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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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Last week
Last Week

Bilateral difference in maximal unloaded knee extension velocity?

CMJ vs. SJ?


Force generation
Force Generation

  • Muscles - peripheral factors

  • CNS - central factors


Peripheral factors
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)



Hypertrophy
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



Hypertrophy cont
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


Body weight bw
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



Bw cont
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


Nutritional and hormonal
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?)


Hormonal levels

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



Hormonal training
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


Neural factors
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


Neural cont
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



Recruitment
Recruitment

  • Size principle - small to large (threshold?)

  • In mixed muscle ST continue to fire even when recruiting FT

  • 100% recruitment is impossible (95%-99%)



Rate coding
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



Intermuscular
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?


Taxonomy of strength
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


Next class
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