Carbohydrate is the bodies preferred energy source, it comes in the form of monosaccharide’s, disaccharides (sugars), and oligosaccharides and polysaccharides (starch). An example of a monosaccharide is blood sugar aka Glucose, and fruit sugar aka Fructose, a common disaccharide we consume via the diet is Sucrose, and the hidden sugar found in milk, Lactose. Polysaccharides come in the form of starches such as pasta, potato, bread and cereals delivering our bodies with a sustainable source of energy, and chains of glucose such as Maltadextrin. Starchy polysaccharides are the main fuel for any activity above and beyond 65% of maximum exertion, whilst the immediate, rapid replenishment of energy is provided by, for example, the monosaccharide Glucose or the disaccharide sucrose.
Every top athlete in the world maximises carbohydrate when they train and perform, whether it is the endurance phenomenons of the Tour de France, the fast twitch powerhouses of the 100m sprint, or the endurance and power hybrids that are professional footballers, rugby players or triathletes. The fact is; carbohydrate is integral to sporting performance and the acute and chronic delivery of energy. Therefore we must keep our glycogen (glucose stores) stores topped up in order to fuel training, when we need it! An abundant glycogen supply means the body has a readily accessible reservoir of glucose; consequently your body receives a ‘drip feed’ of glucose resulting in a sustained flow of energy to the blood stream and muscles.
A constant, sustained delivery of glucose means the body remains energised and prevents peaks and troughs (ups and downs) in energy levels which could result in periods of reduced performance. It’s inevitable that glycogen and thus energy levels will become depleted during endurance or prolonged intense activity, therefore a source of quick release, readily absorbed energy is integral to fuel training. The average isotonic beverage delivers fluid, salt, glucose, fructose, maltadextrin and minerals, meaning the athletes receive a surge of semi-sustainable carbs lasting approx 30mins, plus a faster fluid and electrolyte absorption rate via osmosis (salt is rapidly absorbed drawing fluid into the circulation) to sustain muscle mineral balance and hydration (Metzger, 2008).
We have all hit that ‘wall’ when running, cycling or performing endurance sports due to the depletion of your bodies preferred energy source, glycogen. Glycogen stores usually range from 100-120mmol/kg of bodyweight, but if these stores diminish, your body begins to mobilise its fat stores for energy. Despite fats higher energy content per gram, it is not broken down as quickly or efficiently meaning you hit a low spot during exercise until the energy can be utilised. This ‘low’, or the window of time just before its onset is the optimum time to consume an isotonic beverage, but in order to increase the time until onset or reduce the duration of the ‘low’, an athlete can/should stock up on starchy polysaccharides 2-3 days prior to the event...this is known as Carb - Loading! During the loading phase, an ideal diet would consist of approx 80-90% carbs, aiming for approx 5-10 grams of carbs per kg bodyweight (Minehan, 2004).
Below is a typical Carb – loading diet providing 3300kcal and 560g Carbohydrate equating to 70% Carbs and 7g Carbs per kg bodyweight for an average 75kg person:
45g porridge oats with 350ml skimmed milk (250kcal; 16.5g Protein; 42g Carbs)
low fat yoghurt + 1x Banana and blend (460kcal; 56g Protein; 38g Carbs)
200ml Fresh orange juice (100kcal; 1g Protein; 20g Carbs)
1x Apple (46kcal; 11g Carbs)
2x Tangerines (50kcal; 10g Carbs)
350ml can soft drink (150kcal; 35g Carbs)
350g baked sweet potato (250kcal; 4g Protein; 69g Carbs)
30g low fat cheese (117kcal; 7g Protein; <1g Carbs)
200g baked beans (164kcal; 10g Protein; 27g Carbs)
High 5 Sports Bar (203kcal; 3g Protein; 37g Carbs)
500ml isotonic drink (70kcal; 17g carbs)
80g cooked wholemeal pasta (250kcal; 10g Protein; 59g Carbs)
160g boiled chicken breast in 300ml (146kcal; 32g Protein)
200g tinned chopped tomatoes (44kcal; 1g Protein; 7g Carbs)
½ clove garlic
500ml isotonic drink (70kcal; 17g carbs)
Banana smoothie made with 200ml semi-skimmed milk, 1x banana and 15-20g honey (200kcal; 8g Protein; 47g Carbs)
2x slices wholegrain bread and 50g Jam (210kcal; 50g Carbs)
Metzger, J. (2008). Carbohydrate Super‐compensation: Fact or Fiction? Understanding the Truth Behind ‘Carb‐Loading. Retrieved July 25th, 2012, from http://www.scisport.net/SciSport_page/Downloads_files/CARBOHYDRATE%20SUPERCOMPENSATION_1.pdf
Minehan, M. (2004). Department of Sports Nutrition, Australian Institute of Sport.
Carbohydrate Loading. Retrieved July 25th, 2012, from http://www.ausport.gov.au/ais/nutrition/factsheets/competition_and_training2/carbohydrate_loading