Midterm 2 Flashcards
4 mechanisms of SSC Potentiation. Which ones are the most important?
80%
- higher initial force
- taken up SEC
- storage of elastic energy
20%
-reflex potentiation
T or F: 0 displacement is possible if a muscle is attached to a tendon
T - muscle shortens, tendons stretch - overall 0 displacement
Give 2 examples of reflex potentiation. So how does it add to contraction force?
falling asleep in class, knee reflex
during an ECC contraction, the reflex is initiated, muscle CON contracts adding to CON force produced
Fx of V on SSCP
T or F: at higher V, ECC has more to gain and CON has more to give
F - v.v.
T or F: V of E affects SSC potentiation even if V of CON does not change
T
T or F: Most of the time fast ECC is harder to do than fast CON
F - v.v.
greater ________ or % potentiation at higher velocities
relative
T or F: It possible to have a ECC submax lead into a CON max
T - it is dependent on velocity of the ECC phase
Examples of scenarios…
ECCmax - CONmax
ECCsubmax - CONmax
ECCsubmax - CONsubmax
isokinetic dynamometers
jumping, throwing
weight training
SSCP used when we do a squat jump with a counter movement (down than up, vs. up only) resulting in a higher jump height. Similarly, this occurs when we jump off platforms of various heights. However…what if the platform is too high?
Too much momentum due to gravity on the way down to the floor, causing a PAUSE = loss of SSCP (golgi tendon - protective fxn)
When is SSC inappropriate? (3)
when time needed for ECC phase can’t be spared
- push off in swimming
- tip off in bball
- no telegraphing (give hints to opponent) of punch in boxing
when a rule forbids its use
-competitive weight lifting
when overused = injury
-CN tower example
Fx of training on the SSC and its mechanisms (3)
increased ECC force/strength due to increased muscle hypertrophy and neural activation/synchronization
increased storage of elastic energy (stiffer elastic structures)
increased reflex potentiation
-increase neural activation
Study: vball players vs. PE students (M)
there was a only a significant difference at 60 cm height
Study: gymnasts vs. PE students (F)
training decreased inhibition by the body because they were used to the elevated heights; therefore SSCP was higher/more effective
Calculation for Efficiency?
E = Eout/Ein x 100
or E = mechanical power (out)/metabolic rate (in) x 100
T or F: SSC increases Eff
T
3 reasons why SSC increases Eff
increases EFF force from stretched CBs (no ATP cost) - positive braking force
storage and release of elastic energy
prevention of wasted CB action taking up SEC
T or F: walking is less EFF than running
T
T or F: running faster will burn more energy
F - same cost despite time and speed of running
FLR is also known as the….
length-tension relation (LTR)
What is the difference between active/passive force? What is total force?
active - force produced during contraction
passive - resistance of a relaxed muscle to stretch - similar to the positive braking force (note: tighter muscle = higher passive force due to less elasticity)
total force - passive + active
Optimal length (L0) is the length of which the greatest ______ force occurs
active
Resting length is the length of which….
passive force begins to develop
In anatomical position, resting lengths are limited by….
human bone
T or F: relationship between optimal and resting length varies with different muscles
T
What are the mechanisms for variation in passive force?
elastic structures in the muscle
What are the mechanisms for variation in active force?
length of sarcomeres - long, optimal, short
Name the length
Midpoint of one Z line to the other Z line
Length of actin
Length of myosin
Length of the bare zone
- 6 um
- 95 um
- 6 um
- 2 um
Optimal length….
What is occurring?
2-2.2 um - vary because of bare zone
plateau at max force b/c all CBs are bound; plateau is due to the bare zone, no more/less CBs bound
What happens when the length exceeds the optimal length?
force decreases linearly
Less CBs bound
What happens when the length is below the optimal length (1.7-2 um)?
force decreases - actin filaments overlap one another (blocking myosin binding)
What happens when the length is below the optimal length (<1.7 um)?
decrease in force - Z disks compress myosin filament, preventing shortening
T or F: when comparing two species such as a frog and a human, there is little variation in the actin filament length and a large variation in the myosin filament length
F - vv - more variation in actin - this explains the larger length of a human sarcomere (4.24 um) - proportional to the size of the species
How does a human FLR graph compare to a frog’s?
shifted to the right
What are the two main factors affecting the shape of strength curves?
FLR
Muscle MA
In terms of the FLR relationship, order the muscles in low to high active force.
hamstrings, calf muscles
biceps, quadriceps
triceps
How does MA length vary the FLR (aka strength curve) relationship?
Every muscle has its own FLR or strength curve, and has it’s optimal MA and angle
T or F: the MA, strength and FLR have similar curves
T
Give in an example where the force produced is dictated more by the FLR since the MA doesn’t change by much
Quads
Cost of smaller MAs
lower torque and strength,, increase risk of injury (avulsions)
Advantage of smaller MAs
increased ROM and speed
For two muscles of the same CSA,
B’s MA is twice of A’s therefore double the torque but….
