Chapter Five: Adaptions to Anaerobic Training Programs Flashcards
Neural Adaptations: Occur via
- Maximization of muscular strength and power
- Augmented neural drive
- Increased agonist muscle recruitment
- Improved neuronal firing rates
- Greater synchronization
- Timing of neural discharge
- Reduction in inhibitory mechanisms
Central Adaptations
- Motor cortex activity increases
- Adaptations to the descending cortico spinal tracts in the spinal cord
- Increased recruitment of fast twitch motor units
Adaptations to Motor Units
- Improved summation of overlapping action potentials is expressed as augmented contractile strength
Gains in maximal strength and power of agonist muscles are generally associated with
- Increase in recruitment
- Increased rate of firing
- Greater synchronization of neural discharge
- A combination of all these factors
Size Principle
- Motor units are required from low to high threshold motor units
- Low recruitment threshold and force production to high recruitment threshold and production
- Typically small type one fibers first, large type I and small type II second, large type II last
Selective Recruitment
- Athletes can develop the ability to perform selective recruitment or the ability to preferentially recruit fast twitch motor units
- Typically takes place in athletes who require quick ballistic movements and due not have enough time to recruit the entire motor unit pool including Olympic weight lifting, plyometrics, speed, power, and agility
Adaptations to Motor Units: Smaller motor units vs Larger motor units
- Smaller motor units rely more on an increased firing rate to enhance force production
- Larger muscles depend more on recruitment to enhance force production
Adaptations to Motor Units: Synchronization
- Improved synchronization of motor units with training
- More critical to the timing of force production and less critical to the overall level of force developed.
Neuromuscular Junction: Anaerobic training appears to induce beneficial morphological changes to the NMJ including
- Increased NMJ total area
- More dispersed irregular shaped synapses
- Greater total length of nerve terminal branching
- Greater endplate perimeter length and area
- Greater dispersion of acetylcholine receptors within the end plate region
Neuromuscular Reflex Potentiation
- Increased response of the reflex
- Enhanced magnitude and rate of force development
- Increased potentiation of the reflex in trained individuals
Anaerobic Training and Electromyography Studies
- EMG studies show increases in neuromuscular activity as training begins and increased neural drive is the predominant factor with training
- As hypertrophy begins to increase this takes over as the primary training adaptation and EMG dats decreases
- If new training stimuli are introduced neural stimuli increases as shown via EMG studies
EMG: Cross Education
- Increased strength and neural activity in a muscle contralateral to a muscle being trained
EMG: Bilateral Deficit
- The force produced when both limbs contract together is lower than the force produced in one limb when contracting unilaterally
EMG: Bilateral Facilitation
- An increase in voluntary activation of the agonist muscle groups occurs
EMG: Antagonist Muscles
- EMG activity of antagonist muscles changes with contraction of agonist muscles
- Co-contraction of agonist and antagonist muscles serves as a protective mechanism to protect the joint
- Antagonist muscle force can lower with resistance training in individuals that need less antagonist muscle force to facilitate agonist muscle firing.
- Antagonist muscle firing can also increase in individuals who need increased stability in the joint.
Muscle Adaptations: Hypertrophy
- Enlargement of the muscle fiber cross sectional area
- Increase in net accretion of the contractile proteins actin and myosin within the myofibril within a muscle fiber
- Increased synthesis of titin and nebulin
- Increased protein synthesis and muscle cross sectional area.
Muscle Adaptations: Muscle Building Pathways
- mTOR
- AMPK
- MAPK
- Akt/mTOR pathway are particularly important for regulating muscle growth
Muscle Adaptations: General Pathway Signals
- Increase in protein and muscle building pathways
- Down regulation of inhibitory factors
Muscle Adaptations: Exercise Induced Muscle Damage
- Exercise induced muscle damage and the subsequent remodeling process play a roll in muscle growth
Muscle Adaptations: The steps of protein synthesis
- Water uptake
- Non-contractile protein synthesis
- Contractile protein synthesis
- Simultaneous reduction in protein degradation acts to maintain the size of fibers by reducing net protein loss
Muscle Adaptations: Hypertrophy in response to training
- Hypertrophy does not begin for around 1 month post initiation of resistance training. Early strength gains are neuromuscular adaption.
- Hypertrophy begins around one month/16 workouts into a program and is rapid at first.
- Hypertrophy then tapers off over time and slows.
Muscle Adaptations: Hyperplasia
- An increase in the number of muscle fibers
- Concept is not fully accepted is a mechanism of strength building. It is contested whether it takes place in humans or not.
Fiber Size Changes
- Muscle fiber size change follows the size principle
- Type II muscle fibers manifest greater increases in size than Type I fibers
- It has been hypothesized that individuals possessing higher proportions of type II fibers have a greater predisposition to muscle hypertrophy due to the increased capacity of type II fibers.
Fiber Type Transitions In Order
- IIx, IIax, IIa, IIac, IIc, Ic, and I
- With concomitant myosin heavy chain expression
Fiber Type Transitions: Training and Activation of High Threshold Motor Units Causes
- Transition from type IIx to type IIa
- IIx muscle fibers transition to slightly more oxidative causing their transition to IIa
- Changes in type IIx to type IIa do not impact the rate of change in CSA
Muscle Adaptations: Type I to Type II Muscle Fiber Transitions
- Type I to Type II muscle fiber transitions do not occur.
Structural and Architectural Changes
- Angle of pennation increases with resistance training
- Fascicle length is larger with resistance training
Other Muscular Adaptations
- Increased myfibrillar volume
- Increased Cytoplasmic density
- Sarcoplasmic reticulum and and T-tubule density
- Increased sodium-potassium ATPase activity
- Mitochondrial density in relation to increases in CSA occur disproportionately. CSA increases faster than mitochondrial density.
- Improved hydrogen buffering capacity causing improvements in ability to tolerate acid buildup.
- Increased storage capacity of ATP and Creatine Phosphate
Connective Tissue Adaptions: Bone
- Mechanical loading creates tension on bones causing osteoblast activity to lay own new bone
- New bone formation occurs predominantly in on the periosteum
Connective Tissue Adaptions: Cortical Bone
- Dense and forms a compact outer shell
Connective Tissue Adaptions: Trabecular Bone
- Spongy soft inner layer
Connective Tissue Adaptions: Bone Marrow
- Adipose tissue inside a bone
- Blood supply to the bone located here
Connective Tissue Adaptions: Response to Stress
- Trabecular bone more responsive to stress due to its soft flexibility.
Connective Tissue Adaptions: Minimal Essential Strain (MES)
- The minimal amount of strain required to stimulate new bone formation