Chapter 10: Nutrition & Fitness
Designing a Fitness Program
Phase 1
Getting Started Means Getting Going
Short periods of physical activity incorporated into the daily routine
Total of 30 minutes
Phase 2
Seeking Greater Fitness Requires Greater Exertion
Regular moderate-intensity activity
20-60 minutes 3-5 days per week
Physical Activity Pyramid
Fuel for muscle work
ATP
Chemical energy used by cells for muscle contractions
Only a small amount is stored in resting cells (2-4 sec. of work)
Other sources of energy are needed
Fuel for muscle work
Phosphocreatine (PCr)
A high-energy compound that is formed and stored in the muscle cells
PCr + ADP Cr + ATP
- Activated instantly and replenish ATP
- Not enough is stored or made in the muscle to sustain ATP for more than a few minutes
Glucose - a major fuel
Anaerobic glycolysis
Limited oxygen to the muscle cells
Intense physical activity (sprinting)
Produce lactic acid
Produces 2 ATP per glucose
Provide energy for 30 seconds to 2 minutes of work
Glucose - the major fuel
Aerobic glycolysis
Plenty of oxygen available
Low to moderate intensity (jogging)
Produces 36-38 ATP per glucose (95% of energy potential)
Provide energy for 2 minutes to 3 hours of work
Glycogen
Temporary storage of glucose in the liver and muscle
Muscle glycogen is used only by that muscle; liver glycogen is released into the blood stream
Low to moderate intensity; sustain work for up to 2 hours
Once depleted, can only work at ~50% of maximal capacity ("hitting the wall")
CHO loading
A method of increasing CHO intake and decreasing exercise
Beneficial for events lasting longer than an hour
Diets high in CHO build up muscle glycogen stores
Delay fatigue and improve endurance
Fat fuel
The more fatty acids released into the bloodstream, the more fat will be used by the muscle
As exercise prolong, fat becomes the main fuel
Not a major source of fuel for intense activity
Requires more oxygen for aerobic breakdown (than glucose)
Protein--a minor source of fuel
Provides 2%-5% of energy needs during rest and low/moderate exercise
Provides ~10% of energy needs during endurance exercise
Average diet provides ample amount of these amino acids -- supplements are not needed
Effects of exercise
Hypertrophy
Increase in cell size
Muscles enlarge as a result of repeated work
Atrophy
Wasting away of tissues
Result of non-movement
Effects of aerobic exercise
Increased red blood cell production to deliver oxygen
Increase total blood volume
Increase the number of capillaries in muscle tissue
Strengthen the heart (muscle)
Increase in number and size of mitochondria
Increase in muscle glycogen stores
Energy needs for athletes
Estimate needs by monitoring weight and body fat
Desirable body fat for male athletes: 5%- 15%
Desirable body fat for female athletes: 10%-25%
If weight falls, increase intake
If body fat increases, cut back in fat (& kcal) and maintain activity
"Making Weight" the wrong way
Lose weight so to qualify for a lower weight class
Many will lose pounds by intense diuresis leading to dehydration
Dehydration adversely affect performance
Increase risk for decrease growth and development, abnormal psychological state, poor school performance, pulmonary problems, pancreatitis, kidney malfunction, heart problems, etc.
"Making Weight" the right way
Gradual reduction in food intake long before competition
Lower body fat composition
If there is very little body fat to lose, athlete should consider competing in the higher weight class
Carbohydrates
Main fuel for many types of activity
Need to consume a diet moderate to high in CHO (~60% of total kcal)
Adhere to the Food Guide Pyramid
For aerobic and endurance activity, recommend 8-10 gm CHO/kg body weight
Marathoners should consume ~ 600 gm of CHO/day
Proteins
Recommend 1.2 - 1.6 gm protein/kg body weight
The higher value for individuals participating in endurance exercise
Needs are easily met by a normal diet
Protein supplements are not necessary
Vitamins and Minerals
Slightly higher needs for vitamin E and C (antioxidant properties)
Thiamin, riboflavin, vitamin B-6, potassium, magnesium, iron, zinc, copper, and chromium needs may also be higher (role in metabolism or sweat)
Extra vitamins and minerals needs are easily met by diet, especially by increasing intake of fruits and vegetables
Fluid needs
Average adult needs 1 ml/kcal of fluid per day
Equivalent to 6-8 C per day
Athletes need this and more
Fluids are needed to maintain body’s cooling system
Avoid losing more than 3% of body weight during exercise
Heat exhaustion
A depletion of blood volume from fluid loss by the body
Body heat is lost primarily through evaporation of sweat
Fluid loss through sweat is about 3-8 C per hour
Decrease endurance, strength, performance
Heat cramp
Occurs in the skeletal muscle
A complication of heat exhaustion
Painful muscle contractions for 1-3 minutes at a time
Ensure athlete has adequate salt and fluid intake
Exercise moderately at first in the heat
Heatstroke
Internal body temperature reaches 105 F
Symptoms: nausea, confusion, irritability, poor coordination, seizures, and coma
Athletes should replace fluids and monitor weight change (fluid loss)
Avoid exercising under hot, humid conditions
Sports drink for endurance exercise
Recommended for activity > 90 minutes in duration
Sweat, CHO, and electrolytes lost in events <90 minutes are easily replaced by diet
For events > 90 min. sports drink can help maintain blood glucose level and blood volume
Pre-Event meal
For endurance events
Consumed 2-4 hours prior to event
Consist primarily of CHO (50-150 gm)
Low fat (<25% of energy intake)
Little fiber (prevent bloating, gas)
Moderate protein
Avoid fatty, fried foods
Recovery meal
Consumed within 2 hours after endurance event
CHO rich (50-100 gm) to replace glycogen
Repeat CHO meal over the next 2 hour interval
Sugar candy, soft drink, fruit, juice, sports drink are convenient choices
