As endurance athletes we don’t need to completely restrict carbohydrates, but time them effectively day-to-day and use them strategically in training and racing. This is known as “train low, race high” and it could be the key to your endurance success.
1. Fasted training, when practiced in training (ideally in the ‘off-season’) for 8-12 weeks, enhances fat utilization and decreases your reliance on exogenous fuel sources (i.e. gels). To begin with, start with lower intensity sessions of 60-90 minutes in duration. As your fat adaption progresses, see what you are comfortable extending this out to. I can comfortably ride for 2-2.5 hours on just a fat black, but that doesn’t mean it will work for you.
2. A low carbohydrate high fat (LCHF) approach is particularly useful in your off-season to enhance fat adaption, as it decreases your physiology of being a “sugar burner” (that comes with a high carbohydrate intake) and allows for four or more hours between meals based on the satiety and blood sugar response it creates. This allows for metabolic efficiency on a day-to-day basis (train low). A total intake of 15% carbohydrates per day is possible if you are also consuming 65% good fats (the remaining 20% is protein)*. As your season builds you can add carbohydrates, but please base this on your session intensity, recovery and subsequent performance. More on this to follow. Please read “How to LCHF (low carb, high fat) the healthy way!” before proceeding here.
3. You need smaller amounts (30-45 grams) of carbohydrate post training for muscle glycogen replenishment (nutrient timing). Scale this based on session intensity and subsequent recovery and performance. For example, if you start with 30 grams post training and your recovery is not optimal in the days following, increase to 45 grams after a similar session and compare. Being initiative is important here.
4. Train low applies right up until race morning, as although an Ironman is a 9 or even 17 hour day, your fuelling can begin as early as heart rate stabilization on the bike. It’s therefore, on average, a 60-90 minute fasted session, depending on how fast you swim. No matter how lean you are, you have more than adequate fuel reserves to do this fasted (particularly if you’ve nailed the above). Your muscle glycogen levels are full (provided you’ve refueled and tapered well) and only your liver glycogen would have depleted slightly over night, making it unnecessary for more carbohydrates at this time.
NB. If you are hungry and/or prefer to eat on race day (and have practiced this in training) then by all means eat, but keep it low carbohydrate and eat good fats and moderate protein like bacon and eggs or a smoothie you could even prepare the night before. Waking up three hours earlier than you need to, in order to eat your carbohydrate rich meal, is not only a logistical nightmare, but setting up the cycle to need more carbs at most likely the very inconvenient time when you are face down in a body of water. Not ideal.
5. The strategic use of carbohydrates on race day (race high) is essential for top end/high intensity. When you are fat adapted, you utilize the carbohydrate far more efficiently, and in general will still be using less than a traditional sports nutrition model. On race day this is beneficial from both a digestive and logistical sense. The amount you need is of course extremely relative, so please work with your Sports Nutritionist here and make sure you have practiced your race day fuelling strategy in training (you should only need a handful of trial runs and therefore not detract from your fat adaption).
In summary, train low, race high is a strategy to become a fat adapted, lean and fast endurance athlete. If Bevan McKinnon can race a 9 hour Ironman at 43 years of age, with the science to improve how and why, it’s good enough for me. Say no to the pasta party.
*Please note: this is just a guide and needs to be interpreted relatively, like all things nutrition should be.
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Phinney SD, Volek JS. (2012). The Art and Science of Low Carbohydrate Performance. Beyond Obesity LLC.
Schofield G (2013). How to win the Ironman on LCHF. Available: http://profgrant.com/2014/03/04/how-to-win-the-ironman-on-lchf/