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Pre-ride and on-the-bike nutrition quantities
I have one question relating to the amount of carbohydrate you should consume per hour during your long ride if you have had a pre-ride meal three to four hours, two hours, or one hour before the start of your ride. Do you consume different amounts of carbohydrate per hour during your ride depending on the size and timing of your pre-ride meal? For example, would you consume more per hour of the ride if you have only had a small pre-ride meal one hour before you ride? Do you increase the amount of carbohydrate consumption per hour of riding depending on the length of your ride (say, a four-hour ride versus a six-hour ride)?
What amounts of carbohydrate should you consume per hour of your long ride?
Just to recap the March 28th posting, fueling properly before a long ride ensures that you begin the ride with adequate muscle glycogen and liver glycogen stores. Eating a large meal 3 to 4 hours before a long ride can top off muscle glycogen stores and fill liver glycogen. Consuming some easily digested carbohydrate in the hour or so before training helps to maintain blood glucose levels early into your long ride. So whether you plan on riding 2 hours, 4 hours, or 6 hours, pre-fueling is important as these rides all rely on some amount of muscle glycogen for fuel.
Plenty of research has shown that consuming carbohydrate during training rides lasting even only one hour and when racing can enhance performance as this provides fuel when muscle and liver glycogen stores run low. How much you consume each hour during a long ride is really determined more than anything by your carbohydrate choices and how these choices are tolerated and absorbed. Of course more carbohydrate means more fuel, but this only works if your absorption can keep up with your intake, and you also have to address hydration needs as well.
Numerous studies have found that the amount of carbohydrate that could be burned for fuel topped out at 1 gram per kilogram of body weight, or 70g of carbohydrate for a 150 lb. cyclist. In these studies, even if greater amounts than 1g/kg was consumed, more carbohydrate was not burned for fuel. Carbohydrate sources ingested were mainly glucose or glucose polymers. Carbohydrate that you consume during training empties from your stomach (hopefully quickly) and then must be absorbed through your small intestine so that the carbohydrates enters your bloodstream.
It is believed that the absorption capacity of glucose in the intestine is the factor that limits how much carbohydrate can be burned for fuel. However, in the past several years, a series of studies conducted at the University of Birmingham have measured the results of combining several sources of carbohydrate at one time.
What this series of studies has determined is that doubling or tripling up on your carbohydrates can likely push your carbohydrate burning above the 1 gram per kilogram per hour. Glucose and glucose polymers that are chains of glucose molecules (often in the form of maltodextrin), and fructose are believed to use different transporters to cross the small intestine and then enter your bloodstream.
The idea is to use two to three carbohydrate sources in order to maximize simultaneous use of these transporters and make more fuel available to you the cyclist during long training rides. This is especially helpful for rides lasting longer than two to three hours. If the carbohydrate you consume during exercise is more quickly absorbed, it will not sit in your gut and cause gastrointestinal upset, but rather provide more fuel for training and racing.
Basically, what the researchers found was that a combination of glucose and fructose could be burned for fuel at a rate of 1.3 to 1.8 g per kilogram, increasing the 150 lb. cyclist to 88 g to 122 g of carbohydrate per hour. Try out some carbohydrate combinations during long rides and see how far you can push your tolerance limits. Keep in mind that more concentrated carbohydrate sources empty more slowly from your stomach. Of course a sport drink is your primary carbohydrate source, and your fluid intake should match or minimize your sweat losses as closely as possible. Sports drinks mixed to their standard recommended concentration empty quickly from your stomach.
Hard group training rides that mimic race conditions also provide good opportunity for experimentation. These studies found that subjects experienced more side effects when large quantities of glucose were consumed, whereas a glucose and fructose combination or a glucose, sucrose, and fructose combination were better tolerated.
So let’s translate some of these numbers. Let’s revisit the 150 lb. lean cyclist. He can consume at least 70 g of carbohydrate per hour and up to 122 g of carbohydrate per hour. Most sports drinks provide about 14 to 19 g of carbohydrate per 8 ounces. Filling a 24 ounce fluid bottle provides anywhere from 42 to 57 grams of carbohydrate per bottle. Sweat rates can range greatly among cyclists, from 1 to even 3 quarts per hour. Below is a grid that outlines fluid intake of a higher sodium sports drink providing 15 g of carbohydrate per 8 ounces from glucose and fructose.
|Volume/hr||Calories||Carbohydrate (g)||Sodium (mg)|
Other sources of carbohydrate that provide a welcome anti-bonk carbohydrate boost during long rides include gels, blocks, jelly beans, and energy bars. Carbohydrate amounts can reach 50 g per serving, but these items should be consumed with plenty of water. Add in these items carefully. You likely have experienced more hunger during longer rides, so it makes sense that a six-hour ride may call for more gels or solid items than a three-hour ride.
Any risks to trying to consume too much? Of course your stomach can only handle so much fluid at one time. But drink large gulps when possible to train yourself to tolerate larger fluid amounts to better match up to your sweat rate, and also to encourage stomach emptying of these drinks which are typically a 6 to 8 percent concentration. Just keep in mind that if you mix up more concentrated drinks and push more solid items may take longer to leave your stomach. This would only defeat the purpose of trying to take in more carbohydrate. Cyclists with lower sweat rates should also be careful to not over drink and put themselves at risk for fluid overload — though this is less likely to happen than finishing a long ride with some degree of dehydration.
So before those long rides, plan a good pre-ride meal or snack and pack a sports drink with multiple carbohydrate sources. Check your sweat rate by weighing before and after training, and see at what fluid level you can maximize your intake. It may just make you a faster cyclist.
Monique Ryan, MS, RD, LDN is a nationally-recognized nutritionist with over 22 years of experience and is owner of Personal Nutrition Designs, a Chicago based nutrition consulting company that provides nutrition programs for endurance athletes across North America.