Training and recovery are only two parts of the equation when it comes to high-performance athletics. World-class athletes realize that proper nutrition and the usage of ergogenic aids will only enhance their training, performance and recovery. As a result, tremendous amounts of science have been devoted to the topic of nutrition and enhancing performance. Plenty of people have tried to take advantage of the vast public interest in nutrition by creating diet protocols. But which of these diet protocols are optimal and which are merely flashy attention-grabbing scams? When it comes to increasing performance, the body needs energy and this energy comes from macronutrients. Carbohydrates, lipids and protein act as a biologic fuel and preserve the structural and functional integrity of an organism.
The Role of Carbohydrates in Exercise
Carbohydrates have gotten a bad rap in the mainstream media by people touting the benefits of low carb dieting. The fact is avoiding carbohydrate consumption is completely unnecessary, especially in a high performance athlete. Carbohydrates play four important roles in the enhancement of athletic performance.
Although carbohydrates play an important role in exercise, people in favor of low carbohydrate diets have continued to associate carbohydrates with obesity, diabetes and GI disorders. The flaw in this argument lies in the exclusion of fiber. Research has shown that women who ate a low fiber, starchy diet had a rate of diabetes 2.5 times higher than women who ate less starchy foods and more fiber-containing unrefined whole-grain cereals, fruits and vegetables.
High fiber diets correlate with with decreased obesity rates, diabeties, digestive diseases and heart disease. Possible explanations for the positive effects of a high fiber diet are that fiber lowers the glycemic index of a meal, which lowers the amount of insulin released. Fiber also modestly reduces serum cholesterol by lowering low density lipoprotein levels.
One of the main reasons people get so confused about carbohydrate consumption is that the need for carbohydrates is greatly different between a high performance athlete and a stay at home soccer mom. The analogy of gas in a car has been used numerous times but it really applies to the bodies need for carbohydrates. If your car is sitting in the garage all day (sedentary) with a full tank of gas it will not need to be filled up. However, if you are out and about driving around all day you have the potential to use up the gas and the need for gas greatly increases. The same can be said about the body’s need for carbohydrates. If you are a sedentary individual your needs for carbohydrates (and calories in general) is not very high. One of the reasons carbohydrates have gotten a bad rap is because when sedentary people gorge on carbohydrates while their glycogen stores are full (muscle stores ~400g, liver stores ~ 100g) the excess glucose “spills over” and remains in the blood stream where it has the potential to be stored as fat.
Carbohydrate Recommendations for Performance
- During periods of intense training carbohydrate intake should increase to 55-75% of daily caloric intake.
- Fiber intake for men ~40 grams
- Fiber intake for women ~25 grams
- Starches with high amounts of amylopectin digest and absorb rapidly, whereas starch with high amylose content hydrolyze slower.
- Approximately 50% of daily carbohydrate should come from starch.
Glycogen Supercompensation
The most common method of manipulating carbohydrates to enhance athletic performance is carbohydrate loading. Research indicates that there is little no effect of elevating pre-exercise muscle glycogen contents above normal resting values in high intensity exercise lasting less than 5 minutes. Nor is there any benefit of increasing muscle glycogen for moderate intensity exercise lasting up to 90 minutes.
In endurance events, there is evidence that shows that elevated starting muscle glycogen content will postpone fatigue by approximately 20% in endurance events lasting more than 90 minutes. During endurance exercise, exhausting correlates with critically low muscle glycogen contents, suggesting that the supply of energy from glycogen utilization cannot be replaced by an increase in oxidation of blood glucose.
A final point to consider about carbohydrates related to endurance performance is the importance of having glycogen stores that are nearly full before any endurance type of performance. There may not be evidence to support glycogen supercomensation in events lasting under 90 minutes, however it only takes between 60-90 minutes of 60% VO2 max to run through all stored glycogen in the body. This can easily be accomplished with a balanced macronutrient distribution in the days leading up to an event without the need for carbohydrate loading.
The Role of Fats in Exercise
Fats play a crucial role in long-term, low-intensity energy supply. The aerobic system depends on fats for energy. Lipids carry a large quantity of energy per unit weight, transport and store easily, and provide a ready source of energy. Lipids are responsible for providing the majority of the bodies energy at rest (80-90%).
Simple Lipids
- Triacylglycerols constitute the major storage form of fat in adipocytes (cells that compose adipose tissue)
- Saturated fatty acids – carbon within fatty acid chains bind to maximum amount of hydrogens, caused by single bonds.
