Monday, March 9, 2015
EATING AND SPORT Part 1 of 3 Before Exercise
My next three blogs will focus on the role food/fluid plays in relation to sports performance-specifically before, during and after sport respectively. For clarity, when referring to a *sporting event/exercise in what follows I am referring specifically to endurance sport (football, soccer, distance running, Ultimate Frisbee) rather than a resistance OR muscle building ‘workout’. This advice can also be adapted to cardio aspects of gym, spin class or cross fit.
WHY SHOULD YOU EAT AND DRINK BEFORE EXERCISE?
What you choose to eat before exercise can be important for a number of reasons. These meals will provide the necessary fuel and fluid the body needs during a nutritionally challenging event or a simple psychological boost by following a pre-game eating ritual. Whatever the reason for eating before participating in sport, your food and drink choices should leave you feeling comfortable and confident to start your event without experiencing hunger or stomach discomfort during the event.
Carbohydrates are of utmost importance when pre-event meals are considered. Carbohydrates are stored as excess glucose in the form of glycogen in the body`s muscles and liver. This glycogen is a critical fuel source for both muscle function and maintaining energy levels when the body is fatigued. Therefore, the more glycogen that gets stored in the body the greater both physical and mental performance during prolonged workouts or endurance events should be.
Fluids:
Dehydration in sport can reduce both your pleasure and performance, especially in hot conditions. Most physical activity will lead to a sweat loss far greater than the amount of fluid an athlete can replace. Hydrating at the beginning of an event will minimise the fluid deficit that will inevitably occur. However, there is no need to drink excessive amounts in the lead up to exercise (this can lead to low salt levels in the blood - hyponatraemia). Normal daily fluid intake (~2L/day) should be adequate.
The total carbohydrate content of the menu plan you choose before exercise should be most important and based on foods that you know will be well tolerated by your body. Experimenting with different foods in the lead up to competition is highly recommended. However, trying new foods or fluids on the day of competition could be unwise.
SUMMARY:
Russell Nassim (APD)
References:
www..sportsdietitians.com.au
Carbohydrates are of utmost importance when pre-event meals are considered. Carbohydrates are stored as excess glucose in the form of glycogen in the body`s muscles and liver. This glycogen is a critical fuel source for both muscle function and maintaining energy levels when the body is fatigued. Therefore, the more glycogen that gets stored in the body the greater both physical and mental performance during prolonged workouts or endurance events should be.
Fluids:
Dehydration in sport can reduce both your pleasure and performance, especially in hot conditions. Most physical activity will lead to a sweat loss far greater than the amount of fluid an athlete can replace. Hydrating at the beginning of an event will minimise the fluid deficit that will inevitably occur. However, there is no need to drink excessive amounts in the lead up to exercise (this can lead to low salt levels in the blood - hyponatraemia). Normal daily fluid intake (~2L/day) should be adequate.
WHAT SHOULD YOU EAT BEFORE EXERCISE?
A guide when choosing a pre-event meal or snack:
- Rich in Carbohydrate
- Low in fat
- Easy to digest
- Provide adequate amounts of fuel
- Include food and fluids that you are familiar with and do not cause stomach upsets.
Is Glycaemic Index (GI) important?
It has been suggested that eating carbohydrates which are lower GI may provide a sustaining energy release and longer carbohydrate availability that may help increase endurance of those undertaking moderate intensity exercise.
However, follow up studies have not always shown benefits from choosing low GI foods pre-exercise, especially when speed as opposed to endurance is considered. Lower GI foods often have higher fibre contents which may cause stomach upsets and loose bowels in some athletes which may inhibit optimal performance. In fact, the GI of the pre-event meal is often outweighed by what is consumed during exercise.
However, follow up studies have not always shown benefits from choosing low GI foods pre-exercise, especially when speed as opposed to endurance is considered. Lower GI foods often have higher fibre contents which may cause stomach upsets and loose bowels in some athletes which may inhibit optimal performance. In fact, the GI of the pre-event meal is often outweighed by what is consumed during exercise.
The total carbohydrate content of the menu plan you choose before exercise should be most important and based on foods that you know will be well tolerated by your body. Experimenting with different foods in the lead up to competition is highly recommended. However, trying new foods or fluids on the day of competition could be unwise.
Examples of carbohydrate-rich foods and their Glycaemic Index | ||
Food | GI (glucose = 100) | |
High GI | Instant mashed potato White rice (medium grain) Jelly beans Gummy lollies Sports drinks White bread Cornflakes Watermelon | 86 83 80 90 78 78 77 72 |
Moderate GI | Weet Bix Sultana Bran Light n Tasty Soft Drink One-minute oats Muffins | 69 60 65 68 66 60 |
Low GI | Muesli Bar Pasta Banana/Apple/Orange Porridge Kidney beans Multi grain bread All bran Milk Yoghurt | 50 50 51 42 36 34 30 20 33 |
Source: http://www.glycemicindex.com/ | ||
WHEN SHOULD YOU EAT BEFORE EXERCISE?
Carbohydrate foods eaten in the last hours before exercise will play a significant role in continuing to top up muscle glycogen stores.
Typical recommendations suggest that the pre-event meal should be consumed 1-4 hours before competition.
This will vary according to the type and timing of your event and should allow time for gastric emptying (food to leave the stomach) as well as delayed gastric emptying often caused by pre-match nerves. It is also important to get a good balance of gut comfort - neither being too full nor too hungry at the start of exercise.
Type of Food | Time to leave the stomach |
High GI foods | ~10-30mins |
Moderate GI foods | ~60-90mins |
Low GI foods | ~90-180mins |
An example:
For events in the morning, an individual might have their (moderate to low GI) breakfast 2-3hours beforehand.
In the case of a very early start, another option is to have a larger supper the night before and a lighter (higher GI) snack or fluids 1-2hours before the event.
Those competing later in the day may choose to eat their normal daily meals in the early part of the day and then have a light snack (moderate to high GI) 1-2hours prior to the event.
SUMMARY:
- Choose high carbohydrate, low fat foods that are familiar and well tolerated.
- Try a liquid or low fibre pre competition meal if nerves or other factors cause GI upset.
- Practice different pre-exercise eating ideas during training NOT during competition.
- Monitor the effects of food and drink choices on your performance to see what works best.
Russell Nassim (APD)
References:
www..sportsdietitians.com.au
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