Transcript Lecture 14 - Angelfire

Physical Activity and
Nutrition
Readings: Chapter 14, pages 466 and 467, 471 - 487
Next Lecture: Chapter 10, pages 307 - 335
• an estimated 57% of Canadians are not physically active
enough to benefit their health (2001 data)
• physical inactivity declined from 62% in 1994 to 55% in
1998
• British Columbia has the lowest inactivity rate of
Canadian provinces at 46%
• it’s estimated that reducing the percent of the population
that is physically inactive to 10% would save
approximately $5 billion in lifetime costs for medical
care, sick leave, and lost tax revenues
• sedentary individuals have 50% more health problems
than active individuals
• over one half of Canadians aged 5 - 17 are not active
enough for healthy growth and development
Canadian Fitness and Lifestyle Research Institute: www.cflri.ca
What is Physical Fitness?
Definition
• the characteristics that enable the body to perform
physical activity
• the ability to meet routine physical demands with
enough reserve energy to rise to a physical challenge
Benefits of physical fitness
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improved sleep
nutritional health
healthy body composition
healthy bone mineral density
improved immune function
reduced risk of cardiovascular disease, Type II
diabetes, and some cancers
reduced stress and anxiety
improved self-esteem and lowered risk of depression
improved cognitive functioning, alertness and memory
injury reduction and low back pain
greater longevity and quality of life
Sources of Energy During Physical
Activity
Physical activity increases the energy needs of working
tissues including the muscles and the heart…where
does this energy come from?
1.
: Quick Energy Compounds
• very small pool of ATP available in cells
• CP (creatine phosphate) can release phosphate
which combines with ADP to form ATP but supplies
are limited
• anaerobic
creatine phosphate + ADP
creatine + ATP
Sources of Energy During Physical
Activity
2. Carbohydrate:
• derived from muscle and liver glycogen stores
• in activities of extreme intensity (20s to 3 minutes):
– oxygen needs of muscle exceed the ability of
cardiovascular system to supply oxygen
– glucose is used
to produce ATP
– by product is
• in activities of high intensity (3 to 20 minutes):
– glucose is used AEROBICALLY to produce ATP
• in activities of moderate intensity (> 20 minutes):
– glucose oxidation is supplemented with
Sources of Energy During Physical
Activity
3. Fat
• initially during exercise blood [fatty acid] decreases
• after 20 minutes there is an increase in release of fatty
acids from stores
– due to actions of hormone
(adrenalin)
• endurance training produces adaptations that
– increased size and number of
is
muscles
– increased number of capillaries to supply oxygen
and nutrients to muscles
Sources of Energy During Physical
Activity
4. Protein
•
• contributes about 10% to energy expenditure both
during activity and at rest
Factors that influence protein use during activity:
• high dietary protein
use of protein as a fuel
• increased duration of activity
protein use as
a fuel
• increased intensity of activity
protein use as
fuel
• increased training (especially strength training)
use of protein as fuel
Influence of Intensity and Duration on
Fuel Use
increased duration
fatty acid oxidation
decreased intensity
glucose utilization
decreased duration
fatty acid oxidation
increased intensity
glucose utilization
Duration
Intensity
8 – 10 seconds
EXTREME
20 sec – 3 min
VERY HIGH
3 – 20 minutes
HIGH
> 20 minutes
MODERATE
Preferred Fuel Source
Effect of Diet on Physical Endurance
Maximum Endurance Time
fat and protein diet
normal mixed diet
high carbohydrate diet
Figure 14-3, page 473
Diet to Support Physical Activity
Water
• nutrient required in largest amounts by the body
• needs increase during physical activity
Body can lose water in four ways:
1. urine
2. feces
3. sweat
4. respiration
Diet to Support Physical Activity
Water and Temperature Regulation
• heat production increases 15-20x during exercise
compared to rest
• body cools itself by sweating
– 1 L of sweat dissipates about 600 kcal of heat
– prevents an increase in body temperature of about
10°C
•
of sweat cools the body
• blood is rerouted through capillary beds that lie just
beneath surface of skin to cool the blood
• endurance athletes can lose
of water or more
during each hour of activity
Diet to Support Physical Activity
Water and Temperature Regulation cont.
• in hot humid weather, need for water increases even
more
• dehydration not only decreases performance but can
cause dizziness, cardiac arrhythmias, muscle spasms,
delirium, and death
Hydration Schedule
2 hrs before
2 – 3 cups
15 min before
1 – 2 cups
every 15 min during ½ - 1 cup
after
at least 2 cups for each lb body
weight lost
Diet to Support Physical Activity
Electrolytes
• in addition to contributing to water loss, sweat also
results in loss of ELECTROLYTES
– electrically charged minerals
– sodium, potassium, chloride, and magnesium
• minerals are important for water balance
• losses normally replaced through regular
• for exercises lasting longer than one hour,
replacement of fluids with water AND electrolytes may
provide a slight performance advantage
• more important for athletes in competitions lasting 4+
hours with heavy sweating
Diet to Support Physical Activity
Energy Bars and Drinks
• during endurance activities lasting longer than one
hour, glycogen supplies risk
• maintaining blood glucose levels can prolong time to
exhaustion
Replenishing Energy DURING activity…
• glucose replacement (200 g) useful in activities lasting
longer than 2 hours
• sports drinks with 6 - 10% carbohydrates (50 - 100 kcal
per cup)
Diet to Support Physical Activity
Replenishing Energy AFTER activity…
• a high carbohydrate meal eaten within 15 minutes
accelerates rate of glycogen storage by 300%, called
“glycogen window”
Are energy bars or drinks necessary?
Diet to Support Physical Activity
Protein
• discuss previously in Lectures 8 and 9
• athletes have increased need for protein
– due to need to repair and build muscles after activity
– see Table 14-4 for recommended intakes
Too much protein?
• supplements may result in
– dehydration
– displacement of carbohydrates from diet, may result
in insufficient replenishment of glycogen stores
– kidney problems
Diet to Support Physical Activity
Vitamins and Minerals
• many vitamins and minerals are important for energy
metabolism
• supplements DO NOT enhance physical performance
•
impair performance
Iron
• physically active young women prone to iron deficiency
• multiple contributing factors
• supplementation should be based on blood tests, not
self-assessment