B has half the ROM - B has to shorten twice as much as A for a given change in joint angle
3 other factors of the strength curve shape
training
fatigue
injury
2 adaptations due to training in the first 6 wks
neural and muscle adaptation
T or F: if there was muscular adaptation, there would be a uniform increase in strength
T
T or F: neural adaptations increases at only certain joint angles
T
For all men, regular or body builder, the optimal joint angle for the bicep was higher than it was for women..why?
in men, bicep bulge comprises the LOA of the muscle at smaller JAs, therefore the force produced
If you are looking at a graph, how do you tell the difference between fatigue and an injury?
injury - most likely one JA is affected; fatigue lowers the whole strength curve
T or F: during training you want to match the load with the strength curve
T - not being too high or low
Alternative, when you are doing shoulder abduction to better match the strength curve of the deltoids?
lay on your side
What is a cam pully? why was it flawed?
a type of machine that varies the resistance by changing the ratio of the radius of the pully (2x length = 2 force)
they thought the angle and % max relationship was negatively linear - their system did not match the strength curves of every muscle
So what is the best system or machine to match strength?
isokinetic devices
2 components of a motor unit
motor neuron + innervated muscle fibre
Fibres/MU decreases with (increase/decrease) complexity of movement/fxn
increase
of varies with the _______ of the muscle and ______
size of muscle and size of MU
T or F: Med Gastroc would have more fibres/MU than FDI
T
T or F: Med Gastroc would have less MUs than FDI
F
What does it mean when we say that the MU territories produce a mosaic?
branches of MUs overlap each other and intermingle; there is no sectioning in terms of with MU is in charge of which section of the muscle
What are the advantages of having MU territories? (2)
smoother contraction - more MU force distributed over a larger area
may help delay fatigue - inactive and active fibres, or different fibre types sharing metabolites and capillaries
Type I - also known as (2)
Type 2 - also known as (1)
-2 subtypes (2 names for each)
slow twitch (ST) or slow oxidative (SO)
fast twitch (FT) – fast oxidative glycolytic (FOG) or IIA and fast glycolytic (FG) or IIX/IIB
IIX > IIA > I for:
motoneuron soma size
axon diameter
fibre size
?
fibre number
In male body builders, what affect does testosterone have? Effects of training?
increased muscle growth - larger muscle fibre, increase in type II fibres esp
fx of training - increase in type II as expected (compared to the untrained group)
What are units of ABS and REL force? Another name for REL force?
N
N/cm2 - specific force
Compare ST and FT fibres in terms of force
FT - are larger and more numerous therefore generating a greater ABS force
How is it possible that 20% of the muscle forces are unused in the triceps brachii?
Triceps - 750 fibres/MU
IIX fibres are difficult to recruit unless it is a very high force demand
75% of the MUs can be type I however it can makes up around 33% of the muscle fibres. How is it possible for 50% of the muscle fibres be type II when it only makes up 21% of the total # of MU?
Type II are larger in size and have more branches (muscle fibres)
T or F: ST fibres generate a lower ABS force because they are smaller in size and, but a similar SPECIFIC/REL force compared to FT
T
Why does type II produce a greater specific force? (3)
stronger CBs - greater F/CB
more # CBs attached - assumes max activation - saturating Ca
similar myofilament density, similar myofibrillar density- packing
T or F: SO have a lower peak in force than FG and FOG
T
T or F: Looking at tetanic ISO and CON contractions, SO has a higher ISOmax force but a lower Vmax value.
F
ISOmax - FG>FOG>SO
Vmax - FG>FOG>SO
Describe the shape of the velocity vs. power graphs for type I, IIA, IIX
all upside down Us that have different magnitudes and ranges in x and y axis
What possibly accounts for differences in velocity vs. power?
genetics
What’s the advantage of having a mixed muscle, in terms of power?
the muscle can be active over a wider range of velocities; nervous system recruits them consecutively
I - slower Vs - quick peak, slow fall
II - faster Vs - slower peak - slower fall
List the 3 determinants of contraction speed. Describe each and what’s the trend among the types?.
Myosin ATPase activity determines speed of CB cycling (avg 50ms); IIX>IIA>I
CB power stroke speed - we don’t know this mechanisms for sure; IIX>IIA>I
Ca release and uptake - IIX>IIA>I; larger/more extensive SR = more rapid release & uptake of Ca = INCREASED rate of contraction/relaxation of the muscle
T or F: for CON contractions, the difference in force between Type I and II increases as velocity decreases
F - velocity increases
T or F: for ECC contractions, the difference in force between Type I and II increases as velocity increases
F - force decreases
T or F: Type II have a higher ISO max as well as Vmax
T
Compare the soma, axon, and muscle fibre size of FG and SO
SO<FG in size
T or F: FG has a faster conduction velocity
T - think of it as water flow in a pipe diameter
T or F: muscle fibres conduct faster than nerve axons
axons are myelinated and have Nodes of Ranvier at allow SALTATORY conduction
T or F: increased diameter = decreased resistance and increased conduction velocity
T
Another reason why MAP maybe slower….
