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Fluids
Keeping yourself well hydrated isn't easy, and even inactive people
often suffer the effects of dehydration (such as dull headaches and
an inability to concentrate). For athletes, the importance of staying
hydrated cannot be overstated. 80% of our body is water and it is
vital for our survival, intricately involved in every body process.
Fluid leaves our body every day, even without exercising during breathing,
urination and sweating. Dehydration upsets the fine-tuning of all
our bodily functions as it causes the blood to thicken and become
sludge like.
During exercise, this will put a huge strain on our heart and the
circulatory system, as we have to work much harder to keep up the
same speed on the bike. At the same time, it becomes more difficult
to control our body temperature and we start to overheat, compromising
our internal organs even further. Mental function can be reduced,
associated with light-headedness or dizziness and so our ability to
balance and control the bike on technical tracks is also affected.
It only takes a small amount of fluid loss to adversely affect performance
as this chart, based on an 80kg person, shows:
| Fluid Loss |
Litres of fluid lost |
Symptoms / effects |
| 1-2% |
0.8- 1.6 litres |
Performance reduces by 4% Increased stress on heart and circulation |
| 2-3% |
1.6 – 2.4 litres |
Difficulty controlling body temperature and decreased endurance |
| 4-6% |
3.2 – 4.8 litres |
Decreased strength generated by muscles |
| 7% |
5.6 litres |
Heat stroke |
| 10% |
8 litres |
Death |
During exercise the amount of sweat produced varies hugely from person
to person according to body size, gender, exercise intensity and environmental
conditions. A simple experiment to try is to weigh yourself before
and after you go for a long cycle ride and see how much fluid you
have lost. Monitor exactly how much fluid you drink during the ride
and add this to your pre-ride weight. Then subtract the post-ride
weight from your pre-ride weight. Every kilogram of body weight lost
equates to 1 litre of fluid depletion. The average sweat rate for
an 80kg person cycling at a moderate intensity in 20 deg C heat is
1 litre / hour. So dehydration can occur very quickly if we are not
making an effort to replenish lost fluids. The scientific method of
determining whether you are taking on enough fluid is useful but there
are other indicators as to your state of hydration: urine colour and
frequency. You should be peeing every 3 hours and it should be straw
coloured (not bright yellow!).
Thirst unfortunately is not a good indicator
of the need for fluid as by the time our thirst mechanism has kicked
in, we are already dehydrated. This is why it is important to drink
on a regular basis before, during and after riding as well as on non-exercise
days. |
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