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Biomechanics

CH Factors affecting force production

QuestionAnswer
Can we change fiber types? Only happens from type IIX -> IIA Not well with type IIX -> I
What does a neutralizer do? concept! to prevent unwanted movement
Hypertrophy increase in the # of myofibrils & myofilaments (myofiber diameter increases = more cross bridges)
Hyperplasia increase # of fibers
Series optimal force velocity of shortening & range of motion
Parallel Optimal for force production
How can you get stronger without hypertrophy? improving nervous system to regulate force
How do you regulate force? release more calcium = more cross bridges
Rate coding increase frequency stimulation
Spatial recruitment increase # of active motor units (MU's)
Order of recruitment type I -> IIA -> IIX
Henneman's size principle Motor units are recruited in order of their size from small to large
order of de-recruitment type IIX -> IIA -> I
Small muscles contribution of rate coding & spacial recruitment all MU's recruited @ aprox. 50% max force; there after rate coding is responsible for force increase up to max
Large muscles contribution of rate coding & spacial recruitment all MU's recruited @ appprox. 80% max force
velocity of shortening when resistance (force) is negligible, muscle contracts with maximal velocity
what is power? P = F V
isometric length-tension curve generated by maximally stimulating a skeletal muscle at a variety of discrete lengths and measuring the tension generated at each length
sarcomere length of 3.65 μm or greater has an active force of what? 0- NO FORCE
what happens to the force of a sarcomere length decreases to 2.25 μm to 2.00 μm ? increases
Length-tension relationship tension generated in skeletal muscle is a direct function of the degree of overlap between actin and myosin filament
Descending limb As the muscle is allowed to shorten, overlap between actin and myosin is possible; thus, cross-bridge formation and force production increases as sarcomere length decrease
Plateau Region sarcomere length shortening over the 2.0-2.2μm range results in greater filament overlap, it does not result in increased force production because no additional cross-bridges are made due to the central “bare” region of the thick filament
Po the maximum tetanic tension generated by muscle in this plateau region
Ascending limb 2.0 μm - decreased force actin filaments from one side of the sarcomere exist in a “double overlap” state as they overlap both with the opposite actin filament and the myosin filament
What is PNF? Proprioception Neuromuscular facilitation
Where does passive tension come from? Tinin
Stretch-shortening phenomenon human movement may be enhanced if the muscles primarily responsible for the movement are actively stretched prior to contractily concentrically -eccentric contraction will enhance the next concentric phase
mechanism storage and release of elastic strain energy
Coupling time delay between concentric and eccentric
Parallel fiber fibers are roughly parallel (II) to longitudinal axis
Pennate fiber short fibers attach at an angle (//) to one or more tendons with the muscle
Which fiber is stronger? Pennate or Parallel Pennate fiber because they are stacked on top of each other and the pull is diagonal. Sarcomeme is parallel with each other
What is the difference between Physiological cross-sectional area (PCSA) and a Anatomical cross-sectional area (CSA) PSCA - perpendicular cut CSA- straight across cut
Electromechanical delay Time between arrival of a neural stimulus and tension development by the muscle
Temperature -affects force-velocity relationship -affects calcium dynamics (hot - improves calcium release b/c there is less Nero-resistance
Two joint muscle advantages -2 actions for the price of 1 muscle -less shortening velocity -more favorable position on both force/velovity & force/legth
Two joint muscle disadvantages -active insufficiency -passive insufficiency
Active insufficiency unable to actively shorten to produce a full rage of motion at each joint crossed simultaneously
Passive insufficiency unable to lengthen to produce a full range of motion at each joint crossed simultaneously
Created by: rmart11
 

 



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