past six months, my daughter Betsy has been coaching Steve and he now has a far smoother and more efficient stroke. Here’s an email I received from Steve this morning,  16 days prior to the 2009 Lake Placid Ironman.
 
Terry I will be swimming two loops of the Ironman course on Mirror Lake Saturday morning trying to duplicate the early starting conditions. I feel my stroke efficiency has come a long way and I am much more confident going into the event.
Steve!

My response:

Steve
It’s a good idea to swim at 7am. This will duplicate how your "circadian rhythms" will operate during the race. You’ll also duplicate how the position of the sun glare affects visibility as you swim and can plan navigational adaptations to its glare. However, the most important thing to rehearse and imprint is the feeling you hope to have while swimming the event.

This calls on you to use a bit of imagination. If you had a swim that exceeded your wildest dreams, how would it feel ? How would each stroke feel and what kind of thoughts and emotions would you experience? To do so, it will help to recall the sensations and emotions you experienced during last year’s race, then make your mental rehearsal for this year’s experience as different from that as possible. E.G. If you swim 30 minutes faster this year, or 1 hr 50 minutes, at a rate of 45 strokes per minute (which I believe is close to what Betsy has had you practice with the Tempo Trainer), it will take you about 5000 strokes. You’d like each of those to feel unhurried and effective — a dramatic departure from what you experienced last  year. And if you were to feel that way as you swim, what emotions would you experience? Probably a sense of physical and psychological flow that causes you to smile as you swim.

Visualize every detail as vividly as you can. For the next two weeks strive to make those sensations and emotions your reality in every practice swim. How far you swim in these practices is probably less important than your ability to capture and maintain that sensation on each stroke.

How will this help affect your racing experience? It will help "insulate you" from what you have already experienced — a congested, even frenzied, environment during the first 10 minutes after the start. For triathletes with little experience in open water, this environment often creates extreme anxiety that releases stress hormones, first adrenaline, then cortisol.

Adrenaline causes your heart to race, and fast, shallow breathing — which causes you to stroke faster. It’s stress, not fatigue, that causes many to stop swimming freestyle and switch to backstroke or breaststroke, or stop swimming altogether and float on the back, trying to calm the panicky feeling and catch a breath. The body secretes cortisol to clear the adrenaline from your bloodstream. It takes away the worst of the "stressed-out" feeling, but it also takes away your energy. This "hormonal whipsawing" is the likely reason for the sick feeling you experienced during last year’s race.

The process I described above is known to be the most effective at creating a "cocoon of calm" that will insulate you from the stress-inducing aspects of the swim. Research in brain science have shown that the more real you can make your visualization the more it will affect both the physiology and psychology you bring into  the race. Your practice will "condition" brain regions that are most active when you feel calm and in control, rather than those that are active when you feel agitated and vulnerable. 

There is little you can control about the environment during the first 400 to 500 meters of the swim. However you can learn to control what and how you think in the midst of it. So focusing more on imprinting a mindset these last two weeks will be the most impactful thing you can do in your lake swims.

I’ll be back in Placid July 18-25. See you then.