Lesson 11: Muscle-Tendon Mechanics Flashcards
Muscle can only control movements transmitting force through… ____
passive components (tendons) to the skeletal segments
MTC is capable of acting as: )_____ ______ _____ and _____
motor (concentric)
brake (eccentric)
Stretch shortening cycle: (spring)
isometric (strut)
an action in which the muscle tendon complex develops greater torque than the external torque acting on it and shortens
bc the force and displacement are in the same direction, the MTC is doing positive work– increasing the energy of the skeletal stytem
concentric action
an action in which the MTC develops less torque than the external torque acting on it and lengthening because the torque and the displacement are in the opposite direction
the MTC is doing negative work
decreasing the energy of the skeletal system
eccentric action
a concentric action immediately after an eccentric action; energy stored during the eccentric action contributes to the movement during the concentric action
stretch shortening cycle
in the stretch shortening cycle, _______ action comes first, and there is a very quick transition to _________ action
eccentric
concentric
an action in which the muscle tendon complex develops a torque that is equal to the external torque acting on it and does not chance its length; because there is no displacement the MTC is doing no work__ the energy of the skeletal system remains unchanged during isometric actions
isometric
_______ determines both the force producing capabilities and operating range of a muscle
muscle architecture
muscle architecture refers to how fibers of a muscle are arranged relative to the _________
vector of force generation
Parallel muscle architecture favors
ROM
pennate muscle architecture favors
force production
_____ is one of the many passive elements within the complex
tendon
have both elastic and viscous properties
viscoelastic
tendons are
viscoelastic
resistance to change in deformation
provides more dynamic stability and greater force production
stiffness
an object with greater stiffness requires ______ forces for the same amount of deformation
greater
the opposite of stiffness
allows for more ROM
compliant
the _____ the material, the more force it provides
stiffer
increase force with _________
increasing velocity of stretch
if ______, the amount of energy is being stored
lengthening
if ______, the amount of energy is being released.
shortening
an increase in the number of muscle fibers
hyperplasia
an increase in the size of muscle fibers
hypertrophy
______ produces more force
eccentric
injuries normally occur during _________ action
eccentric
the amount of force that can be produced per cross sectional area
specific tension
a motor neuron and all the fibers it innervates
motor unit
recruitment governed by two principles
- all or none principle
- size principle
motor units are recruited in an orderly process from _____ to _____
smallest to largest (type 1 recruited first also)
force output is changed by either:
- increasing the firing frequency
- activating more motor units
the time between onset of electrical activity at the muscle and production of measurable force.
electromechanical delay
why is there an electromechanical delay?
- time needed for chemical processes
- time needed for cross bridge formation
- time needed to take up the slack in the tendon
Rate of force development becomes very important when you realize that many activities occur in less time than it takes to develop the _____ amount of force
maximum
time history of activation in the SSC is involved only if : (3)
What 3 conditions will enhance the SSC
- a well timed pre-activation of muscle prior to the eccentric action
- a short rapid eccentric action
- an immediate transition from the eccentric action to the concentric action
what is an immediate transition from the eccentric action to the concentric action known as
amortization phase
any reduction in force-generating capacity of the total neuromuscular system, regardless of the force required in any given situation
fatigue
the inability to continue or complete a desired action
task failure
______ occurs because one or several of the physiological processes involved in force production of the contractile proteins becomes impaired
fatigue
for a sarcomere, at what length can the greatest amount of tension be produced?
resting length bc all the myosin can bind to actin
for a whole muscle, at what length can the greatest amount of tension be produced?
greater than resting length bc of the SSC
electromechanical delay is the time between what 2 events?
onset of electrical activity at the muscle and the production of measurable force
with aging and disuse, there is an overall ________ in the force-producing capabilities of the MTC
decrease
a decrease in the physiological cross sectional area
atrophy
age related decrease in muscle mass
sarcopenia
how is the tendon itself affected by aging?
- rapid decrease in stiffness and elastic modulus
- decrease in CSA
heavy resistance training can alter all the factors in the MTC including: (3)
- increase in PCSA
- increased number of sarcomeres in a series
- increased force production
injury to a muscle
strain
injury to a ligament
sprain
the mechanics that result in an injury
mechanopathology
the mechanics that are a result of an injury
pathomechanics
strains are the result of both a _____ and _____ placed on the muscle
stretch and load
______ occurs during eccentric muscle actions
strains
_______ is the most commonly injured muscle group
hamstrings
tendons under go greater _______ than muscles
strains
repetitive straining can lead to degenerative changes leading to a _____
rupture
has the ability to regenerate
muscle pathomechanics
scar tissue that sometimes replaces muscle
- decreases optimal length
- decreases in ROM
- leads to high incidence of reinjury
alters both mechanical and material properties
tendon pathomechanics
