Behavioral Properties of the Musculotendinous Unit 1) extensibility: ability to be.
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Transcript of Behavioral Properties of the Musculotendinous Unit 1) extensibility: ability to be.
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
Parallel Elastic
ComponentSeries Elastic Component
Contractile Component
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).
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
Fast twitch fibers both reach peak tension and relax more quickly than slow twitch fibers.
Tw
itch
Ten
sion
Time
FT ST
Skeletal Muscle Fiber Characteristics
TYPE IIAType I Fast-Twitch Type IIB
Slow-Twitch Oxidative Fast-Twitch Oxidative Glycolytic Glycolytic
CHARACTERISTIC (SO) (FOG) (FG)Contraction Speed slow fast fast
Fatigue rate slow intermediate fast
Diameter small intermediate large
ATPase concentration low high high
Mitochondrial high high lowconcentrationGlycolytic enzyme low intermediate highconcentration
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 CompartmentHamstring
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
Factors Affecting Muscular Force Generation
The force-velocity relationship for muscle tissue: When resistance (force) is negligible,
Velocity
Forc
e(Low resistance, high contraction velocity)
Factors Affecting Muscular Force Generation
The force-velocity relationship for muscle tissue: As the load increases,
Velocity
Forc
e
isometric maximum
Factors Affecting Muscular Force Generation: length-tension curve
Factors Affecting Muscular Force Generation
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.
Ten
sion
Length (% of resting length)
50 100 150
Active Tension
Passive Tension
Total Tension
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 tetanusTemporal 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