Replacement during moderately
(1 to 4 hours - Marathons, Triathlons, Cycling)
So why write an article on fluid and carbohydrate (CHO) replacement
during exercise? And why should you read this?
Well, it has to be said that most athletes that take part in
events that last longer than an hour do not maximise their fluid
and carbohydrate (CHO) intake during exercise. This applies
at both elite and club/recreational levels.
Yet it is an area that can improve your ability to maintain
a certain level of intensity over a long training session or
a race. By practising the correct and appropriate methods during
training you'll help maximise training gains and, most likely,
in a race situation it will all become second nature to you.
Choosing the right foods in the right amounts at the right
time will not turn an average athlete into a world class athlete.
However, a poor diet will prevent an athlete from realising
their true potential.
The winter is always a good time to try out a change to fluid
and eating plans in your training sessions. The following points
are guidelines only and you should use these as a starting point
to find out what works best for you.
It is now known that consuming Carbohydrates (CHO) and fluids
during a race or a long training session will help you achieve
a performance that reflects your training and natural ability.
Carbohydrates can be stored as glycogen in both muscles (storing
300-400g of CHO) and liver (storing 100-150g of CHO). Glycogen
is the energy source used by the muscles, but the muscle and
liver stores are small compared to the 20kg or more that we
have in fat storage. Athletes may be using as much as 3-4 g
CHO per minute in a race, which quickly depletes the CHO stores
in the body.
Athletes should aim to optimise their glycogen stores before
exercise ("carbo-loading") as well as eating during
exercise. This maximises the CHO availability in your blood
which can be used by your working muscles. As a general guideline
your intake of CHO should be between 30-60g per hour during
a prolonged event. These CHO requirements can be met simultaneously
with fluid needs by consuming CHO-electrolyte drinks. (See
table at end for practical suggestions).
Remember CHO and fluid must be ingested well in advance of
fatigue (approx. 30mins). Therefore, as a general rule, start
drinking early and continue drinking throughout the event.
Other Reasons to Eat CHO
- Benefits for Immune System - There is evidence to
suggest that consuming CHO during exercise is effective in
reducing the rise of certain chemical substances (catecholamines
and glucorticoids) which may be responsible of reducing the
effectiveness of the immune system.
Benefits to Body's Energy Store Recovery - Another
reason to consume CHO during exercise is that it may help
increase recovery of muscle glycogen stores in the post exercise
- Researchers report a reduction in some of the minor
immune infections (especially upper respiratory tract
e.g. colds). While these are not serious infections, they
can disrupt training and cause frustration.
- If you are a regular cold sufferer, it might
be worth consuming CHO during exercise to reduce your
susceptibility to illness.
- This is especially important to those who undertake
a second exercise bout (i.e. multi day events
or intensive training periods).
- This point is not critical to those are going to take
a full day off or more between there next bout of exercise.
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Athletes on the whole do not drink enough , even if there
is unlimited access to drinks. Some athletes are not tolerant
of large volumes in their stomach, but over time most athletes
can increase their tolerance levels and fluid intake levels.
As a general guideline you should be aiming to drink 600-1000ml
per hour of exercise. Take in fluids frequently (every 15
minutes), drinking moderate to large (150-350ml) volumes of
fluid if possible.
The composition of the drinks is also important. A high concentration
of carbohydrate in a drink will reduce the amount of fluid that
is available for absorption, but will increase the rate of CHO
delivery. For examples, fresh orange (unless diluted) or coke
are high CHO drinks and water must move into your intestine
to dilute this high concentration solution. As a result, this
temporarily exacerbates dehydration.
Be aware that your thirst mechanism is not very sensitive and
will not simulate drinking until some dehydration has occurred.
In other words, by the time you are thirsty it's beyond the
time when you should have started drinking fluids. Therefore,
choose a drink that you enjoy the taste as this will encourage
you to consume it consistently. The addition of flavours
(diluting juice) is perhaps a good idea.
- Fresh orange and sugary drinks may be helpful in promoting
glycogen stores after exercise.
- A low CHO-electrolyte drink is probably the most effective
in most triathlon situation 6-8% CHO
- Failure to drink enough fluid during exercise may contribute
to stomach/bowel problems during exercise.
- It is relatively easy to estimate how much water you lose
by weighing yourself before and after exercise. For every
1-kg lost, 1.5 litres of water should be consumed.
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- Begin exercise in a well-hydrated state (frequent &
large volumes of clear/pale straw colour urine)
- Use a fluid plan that has been practised in training
- Choose a drink, which is cool, tastes good and provides
- Begin ingesting fluid early in competition/ cycle
and continue to drink regularly to maintain a high
volume of fluid in your stomach to increase fluid availability
(150-300ml every 15-20mins.)
- Plan to ingest 30-60g of CHO per hour of exercise. Either
in a drink or food or both.
(see table at end of this section)
One last point to consider, when choosing foods to be consumed
during competition do not be preoccupied with total energy intake.
If you are trying to lose weight and don't eat during training
or competition (if intense or/and long duration), then you are
doing so at the risk of decreasing your performance. It would
be advisable to eat and drink to maximise your performance and
concentrate on a healthy balanced diet on a daily basis.
Finally, remember that choosing suitable foods in the right
amounts at the right time will not turn an average athlete into
a world class athlete. However, it is true that a poor diet
will prevent an athlete from realising their true potential!
Practical Guide to Carbohydrate Values
Plan to consume 30-60g of CHO per hour of exercise
The table below should give you an idea of how much/what 50g
of CHO looks like in food terms. You can mix different foods
to try to reach your CHO intake goals during an event.
- When checking foods for CHO content, most foods will tell
you the value per 100g, even if foods weigh more or less than
- Knowing the CHO content of every day foods to use in training
is just as good and in some cases better then some special
sports bars or products on the market.
50g of CHO
||May help prevent hunger during long events.
Fluid needs separate attention
||Low in fat and quickly absorbed. Fluids need
||Low in fat, high in CHO. Fluids need independent
attention. Perhaps not convenience during prolonged running
||Slowly absorbed due to CHO content. Low sodium.
May temporarily increase problem of existing dehydration
due to high sugar content.
||See comment for soft drink. May cause stomach
problem due to high amount of fructose
||2 thick slices & 4 tsp of jam
||Quickly absorbed. Avoid dairy spread (fat
tends to be more slowly absorbed). Fluid needs independent
|Sport drinks (5-8% CHO)
||Easiest and most effective method for providing
fluid and CHO simultaneously.
||Fluids need independent attention. Large amounts
may cause stomach problems.
dep. on make)
|Good for a large fuel boost. Need to practice
in training to avoid gastrointestinal discomfort. Does not
help fluid requirements. Expensive but compact and convenient
||3 medium bananas
||May help prevent hunger but more than one
portion is needed to provide enough CHO. Fluids need independent
1-2 (depending on the brand)
|Convenience and compact but often
have unnecessary vitamins and added extras - no scientific
evidence to show that they improve performance. Expensive.
Some are also relatively high in fat. However, they are
convenient. Fluid needs individual attention.
||May cause stomach problems due to fibre content.
But small and compact packages available. Fluid needs individual
|Rice Krispies Squares - chewy marshmallows
||3 ½ bars
||Large quality needed. Fluid needs individual