A unique aspect of an IronMan is just how much you need to eat and drink while you race, as you will burn thousands of calories and lose a considerable amount of water/sodium through perspiration throughout the race. I typically use the wizardry of the FirstBeat algorithm implemented on my Garmin device to calculate calories expended. Using individual metrics such as gender, weight, height and fitness zones, combined with heart rate information (to estimate metabolic equivalent), the algorithm is considered one of the most accurate out-of-laboratory means to determine calorie expenditure (read more about it here: https://www.dcrainmaker.com/2010/11/how-calorie-measurement-works-on-garmin.html). I typically burn about 600-800cals/hr through all three discplines when approaching race pace, meaning I will comfortably pass 8000calories expended on race day.
Water/sodium loss through sweat is more of an individual/genetic measurement, some people tend to sweat more than others. Most people are pretty familiar with the concept of rehydration after water loss, so I wont cover it here. Sodium loss goes unaddressed more often. In short, sodium aids in water retention and provides the much-needed electrolytes that regulate nerve/muscle function among many other important functions. Getting a sweat test done is probably the best way to find out just how much sodium you lose in your sweat, and allows you to tailor your personal electrolyte replenishment strategy. I have not yet done one, but I know I sweat a ton and often end up with sweat rings/stains on workout gear, which is a good indicator that I need to take my sodium replenishment seriously!
Finding out how much you need to replenish, and equally important, how you will go about doing it (gels, drinks, solid foods,…?), should be a top priority for any level endurance athlete. Like most things when I raced my first half IronMan last March, I didn’t really think my race nutrition through all the way. All I had to replenish my losses during the race was water, GU gels, and everyone’s favorite, peanut butter jelly banana sandwiches! I expended about 4000calories on that course and only replenished about 1200calories during the entire race, putting me in a deep deficit. I estimate my sodium intake throughout the entire race floated around 700mg.
To prep for the full, I needed help with my race nutrition. Luckily I got the help from Cyril at Feed The Machine (www.feedthemachine.com). He is an endurance athlete himself and extremely knowlegeable about all things nutrition. Through his advice, I have gotten a lot smarter about nutrition during both training and during race situtuation. In the simplest sense, it comes down to three main questions:
- How many calories do you expend per hour during the workout/race?
- How much liquid (i.e. water) do you need to intake per hour?
- How much electrolytic sodium do you need to intake per hour?
I already mentioned that I use the FirstBeat wizardry to estimate my calorie expenditure per hour. For training sessions over an hour, I typically replenish at about 500-600calories per hour through both sport drinks (Tailwind, fluid performance, EFS pro) and solid foods (bonk breaker & cliff protein bars). All these are additionally packed with valuable Potassium and carbohydrates. The solid food is easier to eat on the bike, so ill load up on the solid food about 25-50% more about 30 minutes before transitioning to the run portion. I typically reserve the use of gels combined with sports drinks on the runs, as they go down easier than solids. They also come with a nice dose of caffeine and sugar.
My liquid intake is based on past experience and I typically consume about 1L/32oz per hour, though I can get by with 0.75L/26oz fairly comfortable as well. Since I have not yet done a sweat test, the answer to number three requires a bit more experimentation. A good starting point is 400mg of sodium/hr and tailor from there. Given my hypeactive sweat glands, I currently replenish at around 600mg of Sodium through the use of sports drinks (above) and SaltStick caps and have seen a reduction in muscle cramping and heat stress (two common outcomes of a sodium deficit) throughout my longer training sessions.
Carrying adequate amounts of fuel on the bike is critical, as you are most likely already in a deficit after the 2.4 mile swim and need to start replenishing. I currently carry about 3L/96oz of liquid on the bike through a ProfileDesign 35oz drink system and two rear mounted water bottle cages, using 1L/32oz Gatorade bottles. These bottles work well with the quick fill feature on the ProfileDesign system. Through the use of Tailwind, Fluid Performance, or EFS Pro ill have about 1200mg of sodium and 600 calories in the liquid. Liquid-wise this would get me through an entire half-Ironman bike portion (~3hrs target). Ill have to fill up at the half-way marker for the Full. Add in another 210cals/bar (bonk breaker) or 260cals/bar (Cliff), I can pack additional calories as needed through solid foods. Targeting a 6hr bike split, this means ill plan on taking in 3500 calories and 3600mg of sodium on the bike to replenish my losses. My calorie intake/hr will fall a little bit on the marathon due to being limited to gels and sports drinks, and by properly preparing toward the end of the bike. With a target marathon time of 3.5 hours I plan on taking in about 1400 calories and 1800mg of Sodium. This is just a general framework. I will continue to tailor in training as needed throughout my runup to race-day.
Training numbers for T-12 weeks are below. I will have another 2 weeks of strong numbers (including the TriStar Athletes training camp 23-25 Feb) before I start tapering for the March 10 70.3mile race in Long Beach.
