Train Hard, Race Fast: The Role of Carbohydrates

athletes-carbsWelcome to Part III, (of some unknown number), of the Sock Doc Essential Guide to Carbohydrates. I discussed the chemistry behind how your body uses sugar and fat for fuel in Part I. Part II dealt with how to condition your body to run more efficiently by becoming a better fat burning machine. Here in Part III I’ll discuss more about carbohydrates and their place in training and racing. Read on to learn how to beat the bonk and why you don’t want to, and shouldn’t need to, carbo load.

Athletes and Carbs: When and How Much?

mountain runThe amount of carbs you need during training or racing depends on how efficient your body is at burning fat. The more aerobically fit you are, the more fat you’ll burn not just in training, but during your entire day which includes work, daily tasks, and sleep. The more fat you burn, the less carbs you’ll pull from storage and therefore the less carbs you will need to consume. When you train harder, (strength, anaerobic endurance, long aerobic), you need to consume more carbohydrates, even if it’s just a small amount. What it comes down to is that your diet should be reflective of your training duration and intensity, and that means it should change accordingly each and every day to some degree.

A true aerobically fit individual should be able to sustain at least two hours, or even close to three hours, of exercise without any carbohydrates. Ideally you should also be able to do this type of training in a fasted state – without any blood sugar issues such as energy swings or loss of mental acuity. That means if you eat the night before say between 6-8pm you should be able to get up and train around 6-8am for 2-3 hours with no problems. Actually, such training is a great way to utilize fat stores for energy and lean-up!

Whether you burn fat or sugar for fuel is also dependent on what you eat during the day, as well as what you consume before exercise. If you wake up and chug down a glass of orange juice (pure sugar), you’re going to shift your body away from burning fat towards sugar, to some degree. This is going to happen even if you’re aerobic (via HR and intensity) in your training. So ideally you should train without eating just before true aerobic exercise. Actually, there’s no reason to eat then anyway if you’re conditioned properly. If you feel like your blood sugar drops at some point in your training when you don’t eat before, the way to address this is not by eating before but to train a shorter time, less intensely, or focus more on your overall diet.

If you’re going to exercise anaerobically, (such as HIIT), then eating just before that workout really shouldn’t have any effect on performance. You’re going to be burning more sugar than fat anyway which is perfectly fine, and as long as you’re not going into the training glycogen depleted then eating just prior to working would be irrelevant. This same principal also goes for strength training.

Post Exercise Fuel

post race sugar

Easy on the sugar.

There is that window of opportunity after training where your body is more insulin sensitive and you can replenish glycogen levels faster than if you waited much longer. The amount you need to replenish would also depend on how much you depleted, which again has to do with intensity, duration, and your fitness level. Remember, the more fat your body is using for fuel the more glycogen (stored sugar) is spared – so there’s less to replenish after.

Consuming carbs within one hour after anaerobic exercise, (high intensity or strength), in the range of 25 grams to several hundred grams, (if you were training or racing for a long time), will most likely improve your recovery. Some say protein during this time can be beneficial at the ratio of 4:1, carbohydrates:protein. It can take up to 48 hours, or even 72 hours, to fully replenish glycogen levels. So the longer you go without eating, or the more often you skip meals, the more your recovery will suffer and be delayed. This is why if you don’t eat until long after some anaerobic exercise, (or you don’t eat enough), and then you don’t eat well the following day too, you’ll most likely not feel recovered for many days; it’s hard to play catch-up. Some people take entirely too long to fuel glycogen to optimum levels because they don’t eat enough food, or they don’t eat the right foods – they’re always working off low glycogen levels. These athletes suffer low performance and their gains are hard to come by, if they’re making gains at all. So eat some carbs after training hard and if the training is long duration with high intensity, you need to consume carbs during too! (The types of carbs to consume will be discussed later.)

Of course eating carbs isn’t just relative to your training. If you handle carbohydrate foods well then you can eat them through the day. But if you’re properly burning fat for energy rather than glucose, you shouldn’t need to or want to consume a whole lot of high carbohydrate-based foods such as grains, or even a lot of fruit.

Beat the Bonk!

race bonkWhether you need a lot, some, or zero carbs during a race will depend on how well you have adapted your body to burn fat, which is also a reflection of how well you trained to run a certain distance at a given speed. If you choose to race, or even train a certain distance, your body requires a certain amount of fuel to get you through it. You just can’t run fast and pull an IV of glucose along with you to keep your body strong; it’s all about how you have adapted your body physiologically and metabolically that will determine your success. (Of course there’s often a huge mental component to racing too and as discussed in Part I, carbohydrates have a lot to do with brain function.)

