One of the toughest challenges faced by athletes is determining what to consume during exercise. Selecting a nutrition strategy tends to be over-complicated and overthought, particularly by those going long. There is no one size fits all when it comes to nutrition intake during exercise as everyone has different preferences. However, there are a number of guiding principles that you can use to help you pick a strategy.
During exercise we use fat and carbohydrate as sources of energy. Depending on exercise intensity we utilise our fat and carbohydrate stores differently. During long slow steady swims, cycles and runs we burn fat with a little carbohydrate. Carbohydrate on the other hand is used when intensity increases and we are pushing hard in a race or during an interval. If we think of fat and carbohydrates as fuel sources then we can consider fat as diesel and carbohydrate more like rocket fuel.
Our body stores roughly 500g of carbohydrate (2000 kcal) in the liver and muscle as glycogen and converts this to energy during exercise as the body requires it. In theory this should be enough to get you through at least 2.5-3hrs worth of exercises before your stores are completely depleted and you get the dreaded bonk. Our stores of fat are a lot more abundant and you can tap into up to 20hrs worth of energy by burning fat during exercise. This is why the latest craze in the diet industry, Low Carb High Fat (LCHF) is becoming increasingly popular amongst endurance athletes and in particularly triathletes. The more and more you read there is a familiar theme of becoming "fat adaptive". While there are certainly some benefits to the LCHF diet I am still waiting for more research on the impacts of the diet on endurance performance. I will touch base on this again in another piece, for today I want to focus on nutrition intake for during exercise.
We know that we use carbohydrate, fat and a combination of both as sources of energy while training and racing. Our fuelling requirements should always be guided by the duration and intensity of sessions and scientific principles. Below is an infographic created by Asker Jeukendrup a well renowned sports exercise physiologist and Sports Nutritionist.
Source: Asker Jeukendrup (http://www.mysportscience.com)
The infographic gives a really great break down of what some of the research is suggesting with regards to duration of exercise and the benefits of ingesting small to large amounts of carbohydrate. For the first 30 to 60 mins of exercise there is no need to take on board nutrition. However, it has been shown that a small dose or mouth rinse (take into mouth and rinse then spit out) of carbohydrate solution is beneficial. Ultimately, this depends on exercise intensity. You may not need this for a steady long run but it may be advantageous for interval run or 10K run where you are pushing hard. This was a tactic used by Simon Whitfield, first triathlete to win a gold medal at the Olympic games during his racing days. For exercise between 1 and 2 hours' research recommends 30 grams of carbohydrate per hour. If you are not doing this for your long runs above 75-90 mins then I suggest you start now. It will mean that you can finish the run strong, get the most out of your training and racing. If your runs are longer than 75 mins then start taking nutrition from 60 mins onwards. Exercise between 2 and the 3-hour mark is where you need to increase the amount of carbohydrate intake. 60 grams per hour tends to be the magic number here. Exercise above 3 hours, the suggested amount in the infographic is 90 grams per hour, but there is a catch. You need to be careful with what you use as ingesting more than 60 grams per hour of the same carbohydrate source may lead to gut issues. There is a way around this by carefully mixing different sources of carbohydrate. For practical reasons sticking with the 60 gram rule is perfectly fine. We will cover this again in another blog piece about different sources of carbohydrates to fuel your training and racing. The above are guidelines based on the available scientific research. Everyone has different requirements and needs during training and racing. Determining what your nutritional intake should be and the amount your body can handle needs to be practiced in training. It should also be guided by the duration and intensity of exercise. For example a 3 hour bike ride at low intensity will be less demanding than a higher intensity session of the same duration. So get out there, trial and practice different strategies and find out what works for you. Some final thoughts I hear you ask what does 60 grams of carbohydrate look like and what should I use. You can get your sources from a combination of sports drinks, gels and solid food. It really comes down to personal preference with some people leaning towards solid bars on the bike. Just check the carbohydrate content in your bar to see how many you need per hour. If you prefer gels double check the label too to see how many grams of carbohydrate are in each gel but typically 3 gels per hour get you 60 grams of carb. Also not all carbs are equal some are very sweet and sugary such as bars/gels with high glucose and sucrose content. Maltodextrin and starches are not as sweet and with a lower sugar content. At the moment I tend to make my own gels and bars to insure that I can control my sugar intake (I can provide some recipes). This can be difficult when you are travelling overseas so there are plenty of market gels and bars out there that you can use. High 5 products are very popular but stay away from the 4:1 drink as it has been known to cause gut issues. Clif Bar and SIS are other brands that I personally have never had an issue with. If you want to avoid some of the higher sugar products then I recommend Hammer Nutrition and UCAN Superstarch which are developed using more starchy carbohydrates reducing the sugar content. It is really important that you drip feed throughout your training and exercise. Ramming 60 grams of carbs into you in one go is never a good idea. Your body needs time to process the carbohydrate and can only process 1 gram per minute of exercise. There are some horror stories out there where people have gotten serious GI distress by throwing too many gels into their mouth at once. Finally, and most importantly, we use nutrition during training to improve our performance. But it also has another role in reducing soreness of limbs during exercise and stopping muscle cramp. A lot of people blame lack of liquid for cramps during training or racing but more often than not it could boil down to lack of food.