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: joint ROM:

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 Twitch Tension Time FT ST Fast twitch fibers both reach peak tension and relax more quickly than slow twitch fibers.

Skeletal Muscle Fiber Characteristics TYPE IIA Type I Fast-Twitch Type IIB Slow-Twitch Oxidative Fast-Twitch Oxidative Glycolytic Glycolytic CHARACTERISTIC (SO) (FOG) (FG) Contraction Speed slow fast Fatigue rate intermediate Diameter small large ATPase concentration low high Mitochondrial concentration Glycolytic enzyme

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

Factors Affecting Muscular Force Generation Velocity Force (Low resistance, high contraction velocity) The force-velocity relationship for muscle tissue: When resistance (force) is negligible,

Factors Affecting Muscular Force Generation The force-velocity relationship for muscle tissue: As the load increases, Velocity Force isometric maximum

Factors Affecting Muscular Force Generation: length-tension curve

Factors Affecting Muscular Force Generation Tension Length (% of resting length) 50 100 150 Active Tension Passive Tension Total 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.

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