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Archives for May 2014

Nutrition basics

Following a question asked on a recent pub ride, it became apparent that many (some?)  riders do not know how the body gets it’s fuel. This post outlines the basics of the mechanisms used by the body. In order to keep it easy to follow I have made some generalisations and simplifications. Also I have lent my physiology books out so I can’t check stuff where my memory is a bit hazy. Bear in mind that although qualified as a BCCS/ABCC coach (equivalent to BC level 3 coach), and having taught A level Sports Science a few years ago, I am not a Sports Scientist.

There are some very interesting methods different successful athletes use when it comes to pre, during, and post event nutrition. If it works for you, use it, however don’t blindly follow what others may say or what you read on the internet 😉

The Basics:

#1 The body converts energy stored in food to movement energy in muscles. Until it is needed by the muscles, it is stored either as fat, or as glycogen (carbohydrate) in the liver and muscles. The body stores about 2000 kcal in glycogen but an almost limitless amount (for sports purposes) of energy stored as fat.

#2 As the body works harder it varies the amount of energy it gets from each fuel. (I’ll add a graph later when I get my books back.) At low intensity almost all the energy is coming from fat, as the intensity increases then the ratio of glycogen/fat use increases until at your aerobic threshold, you are only using glycogen. Fat burning is only half as effective as using glycogen, so once your glycogen stores are all gone you become limited as far as power output is concerned, called bonking in cycling terms, or hitting the wall in running.

#3 Obviously people are different but as a generalisation, youlive up to about 90 minutes of glycogen stores, so any event longer than this needs to be done at less than threshold. Very long endurance events will be done mainly using the fat burning mechanism.

#4 A technique for increasing the amount of glycogen stored in the body is called carbo-loading. This technique involves minimising carbohydrate intake for a few days, followed by a day or two of eating lots of complex carbs before a big event. (This is why you often get pasta parties before marathons.) The principle being that the body starved of carbs will when given the opportunity overcompensate and store more than normal (as glycogen). However, recent studies indicate that the initial low carb phase is not required, other studies suggest that this technique doesn’t actually work at all. Hey that’s science for you!

#5 Food you eat contains fat (concentrated energy source), proteins (for growth and repair), carbohydrates, vitamins, minerals and fibre. Fat contains 9 kcal/g, and proteins & carbs contain 4.5 kcal/g. Any calories from fat/protein/carbohydrate not used by the body will be converted and stored as fat.


#6 Eating during an event: Obviously no point eating fat or protein for energy purposes during an event, but what about carbohydrates? Basically there are two forms of carbohydrates, simple sugars and complex carbohydrates. As you would expect, simple sugars are broken down and release their energy more rapidly than the complex carbs. If you consume an energy drink, gel, chocolate bar, etc then you will get a short term boost but the increased blood sugar levels gives negative feedback to the body and shuts down glycogen release resulting in a subsequent energy ‘low’. If you have already ‘bonked’, that doesn’t matter has you no glycogen left anyway. I do not use simple sugars until I have to, usually not until the last hour or 2 hour of a long day. Sometimes I eat them for energy, sometimes just for a mental boost; 2 bottles of energy drink, a chocolate bar and a big bag of jelly sweets is a common purchase on the last stop of the day.

#7 If not simple sugars, what about eating complex carbohydrates during the event? Depends on the event obviously, but you don’t really need to eat at all on a single day event. For multi-stage events, you quite often are eating for the next day as it takes a while for the digestion to happen. If you are riding all day you may well get through in excess of 10,000 kcal, you cannot eat all that in the evening so you need to eat throughout the day.

#8 Eating before an event. Before intensive efforts such as time trials I would not eat less than three hours before the start, some people say 4 hours, but three worked for me. For a low intensity effort such as an all day ride, then eating immediately before starting is not an issue unless you intend to start by blasting up a hill!

#9 Although you don’t need to eat, you do need to drink. A small amount of dehydration results in a large drop in performance (yellow pee – bad, clear pee – good). Up to an hour max effort you can probably manage without a drink, longer than that and you’ll probably need some fluid, particularly if racing.

#10 Plain water or energy drinks? Personally I usually only use plain water except near the end of  ride (see #6), as plain water is absorbed quickly, and you can use it to wash sweat out of your eyes if needed. Concentrated energy drinks actually slow the absorption of the water and are therefore not as effective at rehydrating the body.