Carbohydrates – Pt 2

In part 1, I discussed the types of carbohydrates and how they are used for energy in the body.  In part 2, I will be discussing the benefits of consuming carbohydrates pre, during and post training/ race.

Carbohydrates before exercise

Carbohydrate intake prior to exercise has been shown to improve endurance capability.  Eating carbohydrates more than 60 min before exercise will top up blood glucose levels; enhance muscle glycogen stores and restore liver glycogen content.  This is especially important if the competition or training is:

• first thing in the morning;
• if the event is high intensity;
• If the event continues beyond 90 minutes in duration, as the limited glycogen stores in the body will only last for approximately 90 minutes

For triathletes doing brick training sessions and before an event, this will be very important.   Aim to eat carbohydrate rich foods and fluids which are low in fats and fibre

• Breakfast cereals: Future Life/ Oats with a fruit
• Toast and a fruit
• Sandwich/ roll
• Liquid meal replacement

If you are unable to eat 60 min before exercise you can try:

• Sports drink
• Carbohydrate gel
• Sports bar

It is especially important to train with the meal you intend to have on race day to prevent any gastric discomfort.

Carbohydrates during exercise.

To ensure peak performance is achieved, carbohydrates need to be taken during exercise.  If insufficient carbohydrates are consumed this will result in low levels of energy, heavy legs, fatigue or “hitting the wall”, a slow rate of recovery, loss of concentration, dizziness, irritability and fainting.   The type, amount and timing of carbohydrate intake during exercise is important, and should take individual needs into account.  Athletes must also train/ practice eating various carbohydrate foods as intended to be consumed during a competition.  The longer the duration of the event the higher the carbohydrate needs to fuel performance.  It is best to start taking in carbohydrate soon after the exercise session begins because of the delay in absorption.

An intake of 60 grams of carbohydrate an hour is recommended.  This is about the maximum your muscles can take up from the bloodstream during exercise. Greater amounts have no further benefit.  As an example, the table below shows foods which contain 50g of carbohydrate.

Foods containing 50 g of carbohydrate

2 medium- large bananas	15 dried apricots
2 slices thick sliced bread ­+ 4 teaspoons of jam	600 – 1000 ml isotonic sports drink
1 large bowl (60g) breakfast cereal	500ml fruit juice/ soft drink
150-160g cooked pasta/rice	2 carbohydrate sports gels
1 large potato ( 250g)	3 (25g) cereal bars
560 ml flavoured milk	50 g jelly beans

Research shows that we can boost carbohydrate oxidation by taking carbohydrates in combination.  These are called Multiple Transportable Carbohydrates.  For example glucose and fructose combined increases the absorption by 75% as a second transporter is used.

Multiple Transportable CHO:

• Glucose + Fructose
• Glucose + Sucrose + Fructose
• Glucose + Sucrose
• Maltodextrin + fructose

Benefits

• Increase energy delivery
• Large amount of carbohydrate are absorbed
• Decrease gastro intestinal problems
• Increases fluid delivery

Most isotonic sports drinks and sports supplements have a combination of these carbohydrates.

In practice, the cycle ride during triathlons is a great time to eat.  We like to call this the ‘rolling buffet’.  It’s a good idea to have a combination of foods to ensure you are getting different carbohydrates as well as vitamins and minerals.  I always feel the sports drinks and supplements can become really sweet so having a sandwich or baby potatoes available can be a great change.  Here are some examples:

• Sandwiches/ provitas/ baby potatoes
• Bananas; dried fruit; fruit bars – this may cause gastric problems in some athletes (I like dried mangos)
• Sports bars/ cereal bars, gels, jelly beans

Carbohydrate intake after exercise

Carbohydrate intake after exercise is essential for optimum recovery of glycogen stores.

The most effective refuelling occurs within 30 – 60 minutes after exercise and is generally referred to as the ‘golden hour’.   Failure to restore muscle glycogen stores between training sessions can lead to fatigue.  This is particularly true for triathletes doing brick training sessions.  If you are doing only light exercise, then 50g carbohydrate should be enough. You must however, ensure your main meal contains plenty of carbohydrate rich foods.

Top Tips:

• Choose nutrient-rich carbohydrate foods such as pasta, rice, potatoes, cereals and breads for main meals and as a recovery snack
• Have portable choices such as fresh fruit, dried fruit, cereal bars or some low fat chocolate milk available
• Sports drinks, sports bars and carbohydrate gels can boost your carbohydrate intake around training and competition. Sports drinks in particular contain both carbohydrates and electrolytes and can be drunk before, during, and after exercise to help maintain blood glucose concentration, provide fuel for muscles, and decrease risk of dehydration and hyponatremia.
• Always remember to refuel as soon as possible after exercise

Here is an example of carbohydrate intake during a brick training session and race day.   N.B.  Carbohydrate intake will vary in individuals.  Training diet and competition day will also vary considerably so consulting a registered dietitian who can work out your personal needs is beneficial.

Brick Training:          

Pre morning training < 60min:         Sports drink

After training:                                    Cereal and a fruit/ Sandwich

Pre afternoon/ evening training:     Fruit and chocolate milkshake drink

After training:                                    pasta/ rice/ potato as part of an evening meal

Race day:

Breakfast:                   Cereal and a fruit + Sports drink

During Exercise:        Dried fruit + cereal bar + sports drink + gels/ jelly beans

Post Exercise:            Sandwich + chocolate milky drink

References:

Potgieter, S.  Sport nutrition: A review of the latest guidelines for exercise and sport nutrition from the American College of Sport Nutrition, the International Olympic Committee and the International Society for Sports Nutrition.  South African Journal of Clinical Nutrition 2013; 26(1):6-16.

Jeukendrup, AE.  Nutrition for endurance sports: Marathon, triathlon, and road cycling Journal of Sports Sciences, 2011; 29(S1): S91–S99.

Jeukendrup, AE et al. Nutritional Considerations in Triathlon. Review Article. Sports Medicine 2005; 35 (2): 163-181.

Australian Institute of Sports: www.ausport.gov.au

Email: nicoladrabble@gmail.com

Website:  www.nicoladrabble.co.za

Facebook:  Nicola Drabble – Registered Dietitian

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