Crispin’s
Guide to Stirling Cycling – General
The article below is based
on a talk I gave several years ago to a group of racing cyclists in Herts
Wheelers. The same nutritional
principles apply whether you are racing, audaxing or touring. I am not an expert on sports nutrition but
my background in animal nutrition has
allowed me to pursue an interest in this area.
I hope that this article will
help dispel some myths...
There are three basic food
groups
1) Protein: Required for muscle formation and energy. Takes several hours to digest. Daily requirement only 30-35g, assuming
sufficient intake of fat and carbohydrate.
2) Fat: Long-term energy store.
Takes best part of a day to digest.
Recommended that no more than 30% of daily energy intake is supplied by
fat. Doctors advise avoidance of excess
saturated or animal fat.
3) Carbohydrate: Short-term energy store. Carbohydrate consists of simple sugars which are absorbed in 5 to
10 minutes (eg table sugar), and long-chain complex molecules which can take up
to an hour to digest (eg starch in plants, maltodextrin in energy drinks). Carbohydrate is stored in muscles as
glycogen. It is important to remember when looking at the carbohyrdrate figures
for a food, that this figure often includes both simple-sugars and long-chain carbohydrates. Try and avoid taking in too much simple
sugar. Nutritionalists often refer to
the sugars such as table sugar that are found in food as empty calories,
because while supplying energy, and often excess energy at that, they contain
none of the minerals and vitamins that are found in non-refined food.
Which brings us to Vitamins and Minerals: Supplied by a
balanced diet, but a daily supplement is a good idea (especially iron for
ladies and folic acid for both ladies and men).
And Water: If in doubt, drink.
Energy values for food can
be deceptive as water mixes with protein and carbohydrate to add to their
weight, and fat is very dense. One pat
of butter can contain as much energy as an entire helping of potato.
1g carbohydrate = 4
Cal, 1g protein = 4 Cal, 1g fat = 9 Cal.
An ‘ideal’ diet for an
athelete consists of 60-70% carbohydrate, 10-15% protein and 20-30% fat.
Some typical food contents are :-
|
Food |
Carbo’/% |
Protein/% |
Fat/% |
Cal/100g |
|
bread |
50 |
9 |
4 |
268 |
|
butter |
0.5 |
1 |
80 |
720 |
|
cheese, cheddar |
2 |
23 |
32 |
393 |
|
chocolate |
18 |
6 |
53 |
570 |
|
pasta, cooked |
26 |
5 |
< 1 |
130 |
|
potatoes |
19 |
2 |
< 1 |
85 |
|
beef, medium |
1 |
18 |
22 |
268 |
4.2 J(oules) = 1 cal(orie). 1000 cal = 1 kcal = 1 Cal = 4.2 kJ
On foods, the contents are labelled such that the
main ingredient is the first on the list.
Approximate daily energy requirements for a 70kg
male
non-active adult - 2000-2200
Cal/day teenager - 3000 Cal/day
touring cyclist (50-60
miles/day) - 5000+ Cal/day Tour de France
cyclist - 8000 Cal/day
Ranulph Fiennes on polar walk - 10,000 Cal/day
(highest ever recorded)
1000 Cal/hour is the upper
limit for energy consumption: Cycling 25 miles requires roughly 1000 Cal, but
using tri-bars and other aids will reduce this figure considerably, as will
freewheeling on an afternoon potter !
FUEL FOR SPORT
During exercise, fat and
carbohydrate are the main fuel sources.
Carbohydrate reserves (glycogen)
are present in muscle and liver, but stores limited to 1500-2000 Cal.
Fat stores are practically
unlimited (135,000 Cal for a typical male), but fat requires much more oxygen
to produce a given amount of energy than carbohydrate.
