Transcript Training - Human Kinetics

C H A P T E R
8
Aerobic Fitness:
Stamina and Efficiency
Chapter 8
Objectives
This chapter will help you do the following:
• Understand the terms aerobic and anaerobic
• Determine the meaning of aerobic exercise and aerobic fitness
• Experience the concept of exercise intensity and the lactate
thresholds
• Differentiate between aerobic and anaerobic effort
• Understand the factors that influence aerobic fitness
• Define the effects of aerobic training
• Understand how systematic exercise (training) stimulates changes
in muscle fibers, respiration and oxygen transport, blood volume, the
heart and circulation, the endocrine system, fat metabolism and
body composition, and bones, ligaments, and tendons
• Understand the specificity of training and its importance for the
design of effective programs
Definitions
• Aerobic
In the presence of oxygen
• Anaerobic
In the absence oxygen
Aerobic Exercise
• Oxygen used to convert fat and CHO to ATP
• Low to moderate intensity
• Higher energy yield
• Slower energy yield
• “Fat burn” zone (use caution)
Anaerobic Exercise
• No oxygen necessary to convert CHO to ATP
• Moderate to high intensity
• Immediate, short bursts of exercise
• Lower energy yield
• Faster energy yield
• “Cardio zone”
• Symptoms
• Lactate versus hydrogen ions
Fat
• Involved in energy production
• Low-intensity and long-duration physical activity
– Train muscles to use fat more efficiently
– Performance implications
• ~130 ATP per fat molecule
• Stored in unlimited quantities in the human body
Carbohydrate
• Involved in energy production
• High-intensity and long-duration physical activity
• Preferred energy source during exercise and physical
activity
• 2 ATP molecules via anaerobic pathways
• 38 ATP molecules via aerobic pathways
• Stored in small quantities in the human body
Muscle Fiber Types
• Slow oxidative
Efficiently use oxygen
• Fast oxidative glycolytic
Faster contracting that can work with or without
oxygen
• Fast glycolytic
Short, intense contractions that use muscle glycogen
Figure 8.1 Lactate Thresholds
Levels of Exercise Intensity
Aerobic Fitness
• Maximal oxygen uptake and utilization
– VO2max or VO2peak
• Collect all expired gases
• Increase intensity
– Graded exercise test (GXT)
• Continue to volitional exhaustion
• Marker of fitness
– Use some caution here; genetics, age, training
– Newer, more appropriate measures of fitness
Absolute Versus Relative Fitness
• Absolute = L/min
– Larger people tend to have higher numbers.
– Can be used to assess performance in non-weightbearing activities.
• Relative = ml/kg/min
– Relative to body weight to eliminate influence of
body size.
– Can be used to assess performance in weightbearing activities.
Factors Influencing
Aerobic Fitness: Heredity
• Heredity
– 47 percent of variability in VO2peak
– At least 50 percent of variability in maximal power
– Maternal DNA
– Mitochondrial DNA = 60 percent of inherited
component
– LT1 very trainable—80 percent variance
(continued)
Factors Influencing
Aerobic Fitness: Heredity (continued)
• Respiratory
• Cardiovascular
• Heart size
• RBC and Hb
• Percent of SO and FOG fibers
• Mitochondria
• ALL MOM!
(continued)
Factors Influencing
Aerobic Fitness: Heredity (continued)
• Ability of muscle to be trained
– Improvements in fitness 5 percent in some, others
30 percent
• Physique
• Body composition
Factors Influencing
Aerobic Fitness: Training
• Improvements in VO2peak
– Most people can improve 20 to 25 percent.
– If you start training harder right now, 20 to 25
percent gain.
• Improved function
– Respiratory, cardiovascular, blood volume, and
changes in fiber type
(continued)
Factors Influencing
Aerobic Fitness: Training (continued)
• Increased fat utilization
– More mitochondria, more enzymes
– Reduced fat storage
– Reduced fat in blood
– Insulin more efficient
– Reduced risk of cancer
• Long duration = improved LT1
• High density = improved LT2
Factors Influencing
Aerobic Fitness: Sex
• No difference before puberty
• Males have 10 to 20 percent higher aerobic fitness
• ~10 percent reduced performance
– Why?
Hemoglobin
Muscle mass
Body fat
Factors Influencing
Aerobic Fitness: Age
• ~10 percent decline in sedentary people regardless
of starting point
• ~5 percent decline in active people
• ~2 percent decline in highly fit people
• Start at any age for improvement
Factors Influencing
Aerobic Fitness: Body Fat
• Calculated by body weight
– 4 L/min for a 100 kg person = 40 ml/kg/min
– 4 L/min for a 90 kg person = 44.4 ml/kg/min
• With training at 20 percent improvement
– 53 ml/kg/min
Factors Influencing
Aerobic Fitness: Activity
• Years of training can be lost in 12 weeks
• Three weeks bed rest = ~30 percent decline
• Good news: You’ll gain it back!
