CYCLING PERFORMANCE TIPS
First, let's review the basic physiology of energy the energy transfer from food to your muscles. Food energy is released through a chemical reaction with oxygen in a process called oxidation. When this occurs outside the body - for example the burning of oil (a fat) in a lamp or the use of a flaming sugar cube (a carbohydrate) as a decoration in a dessert - this energy is released as heat and light. In the body however, food energy needs to be released more slowly and in a form that can be harnessed for basic cell functions and transformed into mechanical movement by the muscle cells.
All foods are composed of carbohydrates, fats, and protein. Carbohydrates are the primary energy source for the average cyclist and for all athletes involved in short, maximum performance events. Fats, which can also serve as an energy source for cell functions assume more importance in endurance events done at less than 50% VO2 max. Proteins are used to maintain and repair body tissues.
The energy contained in equal weights of carbohydrate, fat, and protein varies. It is measured in Calories ( note the capital C). Carbohydrates and protein both contain 4.1 Calories per gram (120 Calories per ounce) while fat contains almost twice as many per ounce at 9 Calories per gram. The disadvantage of the high energy density of fat as a fuel to support exercise is that it is metabolized through pathways that differ from carbohydrates and will support exertion at 50% VO2 max. at most. This makes it ideal for endurance events, but unacceptable for high level aerobic activities which are fueled by carbohydrates in the form of muscle glycogen or blood sugar (glucose).
Over the last few years it has been suggested that a diet composed of at least 30% fat Calories improves competitive aerobic performance over a high carbohydrate diet - relatively restricted in fat Calories (20-25%).
Although various arguments have been put forward:
There have been two well controlled studies of high fat diets (70% fat in one, 38% in the other) showing an increase in the exercise to exhaustion time for activities at 50% VO2 max (80 vs 42 minutes of cycling in one, 76 vs 70 minutes of running in the other). Glycogen sparing effects were studied to determine if there was a preferential shift to fat metabolism during exercise, but none were found. A third study tracked Calorie replacement after exercise in two groups (a low fat diet vs normal/high fat foods) and found that those on a low fat diet did NOT replace the Calories expended during their training program while those on a more liberal fat diet did, suggesting another reason for poor performance on a low fat diet - long term Caloric deficit during the training program with limited muscle glycogen stores going into the event.
On the other hand, there are a number of physiologic studies that demonstrate fat CANNOT sustain high level (high VO2 max.) aerobic and anaerobic activity (the cause of the "bonk" as glycogen stores are depleted), and that a high carbohydrate diet is best for replacing glycogen stores post exercise (a chronic deficit in replacing carbohydrates has been proven to lead to chronic fatigue). The cycling study mentioned above demonstrated no difference in the cycling time to exhaustion at 90% VO2 max on a high fat (70%) vs a low fat (12%) diet eaten for 2 weeks before the event.
In addition to the questionable exercise performance benefits, it has been proven beyond any doubt that a long term high fat diet leads to heart disease. And for those who still aren't convinced, it should be remembered that even the leanest athlete has plenty of stored fat available (approximately 100,000 Calories worth in a 70 kg male) without any need for diet supplements.
FACT NUMBER ONE - BASED ON NUMEROUS PHYSIOLOGIC STUDIES, GLUCOSE OR CARBOHYDRATES ARE THE PREFERRED ENERGY SOURCE FOR MAXIMUM PERFORMANCE AEROBIC EVENTS (GREATER THAN 50% VO2 MAX).
Let's look at the basic energy bar and energy gel.
Commercial powerbars are mainly carbohydrates (of varying types) and also contain those special supplements that Ill mention below. Their main advantage is that they are prepackaged, are readily available commercially, and do offer another taste and texture option for a snack. But as a carbohydrate snack, they are no more effective on a gram for gram basis as an energy booster than other carbohydrate snacks. In fact a recent study from Ball State University demonstrated that a pre event meal of old fashioned oatmeal gave the same boost to endurance performance as a commercial energy bars.
Energy gels offer an alternative to the hard to unwrap, difficult to chew, and relatively tasteless commercial energy bars. These products contain a combination of simple and complex carbohydrates in a palm sized packet of plastic or foil with a tear off end to allow the contents to be "sucked" out rather than chewed. They contain between 70 and 100 Calories per packet (17 - 25 grams of carbohydrate) and have the advantage of being completely fat free. Being a semi-liquid, they also empty more quickly from the stomach and their only advantage may be in the fact that this may provide a more rapid absorption and thus a more rapid energy boost than the solid energy bars. There is no proof of their benefit over more traditional forms of carbohydrate (fig newtons for example).
FACT TWO - THERE IS NO EVIDENCE THAT THE CARBOHYDRATE IN ENERGY BARS OR ENERGY GELS IS MORE EFFECTIVE TO SUPPLY MUSCLE ENERGY THAT, FOR EXAMPLE, THE CARBOHYDRATE IN TRADITIONAL ENERGY SNACKS SUCH AS FIG NEWTONS.
