Triathlete Tim O’Donnell’s Tips for Ironman Racing and Training Nutrition
Triathlete Tim O’Donnell’s Tips for Ironman Racing and Training Nutrition
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Triathlete Tim O’Donnell’s Tips for Ironman Racing and Training Nutrition

It’s a crazy thought, here I am writing a blog about triathlon race nutrition but there are no events to race in the foreseeable future.  With the current health and economic crisis, the world has a lot on its plate right now…athletes missing their favourite races definitely isn’t high on the list of priorities!  However, triathlon is an important part of how many people bring physical, mental and social health into their lives. While we don’t have races right now and training is limited, things will get back to normal at some point.  As sure as triathletes (and cyclists) like to wear spandex to coffee shops…surely we will toe the start line again! So why not take advantage of this time to focus on details of training and racing that often get overlooked? One of the most neglected details athletes overlook is nutrition.  Nutrition can really be the piece of the puzzle that makes or breaks your race. I hate to see athletes spend so much time training and so much money travelling to races only to have their day ruined by nutritional issues. I’ve experienced this myself and trust me when I say take time now to figure out your nutrition, it will pay big when we get back to racing!


Race day nutrition doesn’t start on race day, it starts in training.  The golden rule of racing is don’t try anything new on race day! This is particularly true for your nutrition plan.  While how you fuel for training is very dependent on the type of session you are doing, there are absolutely days in your training when you’ll need to practice your race nutrition.  When it comes to how I fuel in training I loosely categorize my session into three categories:

  • Aerobic Training
  • Interval Training
  • Race Simulations

Aerobic Training


For aerobic sessions, I focus on improving my metabolic efficiency with a lower caloric consumption.  When training aerobically we can rely more on our body’s ability to oxidize fat for the energy our body needs in training.  You use less energy per hour and a higher percent of that energy comes from fat. When combining this with the fact that the liver stores approximately 125g of glycogen and (depending on the person) the muscles store another 250g of glycogen, you see that the body is quite well equipped to handle aerobic training without copious amounts of gels and bars.


Interval Training


When I’m doing sessions under 2 hours I tend to train with just water and low-calorie electrolyte drinks.  For longer 2-4 hr sessions I rely on UCAN (low-glycemic carbohydrate) to provide a steady energy source. If I’m riding for over 4 hours then there is probably a coffee shop or gas station stop for a treat and a cold drink.  It’s important to note that this is also very dependent on one’s physical condition and metabolic efficiency. For example, when I am coming off of break and getting back into early season training, I usually need a little extra calories as I’m just not as efficient.  I also always have a little extra nutrition on me just in case…trying to train through a bonk is never fun!


When you start bringing intensity into your training is when consuming carbohydrates becomes more important.  When you increase your intensity into tempo, threshold and VO2 zones your body will begin to metabolize less fat for energy and begin to heavily utilize carbohydrates.  At very high intensities your body will almost completely shift to carbohydrates as