Why are carbohydrates needed in sport and exercise?
Carbohydrate is your body's preferred energy source and most physical activities including cycling and running are dependent on the amount of carbohydrate available to our muscles.
Carbohydrate from our diet is stored as glycogen in our muscles and liver to be used as energy. To put it simply, a high muscle glycogen will allow you to exercise harder for longer and a low muscle glycogen will result in early fatigue and a lower training threshold.
The Glycaemic Index
The glycaemic index (GI) is a value at which carbohydrate food and drinks affect blood glucose levels. High GI foods and drinks cause a higher blood glucose response and low to medium GI foods can cause a lower blood glucose response. Sticking to low to medium GI carbs most of the time can produce a steady state blood glucose level which is desirable before and between training for sustained energy levels and to replenish glycogen stores. However, high GI sources are needed during exercise (duration more than one hour) and immediately after, supplying a rapid uptake of glucose for energy and recovery.
Chart 1: GE GB Elite Triathlete Stuart Hayes' typical training day diet
| Meal | Menu | Carbs per meal (g) |
|---|---|---|
| Breakfast | Porridge oats, chopped banana, raisins and skimmed milk 2 tbsp honey |
101g |
| Mid-morning | 4 oatcakes 2 tbsp peanut butter Viper Boost bar |
73g |
| Training - cycle | During: Viper Active 1 Viper Boost gel After: Recovermax |
110g |
| Lunch | Tuna salad with spring onions, tomatoes and balsamic dressing 100g basmati rice Banana 200ml fresh orange juice |
115g |
| Mid-afternoon | Viper Active bar 125g low fat fruit yoghurt |
53g |
| Training - Run | During: Viper Active 1 Viper Active gel After: Recovermax |
110g |
| Evening meal | Chicken, tomato, chilli and pepper pasta bake with tomato sauce 125g low fat fruit yoghurt A handful of grapes |
100g |
| Before bed | 250ml warm/cold milk mixed with 1 tbsp honey Banana |
38g |
How much do I need and when should I have carbohydrates?
We all need carbohydrates as part of a healthy balanced diet but regular exercisers and athletes need much more than nonexercisers. The amount and timing of carbohydrate intake is dependent on how much exercise is being done.
Carbohydrate is calculated as grams per kg of body weight and this can vary day to day depending on the duration and intensity of your training. Exercisers should also be aware of the best 'times' to take carbohydrates to support their training and optimise their recovery.
Chart 2: How much and when?
| Training duration/ situation |
Grams of carbohydrate |
Best time to take |
|---|---|---|
| 3-5 hours per week | 4-5g per kg of body weight |
Each day |
| 5-7 hours per week | 5-6g per kg of body weight |
Each day |
| 1-3 hours per day | 5-7g per kg of body weight |
Each day |
| 2-4 hours per day | 7-8g per kg of body weight |
Each day |
| 4 hours+ per day | 8-10g per kg of body weight |
Each day |
| Very intense exercise – 6-8 hours/day |
10-12+g per kg of body weight |
Each day |
| Befor training/event | 1-4g per kg of body weight |
Between 1-4 hours before training/event |
| Training sessions/events lasting longer than 1 hour |
30-60g per hour | Start taking 45 minutes in |
| After a training session or between multiple events |
1-1.5g per kg of body weight |
Immediately after, aiming for 6-10g/kg over rest of the day |
Carbohydrate Sources
Food portions providing 50g carbohydrates (note that foods are included to highlight the carbohydrate content only).
| Food category | 50g carbohydrate |
|---|---|
 |
9 tbsp dry porridge oats (85g) 4-5 wholewheat biscuits 8 tbsp medium bowl muesli (75g) 1 medium bowl Fruit and Fibre (75g) 16 tbsp bran flakes (75g) 3 shredded wheat biscuits 2 cereal bars (60g) 1½ Viper Boost bar 1¼ Viper Active bar |
 |
90g whole wheat pasta 6½ tbsp dry basmati rice (63g) 70g egg noodles Tin of spaghetti in tomato sauce (400g) 75g wholemeal spaghetti 9 tbsp couscous (100g) 8 tbsp quinoa (90g) |
 |
Large can of new potatoes (350g) 280g new potatoes in skins 1 medium jacket potato (155g) 5 scoops mashed potato (325g) 170g frozen oven chips 3 medium sweet potatoes (350g) |
 |
Can baked beans (440g) 10 tbsp chickpeas (275g) 10 tbsp (300g) of either sweetcorn or red kidney beans |
 |
18cm slice French baguette (90g) 1¾ bagel (90g) 3 small pitta bread 4 slices rye bread 4 slices medium cut wholegrain/white bread |
 |
2½ grapefruit,
4 tbsp raisins,
9 dried apricots, 6 slices pineapple, 8 dates, 12 kiwi fruit, 20 slices watermelon, 2½ small bunches of grapes, 4½ oranges, 4½ peaches, 12 plums/nectarines/apricots, 2 large pears, 3½ apples, 2 large bananas, 3 tbsp honey/jam |
 |
7 rice cakes 6 rye crisp bread (75g) 6½ digestive biscuits 6 oat cakes |
 |
50g scoop Viper Boost 2 x 30g scoops Viper Active 543ml orange juice 600ml Viper Active 367ml pineapple juice 446ml apple juice |
 |
4 x 250ml glasses skimmed milk 560ml chocolate milk 350g low fat fruit yoghurt 800g low fat plain yoghurt 300g low fat rice pudding |
 |
2 x 70g Viper Boost gel 2 x 70g Viper Active gel |
