Physiology Year 3 - Physiological adaptations to resistance training PDF

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How the body adapts to resistance training from a physiological view...

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Physiology Year 3 Week 8 Physiological adaptations to resistance training Aims ● Understand influence of resistance training on muscle strength ● Highlight contribution of neuromuscular adaptations

Resistance training is a form of PA that is designed to improve muscular fitness by exercising a muscle or muscle group against an external resistance

Strength gain ● Neural ● Architectural ● Cross sectional area

Muscle type ● Circular ● Convergent ● Multipennate ● Parallel

Neural adaptations to resistance training ● Surface electromyography - Agonist (muscle being activated) - Antagonist (muscle stabilizing, less activation) - Torque (force output of muscle)

Motor learning occurs much quicker than isometric strength gains - Learning the muscles to coordinate the activity increases strength more so than isometric strength of the muscles - Cross sectional area increases at much slower rate than strength and EMG activation - Increased strength with standing tricep extension did not translate to supine lying tricep extension, we gain lots of strength because of learning and neural drive Changes in muscle architecture - An increase in pennation angle increases the number of fibres attaching to the aponeurosis. This allows more muscle fibres in parallel to attach to aponeurosis, allowing force to be transferred to the tendon - Pennation angle and fibre size both increase with RT resulting in greater force

production Hypertrophy adaptations to resistance training - ‘Gold standard’ to measure this is MRI scanning - Anatomical CSA is a fair determinant of strength (not directly), about 60% - Fibre cross sectional area increases with resistance training (test with staining muscle fibres in labs), limitation is what angle you cut the fibres at, as the increase could be due to the pennation angle against the aponeurosis - Not just muscle size that changes with RT, but the pennation angle of the fibres. As such it is a combination of single …. - Physiological cross sectional area: PCSA = Muscle volume x cos / Fibre length x muscle density - Anatomical CSA does not take into account fibre length and muscle density, PSCA is more accurate as it considers these factors - Single fibre CSA increases, preferential type 2 hypertrophy in resistance training specific to resistance training (type 2) Is there a difference in adaptation between eccentric and concentric contractions? ECC = greater force CON = higher energy cost ECC = higher EMG activity No clear differences in literature hypertrophy between ECC and CON ECC results in a markedly greater increase in fascicle length while CON promotes greater changes in pennation angle Mechanisms of muscle hypertrophy ● Mechanical stress - sensed by proteins - unlock DNA and copy into mRNA (transcription) - mRNA carries a message to create chains of amino acids - … ● Time course of these adaptations: mRNA - rapidly after RT, changes in total protein is small - happens incrementally over time hence why it takes weeks and months for muscles to grow ● Net protein balance of MPS and MPB Always occurring simultaneously. Net positive protein balance requires MPS to outbalance MPB for a sustained period ● Fractional synthetic rate is measure of MPS and MPB MPS lasts for 48hrs after RT Molecular drivers of this are: mTOR from mechanical stress Molecular mechanisms are very important to overall hypertrophy of muscles - specific proteins to type of stress you put on muscle ● Comparison of protein doses on WBPS after RT in strength athletes and sedet ry controls Protein ingestion stimulates protein synthesis after RT and protein ….. ● Adding leucine to a suboptimal dose of whey is as effective as 25g whey at stimulating fed rates of MPS; however 25g of whey is better suited to increase resistance exercise-

induced muscular anabolism Outcomes ● RT increases muscle strength rapidly ● Neuromuscular adaptations to strength gains characterise early increase in training weight ● Muscular hypertrophy is delayed but underpins much of the true increase in muscle force producing capacity ● Muscle architectural……...