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Biomechanics
CH Factors affecting force production
Question | Answer |
---|---|
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 |