Biomechanics Exam #2 (Muscle Phy.)
Muscle fiber
individual cell with multiple nuclei
Sacromere
Fundamental unit within each muscle fiber
Contractile proteins [AKA active] (actin & myosin)
shorten the muscle & generate force
Noncontractile proteins [AKA structural]
provide supporting structure for contractile proteins
Structural proteins/skeletal muscles are important:
Collagen & elastin
structural support & elasticity to the muscle
Skeletal Muscle Types
Epimysium
tough outer covering that separates the muscle belly from other structures in the body
Perimysium
divides the muscle into fascicles & allows room for blood vessels & nerves to travel
Endomysium
Muscle Morphology
Fusiform & pennate are most common
Physiologic Cross-sectional Area (PCSA)
Pennation Angle
Generating Force: Passive Length-Tension
Curve
Muscles during Passive Length-Tension Curve
Passive Length-Tension Curve: Elastin
Generating Force: Active Length-Tension
Generating Force: Active Length-Tension (Sliding Filament Theory)
Sliding Filament Theory
Sliding Filament Theory (sarcomere)
The TOTAL length-tension relationship
Internal Torque-Joint Angle Curve
Internal Torque-Joint Angle Curve (muscle)
Force-Velocity Curve
Force Velocity Curve: 3 contractions
Concentric (FVC):
Eccentric(FVC):
Isometric(FVC):
Max effort concentric contraction (FVC):
Max effort eccentric contraction(FVC)
directly proportional to the velocity of muscle lengthening
Eccentric force production >> concentric
force production
Power equation
Work/time
Alpha Motor Neurons
motor unit
alpha motor neuron and all of the muscle fibers it
innervates
Motor unit recruitment
Henneman’s Size Principle
Small motor units
Large motor units
Fiber typing
Rate coding // Neural Drive
Choosing between recruitment & rate-coding: eccentric activation:
High force per crossbridge ==> less motor units required
Choosing between recruitment & rate-coding: Concentric activation
Lower force per crossbridge ==> more motor units required
Choosing between recruitment & rate-coding: Rapid task
Higher rate coding
Electromyography (for muscle recruitment)
The Law of Parsimony