Saturday, February 12, 2011

The Humble Carbohydrate

Carbohydrates are an important fuel for your day - Even more important for athletes and those who use a lot of energy.

Sports nutrition and low GI energy foods are easy to find in supermarkets and in sports stores

Energy for our body (Calories or kilojoules), is available in four forms:-

a) Carbohydrates (which contain 4 cal/17kJ per gram)
b) Proteins (which also contain 4 cal/17kJ per gram)
c) Fats (which contain 9 cal/37kJ per gram)****
d) Alcohol (which contain 7 cal/29kJ per gram)
****Fat is energy dense as it provides a lot of energy in a smaller amount of food.

The difference between each one is how it is processed when it enters the body and how quickly the energy is available for use.

The simplest form of carbohydrate is glucose and when the body consumes excess glucose, the excess is stored in the form of glycogen in the muscles and in the liver. HOWEVER we don't eat glucose and glycogen. It is when we eat carbohydrate rich foods that our body receives glucose for immediate energy and converts excess energy to glycogen for reserves. It is without question that the amount of glycogen stored in your muscles and liver has a direct effect on exercise performance.

• High muscle-glycogen concentration will allow you to train at optimal intensity and achieve better results

• Low muscle-glycogen concentration will lead to early fatigue, reducing the intensity of your training and this will be reflected in your race/performance results.

How much Carbohydrate should I eat?

Whether you are recreational or professional,
your diet will affect your performance
 The body uses Carbohydrate for energy and excess is stored in the muscle and liver as glycogen, BUT the liver and muscles can only store a limited amount so eating TOO MUCH carbohydrate which cannot be stored contributes to weight gain. Inadequate carbohydrate, will only look after immediate needs but not restock the liver and muscles with that valuable and fatigue resisting glycogen. Getting the balance right means reviewing your daily consumption to ensure that you have are consuming an optimum amount.

Once upon a time, carbohydrate recommendations were based on a percentage of your daily caloric needs and although sports nutritionists recommend that all regular exercisers and athletes consume a diet high in carbohydrate and low in fat the amount of carbohydrate consumed is based more on the level of activity of the individual.

So your daily carbohydrate intake will vary depending on your activity level.

General exercise – (up to 1 hr of daily exercise) 5-6g/kg body weight of carbohydrate per day.

Moderate exercise – (1-2 hrs of moderate to high intensity training) 6-8g/kg body weight

Endurance exercise (greater than 120 minutes of high intensity training) 9-10g/kg body weight

Extreme Exercise (greater than 4 hours of intense exercise eg: a cycling tour) 10+g/kg body weight

Training over 1 hour means you should have some carbohydrate intake DURING the exercise 30-60g per hour
KICK STARTING RECOVERY - During the 2 hour post-exercise period, consume 1g/kg body weight of moderate to high GI food.MOST IMPORTANT - But if you train twice a day, this is ESSENTIAL!

What does 30g of Carbohydrate look like?
2 slices of bread
1 average bread roll
3 weet bix
1.5 cups cooked lentils
600ml of Milk
2 tblsp of susteagen powder
2 medium apples
1 medium to large banana
1 cup of pasta
0.5 cups baked beans
0.75 cup of cooked rice
0.5 cup creamed rice
10 Jelly Beans
500ml sports drink
0.67 Power Bar
 * Check labels on your foods and ensure you use low fat varieties where possible

The Glycaemic Index

Carbohydrates are all different and will be absorbed and used at different rates and the effect of other items in your body, such as fat may slow down the absorption of the carbohydrate even more. The glycaemic index was developed to describe the effects of foods on your blood sugar levels by how quickly the carbohydrate is absorbed from your small intestine into your bloodstream, and this is found to make a difference to training and recovery.

Foods with a low GI (glycaemic index) will provide a glucose response for longer and a high GI will provide more of a rapid energy. To find out more about Glycaemic Index, refer to the Glycaemic Index website which is written by the University of Sydney and provides a range of information about the glycemic index of foods and what it means to you.

The most important thing to remember is that choosing low GI foods should NOT be confused with  low Carbohydrate foods, as an athlete, you want to keep your carbohydrate level high.

Considerations to be made on Carbohydrate Consumption

- Duration and Intensity of Exercise

Exercise lasting less than an hour

Provided you have enough glycogen stores and have eaten a meal with carbohydrate 2-4 hours before exercise, you should only require water and not require any further intake of carbohydrate. If you are racing though, you can delay fatigue by consuming carbohydrate during exercise to assist with the high intensity and delay fatigue.

