Sports Nutrition

Before you read this factsheet, it would help in your understanding if you knew how your body processes the food you eat.  To help, why not read the Digestive Process Factsheet?

Food energy contents
All foods are made up of the nutritional building blocks of carbohydrates, fats, and protein plus a certain amount of water and fibre (indigestible and without any food value).

Carbohydrates contain 4.1 Calories per gram and are the primary source of energy for most cyclists and endurance athletes.  Fats are more important for slower endurance events and contain 9 Calories per gram. Protein's main use (again 4 Calories per gram), is to maintain and repair the body's cells and is rarely available as a source of energy to an athlete.  But that doesn't mean it should be ignored!

The chart below is the replacement for the now considered outdated food pyramid.  It shows the correct ratio of what should be eaten to maintain a balanced diet.  When training, these ratios may need to be "tweaked" and to do that you need the advice of a qualified sports nutritionist.

Muscle energy supply
Although carbohydrates supply the majority of the energy for muscles during vigorous activity, fats can be a major contributor for less strenuous activities.  Carbohydrate is stored as glycogen in muscle and liver cells. In a balanced sports diet there is enough glycogen to support around 90 minutes of aerobic exercise before depletion occurs.  Or, to put it another way, the fuel tanks run dry. 

Obviously, these internal stores can be replenished "as you go" through eating carbohydrates.  Begin eating at the start of the event as eating after the bonk has occurred is infinitely less effective and desirable from a performance view-point.

A shift toward fat metabolism may be the physiological explanation for the "second wind" that occurs during long exercise sessions or races.   It may be that, once internal carbohydrate stores have been depleted and fatigue sets in, the body's survival instinct awakens and shifts to fat metabolism.  The "second wind" or feeling of a renewed source of energy returns. 

However, the trade off is the inability to maintain performance at the same %VO2max possible with carbohydrate supported metabolism.  In other words, you may go further but it wont be as fast as if you maintained your carbohydrate levels.

Factors effecting digestion & absorption
When planning a nutritional strategy to supplement the body's energy stores for a big race, the rate of digestion and absorption of foods must be taken into account.  The time needed for the stomach to start the digestive process, empty its contents into the small intestine, and have the food components absorbed into the bloodstream will directly affect how quickly any food will be available to the muscles to provide energy for the ride.

As an athlete you have control over four major factors that influence the digestive process.

Solid v liquid ~ liquids are metabolized quicker than solids
Fat content of the food ~ fat slows the digestive process
Sugar concentration ~ more than 10% slows stomach emptying
Physical activity level ~ digestion is slowed over 70% VO2max

From the above four points, it is easy to see that the optimal food for a rapid, high energy boost during a ride would be a semi-liquid (gels) or liquid carbohydrate with minimal if any fat.

On the other hand, for endurance events competed at a lower VO2max (Cyclosportives, Iron Man Triathlons, End-to-End attempts), a complex, solid form of carbohydrate (energy bar), with some fat added to improve taste will slow emptying from the stomach and even out absorption over a longer period of time.

Effects of exercise on digestion
Studies have demonstrated a reduced blood flow to the digestive system during vigorous exercise ~ an 80% reduction after 1 hour of cycling at 70% VO2max.  Exercise delays stomach emptying, and the more vigorous the exercise, the greater the delay.

Training Nutrition
It is suspected that one component of overtraining may be a failure to adequately replace the muscle glycogen depleted as a result of daily training.  Therefore, to minimize the risk of the short-term bonk and long-term overtraining, it is important to maximize your body glycogen stores through:

a high carbohydrate diet in the days and hours before your ride
using carbohydrate supplements, gels, bars & drinks, while riding
making full and immediate use of the post ride recovery interval

Pre-Event Nutrition
The good old days?  As far as the pre-race period is concerned, dismiss from your mind everything you've heard about traditional carbo-loading.  All the rage when I started racing in the 80's, which is where it should remain.  It involved avoiding all carbohydrates for several days in the week prior to the event, while still training hard, to ensure complete and absolute muscle glycogen depletion.  Once that point had been reached you'd eat nothing but carbohydrates for the 3 days immediately prior to the key event. 

Although this regimen does maximise muscle glycogen stores, the price paid was significant physical, mental, physiological and digestive drawbacks.  Nutritional science has advanced greatly since this program was devised.  In those days we were led to believe steak was the optimal race fuel!  Sticking to a normal high carbohydrate diet, without a depletion phase, will provide 90% of the benefits of the loading program while avoiding digestive turmoil. 