T-tubules with the MAP may slow it down
Why do we have small stores of ATP?
ATP are large and heavy
Duration of the PC system?
~10 seconds
In terms of METABOLIC power…FG have a greater…(2)
CK, myosin ATPase, glycolytic ENZYME ACTIVITY
SUBSTRATE STORES of PCr and glycogen
Differentiate mechanical and metabolic power, for each fibre type.
mechanical - P = Fv; FG>FOG>SO
metabolic - activation of and fuel for engine (demand)
FG>FOG>SO
T or F: isolated muscle fibre type contractions is possible in humans
F - impossible to isolate due to the mosaic
Compare the MF types in terms of fatigue resistance. What is the reason behind his?
SO> FOG >FG
OXIDATIVE
T or F: SO contraction force can go on “indefinitely”
T
4 determinants of fatigue resistance. Describe each
mitochondrial size - larger mito = >ox enzyme activity = >utilization of O = > fatigue resistance
Mb concentration - Mb helps carry and store O, >Mb = >O utilization
MF diameter - smaller the fibre = less distance travelled to the center of fibre
capillarization (technically external to MU) - SO have more capillaries around it for higher O delivery and utilization
T or F: IIB or IIX is only recruited with very high forces, otherwise the body would recruit SO
T - IIs are recruited as backup to compensate for what the Is are lacking
What is recruitment threshold (RT)?
% of max force/effort at which a MU is recruited/activated
low threshold - recruited at low % OF MAX
high threshold - recruited at high % OF MAX
What’s the size/Henneman principle? What’s the order of recruitment?
MU are recruited in order according to the size of the MU’s soma
SO, FOG, FG - larger size = larger RT
T or F: SO fibres have smaller somas therefore less resistance to excitatory input.
F - more R
T or F: depol threshold or voltage is increases with cell soma size
T
What’s Ohm’s law? Explain it in terms of MU recruitment
V = IR
I = input V = threshold
SO = smaller soma = more resistance, greater V when reaching excitation - more likely to fire FT = larger soma = less resistance lesser V when reaching excitation - less likely to fire
So which fibre type would be more likely to fire, for the same I (input)?
SO!!!!
T or F: FT generate a larger action potential than SO
F - same AP due to all or none principal
T or F: larger soma = harder to excite = harder to recruit = lower activation (I) needed to reach threshold
F - higher
Depolarization threshold is the same for all MUs, so what differentiates them as low/high threshold MUs?
differ in degree of activation required (I) to cause them to reach threshold in order to fire
What is the Central Wisdom principle? Differentiate low excitation/effort with the high
CNS matches MU recruitment with the demands of the task
low excitation/effort levels prefer to small motor neurons (type I) first
high excitation/effort levels recruit larger motor neurons (type II) in addition to type I
Name examples of when you’d use low and high excitation recruitment.
low - endurance
high - sprinting, lifting, jumps
Define gradation of contraction.
varying force of contraction
2 ways contraction force is graded?
MU recruitment
MU firing rate
MU recruitment mechanism is based on…
central wisdom + size principle
MU firing rate is…
nerve impulses/second
sent from soma to muscle fibres
T or F: 20 impulses/s = 10 MAPs/s or Hz
F - its a 1 for 1 relationship
T or F: minimum MU firing rate (FR) for FG>FOG>SO
F - SO> FOG> FG
Why do faster MUs require a higher FR?
stimuli must be closer together to form a tetanus (summation) or else force gradation cannot occur
T or F: SO have a lower FR but hits its max faster
T - because it is slower in rising and falling
FG need a higher FR to hit its max force and plateau
Below 50% MVC it is the _______ mechanism dominants.
Above 50% MVC it is the _______ mechanism
dominants.
recruitment
FR
T or F - %MVC vs. # of MU recruited = linear relationship shape…
F - increasing curve - non linear
note: both mechanisms are at play throughout contraction
How is muscle unit activation measured?
EMG
How do we quantify an EMG?
of recruited MUs + FR = size of fibre MAPs = quantity
Differentiate between sustained MVC and submax contraction (to failure)
signal starts larger and gets smaller (negative linear)
signal starts smaller and gets larger (positive linear)
MUA and exercise…3 fxs
fx of exercise on intensity
fx of contraction type
fx of contraction V
3 types of intensity of exercise - describe and give an example
brief, max effort
submax effort
progressive/incremental
- 100% MUA; lifts/throw/jumps and sprints (longer duration)
- <100% MUA - walking, jogging, running
- aerobic power tests (VO2max) - % MUA increases in steps
T or F. In lifting the same weight, the CON phase of the lift has a higher % MUA/magnitude of signal than the ECC phase
T - because
CON = # CBs required = >muscle fibres required = >MU needed therefore >signal
T or F: during a max CON or ECC contraction, there is a same a REL force and EMG signal
T - BECAUSE IT IS AT MAX!
