Hydration, Calories and Sodium Considerations by Mark Allen

Now is the time to develop your personal plan, and the only way to do this is to experiment during your workouts.

The three biggest considerations for your race nutrition are hydration, calories, and sodium. Getting enough of each one in an Ironman distance race is as important to your results as the training you are doing right now to get prepared for them. And now is the time of year when you can experiment with each of these as the weather slowly begins to warm over the next few months and you start to encounter heat and humidity for the first time this season. Here are some tips to keep in mind about how each of these plays into your performance and how you can develop a race day plan that will keep in the safe zone for peak performance with each one.


Hydration is the easiest to experiment with. The main issue is to make sure that you take in enough liquid to sustain your body weight during your long workouts. How you do this is simple. Weigh yourself before you head out the door for your long rides and runs. Keep track of the amount of time your workout takes you and also how much liquid you take in during your session. Then when you get home, weigh yourself again. If you have hydrated well, your finishing weight should be within a pound or two of your starting weight. Even in the longest workout, you will lose at most a pound due to fat burning. So if you lose five pounds or more during your workout, the bulk of it is due to water loss. And even a small percent loss of water as it relates to your total body weight and your performance will start to drop off.

Your maximum sweat rate is reached well below your aerobic maximum heart rate when the heat is high. This is a good thing because it enables you to start to collect a mental log of how much you need to drink to maintain your body weight without going at race pace to do it. If you find that you are good at keeping your weight up during the workouts, great! If you are coming home significantly lighter than when you start, work at upping the amount of liquid you take in during your workouts.


The amount of calories you will need to sustain a high level of output will vary widely depending on how consistent your workouts have been, the amount of food you eat before the workouts and in the day before the long workout, and also whether you are well rested or tired.

Start with the average amount of food that research says you can absorb per hour (approximately 500 calories) and see how this works for you. Depending on your body weight and effort level, you may need slightly more or less than this. Keep in mind that at a high output level you can burn as much as 750 calories per hour.

So you can see that there is a difference between what science says you can absorb and what you may be burning up. The difference can be made up over time training your body to absorb more calories per hour than the lab results say is possible. The ideal amount of calories to take in is the amount that will leave you feeling well fueled at the END of your long bike rides, as opposed to the amount that leaves you feeling like you are running on fumes by the finish.

Remember, in an Ironman you have a marathon after the bike, and the ideal situation is to start that run well fueled and well hydrated. Doing this will give you both the information and the confidence you need to have a calorie game plan in place well before your race day.


The third and final section to work on right now is whether or not you need to supplement your fuel intake with sodium. The first question to ask about this is whether or not you ever crave something salty during a long ride? If so, you might benefit from having a source of sodium with you during your race. A key note is that if you have any history of hypertension, consult with your primary health care provider before experimenting with this.

Research has shown that after about three hours of maximum sweating, performance begins to drop off if sodium is not taken in. On average, a person loses 350mg of sodium per hour. So after you lose about 1000mg of sodium the performance begins to drop. Keep in mind that this is VERY individual. Some people will sweat out twice this and others only half. Experiment with what you need.

One sign that your sodium intake is not enough to keep up with your sodium sweat rate is that if you are drinking enough and eating enough calories but still feel like you are flat or feel like you are sort of bonking and are having trouble concentrating and are losing motivation, this is a sign that you may be low on sodium. The best source of sodium is buffered sodium tablets that you can get at any pharmacy. There are a lot of electrolyte tablets available, but most of them are in a capsule that makes it impossible for you to taste the salt when you take it. It is very important to be able to have the tablet melt in your mouth. This will enable you to keep it in until your body says “enough” at which point you can spit out any remaining part of the tablet.

Keep track of how much sodium your electrolyte drink is providing. Keep track of how you feel during your workouts, especially after about three hours. Try sucking on a buffered salt tablet and see how your body and energy levels respond. Start conservative and build up until you find the right amount for you, especially during hot and long workouts.
There you go! Refining the liquid amount, calorie amount, and sodium amount of intake you will need can answer a lot of questions about what to do during your race.

2007, Luis Vargas.

Plan your hydration.