Exercise over an hour

Racing and high intensity training increases the requirements
 for carbohydrates and increases the need to
 replenish the valuable muscle glycogen stores
IN the first hour of exercise, most of the carbohydrate energy comes from muscle glycogen (which you have looked after your stores by eating a good amount of carbohydrates in your daily diet). After an hour your muscle glycogen stores deplete rapidly and exercising muscles will use carbohydrate from another source, they will go to the bloodstream to grab any blood sugar (glucose they can find). After around 2-3 hours your muscles will be fuelled by blood glucose and fat...but have you ever hit the wall? This is your own fault......eventually blood glucose supplies dry up, blood glucose comes from amino acids and liver glycogen and once this runs out you just cannot keep going at the same begin to feel tired, light headed and your muscles just don’t work any just gets too hard to keep going and on the bike it is an effort to turn the pedals.

SO BEFORE fatigue sets in you need to take some action. Your muscles can take up around 30-60g of carbohydrate in an hour during aerobic exercise, so it is important to consume some energy during exercise. Medium to high GI foods are generally best as they move quickly into your bloodstream and therefore become available for these working muscles. Sports drinks and energy gels are a choice for many athletes to replenish energy stores.

A study in 2003, demonstrated that consuming a drink containing protein and carbohydrate improves endurance to a greater extent than carbohydrate alone. The study of cyclists showed they were able to exercise for 36% longer by consuming a carbohydrate/protein drink before exercising then every 20 minutes during exercise than just a carbohydrate drink. Other studies have suggested that consuming protein and carbohydrate during exercise improves recovery and results in less muscle damage. Most of these trials used a ratio of around 4:1 carbohydrate:protein. So for every 40g of carbohydrate, the drink would have 10g of protein. Check the labels of your foods to find items that will suit your requirements. You also need to find foods that don't cause you unnecessary discomfort. Bloating, nausea and headaches are some side effects caused by foods, so ensure you practice during training with the foods that you plan on using during racing to eliminate any unnecessary side effects 

After exercise

In cycling, the large muscles of the legs are working at a high intensity,
especially during racing

Factors that influence your recovery include:-

1. How much your glycogen stores were depleted. Were they good before you started and did you eat along the way?
2. Muscle damage
3.Your fitness

If you fully deplete your glycogen stores, they can take anything up to a week to fully restore. Ask a marathon runner, when they feel recovered enough to take on another one.

If your muscles get damaged from intense efforts, or heavy weights, glycogen storage may be delayed.

Finally as your fitness improves your body's adaptation to ensuring the glycogen storage levels are at optimum improves.

Within a few hours after exercise (without fail), you should begin your replenishment of the muscle glycogen stores. Think - a shake, or a sandwich, cereal, fruit, and if you have the milky options, your body is getting the protein which will help with muscle recovery too. A high carbohydrate meal eaten within 15 minutes of the end of a training session will accelerate the rate of glycogen storage by 300 per cent. You have a window of approximately 2 hours after training to replace carbohydrate to ensure that your muscles will accumulate glycogen.

I mentioned the benefits of chocolate milk in a previous blog post


High Carbohydrate diet, will assist with muscle -glycogen storage which helps with endurance and delays fatigue.
Read about GI index to understand why some foods are better for stabilising glucose and therefore energy levels than others.
High workload/intense efforts require additional carbohydrate
Don't forget to "top-up" carbohydrates during longer training sessions, during races.
RECOVER faster by replenishing your muscle-glycogen storage.
Protein will assist with recovery and endurance
Although I haven't mentioned it here, carbo-loading (later topic) can improve endurance capacity by up to is that muscle-glycogen level AGAIN!

Carbohydrates can be found in many foods, not just those traditionally thought to be high carbohydrate foods. Foods containing theses ingredients as well as Lactose (milk sugar), Fructose (fruit sugar) are carbohydrate foods.

DeCastella. R., Clews.W., (1996). Smart Sport - The Ultimate Reference Manual for Sports People. Paragon Printers.
Wahlqvist, M.L., (2...). Austyralia and New Zealand Food and Nutrition.
Whitney, E., Rolfes, S.R. (  2008  ). Understanding Nutrition 11th ed. Thomson Wadsworth
Bean, A., (2010). Sports Nutrition.

All photos courtesy of actionpactpix


Donna said...

I love this entry and how you break it down! Nicely done!

Buttsy said...

Thanks Donna, I just want to start to move my blog towards nutrition information as I am studying Nutrition and to write it down, means researching and also thinking about what bits of that research are informative and easy to understand and relevant to sport.....Next post will be protein, hoping to write an entry once a week...maybe fortnight if I get too busy......Might have to get your help with some good nutritious snacks that you can make and use for sport.


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