Tag Archives: Isometric exercise

MUSCLE CONTRACTION-MECHANICS-BIOMECHANICS NOTES

Muscles Are Organized Into Motor Units

  • When a single nerve enters a muscle it splits and makes neuromuscular junctions (NMJs) with several muscle cells
  • A nerve and the muscle cells it makes NMJs with is called a motor unit
  • When the nerve fires the whole motor unit is stimulated and the muscle cells contract together
  • Muscles with large motor units have coarse movements
  • Muscles with small motor units give fine, graded movements
  • This is a small motor unit with only 3 muscle fibersTwo Basic Types of Contraction Are Isotonic and Isometric
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INTRODUCTION TO BIOMECHANICS (BASIC DEFINITIONS) MUST KNOW

Definitions

  • Bio mechanics – application of the principles of mechanics / physics to biological organisms
  • muscle action vs. function
    • action – motions produced by a muscle’s shortening; described in reference to axes and planes of body
      • – determined by architecture of joint and position of muscle around it
      • – pure mechanics which can be inferred
    • function – how the organism chooses to use a muscle
      • – can involve positive, negative or non- work (see below)
  • agonists (Gr., contestant)– muscles with an identical action; usually restricted to single axis or plane of reference
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