Let’s take the marathon and see how you can either bonk or finish strong. Say you’re running the race at a relatively high intensity and you’re burning 70% sugar and 30% fat. Let’s assume that the average person burns 100 calories a mile. So 70 calories of sugar, (roughly 17-18g), are going to be burned per mile. Let’s assume you have stored 400g of glycogen in your muscle and liver – but it’s not all going to be used just to move your body – you’ve got to stay alive and alert don’t forget. But even if we want to assume you have those 400g just for the race, you’ll see that you’re going to run out of sugar around mile 22-23. Actually, you’ll probably bonk much sooner because if you’re starting the race at 70% glucose then most likely you will be closer to 80% by the half-way point if not even higher. This is why people bonk in a marathon around mile 20. Now, if you’re running at 50/50 sugar/fat then at mile 20 you’ve perhaps only used up 250g of sugar and you (should) have plenty left in the tank to not only finish without the bonk, but pick up your pace during that last 10K and finish strong. Unfortunately, most people running endurance events are not trained properly in so many areas, including their diet.

So should you use gels or other carbohydrate products (including soda) in a race? This also depends on whether you need the sugar at a certain distance per your intensity. Ideally, you should train as long as possible without any sugar; this will help your body to become accustomed to burning fat. During a race it’s often fine to consume the carbohydrates you need to perform your best – after all, it’s a race and you will most likely (hopefully) be pushing yourself harder. But this doesn’t mean you go from eating no food during training to carb-crazy in a race. The amount and type of carb you eat during the race is based upon what you know your body needs. Don’t wait until you start to feel depleted. Have a plan and consume a certain amount of carbs during certain periods in a race.

For me, when I race well over two hours, I shoot for 200-400 calories per hour starting around the 60-75 minute mark. So I might consume 100 calories around 75 minutes into the race, and another 100 calories every 20 minutes depending on my intensity level, up until 15-20 minutes before I expect to finish the race.

If you need to consume a gel at every mile in a marathon, or even just one during a 10K, then you’re either improperly trained, racing above your means, or both. The slower you race, (and maybe you should be racing slower), the less fuel (sugar) you need. Personally, I don’t think any fuel other than perhaps water is necessary in a half-marathon or shorter distance race. If you’re out on a long hike (meaning hours) or cycling at an easy pace for hours then really you shouldn’t need to eat, as long as the intensity is aerobic for you – that’s truly primarily fat burning aerobic.

Pasta Party and Carbo Loading!

pasta partyI’ll keep this section short; hell I never went to one Ironman pre-race meeting/pasta party anyway. You shouldn’t need to carbo load if you’re already burning fat properly and storing normal amounts of glycogen. You only can only store so much and if you’ve done all the right things, there’s no need to “top-off” the tank either the night before or two nights before the race. Actually, for many this can cause gastrointestinal problems and even shift the metabolism somewhat away from optimum fat-burning. If you have raced better with carbo loading in the past, it is most likely because you already burn way too much glucose rather than fat and/or you were glycogen depleted going into the race.

So if you go to the pre-race meeting for the food, stick with protein, fruits, and vegetables – and especially stick with what you’re used to eating. Definitely skip the dessert which is often full of processed ingredients and inflammatory fats on top of the high sugar content. The pre-race meal isn’t going to make you any faster or stronger if you’re well prepared, but it can definitely ruin your race if you’re trying to get the most out of the “free” food.

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  1. SteveL says

    Thanks again. You have solidified in my mind what I have been doing since I found your web site and put myself on the TWT. I found from there iI’m pretty darn carbohydrate intolerant so I only take a gel on really long runs or racing half marathon and up and after I’ve been out for at least an hour and that has worked really well.

  2. Ian says

    I train every weekend my long run in a fasted state and with no food during the run, only water, for up to 2.5 hours so far on trails. I get a little sluggish and tired towards the end, but it is training your body to make a adaptation after all.

    For anything longer or for races (training for a 50k at the moment) I use Tailwind Nutrition, which is only really a pure glucose/electrolyte drink. Organic flavors, no corn syrups or crap, cottage business and this stuff is legit! Love it. (Thanks TRN!)

  3. Allan says

    Another good article sock-doc. Thanks. There will be a lot of controversy and question about carbo loading. I think there are some including me who make endurance activity as an excuse to “carbo load” and ultra- eat.

  4. Jess says

    Hi Doc,

    I would like your opinion on something. I am a college athlete with an intense schedule. My day consists of often 3 workouts that when combined adds up to 4 or more hours of training when including skill work and weight training. I am a basketball player who plays the post position. I am naturally a skinny person, but I need to put on weight in order to maximize my play down low in the post. Therefore, during the season I find it extremely hard to keep on my weight, let alone put extra on.

    I have read your post about Paleo, and I agree with the importance of eating well for a whole body. But how do I possibly consume enough calories when I burn off so many every day? I remember reading about Michael Phelp’s diet during his training. I do not want to resort to eating pizzas and pastas all day, but I do wonder if this is what I need. My teammates, who seem to be performing just fine do not care about their nutrition, and frequently eat fast food and desserts as often as they want. What are your thoughts on this? Thanks so much.

    • says

      If you feel & perform well on those carbs you might consider using them. Potatoes, rice, or oats might work too. Don’t forget about more fat in your diet too. The harder you train the more carbs you’ll need to replace. Going hard core Paleo might be tough; you don’t want to go fruit-silly.

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