Strength and Power - MTU and Architecture slides

MTU Mechanical Model: Contractile Component

represented by muscle fibers… only tissue with contractility

Series elastic Component (SEC)

Tendons

MTU Mechanical Model: Parallel elastic component

epi, peri and enodmusiums, each can be modeled like a rubber band

Force production by the Contractile element (CE) is

Active

Force production by the SEC and PEC is considered

Passive

When a MTU is undergoing a concentric contraction all the load is distributed by

the CE

When a MTU is sundering a eccentric contraction

some of the load is distributed by the SEC and PEC and the rest is distributed but the CE

With a constant load eccentric contractions require less energy because

the load is taken by the elastic component

For a constant energy expenditure more load can be managed with an eccentric contraction than a concentric because…

you’re working with gravity

In a maximum contraction, the amount force/tension on the MTU in order is

eccentric > isometric > concentric

Series arrangement

arranged end to end (ex: tendons and the muscle fibers)

Parallel arrangement

arranged side by side or in layers (ex: the mysiums)

In a series arrangentment force production is equal to what?

amount of force a single component can produce

In a series arrangement the amount of shortening is equal to what?

the sum of the amount of every component

In a parallel arrangement force production is qual to what?

the sum of of the force that every component can produce

In a parallel arrangement the amount of shortening is equal to what?

the amount of shortening of a single component

Longitudinal/Parallel

Muscle whose fibers lie parallel to its long axis

Examples of longitudinal/parallel muscles

sartorius, rectus abdominis

Fusiform/Spindle shaped muscles

rounded muscle which tapers at either end

Examples of fusiform/spindle shaped muscles

biceps brachii, brachialis, brachioradialis

Fan-shaped/triangle/Radiate muscle

flat type of muscle whose fibers radiate from a narrow attachment at one end to a broad attachment at the other

Examples of fan-shaped/triangle/Radiate muscles

pec major/minor, gluteus medius/minimus, internal oblique

Penniform muscle

muscle fibers arranged in a feather like pattern

Unipennate

muscle fibers extend diagonally from one side of a long tendon

Examples of Unipennate muscles

tibialis posterior, flexor pollicis longus, flexor/extensor digitorium longus, semimembranonsus, peroneus Tertius

Bipennate

long central tendon with fibers extending diagonally in pairs from either side of the tendon

Examples of Bipennate muscles

rectus femoris, soleus, vastus medialis/lateralis, flexor hallucis longus

Multipennate

combination of several bipennate fibers

Examples of multipennate muscles

deltoid, gluteus maximus, infraspinatus

Muscle force production is proportional to…

the product of the size and # of fibers

Anatomical CSA (ACSA)

the CSA of a given muscle at its widest point

Physiological CSA (PCSA)

The CSA of every fiber within a given muscle

For a given ACSA the fiber arrangement will affect…

the # of muscle fibers within the same PCSA

Penniform fibers when compared to longitudinal fibers, with a given ACSA will have:

greater # of fibers, greater force production potential and smaller ROM

Do penniform muscles typically have short or long tendons when compared to longitudinal, fusiform and radiate muscles?

short

In shorter tendons there is less stretch before the tendon reaches its load-dependent length which requires what of penniform muscle?

less shortening

The result of a short tendon for a penniform MTU is

increased ROM

In penniform MTU there is a large what

muscle to tendon length ratio

As the muscle to tendon length ratio of non pennate muscles decreases…

greater shortening of the muscle is required to stretch the tendon to load-dependent length

As muscle to tendon length ratio decreases the overall shortening of the MTU is:

compromised

A longer tendon allows for what?

greater potential elastic energy