DURING EXTREME EXERCISE
Blood glucose concentration
(mobilised liver glycogen) drops steadily during exercise as liver reserves are
reduced as a consequence of blood glucose being used by muscle. After 30 minutes, short chain fatty acids are
mobilised from fat deposits and their blood concentration starts to rise
gradually. This acts to spare
glycogen. Additional energy
requirements are supplied from muscle glycogen stores and depletion of these
reserves results in exhaustion (eg. the knock, hitting the wall). A less extreme effect is the feeling of
fatigue. Increasing exercise intensity
increases rate of liver and muscle glycogen utilisation, resulting in a more
rapid onset of exhaustion. The brain
has an absolute dependence for blood glucose and a severe reduction in blood
glucose levels results in “star gazing” or other near-coma experiences that can
occur at the end of a marathon or long Audax ride. At this point the body starts producing ketone bodies from fatty
acids as an alternative fuel to glucose and it is these that result in the acetone smell on the breath of
someone in such a state.
To avoid exhaustion:
- ensure glycogen reserves
are fully stocked by eating a high-carbohydrate (70%+) diet. Pasta and rice is an easy way of achieving
this.
- high-mileage training to
boost body’s reserves (increased fitness also reduces glycogen utilisation at a
particular pace), but ease up on training for several days before a major ride
to avoid depletion of glycogen reserves
- a fast starting pace can
deplete muscle glycogen before liver glycogen is mobilised. Cycle slowly for at least 5 minutes (ideally
10- 15 minutes) before riding at a fast pace.
This is especially important for rides of more than an hour
- reduce
ride-pace to decrease utilisation of glycogen stores
- feed on the move.
- use caffeine to mobilise
fatty acids more readily (cup of strong black coffee 1 hour before the ride and
then sip water to avoid dehydration - repeat at rest stops). Tea contains the equivalent of one-third the
caffeine of coffee.
Meals: Night before the ride (and every night to replenish reserves)
Eat lots of carbohydrate
(rice and pasta). This is called
carbo-loading. Extreme carbo-loading
with an initial carbo-depleting phase appears to have gone out of fashion.
Pre-race breakfast
Needs to be eaten more than
three hours before ride to benefit performance if in a race. Otherwise. eat anything that is digested
rapidly (little fat and protein) eg American pancakes, cereal & skim milk,
bread & jam. If racing, avoid eating during the hour preceding the start or
drinking sugary drinks. With an
audax-style ride, timing is of less importance but the same principles apply if
you want a fast start. Otherwise the
suggestions regarding timing can be ignored.
On the road: start feeding
as soon as the ride has started (energy drinks/bars, jam butties, rice
pudding). If you delay eating too long
you will deplete your glycogen reserves and they will not recover until the
ride is over.
Water: If in doubt, drink
Dehydration results in poor performance. A loss of the equivalent of a water bottle’s worth of water can have a significant effect on your performance. A loss of two bottle’s worth (1.4 litres) results in a 20% decrease in performance. It’s worth noting that if you delay drinking until you are thirsty, you have left it too late. In addition, if your urine is straw-coloured at the end of a ride you are dehydrated. It is for this reason that I say, “If in doubt, drink.”
In extreme summer heat, water
replacement alone cannot match the rate of water lost through sweating. In these circumstances, electrolyte drinks
that increase the rate of water uptake should be considered. However, most of the time drinking water,
little and often, should be adequate.
Suitable electrolyte drinks include Gatorade, Lucozade Sport and
Isostar. Beware of so-called sports
drinks such as Original Lucozade, Red Bull, or Coca-Cola, which contain
excessive sugar that slows water absorption.
Caffeine causes dehydration when not exercising, but this effect is
over-ridden during exercise. Alcohol
also causes dehydration. Hydration can
take days to achieve and minutes to lose.
Drink plenty of water regularly in the days before a big ride. This is doubly-important if you are
carbo-loading.
I have only had space to
outline the basics of good nutrition. Follow these suggestions and you won’t go
far wrong: You may even surprise yourself.
There is much information in the press, but far too much of it concentrates
on a quick story and gives misleading advice.
One exception are the articles by Joe Beer in Cycling Plus. Although many of his articles are directed
at racing cyclists they contain very valid advice.
Test any changes in nutrition several times before the big day
Crispin Bennett 12 December 2002