Event Nutrition
Maximizing carbohydrate replacement while competing is important for events of more than 2 hours. Up to 2 grams of carbohydrate per minute can be absorbed and utilized to supplement pre-ride glycogen stores and help sustain prolonged exercise.

As a rule of thumb, the higher the level of intensity of the ride (closer to your VO2max), the simpler the carbohydrates (energy drinks, gels, and fruits) should be. 

On longer rides and at lower heart rates, more complex carbohydrates and a higher fat content offer other alternatives. A reasonable goal during high intensity rides is 200 to 300 Calories (60 grams of carbohydrate) per hour.

Commercial power bars and sports drinks are often advertised as providing a particularly potent combination of ingredients and secret "supplements".  However, they are no more effective on a gram for gram basis as an energy booster than any other carbohydrate snack.  One big advantage is that they are pre-packed, readily available and do offer a potentially better taste and texture option for a mid-competition snack.

Recovery Nutrition
Take advantage of the "glycogen window" that is open immediately following vigorous exercise.  During this interval, ingested carbohydrate will be converted into muscle glycogen at about 3 times the normal rate and "the earlier recovery starts the better".  

Food taken during the first twenty minutes of finishing exercise gets on the glycogen autobahn and screams into the muscles and liver at a phenomenal rate.  Your body acts like a sponge sucking up all the nutrients it can in a mad panic before the "twenty-minute window" begins to close.   After four hours it's shut altogether and nutrient absorption returns to it's country lane way off life.

Be careful what you eat.  Many simple carbohydrate snacks such as biscuits are more than 30% fat and if eaten in large quantities to boost recovery (which they wont), you might exceed your planned daily fat intake.  In contrast, complex carbohydrate foods such as pasta, bread, and rice offer significantly more carbohydrate per gram.  There are even special "recovery drinks" available to give you what you need when you need it.

There is also suggestive evidence that the muscle stiffness occurring after vigorous exercise (DOMS) may be related to muscle glycogen depletion.  So, rapid repletion may have the added benefit of minimizing this day after effect as well.  Lots of "mays" there but it may work for you, so why not try it?

Hydration
Water does not provide any calorific energy whatsoever.  However, adequate hydration is as important to performance as the food you eat.  One of the biggest mistakes made by new, and many experienced, cyclists is the failing to replace fluid losses associated with exercise. 

 

In cycling rapid skin evaporation decreases the sense of perspiring and imparts a false sense of only minimal fluid loss.  Sweat production and loss through the lungs can easily exceed a pint per hour.  When standing in the cold waiting for your club run to start, look at the steam coming from your breath.  That's water that is. 

Fluid losses during exercise result in decreased plasma volumes as well as muscle water content.  Dehydration of 2% of begins to impact heat regulation, at 3% there is a measurable effect on muscle cell contraction and when dehydration reaches 4% there is up to a 10% drop in performance. 

You may think a 4% drop is a lot.  But what happens if you come to the start line 2% dehydrated.  If you work in an air-conditioned office or spend Saturday in the garden it's very likely that you may not be fully hydrated when you start your event.  Hydration is an important part of your race preparation.  Practice until you get it right.

The Message
Nutrition and hydration strategies are as important a part of your competition as the training you undertake, the equipment you buy and the mental preparation you put in.  You can do as much of the others as you like but if your nutrition is wrong, it will be reflected in your results.

Would you feed a Grand National prospect the same food you'd give a beach-ride donkey?  Absolutely not!  As athletes who train or race more days than we rest, we can't get away by eating the same as "normal" people.  Performance humans require performance nutrition.  Give the food you eat the attention it deserves.  As the old computer phrase goes, "rubbish in ~ rubbish out". 

There are two sets of bottle cage bosses on your bike for a reason.  Drink a little often, rather than gulping mouthfuls every half-hour.  Keep topped up and keep your performance levels consistent.  Eat before you're hungry and drink before you're thirsty.  By the time you feel either, it's too late.

Money spent on the advice of a qualified sports nutritionist may help you find that extra 1% that you need to win races or go for your personal best.  For the price of a pair of tubs you can improve your results by factors greater than any pair of wheels or fancy frame could ever do.  Check-out our services page to find someone who has already helped some of our riders to improved performance.