Carbohydrates sometimes get a bad press, but the right carbs at the right time are the cyclist’s friend. Recent research from the University of Bath shows that athletes who drank carbohydrate sports drinks during an Olympic distance triathlon improved their performance times.
“We showed that ingesting a relatively high concentration of carbohydrates, as opposed to taste-matched water, during the cycle section resulted in a significant improvement in subsequent run performance,” explains University of Bath’s lead researcher Dr Kerry McGawley.
The study shed new light on the topic of energy conversion from carbohydrates and gave Cycling Plus a chance to discover the optimum ways of creating energy from carbs – as well as tasting loads of sweet things in the process.
The selection of energy drinks, gels and bars on the market is bewildering. To see what works best it’s useful to look at the hierarchy of energy – and how we get it from our food. We explain below how your body converts food into glucose (blood sugars), which in turn provides the fuel for the body’s energy.
The production of energy from carbs is also affected by the type of carbs you’re taking in. You can control the rate at which your energy supply flows by eating certain types of carbohydrate.
Energy-containing foods are now classed by their position on the glycaemic index (GI). This is a rating of food types that gives each one a score according to its effect on the body’s glucose levels as it’s digested over a two-hour time span.
Pasta is a high-GI option when it comes to carbohydrate
“The higher the GI, the quicker blood glucose levels rise,” says Mayur Ranchordas, senior lecturer in sports science and nutrition at Sheffield Hallam University. The carbs that are rapidly digested so that their glucose is quickly fed into the blood stream have the highest glycaemic index (high GI foods score over 70).
“Carbohydrates that break down slowly drip-feed glucose more gradually into the bloodstream,” says Ranchordas. They have low glycaemic indexes (GI less than 55). Moderate GI foods neither drip-feed nor provide a sugar rush.
Rush hours
When you consume carbohydrates and the type you eat can have a significant effect upon your performance. High carbohydrate foods like pasta and bread can’t be eaten during a race because they aren’t digested quickly enough to be converted to energy in the time you need it.
“The ideal time to eat slow-release, low to moderate GI foods is two to three hours before a ride,” says Ranchordas. “During the ride you want high GI, rapidly delivered carbs – also immediately after the event. Then back to low/medium GI two to three hours after too.”
For a rapidly digested energy boost athletes often look to some very simple sugary snacks that score high in GI but not quite so high in the rapid delivery stakes.
“Jelly babies, Jaffa cakes and even white bread with lots of jam have a very high glycaemic index,” explains Ruth McKean, nutrition scientist with SportScotland, “but they’re not as good as energy drinks, which hit both your glucose needs and hydration requirements.”
Energy drinks contain quick-to-digest soluble carbohydrates, like fructose and dextrose, mixed with water so that they can pass easily from the digestive tract into the blood stream.
“To maintain the constant fuelling athletes need to take these on through the race – which is why liquid glucose is a better energy shot than, say, sugar lumps,” says Ranchordas.
Drinks with a 4:1 ratio of energy to protein have been shown to be effective post-race
During the University of Bath study the two sets of triathletes were given the carbohydrate or a sugar-free fruit flavoured drink every quarter of the way through the cycle section.
Increasingly energy drinks are offering more complex solutions, including sodium and protein in their ingredients. Some research suggests that sodium helps by stimulating thirst and increasing the amount of fluid that athletes consume, while helping replace minerals lost through sweat too.
Protein also plays a role in energy replenishment drinks, with studies suggesting that a post-race drink, gel or energy bar with a ratio of 4:1 grams of energy to protein is the ideal balance to repair muscles, restore energy and rebuild glycogen stores.
Carb conversion
Digestive enzymes in your stomach start converting your food into body fuel, breaking proteins down into amino acids, carbs into glucose, and fats into fatty acids and glycerol.
As your digestive juices go to work breaking down the carbs you’ve eaten, your pancreas releases a hormone – insulin – which helps transfer the glucose to your cells where it’s ‘burned’ via a chemical mix with oxygen to create fuel for the muscles and nerves. The glycerol is then transported to the liver where it’s either stored or released on demand to become glucose.
Studies show that muscles can store enough glucose for up to 120 minutes of high-intensity exercise – after that the drop in available fuel leads to a drop in performance that ends with ‘the bonk’.
Don’t forget – carbs come in many forms, including mid-GI bananas
Carbs table
Time Carb Intake 2-3 hours before the ride Low-mid GI: porridge, muesli, rye bread toast or scrambled eggs 30 minutes before the ride Mid GI snack: a banana During the ride Fast delivery, high GI isotonic energy drinks, energy gels and dried fruit such as raisins are best After the ride Fast recovery, for meals try corn flakes or rice crispies (high GI) with milk (for the protein for muscle recovery) 2-3 hours after the ride Low-mid GI: grilled salmon with steamed broccoli and sweet potato mash (low/medium GI carbs) is ideal
Want to find out how your diet affects your training? Then head over to BikeRadar Training. It's a free online resource for you to record and analyse all aspects of your training, log your training routes, get yourself tailored training plans, see how you're doing on our leaderboards, set goals and plan your season with a comprehensive events guide.
This article was originally published in Cycling Plus magazine, available on Apple Newsstand and Zinio.
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Original: BikeRadar.com Road Fitness
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