Test 6 - Adaptations to Resistance Training

Hypertrophy

increase in muscle SIZE

Atrophy

Decrease in muscle SIZE

Neural Control of Strength Gains

• recruitment of motor units

• increased frequency of discharge from the alpha-motor neuron

• Autogenic inhibition (GTOs)

• Reduction in coactivation of agonist and antagonist muscles

Recruitment of motor units

• increased number of motor units recruited from increased neural drive

• Synchronicity of motor unit recruitment is improved - motor action potential sync

In first few weeks of resistance training, what type of gains occur?

neural gains: better muscle coordination, stability, control

Recruiting more motor units means

increase of muscle force production - strength

Resistance Training affect on muscles:

Type I & II:

• produce more force

• more action neural gains protentional

• more frequent nerve impulses

GTO

• Golgi Tendon Organ

• Measures amount of tension being applied through muscle

Transient Hypertrophy

temporary/short-term

Chronic Hypertrophy

increase in muscle size after long-term resistance training

Net increase in muscle protein synthesis

• more myofibrils

• more actin & myosin myofilaments

• more sarcoplasm

• more connective tissue

Fiber Hypertrophy

• net increase in muscle protein synthesis

• facilitated by post-exercise nutrition

Testosterone plays a role in

promoting muscle growth

Is there a specific workout to induce fiber hypertrophy?

eccentric training

Fiber Hyperplasia

• muscle fibers can split in half w/ intense weight training (cat research)

• each half then increases to the size of the parent fiber

• conflicting study results may be due to differences in the training load or mode

Early gains in strength are influenced by:

neural factors

Long-term strength increases are influenced by:

muscle hypertrophy

Neural adaptations always accompany

strength gains

Neural mechanisms leading to strength gains include

• increased frequency of stimulation

• recruiting more motor units

• more synchronous recruitment of muscle fibers

• decreased coactivation of agonist/antagonist

Chronic muscle hypertrophy reflects

actual structural changes in the muscle

Immobilization

• decreased rate of protein synthesis

• decreased strength (3-4% per day)

• decreased cross-sectional area

• decreased neuromuscular activity

• affects both type I and type II fibers, with greater effect in type I

• muscles can recover when activity is resumed

Cessation of Training

• decreased strength

• little change in fiber cross-sectional area

• maintenance training is important to prevent strength losses

Fiber type alterations with resistance training

• results from cross-innervation or chronic stimulation

• type IIx to IIa

• type I to IIa

Acute muscle soreness

• results from accumulation of end products of exercise in muscles/edema

• usually disappears within minutes or hours after exercise

Delayed-Onset Muscle Soreness (DOMS)

• soreness felt 12-48 hours after strenuous exercise

• Armstrong’s model

• May be caused by inflammatory reaction inside damaged muscles

Armstrong’s model

• structural damage

• impaired calcium homeostasis leading to necrosis

• accumulation of irritants

• increased macrophage activity

Exercise-induced muscle cramps

• decreases in Golgi tendon organ

• Increases in muscle spindle activity

Loss of strength is due to:

• physical disruption in muscle

• failure within excitation-contraction process

• loss of contractile proteins

Reducing Muscle Soreness

• reduce the eccentric component of muscle action during early training

• start at low intensity then gradually increase it

• begin with high-intensity, exhaustive bout eccentric-action exercise

Muscle Soreness Key points

• acute muscle soreness occurs late in exercise bout and during immediate recovery period

• DOMS occurs 12-48 hours after exercise

• occurs mostly eccentric muscle action

• causes include structural damage to muscle cells and inflammatory reactions within the muscles

• muscle soreness may be an important part of maximizing the resistance training response.