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KINE 3301
Biomechanics of Human Movement
Muscle Mechanics
Chapter 17
Instrumentation
used to study
muscle forcevelocity and
force-length
relationship.
Length changes to an individual sarcomere during an
isometric contraction. The sarcomere directly
underneath the end-plate will be the first to develop
tension which causes the sarcomeres to the right and
left to lengthen.
Sarcomere Force – Length Relationship
Force – Length in Normal Joint Range of Motion
Force – Velocity Relationship
(P + a) V = b (Po – P)
Efficiency of Eccentric & Concentric Exericse
Bernard Abbott, Brenda Bigland-Ritchie, JJ Woods
Loiselle D S et al. J Appl Physiol 2010;108:1465-1471
©2010 by American Physiological Society
DOMS – Damage to Muscle Following Eccentric Contractions
Stretch – Shorten Cycle
• The stretch – shorten cycle is defined as an eccentric
contraction followed by an immediate concentric
contraction.
• Additional work is performed during the concentric phase of
a stretch – shorten cycle. This extra work is attributed to:
1. Stored elastic energy (tendon, cross-bridge, and titin).
2. Eccentric phase elicits a stretch reflex.
3. Eccentric phase pre-loads the muscle, so the concentric
phase begins at a higher force.
4. Two joint muscles (rectus femoris, gastrocnemius) transfers
energy and allows the muscle to work at a lower velocity and
a higher force.
Stretch – Shorten Cycle
The area under the force –
length curve is equal to the
work done.
Effects of Increasing the velocity of stretch on the
concentric work done for the concentric phase.
© 1974 by American Physiological Society
Adapted from: Cavagna and Citterio. J Appl Physiol 1974; 239:1-14.
Three Component Muscle Model
Describes the mechanical
response of muscle.
• Contractile Component (CC)
models active cross-bridges.
• Dashpot models muscle
viscosity.
• Series Elastic Component (SEC)
models elastic structures in
series (tendon, passive crossbridges, titin). The SEC
explains extra work done in
stretch-shorten and EMD.
• Parallel Elastic Component
(PEC) models passive elastic
structures (passive crossbridges, connective tissue:
endomysium, perimysium,
epimysium, titin, desmin.