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Carb loading for swimmers

As far back as the 1960's long distance swimmers have been increasing their carb intake pre-swim to improve their performances, with many weird and wonderful ways being trialled. But it wasn't until recent years that the 'art of carb-loading' has been perfected to ensure muscles are fully fuelled and swimmers can delay and reduce the onset of fatigue during a long swim, says* Sports Scientist Ross Edgley.

Firstly it's important to note that the average swimmer can only store enough muscle glycogen (the muscle's form of energy) to sustain 90 minutes of high intensity exercise at the most. After this 90 minutes a swimmer will start to fatigue badly due to the lack of muscle glycogen and hit 'the wall' (something runners experience during a marathon). This means it is essential to take on fuel through carbohydrates during long swims, and also to make sure you are fully carb loaded before you start.
Previous carb loading techniques included one known as 'glycogen stripping'. This involved three days of heavy training combined with a high protein/fat and low carb diet (carbs made up 10% of their total energy intake) followed by three days of light training and a high carb diet (90% of their total energy intake). The theory behind it was that by depleting the body of carbs first (during the first 3 days) the body would better absorb and use the carbs (known as 'super compensation') during the high carb phase (the final 3 days). However studies have shown this method can be exhausting; the heavy training can put stress on the central nervous system, increase the risk of injury and harm the immune system resulting in inconsistent race day performances.
Later studies found that optimal carbohydrate loading could be achieved by simply increasing your carbohydrate intake 3 days before a race, without the 'glycogen stripping' beforehand. Generally speaking, you need around 5-7g per day of carbohydrate per kilogram of body weight or 60 per cent of your daily calorie intake from carbohydrates. This usually works out at around 1,500kcal from carbohydrate per day for most women and 1,800kcal for men. But during a carb-loading period, aim to up your carbohydrate intake to 8-10g per day per kilogram of body weight (see, for example, 'The Complete Guide to Sports Nutrition' A. Bean et al, 2003). For a 75kg swimmer, that works out at between 600g and 750g per day.
To even more efficiently 'carb load' ensure the carbs you eat are spaced out evenly throughout the day. For example if you were to consume 750 grams per day, try separating them into 7 small meals, each containing 107 grams of carbohydrates, eaten roughly 2 hours apart. Not only does this ensure your muscles more efficiently absorb all the carbohydrates, but it also helps to regulate blood sugar levels therefore avoiding making you feel dizzy or lethargic.
For some people, eating this amount of carbohydrates can be hard. That's why it's probably best to add a few high carb snacks in there too, such as:
• 1 large handful of raisins, dried apricots or other dried fruit
• 3 slices of bread thinly spread with honey
• 5 rice cakes spread with jam
• Commercial sports products from suppliers such as MyProtein including:
 - Instant Oats: a low Glycemic Index (GI) carbohydrate that has been milled down in to an ultra fine powder so it can be easily consumed as a drink when mixed with a liquid. £2.49 for 1kg.
 - Vitargo Pure: derived from barley starch it's the main ingredients in most advanced sports drinks. 75 grams will provide 69 grams of carbs. £14.99 for 1kg.
 - Tri Carb: an energy drink blend of 3 different carbohydrates, Palatinose, Maltodextrin and Fructose. 100 grams will provide 94 grams of carbs. £8.49 for 800g.
 - MyBar Oats and Whey: a meal replacement bar containing 43.8 grams of carbohydrates per bar and 22 grams of protein. Each box contains 18 x 88g bars and costs £20.99 per box.
*MyProtein is an on-line supplier of sports nutrition products. Find out more at

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Issue 27 June 2019

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