Now let's look at the additives. Basically they fall into the categories of:
Caffeine is a member of a group of compounds called methylxanthines found naturally in coffee beans, tea leaves, chocolate, cocoa beans, and cola nuts. During prolonged exercise, the onset of fatigue correlates closely with the depletion of muscle glycogen stores (and is delayed if glycogen is spared). The metabolism of free fatty acids as an alternative energy source can lead to decreased use of muscle glycogen. Caffeine can increase blood free fatty acids, and in one study produced a 50% increase at 3 to 4 hours. This effect was seen after 300 mg of caffeine (An average 6 ounce cup of brewed coffee contains 100 - 150 mg of caffeine).
There is also speculation that some of its benefits may be secondary to a central nervous system effect as a stimulant, and some recent work has demonstrated a direct positive effect on the muscle fiber itself.
In one controlled study, subjects were able to perform for 90 minutes to fatigue as compared to 75 minutes in controls (a 20% increase) after the drinking the equivalent of 3 cups of coffee or 6 caffeinated colas 1 hour before, even though values for heart rate and oxygen uptake were similar in both groups.
But there are also potential side effects. Caffeine can cause headaches, insomnia, and nervous irritability. In addition it is a potent diuretic and can lead to dehydration. However its biggest negative is that in high concentrations it is considered a drug and is banned by the US Olympic Committee and US Cycling Federation (to exceed the US cycling Federation's legal limit for caffeine - urine concentration of 12 micrograms/ml - one would have to ingest 600 mg of caffeine and have a urine test within 2 to 3 hours).
The bottom line is that most endurance athletes consider caffeine useful if used correctly. This includes a period of abstinence for several weeks before the event as habitual use induces tolerance.
Guarana is a South American herb used as a natural source of caffeine and can be found as a supplement in energy gels or bars, and cola nut is another natural source of caffeine sometimes found in the ingredient list.
The minerals sodium, potassium, and chlorine are collectively referred to as electrolytes. They are dissolved in the intra (within) and extra (outside) cellular water in your body as charged particles (ions) and are responsible for maintaining a proper electrical gradient across the cellular membrane - required for the proper functioning of each cell.
A normal diet contains these three minerals in excess, and the kidneys control the loss from the body. As a result there is no requirement for diet supplementation except in extreme conditions.
Minerals are chemical elements found in the body either in their elemental form or complexed with organic compounds. Like vitamins, they are essential for normal cell functioning. The two most prevalent minerals, calcium and phosphorus, are major components of bone while sodium and potassium are found in all tissue fluids, both within and around cells. Magnesium, chloride, sulfur, and zinc are other minerals that play a key role in cell function. The trace elements iron, manganese, copper, and iodine are found in much smaller quantities, but play essential roles as catalysts in basic cellular chemical processes.
These minerals, found in all foods, are kept in balance through regulation of both absorption and excretion. As a result of this control, they are easily provided by a balanced diet. Only calcium and iron may be required by some athletes in increases amounts. Because of toxic side effects when taken in large amounts, minerals as a group are not recommended as routine dietary supplements.
FACT THREE - ASIDE FROM CAFFEINE, WHICH MAY PROVIDE PERFORMANCE ENHANCEMENT IF USED CORRECTLY AND IN LIMITED AMOUNTS, THERE IS NO EVIDENCE THAT OTHER ELECTROLYTE OR MINERAL ELEMENTS PROVIDE A PERFORMANCE EDGE.
Then there is the issue of energy bars or gels which contain fat and are alleged to:
Medium chain triglycerides are merely a form of fat which is more easily absorbed from the intestinal tract, but is metabolized by the muscle cells exactly like all other fats and is probably of no more benefit than the extra pat of butter on your pancakes before the ride. And there are at most a few grams per bar or package providing a minimal addition to the Carbohydrate Calories.
An alternative to eating more fat would be to focus on a training program that stresses an increased number of miles at a relatively slow pace (60% VO2 max.) to improve the ability to use your own internal fat stores. Another variation on this theme is to avoid carbohydrates in the pre ride meal and minimize carbohydrate supplementation while on that long slow ride to force the development of metabolic pathways that use fat energy (a planned "bonk' if you will). Then, or so goes the theory, when it comes time for that sprint at the end of a competitive event, ridden with appropriate glucose supplementation, there will be more muscle glycogen remaining to give you the edge.
FACT FOUR - THERE IS NO EVIDENCE OF PERFORMANCE ENHANCEMENT FROM DIETARY FAT SUPPLEMENTATION, EITHER BEFORE OR DURING A COMPETITIVE EVENT.
Finally, there has been the suggestion that a combination of protein (amino acids) and carbohydrates in a ratio of 1:4 is more effective in sports drinks used while riding and as supplements for glycogen repletion immediately after a ride. The data for any benefit post ride recovery period is weak (and seems to be related to the amount of carbohydrate used - 1 gram/kg/hr x 3 hours appears to maximize repletion rates) at best, and at the moment there is no information in the literature to support a benefit to protein enhanced carbohydrate sports drinks while riding.
So what is the message here? Basically that a good balanced diet is the best approach during the pre and post event training program, there are no nutritional shortcuts to improved athletic performance, and although they may do no harm, there is little evidence that expensive dietary snacks provide any advantage over cookies, coke, or other more traditional (and less expensive) snacks aside from providing a variation in taste, consistency, or packaging