Carbohydrate Loading
The importance of muscle glycogen levels to enhance exercise performance is not in bout. The time to endurance during intense aerobic exercise directly relates to the initial glycogen content of the liver and active muscles. In one series of experiments, muscle glycogen content increased six-fold and endurance capacity tripled for subjects fed a high-carbohydrate diet compared with feeding the same subjects a low carbohydrate (high fat) diet of a similar energy content.
Given muscle glycogen's importance in prolonged endurance performance, carbohydrate loading provides a strategy to increase the initial muscle and liver glycogen levels.
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CHO Loading - Classic Procedure |
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Exhaustive prolonged exercise |
Taper training |
Taper training |
Taper training |
Taper training |
Taper training |
Taper training |
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Day 1 |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 |
Competition |
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Normal diet |
Low CHO diet |
Low CHO diet |
Low CHO diet |
High CHO diet |
High CHO diet |
High CHO diet |
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Stage 1 - Depletion
Day 1: Perform exhaustive exercise to deplete liver and muscle glycogen in specific muscles. This should involve 90 minutes of high intensity aerobic exercise using the muscle groups that will be used during the competition.
Day 2-4: Maintain low carbohydrate food intake of 60-100g of CHO per day whilst continuing to train at a moderate intensity as this will further deplete glycogen stores (high % of protein and lipid in the daily diet)
Stage 2 - CHO Loading
Day 5-7: Maintain high carbohydrate food intake of 400-700g of CHO per day (normal % of protein in the daily diet)
Competition Day: Follow high carbohydrate pre-competition meal recommendations
The potential benefits only apply to intense and prolonged aerobic activities unless you begin exercise in a state of glycogen depletion, exercise of less than 60 mins requires only normal carbohydrate intake and glycogen reserves.
For anyone following a daily diet of 60-70% CHO this will provide adequate muscle and liver glycogen reserves and any increase from CHO loading will be relatively small.
2.7g of water are stored with each gram of glycogen. Water retention may make you feel bloated and adds to the energy cost of running and cycling, but can aid in temperature regulation during exercise in the heat.
Glycogen depletion during stage 1 will leave you feeling excessively weak and drained, hypoglycaemic, irritable and unable to train effectively. If you then fail to load sufficient CHO you will not super-compensate.
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CHO Loading - Modified Procedure |
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Taper training |
Taper training |
Taper training |
Taper training |
Taper training |
Taper training |
Taper training |
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Day 1 |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 |
Competition |
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Normal diet |
Mod CHO diet |
Mod CHO diet |
Mod CHO diet |
High CHO diet |
High CHO diet |
High CHO diet |
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More recent research has found that you can achieve equally good results by omitting the depletion phase and eating a high CHO diet for 3 days prior to competition, thus avoiding many of the undesirable side effects.
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CHO Loading - 1 Day Regime |
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Taper training |
Taper training |
Taper training |
Taper training |
Taper training |
Taper training |
WU & 3m v. int. ex |
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Day 1 |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 |
Competition |
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Normal diet |
Mod CHO diet |
Mod CHO diet |
Mod CHO diet |
High CHO diet |
High CHO diet |
High CHO diet 10g/kg BW |
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A final option involves a 1 day regime that has been tested by researchers at the University of Western Australia and found to achieve equally high muscle glycogen levels. The day before competition 10g CHO per kilogram of body weight should be consumed following a single 3-min bout of high intensity exercise (sustained sprint). Apart from this no change to your normal routine is required.