Module 4: Lecture 6 Flashcards
what is a key muscle characteristic that dictates how much force is going to be produced?
- muscle - length relationship
- contraction type
when we talk about length of muscle, what are we talking about?
the overall length of a single one of the sarcomeres
will the amount of overlap between your thick and thin filaments dictate how much force you can generate?
yes
- the idea of length - tension relationship
at optimal muscle length, maximum ______ can be developed.
tension
why is tension production decreased when your muscle length is greater than optimal?
because there will be a decrease in available sites for crossbridge formation
why is tension production decreased when your muscle length is less than optimal?
because the thin filaments will overlap, limiting the number of active sites available for crossbridge formation
what is muscle tension?
the force exerted by a muscle contraction on an object
- lifting an object steadily
what is muscle load?
the force exerted on a muscle by an object
- the object weighing your hand down
what is going to dictate what type of muscle contraction you are going to produce?
the relative balance between muscle tension and muscle load
- dictate whether the muscle shortens or lenghens
is the muscle going to lengthen or shorten if the tension is greater than the load?
shortening contraction
is the muscle going to lengthen or shorten if the tension is less than the load?
lengthening contraction
what is it called when a muscle contracts without any shortening?
isometric contraction
- constant length contraction
what is it called when a contraction involves constant load/tension?
an isotonic contraction
which isotonic contraction involves an increase in muscle length?
lengthening / eccentric contraction
which isotonic contraction involves a decrease in muscle length?
shortening / concentric contraction
during what type of contraction can you produce the most amount of force?
during an isometric contraction
- maximal force can be produced when velocity is zero
the greater the load, the ______ the velocity of shortening.
lower
is there such thing as an unloaded shortening velocity in real life?
no
- only in lab
as the velocity of the contraction increases, the amount of force you can generate rapidly _________.
decreases
what is power a combination of?
force x velocity
when is maximal power produced during muscle shortening?
when optimal load and velocity relationship is determined
what are the three fibre types in human skeletal muscle?
- Type I –> slow twitch
- Type IIA –> fast twitch
- Type IIX –> fast twitch
which fibre type is our fast fatigable?
Type IIX
which fibre type is our fast fatigue-resistant?
Type IIA
what do our slow twitch fibers predominantly rely on?
oxidative metabolism within the mitochondria for ATP generation
- slow oxidative
which fibre type is our fast oxidative glycolytic?
Type IIA
the larger the diameter of the fiber, the more _____ and _____ that are going to be packed within that area, the more _____ that can generate.
- actin and myosin
- force
what are the muscle fibre diameters for each fibre type? what about motor units per muscle?
Muscle fibre diameter
T1- Small
TIIA - Large
TIIX - Large
Motor units per muscle
T1 - More, smaller
TIIA - Fewer, larger
TIIX - Fewer, larger
what is the force production of each fibre type?
T1 - low
TIIA - intermediate
TIIX - High
which fibre type is the most fatigable? least fatigable?
most - TIIX
least - TI
what is TIIX fibres sensitivity to recruitment?
low
is someone given more slow twitch or fast twitch fibers by genetics or training?
more genetics related
- extreme examples will give the shift of fibre type
what are the determinants of whole-muscle tension in skeletal muscle?
- changing the numbers of fibers contracting
- tension developed by each contracting fibre
how do we determine the number of fibres contracting?
take into consideration:
- number of motor units recruited
- number of muscle fibres available to contract
- number of muscle fibres available to contract
- size of muscle
- presence of disease
- extent of recovery from traumatic losses
how do we determine the tension developed by each contracting fibre?
- frequency of stimulation
- length of fibre at onset of contraction
- extent of fatigue
- duration of activity
- amount of asynchronous recruitments of motor units
- type of fibre (fatigue-resistant oxidative or fatigue-prone glycolytic)
- thickness of fibre
- pattern of neuron activity (hypertrophy, atrophy)
- amount of testosterone
