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Athlete Specific Strength

Athlete Specific Strength. Chapter 3. Last Week. Bilateral difference in maximal unloaded knee extension velocity? CMJ vs. SJ?. Force Generation. Muscles - peripheral factors CNS - central factors. Peripheral Factors. Cross sectional area ( CSA ) relates to strength

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Athlete Specific Strength

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  1. Athlete Specific Strength Chapter 3

  2. Last Week Bilateral difference in maximal unloaded knee extension velocity? CMJ vs. SJ?

  3. Force Generation • Muscles - peripheral factors • CNS - central factors

  4. Peripheral Factors • Cross sectional area (CSA) relates to strength • Myofibrils (sarcomeres with actin and myosin) • The result is crossbridges • Crossbridge attachment means strength • Both quantity & # of available attachment sites • Parallel vs. series (strength vs. velocity)

  5. Figure 3.1

  6. Hypertrophy • Strength training increases size of the cell and number of filaments • Result is CSA • Hyperplasia is very small (<5%) • Sarcoplasmic hypertrophy no increase in strength (cell volumization) • Myofibrillar hypertrophy increases strength

  7. Figure 3.2

  8. Hypertrophy cont… • Increase in actin and myosin (protein synthesis) • Training must be done properly (bodybuilders vs. weightlifters) • Muscle protein catabolism with heavy lifting leads to supercompensation with muscle anabolism • Type I – reduces protein degradation • Type II – increase protein synthesis

  9. Body Weight (BW) • Muscle mass is about 50% of total BW • Strength to BW relationship is high in weightlifters and low in normals • Absolute vs. relative strength relationship is inverse

  10. Figure 3.5

  11. BW cont… • Sport picks you - not vice versa • Small athletes have relative strength • Large athletes have absolute strength • Gymnasts vs. football • Wrestlers reduce weight to increase relative strength

  12. Nutritional and Hormonal • Bioenergetics are required for protein synthesis • Amino acids build muscle • Protein requirements vary from 1-2-3g per kg • Anabolic hormones are testosterone and growth hormone (GH) and IGF-1 • Catabolic is cortisol • Male vs. female concentrations? • Strength training increases anabolics (females?)

  13. Genesis of Developmental Differences Between Male and Female Testosterone Boys Upper Body Strength Boys Testosterone Girls Upper Body Strength Girls Puberty 0 5 10 12 15 20 AGE Hormonal Levels

  14. Figure 3.8

  15. Hormonal Training • Heavy strength training increases GH • Hormonal changes are related to: • Muscle mass activated • Amount of work • Amount of rest • Nutrients must be ingested immediately following exercise for up-regulation • Testosterone, GH and IGF-1 increased

  16. Neural Factors • Muscle mass must be activated • Action potentials • Intermuscular coordination • Recruitment • Rate coding • Motor units – motor neuron and all fibers it innervates • Small vs. large motor units (20-2000) • Slow vs. fast – contractile properties

  17. Neural cont… • Slow twitch – low velocity, force and aerobic • Fast twitch – high velocity, force and anaerobic • Type I, IIa or IIx (may be 7-11) • All or none law – no gradation • Percentage varies by human being • http://www.blackwellpublishing.com/matthews/myosin.html

  18. Figure 3.9

  19. Recruitment • Size principle - small to large (threshold?) • In mixed muscle ST continue to fire even when recruiting FT • 100% recruitment is impossible (95%-99%)

  20. Figure 3.10

  21. Rate Coding • Firing rate increases with resistance requirements • Send more signals more quickly • Rate coding is important above 50-80% of max force • MU’s may synchronize for greater force • Psychological factors play a large role

  22. Rate Coding cont…

  23. Intermuscular • Skill requires coordination • Train movements not muscles • Electrical stim does not train the CNS • Bilateral deficit is CNS controlled • Isolated exercises are rehab or ameliorative • Machines vs. free weights?

  24. Taxonomy of Strength • Max slow force is similar to isometric • Eccentric strength is greatest • Force and velocity are inversely related • Maximorum force requires heavy resistance • RFD does not correlate with force max • SSC force is not increased with heavy strength training

  25. Next Class • Lab tonight on fast twitch fiber percentage and CSA (pg. 5 syllabus) • Homework - graphs and explanation • Homework - Table showing comparison of absolute strength vs. relative strength vs. strength per unit of CSA. • Homework – read the Thorstensson fatiguability and fiber comp article • Next week Chapter 4 and lab

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