Download characteristic (so)

Behavioral Properties of the
Musculotendinous Unit
1) extensibility: ability to be
Behavioral Properties of the
Musculotendinous Unit
2) elasticity: ability to return to
parallel elastic component series elastic component -
Behavioral Properties of the
Musculotendinous Unit
3) irritability: ability to
4) ability to develop tension: (the
contractile component of muscle
function)
Behavioral Properties of the
Musculotendinous Unit
From a mechanical
perspective, the
musculotendinous unit
behaves as a
contractile component
(muscle fibers) in
parallel with one
elastic component
(muscle membranes)
and in series with
another elastic
component (tendons).
Parallel Elastic
Component
Series Elastic
Component
Contractile
Component
Structural Organization of
Skeletal Muscle
How are muscle fibers organized?
• parallel fiber arrangement:
•pennate fiber arrangement: short fibers
attach to
Parallel vs
pennate
Parallel vs Pennate
Structural Organization of
Skeletal Muscle
Comparison of fiber architecture
•Effective force to tendon:
•parallel __ pennate
•fibers per unit volume:
•parallel __ pennate
•joint ROM:
•parallel __ pennate
Structural Organization of
Skeletal Muscle
What is a motor unit?
• single motor neuron and all fibers it
innervates
• considered the functional unit of the
neuromuscular system
• innervation ratio (# of fibers per motor
neuron) dictates fine vs gross control
Structural Organization of Skeletal
Muscle
Structural Organization of
Skeletal Muscle
ST
Twitch Tension
Fast twitch fibers
both reach peak
tension and relax
more quickly
than slow twitch
fibers.
FT
Time
Skeletal Muscle Fiber
Characteristics
TYPE IIA
Fast-Twitch
Oxidative
Glycolytic
(FOG)
fast
CHARACTERISTIC
Contraction Speed
Type I
Slow-Twitch
Oxidative
(SO)
slow
Type IIB
Fast-Twitch
Glycolytic
(FG)
fast
Fatigue rate
slow
intermediate
fast
Diameter
small
intermediate
large
ATPase concentration low
high
high
Mitochondrial
concentration
Glycolytic enzyme
concentration
high
high
low
low
intermediate
high
Skeletal Muscle Function
How are motor units (MUs) recruited?
• slow twitch (ST) fibers are easier to
activate than fast twitch (FT) fibers
• ST fibers are recruited first
• increasing speed, force, or duration
(fatigue) of movement involves
progressive recruitment of MUs with
higher activation thresholds (i.e. FT)
Skeletal Muscle Function
Skeletal Muscle Function
Muscles apply tension at origin and
insertion
Actions of muscles dictated by:
•
•
Muscle tries to bring attachment points closer
Skeletal Muscle Function
What terms are used to describe types of
muscle contractions?
• concentric:_________, muscle __ resistance
• eccentric: _________, muscle __ resistance
• isometric: _________, muscle __ resistance
Skeletal Muscle Function
What roles are assumed by muscles?
• agonist:
• antagonist:
• stabilizer:
• neutralizer:
Stabilizing scapula
Neutralizing
Qualitative anatomical analysis
• Divide the activity into phases
• Identify joints involved and joint movements
• Determine type of contraction
– Against gravity (__) or with gravity (__)?
– Increasing (__) or decreasing (__) velocity?
– Overcoming resistance (__) or giving with
resistance (__)?
• What muscle(s) primarily active?
Posterior Compartment
Hamstring
Skeletal Muscle Function: which
muscles need to be active?
What joint motion?
What muscles active and what type of contraction
in each example?
What phase?
What type of contraction?
Skeletal Muscle Function
What are characteristics associated with
muscles that cross more than one joint?
• active insufficiency:
• passive insufficiency:
Skeletal Muscle Function
The force-velocity
relationship for
muscle tissue:
When resistance
(force) is negligible,
Force
Factors Affecting Muscular
Force Generation
(Low resistance,
high contraction
velocity)
Velocity
Factors Affecting Muscular
Force Generation
The force-velocity
relationship for
muscle tissue: As
the load increases,
Force
isometric
maximum
Velocity
Factors Affecting Muscular Force
Generation: length-tension curve
Factors Affecting Muscular
Force Generation
Total
Tension
Tension
The length-tension
relationship: Tension
present in a stretched
muscle is the sum of the
active tension provided
by the muscle fibers and
the passive tension
provided by the tendons
and membranes.
Active
Tension
Passive
Tension
50
100
150
Length (% of resting length)
Factors Affecting Muscular
Force Generation
What is electromechanical delay? (force-time
relationship)
•
time between arrival of a neural stimulus and tension
development by the muscle
Factors Affecting Muscular Force
Generation
Twitch vs tetanus
Temporal vs spatial summation
Muscular Strength, Power, and
Endurance
How do we measure muscular strength?
•
Muscular Strength, Power, and
Endurance
What factors affect muscular strength?
• tension-generating capability of the
muscle tissue, which is in turn
affected by:
•
•
•
Muscular Strength, Power, and
Endurance
What factors affect muscular strength?
• moment arms of the muscles crossing
the joint (mechanical advantage), in
turn affected by:
•
•
Muscular Strength, Power, and
Endurance
What is muscular power?
• the product of muscular force and the
velocity of muscle shortening
• the rate of torque production at a joint
• the product of net torque and angular
velocity at a joint
Where does peak power occur
Muscular Strength, Power, and
Endurance
What is muscular endurance?
• the ability of muscle to exert tension
over a period of time
• the opposite of muscle fatigability