Download Muscle Metabolic Adaptation to Exercise

Muscle Metabolic Adaptation to Exercise
OBJECTIVES
Skeletal muscle metabolic adaptations to exercise:
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Classification of muscle fibers
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Distribution and recruitment of different muscle fibers
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Muscle metabolic adaptations to exercise (acute and chronic )
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Recovery from exercise-EPOC
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Health Advantages of Regular Exercise
MUSCULAR ADAPTATIONS TO EXERCISE
The main tissues of the body that are involved in catabolism during and following exercise are:
1. Skeletal muscle
2. The liver
3. Adipose tissue
So the cells of skeletal muscle, liver and adipose tissue are very different in sub cellular organization,
organelle content, appearance and function.
Metabolic connection between skeletal muscles, liver and adipose tissue
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Exercise increase glucose catabolism in sk.m and production of lactate.
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Cori cycle : lactate release from sk.m, uptake by liver and conversion to glucose by
gluconeogenesis and release back into the blood for uptake by muscle is called Cori cycle.
•
Alanine cycle : Alanine release from sk.m into circulation for uptake by the liver and conversion
to glucose.
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Both Cori cycle and Alanine cycle are more operative during exercise.
ACUTE AND CHRONIC ADAPTATIONS
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The immediate (acute) metabolic adaptations that occur in skeletal muscles are the classic
example of the:
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Responsiveness of sk.m to metabolic stress.
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Acute changes that occur in skeletal muscles metabolism to meet the muscle need to increase the
regeneration of ATP.
CHRONIC ADAPTATIONS
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Apart from acute changes in muscle metabolism, the skeletal muscles can under go long term
(chronic) structural and functional changes when exposed to exercise for weeks or months.
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Chronic adoptions that improve the muscle abilities to regenerate ATP during exercise.
SKELETAL MUSCLE FIBERS
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Skeletal muscle fibers are not alike in composition and function. so not all muscle fibers are
metabolically alike or adapted to perform the same task.
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These fibers vary in their content of myoglobin i.e. the red color protein that bind oxygen in
muscle fibers.
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Those that have high myoglobin content are called red muscle fiber and appear darker. They
contain more mitochondria and are supplied by more blood capillaries.
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Those that have low content of myoglobin are called white muscle fiber and appear lighter.
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Skeletal muscle fibers also contract and relax at different speeds.
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They also vary in metabolic reactions by which they generate ATP and how quickly they fatigue.
CLASSIFICATION OF MUSCLE FIBERS
Skeletal muscle fibers are classified into three types on the basis of their structure and function:
1. Slow oxidative fiber (SO)
2. Fast oxidative glycolitic fiber (FOG)
3. Fast glycolitic fiber (FG)
SLOW OXIDATIVE FIBER (SO)
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They are smallest in diameter and least powerful type of muscle fiber.
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They appear dark red because they contain large amounts of myoglobin and many blood
capillaries.
SO fibers
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They generate ATP mainly by aerobic cellular respiration because they have many large
mitochondria and are called oxidative fibers.
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These fibers are slow because the ATPase in the myosin heads hydrolyzes ATP relatively slowly
and the contraction cycle proceeds at a slower speed.
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Location: Postural muscle such as those of neck , back and legs.
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Function: maintaining posture and aerobic endurance activities (e.g. running a marathon).
FAST
GLYCOLYTIC
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They are intermediate in diameter.
OXIDATIVE
FIBER (FOG)
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They contain large amount of myoglobin and many blood capillaries and thus they
have dark red appearance.
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They generate ATP by aerobic cellular respiration which gives them higher
resistance to fatigue.
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They also have high intra-cellular glycogen level thus they also generate ATP by
anaerobic glycolysis.
FOG FIBERS
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They are called fast fibers because ATPase in a myosin head hydrolyzes ATP faster than the SO
fiber thus their speed of contraction is faster.
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They reach the peak tension more quickly but they have brief duration of activity, less than 100
milliseconds.
FG Fibers
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Functions: weight lifting or throwing a ball.
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The FG fiber of weight lifter maybe 50% larger than those of an endurance athlete.
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The increase muscle protein.
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The overall muscle enlargement is due to hypertrophy .
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in size is due to increased synthesis of
DISTRIBUTION & RECRUITMENT OF DIFFERENT FIBERS
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Most skeletal muscle contain a mixture of all three types of fibers , but their proportion vary with
the:
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Typical action of the muscle
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Person’s training regimen
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Genetic factors.
METABOLIC PATHWAY
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The main pathway that stimulate the regeneration of ATP are:
1. Creatinine phosphate
2. Glycolysis
3. Mitochondrial respiration
MUSCLE METABOLISM
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It generates ATP by different mechanism over the duration of a period of exercise.
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Muscle fiber have three sources for ATP production:
1. Creatinine phosphate
2. Anaerobic cellular respiration (glycolysis).
3. Aerobic cellular respiration (mitochondria)
MUSCLE
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Muscle fatigue results from:
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ATP and Ach depletion
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Loss of membrane excitability
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Accumulation of lactic acid
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CNS mechanisms.
FATIGUE
MUSCLE METABOLIC ADAPTATION TO EXERCISE
Various types of exercise can induce changes in fibers in a skeletal muscle:
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Endurance type (aerobic): such as running or swimming, causes a gradual transformation of
some FO fibers into FOG fibers.
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The transformed fibers show slight increase in diameter, number of mitochondria, blood supply
and strength.
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This also results in CVS and respiratory change.
Metabolic Adaptation to Exercise
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The exercise that requires great strength for short periods produce an increase in the size and
strength of FG fibers.
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The increase in size is due to increased synthesis of muscle proteins.
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The overall result is muscle enlargement (hypertrophy).
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Acute metabolic adaptations.
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Chronic metabolic adaptations.
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Acute metabolic adaptations: acute changes that occur in muscle metabolism to meet the muscle
needs to increase the regeneration of ATP.
ACUTE ADAPTATIONS
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It includes:
1. incremental exercise
2. Steady state exercise
3. Intense exercise

Incremental exercise: Exercise performed at intensities that progressively increases over time.

The pathways involved in incremental exercise are:

Creatine phosphate

Glycogenolysis and glycolysis

Steady state exercise: this is attained when all the ATP demand from muscle contractions is met
by oxidative phosphorylation.

During steady state exercise metabolic pathways involved:
1. Glycogenolysis and glycolysis
2. Lipolysis and beta-oxidation
3. Amino acid oxidation

Intense exercise: it can be defined as any intensity that exceeds ones capability to maintain
steady state condition. it includes:

Sprint running, cycling, swimming, skating and weight lifting.

ATP regeneration must be met by:
1. Creatine phosphate
2. Glycolysis terminating in the production of lactate and the development of acidosis.
CHRONIC METABOLIC ADAPTATIONS
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Chronic metabolic adaptation that improve the muscle abilities to regenerate ATP during
exercise.
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The skeletal muscle can undergo long-term (chronic) structural and functional changes when
exposed to exercise performed repeatedly over several weeks or months
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Chronic muscle adaptations are specific to the type of exercise performed.
Chronic adaptations
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Metabolic pathway involved:
1. Mitochondrial respiration
2. Glycolysis
3. Creatine phosphate
RECOVERY AFTER EXERCISE
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During recovery after exercise: during this phase both catabolic and anabolic reactions occur to
replenish the energy stores used during exercise and removal of waste products.
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During recovery ability of skeletal muscle to replenish energy and substrate stores as rapidly as
possible, prepares the muscle to better tolerate the successive bouts of exercise
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