All elite athletes need to get the most out of their bodies. But athletes in different sports achieve this in very different ways. Sprinters, shot putters and gymnasts, who need quick bursts of power, don’t draw on the same energy sources as athletes such as cyclists and triathletes, who compete in endurance events. Optimizing how a body uses its energy stores is the key to peak performances.
Where does energy come from?
Everybody–not only athletes–stores energy in one of these forms after food is digested.
ADENOSINE TRIPHOSPHATE (ATP)
For muscles to contract
ATP is the most essential energy compound. It is found in small amounts in all muscles. When your body needs to contract its muscles, it breaks one of the chemical bonds in ATP. This releases a small bit of energy. Your body needs to keep replenishing ATP for muscles to keep contracting.
An ATP molecule
Chemical bond
PHOSPHOCREATINE
Used to supply ATP
Phosphocreatine (PCr) is another high-energy compound. Instead of powering muscle contractions, it is used to replenish stores of ATP.
GLYCOGEN
Main source of energy
Glycogen is the form in which carbohydrate energy is stored in the body. About 80 percent of it is stored in muscles and 20 percent in the liver.
FAT and PROTEIN
Deepest reserves
Stores of fat and protein are used during endurance events when ATP and glycogen stores dwindle.
Ways energy is used
Anaerobically (without oxygen): Oxygen isn’t required for short bursts of power using ATP and glycogen. But when glycogen is broken down anaerobically, it creates lactic acid, causing muscles to get tired.
Aerobically (with oxygen): When exercise last more than two minutes, oxygen is needed to burn glycogen and fat stores. Runners, cyclists and soccer players have high aerobic capacities.
The spectrum of energy needs
Athletes in different events rely on a range of energy sources–with varying needs for oxygen–depending on the length of time they are competing:
POWER AND STRENGTH EVENTS
Shot put, Diving, High jump, Weight lifting
Power athletes rely on the ATP and PCr that is stored in their muscles. Short bursts of energy quickly deplete energy stores. No oxygen is needed for this process to function.
Aerobic and anaerobic energy contributions
Anaerobic 100%
Aerobic none
ENERGY USED
Event: Shot put
DURATION: A few seconds
KEY TO OPTIMUM PERFORMANCE: Reserves of ATP must be plentiful, especially if an athlete has to compete in several heats or rounds on the same day.
SUSTAINED POWER EVENTS
Repeated bursts of muscle energy
Gymnastics, 100-meter sprints
After a few seconds of quickly burning ATP and PCr, the body turns to glycogen stored in its muscles. About 90 percent of the energy production at this level is anaerobic; it cannot be sustained for long.
Aerobic and anaerobic energy contributions
Anaerobic 90%
Aerobic 10%
ENERGY USED
Event: Gymnastics
DURATION: 10 seconds
KEY TO OPTIMUM PERFORMANCE: Reserves of ATP and glycogen must be plentiful.
SPEED EVENTS
A mix of stored and replenished energy
Basketball, 100-meter freestyle, 200-meter sprints
Athletes in these events must have well-developed anaerobic and aerobic systems, as about half of the energy needed for two minutes of intense exercise requires oxygen. Breaking down glycogen in the muscles without oxygen creates lactic acid, which causes fatigue.
Aerobic and anaerobic energy contributions
Anaerobic 50%
Aerobic 50%
ENERGY USED
Event: Basketball
DURATION: 2 minutes or less
KEY TO OPTIMUM PERFORMANCE: Developing a high threshold for the amount of lactic acid in the bloodstream.
ENDURANCE EVENTS
Extended use of stored energy reserves
Marathon, Triathlon, Cycling, Rowing
After depleting the ATP reserves in the muscles, the body turns to aerobic process to generate more. After about 10 minutes, more than 85 percent of energy is created aerobically. The body doesn’t start relying on its fat reserves to produce ATP until after about three hours.
Aerobic and anaerobic energy contributions
Anaerobic 1%
Aerobic 99%
ENERGY USED
Event: Marathon
DURATION: Marathon: 2 to 3 hours*
KEY TO OPTIMUM PERFORMANCE: Aerobic capacity. The aerobic system can’t produce ATP as quickly as the anaerobic system, but it produces it in much greater quantities.
* Any event longer than two minutes is considered an endurance event
The training table
A healthy adult usually eats a 2,000-to 2,500-calorie diet, which could contain the three main meals listed below.
Athletes in training often eat three snacks between meals, adding another 1,000 to 1,500 calories each day.
BREAKFAST
1 1/2 cups cereal
2 bananas
2 cups 1% milk
MID-MORNING SNACK
2 apples
1 cup cranberry juice
4 fig bars
LUNCH
Sandwich:
Turkey breast
1 oz. low-fat cheese
1 tsp. mustard on 2 slices of wheat bread
Water
MID-AFTERNOON SNACK
3-oz. bagel
1 oz. cream cheese
1 cup grape juice
DINNER
2 cups spaghetti
1 cup tomato sauce with meat
1 oz. mozzarella cheese
Small salad with 1 cup lettuce, 1 tomato, 1 carrot, 1 tbsp. Italian dressing
1 slice French bread
1 tsp. margarine
1 cup 1% milk
POST-EXERCISE SNACK
Smoothie:
1 1/2 cups skim milk
1 cup yogurt
1 banana
1 cup strawberries
1 energy bar
The main components to fuel a body and the foods that supply them:
CARBOHYDRATES
The body’s main source of fuel is used to replenish glycogen supplies. Carbohydrates can fuel about 75-90 minutes of exercise.
Sources: Breads, pasta, cereal, baked potatoes, fruits
160-pound athlete’s daily requirement (in grams)
360-800
Average man’s intake: 334.7
FAT
Burned with carbohydrates during endurance exercise, fat is more efficient than glycogen. Every pound of fat provides twice as much energy as carbohydrates.
Sources: Butter, oils, red meats
160-pound athlete’s daily requirement (in grams)
70-90
Average man’s intake: 102.8
PROTEIN
Protein contributes about 5 percent of energy when glycogen stores are high and about 15 percent in endurance events.
Sources: Milk, chicken, beef, fish, eggs, beans, legumes, tofu
160-pound athlete’s daily requirement (in grams)
72-144
Average man’s intake: 103.1
NOTE: Average man’s intake based on a U.S. Department of Agriculture survey using 20-39-year-old white males in the U.S., 1994-96.
Sources: Sports and Exercise Nutrition; Complete Guide to Sports Nutrition; Nutrition for Sport and Exercise; interviews with Dr. Jacqueline R. Berning, nutrition professor at the University of Colorado-Colorado Springs; Associated Press; Reuters.
