To run at a steady sustained effort, you’ll have about two hours of stored energy, before your legs turn to jelly and you hit the wall. If you haven’t replaced any carbohydrates during this time, this is the point at which your body turns to its fat stores and you have to begin the slow and painful hike to finish. Finish you will, albeit slower than you wanted, and probably with some emotional turmoil over your efforts. You can mitigate this physical and emotional distress by planning out a hydration and nutrition schedule for yourself. Like always, it’s all about practicing good habits and setting yourself up to succeed.
By the time you hit the half way mark in a long distance race (anything over 3 hours), you will have gone past what your body has stored as readily available fuel. Nutrition planning is a lot about taking care of the last half of the race, when you are fatigued and any major calorie deficit is going to make the day really hard. When you start going into calorie deficit, you are more prone to being emotional, irrational and not coping well with your fatigue. Keep on top of calories, and the late stages of the race will be much more comfortable, your brain will be sharp (better for negotiating tough terrain), and you’ll finish tired, but in one piece.
The energy sources your body will use for racing long distance will come from the glycogen stored in your muscles, and fat. This glycogen is formed when the body breaks down carbohydrates into sugars for energy. Even with the best carbohydrate preparation, your body only has about enough stored glycogen for ninety minutes to two hours. You will then be using your fat stores as energy, a process that is much slower and which requires you to reduce pace considerably. You must constantly ingest carbohydrates and fluids during an event in order to maintain a steady stream of sugar to your muscles and to handle the optimal pace of racing.
You should note that your caloric intake and heart rate are inversely related. As you start to exercise, blood is diverted from your stomach to your working muscles and skin to sweat and help cool you. As your heart rate rises, you are less able to digest the calories you ingest. The food will sit in your digestive system instead of being used: this causes discomfort and gastro-intestinal stress for athletes. Your race day nutrition plan is intimately bound to your racing heart rate.
Fuelling properly means maintaining (as much as possible) your balance in caloric deficit and constantly refilling depleted glycogen stores. Eating or ingesting calories from the beginning is critical. If you wait until you are tired and hungry, you will never catch up.
What to eat and how much to eat is a strategy that each athlete has to work out for themselves. Your training should include a method to work out what your race day nutrition plan should be. Every long training session should include a plan for nutrition and hydration, including how many calories, what specific foods and fluids to take and when to take them. You will have to try out your plan many times in training in order to figure out what works for you. Note that fuelling well in training is not just about planning for race day: eating properly on training runs means you optimize your output for that day and you ensure a proper recovery, both aspects to progressive improvement in fitness.
As a coach, I have seen many training sessions derailed and failed due to one totally avoidable factor: not planning nutrition and hydration.
Quick overview on nutrition
Formulating your personal nutrition plan – the numbers here are not set in stone but guidelines only, and I would have someone start formulating their plan months in advance. If you don’t have months, you’ll have to use some powers of recollection and deduction based on what you have done in training.
There are some athletes who prefer real food – dried fruit, bananas, sandwiches – for endurance events. While I avoid packaged food and eat simple, nutritious whole food in my daily life of training and living, I always stick with sport specific nutrition during races. Packaged bars and gels are easy to carry, easy to consume, have little fibre (way easier on the stomach), and is more precise and efficient when determining calories.
Once again, plan for success, and the success is more likely to happen. Long distance running is one of the coolest things you can do, so take care of the details and enjoy the trails!
Run For Joy!
Common sense and a sense of humour.