- Unsaturated fatty acids – contain one or more double bonds along the fatty acid chain. The maximum amount of carbon bonds is not achieved.
Compound Lipids
- Phospholipids – maintain structural integrity of the cell and myelin sheath around nerve cells.
- High Density Lipoproteins – cholesterol that protects against heart disease by removing cholesterol from arterial wall and delivering it back to liver.
- Low Density Lipoproteins – greatest affinity for the arterial wall, known as the “bad” cholesterol.
Derived Lipids
Cholesterol is the most well known derived lipid, its functions include:
- Forming tissues, organs and body structure in fetal development
- Building plasma membranes
- Precursor in vitamin D, adrenal gland hormones and sex hormones
- Component of bile
Fat Intake Recommendations for Performance
- < 30% of total daily caloric intake
- < 10% saturated fats
- Eliminate trans fats
- < 300 mg cholesterol
The Roles of Protein in Exercise
Alanine-Glucose Cycle
The Alanine-Glucose cycle is the enemy of many endurance athletes. Commonly known as “hitting the wall” or “bonking”, when glycogen and blood glucose levels lower, the alanine glucose cycle accounts for 45% of the liver’s release of glucose. The role of this cycle is to support the availability of carbohydrate during prolonged exercise.
Protein Intake Strategies for Maximal Performance
Tremendous amounts of research on protein dosages and timing have emerged over the last decade. These studies have reshaped the way athletes and coaches view protein metabolism and how timing and dosages impact muscle protein synthesis. There is positive evidence that shows that the amino acid leucine is responsible for stimulating muscle protein synthesis. It has also been shown that it takes approximately 15 grams of essential amino acids to maximize protein synthesis. This would amount to 3.2 grams of leucine in 15 grams of essential amino acids, therefore scientists proposed the idea of a leucine threshold for stimulating MPS.
When MPS stimulated in a meal the next question researches set out to answer was the issue of meal frequency. Research from the University of Illinois shows that the duration of the protein synthesis response to a complete meal is approximately 3 hours long. At the 3 hour mark, protein synthesis levels had returned to baseline, however plasma amino acid levels were still elevated almost 3x above baseline. It was hypothesized that at the point where MPS levels returned to baseline, the signal for MPS was still being transmitted which demonstrates evidence of a refractory period. This data shows that it is unlikely that the consumption of another meal 2-3 hours after the previous meal would maximize MPS as blood plasma amino acid levels are still elevated. These important findings have disproved the theory of frequently eating every 2-3 hours as being more optimal for stimulating protein synthesis.
Quantity of Food at the Olympic Games
There will be 16,500 athletes striving to perform at their peak during these Olympics. The correct food provision will help achieve this, by providing familiar and nutritionally balanced food and drink, available at exactly the right time of day or night.
It is estimated that over 14 million meals will be served up to 16,500 athletes across 40 separate locations during the Games. In the Olympic Village they will be using:
- 25,000 loaves of bread
- 232 tons of potatoes
- 82 tons of seafood
- 31 tons of poultry items
- 100 tons of meat
- 75,000 liters of milk
- 19 tons of eggs
- 21 tons of cheese
- 330 tons of fruit and vegetables
References
Hawley JA, Schabort EJ, Noakes TD, Dennis SC. (1997). Carbohydrate-loading and exercise performance. Retrieved August 5th, 2012 from http://ukpmc.ac.uk/abstract/MED/9291549/reload=0;jsessionid=hdjbX3Z8woVg8WM7Jnfw.20
Norton LE, Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr. 2006 Feb;136(2):533S-537S.
Paddon-Jones D, Sheffield-Moore M, Zhang XJ, Volpi E, Wolf SE, Aarsland A, Ferrando AA, Wolfe RR. Amino acid ingestion improves muscle protein synthesis in the young and elderly. Am J Physiol Endocrinol Metab. 2004 Mar;286(3):E321-8.
Bohe J, Low JF, Wolfe RR, Rennie MJ. Latency and duration of stimulation of human muscle protein synthesis during continuous infusion of amino acids. J Physiol. 2001 Apr 15;532(Pt 2):575-9.
London 2012. (2009) Food vision for the London 2012 Olympic Games and Paralympic Games. Retrieved August 5th, 2012 from: http://www.london2012.com/documents/locog-publications/food-vision.pdf
Souster, Mike. (2011) Macronutrients. Retrieved August 5th, 2012 from the Mount Royal University Blackboard Website.