Bioenergetics of Exercise and Training
Terminology
o Bioenergetics
n
The flow of energy in a biological system
primarily related to the conversion of food to energy sources
o Metabolism
n
The sum of all catabolic/exergonic and
anabolic/endergonic reactions in the biological system
The Energy Systems
o Phosphogen
System
n
ATP and PC provide energy for short-term, high
intensity activities; important at start of exercise
o Glycolysis
n
Fast process
p Glucose→
→ → →Pyruvate →Lactate
n
Slow process
p Glucose
→ → → →Pyruvate →Mitochondria
The Energy Systems
o Oxidative
System
n
Breakdown of CHO and Fats via oxygen
n
Provides energy at rest and during low intensity
exercise
Event Duration Effect on Energy System Used
Rankings of Rate and Capacity of ATP Production
Substrate Depletion and Repletion
o Phosphogens
n
Depletion Aspects:
p Muscle
ATP does not ↓ by more than
60% of initial values regardless of intensity
n
This energy source is spared as a result of
contributions from CP and other sources
p Creatine
phosphate can ↓ 50-70%
during 5-30 sec of high intensity exercise, and can go almost to 0 at
exhaustion
Substrate Depletion and Repletion
o Phosphogens
n
Repletion Aspects:
p ATP
and CP will be replenished shortly after exercise
n
ATP - within 3-5 minutes
n
CP - within 8 minutes
p Repletion
occurs primarily from glycolysis and aerobic metabolism
Substrate Depletion and Repletion
o Training
aspects affecting the phosphogens
n
Training has shown that with a larger muscle
mass, there is a greater phosphagen content
n
Training has not shown ↑ phosphogen content at rest without substantial ↑ in fiber size
n
Changes in phosphogen content occur primarily in
fast-twitch muscle fibers
Substrate Depletion and Repletion
o
Glycogen
n
Depletion
Aspects:
p Rate of depletion is related to exercise intensity
p Muscle glycogen is more important energy source than
liver
p Relative importance of liver glycogen ↑ with exercise duration
p Above 60% of VO2 max, glycogen becomes primary fuel
p Resistance training can cause up to 20-60% glycogen depletion with
greater # of sets and repetitions
Substrate Depletion and Repletion
o Glycogen
n
Repletion Aspects:
p Muscle
glycogen repletion is dependent on post-exercise CHO ingestion
n
This becomes optimal with ingestion of 0.7-3.0
grams of CHO per kilogram of body weight every 2 hours following exercise
p Muscle
glycogen can be replenished in 24 hours, in most instances
p It
takes longer to replenish muscle glycogen content following eccentric work due
to muscle damage potential
Bioenergetic Limiting Factors
o ATP
and creatine phosphate
o Muscle
glycogen
o Liver
glycogen
o Fat
stores
o Lower
pH
Bioenergetic Limiting Factor Rankings (1=least probable; 5 =most probable)
Oxygen Uptake Patterns During Exercise
Possible Factors Increasing Excess Postexercise O2
o Resynthesis
of ATP and CP stores
o Resynthesis
of glycogen from lactate (20% of lactate accumulation)
o O2
resaturation of tissue water, venous blood, skeletal muscle, myoglobin
o Redistribution
of ions within body compartments
Possible Factors Increasing Excess Postexercise O2
o Repair
of damaged tissue
o Additional
cardiorespiratory work
n
i.e. elevated HR and BP
o Residual
effects of hormone release and accumulation
n
i.e. adrenaline (epinephrine)
o Increased
body temperature
Contributions of Anaerobic and Aerobic
Mechanisms in Exercise
Metabolic Specificity of Training
o Appropriate
exercise intensities and rest intervals can allow selective training of energy
systems
o Interval
training
n
Based upon concept that more work can be
performed at higher intensity with same or less fatigue than in continuous
training
Metabolic Specificity of Training
o
Combination
Training
n
Anaerobic +
Aerobic training
p Theory –
improve recovery from anaerobic work since recovery is dependent on aerobic
mechanisms
n
However, aerobic
training has been shown to ↓ anaerobic
energy production capabilities
o Also:
1. reduces gain in muscle
girth
2. reduces max strength
attained
3. reduces speed and power
performance
o Also:
- Anaerobic training can
improve aerobic power and performance; also recovery
Training Specific Energy Systems (via Interval Training)