Relative Fitness
• Aerobic fitness is doing the best with what you have.
• Relative fitness is the percent of maximal aerobic
capacity you can maintain.
• More fit people can sustain a higher percentage of
max.
• You can define this by comparing LT1 or LT2 to
maximal aerobic capacity.
The closer either of these values are to max, the more
effective your training has been.
Terms
• Cardiovascular
• Cardiorespiratory
• Aerobic fitness
Aerobic fitness is the most appropriate term in
explaining the adaptations are occurring.
The target of aerobic training is muscle!
Training Effect on Muscle
• Training increases the concentration of aerobic
enzymes needed for the metabolic breakdown of
carbohydrate and fat to produce energy in the form of
ATP.
• Training increases the size and number (volume) of
mitochondria, which produce energy aerobically (with
oxygen).
• Training increases the ability of the muscle to use fat
as a source of energy.
(continued)
Training Effect on Muscle
(continued)
• Training increases the size of the fibers used.
• Long, slow training improves the oxidative
capabilities of slow oxidative fibers.
• High-intensity training enhances the
capabilities of fast oxidative glycolytic fibers.
• Training increases the storage of muscle
glycogen.
(continued)
Training Effect on Muscle
(continued)
• Training increases the supply of intramuscular fat.
• Training increases the myoglobin (a compound that
carries oxygen from the cell membrane to the
mitochondria) in muscle fibers.
• Training increases the number of capillaries serving
muscle fibers.
Respiratory Improvements
• No increase in lung size.
• Efficiency of breathing muscles improves.
• Reduces residual lung volume.
• Chronic lifetime physical activity reduces the increase
in residual lung volume with aging.
• Improved tidal volume (deeper breathing).
• In general: The respiratory system is overbuilt and is
not a limiting factor for aerobic fitness or performance.
Blood Volume
•
Blood volume may increase 5 to 10 percent.
– Normal blood volume is about 5 L.
– May increase to 5.5 or even 5.75 L.
•
Hemoglobin concentration initially decreases slightly,
but then will increase from about 45 to 50 percent to
up to 56+ percent.
•
These changes may account for up to 47 percent of
the improvements in VO2max.
Heart and Circulation
• Long-term aerobic training increases the volume of the
left ventricle (left ventricle hypertrophy).
– The heart muscle (myocardium) increases strength to maintain
pressure in the enlarged (fit) heart.
– This results in an increased stroke volume and a decreased
HR at rest.
• Heart muscle becomes trained (increases in aerobic
enzymes, fat oxidation, vascularity, and mitochondria).
• Better distribution of blood.
• Muscle capillary density increases.
Nervous System
• Efficiency of movement
• Improved economy
• Improved motor control in CNS
• Improved learning both during physical activity, after
physical activity, and in more physically fit individuals
Endocrine System
The system of glands whose secretions—hormones—are
distributed by circulation.
Hormonal responses to training:
•Adjustments in hormonal response
•Increased sensitivity to certain hormones
•Important metabolic adjustments:
– Catecholamines
– Cortisol
– Thyroxin
– Insulin and glucagon
– Non-insulin glucose uptake
Fat Metabolism
Aerobically trained muscles derive a higher percentage of
energy via fat metabolism at all intensities of exercise
from rest to high intensity.
• This conserves carbohydrate stores.
• Trained individuals mobilize fat better.
Other Effects of Training
• Reductions in stored adipose tissue
– Increased fat burning during all hours
– Increased metabolic rate even when not exercising
This is more true with higher intensity aerobic
training.
• Stronger bones, ligaments, and tendons
Specificity of Training
• The muscles used during any activity will adapt to that
specific stimulus.
• Other types of training may be necessary to avoid
boredom, injury, or muscle imbalances.
Concentrate training on the movements, muscle
fibers, metabolic pathways, supply, and support
systems you intend to use in an activity.
Summary
• Aerobic fitness is the ability to take in, transport, and use oxygen
in the body.
• LT1 is a good indicator of performance during long-duration races.
• LT2 is a good indicator of performance during events lasting less
than 30 minutes.
• Heredity, training, age, sex, and body fat all influence training
adaptations.
• Many systems in the body are affected by aerobic training, but
skeletal muscle is the primary target.
• Choose an activity you enjoy or want to improve for specific
adaptations.