Section 40: Muscle Mechanics Section 40: Muscle Mechanics 40-1 - - PowerPoint PPT Presentation

Section 40: Muscle Mechanics Section 40: Muscle Mechanics

40-1

40-2 From: Hamill

• Smallest MU

recruited at lowest stimulation frequency stimulation frequency

• As frequency of

stimulation of smallest MU increases, force of its contraction increases contraction increases

• As frequency of

stimulation continues to increase, but not before maximum contraction of smallest MU, another MU will be recruited

40-3 From: Brown

• Etc.

Recruitment proceeds from smallest fibers to largest (the size principle) (the size principle)

40-4 From: Hamill

40-5 From: Garner

Nigg & Herzog, 1998

40-6 From: Garner

Nordin & Frankel (1989)

Wave summation & tetanization

Critical frequency Critical frequency

40-7 From: Ju

Muscle Function

• Force – length relationship

40-8 From: Legh

40-9 From: Seeley

interference of overlapping thin myofilaments yields force drop deformation of thick myofilament

Frog skeletal muscle:

deformation of thick myofilament (and possible inhibited activation) yields rapid force drop

thick filament = 1.60 μm thin filament = 0.95 μm Z-disc (at end of thin) = 0.1 μm H-zone (middle of thick) = 0.2 μm zero-force sarc length = 3.6 μm peak-force sarc length = 2.0-2.2 μm drop-force sarc length = 1.7 μm zero-force sarc length = 1.3 μm 40-10 From: Garner

Nigg & Herzog, 1998