Ch 9 and 10 Flashcards
muscle cells are called
muscle fibres
each muscle fibre contains
thousands of myofibrils (these are “rods” that contract to contract the muscle)
within the myofibrils are
sarcomeres (functional units)
two proteins in a myofibril:
1. myosin
2. actin
myosin and actin sliding filament theory
cross-bridges “projections” from myosin attach to the actin. Once bound to the actin, these projections (myosin heads) rotate, causing the sliding action. This causes contractions while produce force
Characteristics of muscle fibre types
-each motor neuron (muscle nerve cell) synapses (connects) with multiple muscle fibres.
-Small motor neurons innervate few muscle fibres and form motor units that generate small forces
-Large motor neurons innervate larger, more powerful motor units.
-Motor units differ in the types of muscle fibres they innervate.
types of muscle fibres
type 1= slow twitch
type 2a= a mix of fast and slow twitch
type 2x= fast twitch
can we train a motor unit to get larger?
NO!
If we recruit all motor units in a muscle at the same time, we will generate 60-80% of max force
–> we can get better at activation of muscle fibres
people who are faster/jump higher are better at
producing force (recruiting motor units)
all or nothing principle
when a motor unit is activated, all its fibres contract fully
a motor unit is
a single motor neuron (nerve cell)
how is force related to fibre type
Fast twitch group= initially higher force/torques, but as contractions increase, force decreases due to fatigue
Slow twitch group= less force/torque initially but they don’t fatigue as quickly
Muscle force production (size principle)
sice principle:
motor units recruited are related to intensity of work
-Slow motor (Type 1) units are recruited first as they are most excitable
-When we require more power, Type 2 are recruited
-As load is increased, Type 2a will be recuited
Can you recruit Type 2 immediately
yes! if power is needed immediately/quickly
elite athletes (nordic skiing etc.) have more
Type 1
sprinters and weightlifters have more
type 2
can you change the distribution of muscle fibre type that you have
no!
but you can train to recruit what you have more efficiently
Hypertrophy
an increase in the SIZE of cells (muscle fibres/fat cells etc.)
opposite= atrophy
Hyperplasia
plasia= number
an increase in the NUMBER of muscle fibres or fat cells
–> this does NOT occur in adults
Training can focus on specific fibre types
ex. training for strength and power will target…
type 2x fibres and hypertrophy will occur in those fibres (principle of specificity)
Isometric contraction
muscle contraction w no change in muscle length
ex. wall sit, plank
Isotonic contraction
a contraction w constant force.
ex. moving a constant mass such as a dumbell, barbell or bodyweight
Isokinetic
muscle shortens or lengthens at a constant velocity
–> does not occur in a training setting, (usually research) must use a machine which controls movement by the viscosity of fluids in the machine
Isotonic: Concentric and Eccentric
Concentric= muscle is both contracting and shortening
Eccentric= muscle is contracting and lengthening
-ex. the loser in an arm wrestling competition (force is overcoming resistance), negative pullups
Is there a difference in arm strength vs. cross sectional area of a muscle in M vs F
no
What is the most important factor in strength gains in early training and detraining
Neuroadaptation
Force-length relationship of human skeletal muscle (muscle fibre/sarcomere)
increased or decreased muscle fibre length in relation to the resting length of a muscle fibre
= less force available to use!!
look at figure 9.4 (normal range of a sarcomere in relation to force)
Force-length relationship of an INTACT MUSCLE
muscle increases force as we approach optimal muscle length. As we stretch past optimal length, passive stretch occurs and force continues to increase!!
Fig 9.5
Force-velocity relationship of human skeletal muscle
The faster a muscle shortens, the less force it is able to generate
Force= mass x acceleration
Force- velocity relationship
for concentric as muscle shortens:
-force decreases as velocity increases
Power-velocity relationship
Optimal power does not occur at high force or velocity
High force= 0 velocity= 0 power
Concentric, shortening muscle at max speed but no force= 0 power
Power= force x velocity
therefore max power occurs at medium forces and medium velocities
Curves from 9.6 (force/velocity) and 9.7 (force/power) confirms that
peak power occurs at 35% of max velocity and 35% of max isometric force (mod velocity)
*these graphs are all for an isolated muscle
Is peak power 35% of your 1RM?
No!!!
this is only for isolated muscle contractions
it is different when multiple muscles are involved
how does optimal warmup connect w force/velocity curve?
increased body temp (muscle temp)= potential for higher force output
–>active warmup–not just sitting in the sauna
torque
force x moment arm (perpendicular distance to centre)
Does torque equal force?
no!!!
force can be equal but diff moment arms (angles)= diff torques
90 degrees= highest torque
co-contraction
agonist muscle= primary mover
antagonist muscle= produces opp torque
–> usually ineffective to contract both, however co-contraction across joints can help joint stability sometimes
(during a squat where both quads and hamstrings contract)
what type of muscle fibre can produce the most force?
type 2x (or 2b)
planes of motion
- Transverse plane (divides body into upper and lower)
–> superior/inferior - Frontal plane (divides body into front and back)
–> dorsal/ventral - Sagittal plane (divides body along axis of symmetry)
–> medial/lateral
Axes of rotation
- Longitudinal (line down the middle of the body)
–> ex. figure skater spins around this axis - Transverse/frontal axis (line through the hips from left to right)
–> ex. a summersault would be around this axis - Sagittal axis (line from front to back of body through the middle)
–> ex. a cartwheel would be rotating about this axis
Muscle action terminology
-Agonist
-Antagonist= opposes agonist
-Target muscle/prime mover
-Synergist= assists another muscle for mvmnt
-Stabilizer= contracts but doesn’t contribute any mvmnt
-Dynamic stabilizer= shortens at one moving joint and lengthens at an adjacent moving joint (no real diff in muscle length)
-Antagonist stabilizer= opposing stabilizer
Uni-articulate
Bi-articulate
uni= muscle that only crosses one joint (ex. brachiallis at the elbow)
bi= muscle that crosses two joints (ex. hamstrings, rectus femoris, biceps, triceps)
Why are functional exercises better than single muscle exercises?
They are more like how you move in real life
-balance and stability and strength in those area
What is the requirement for functional movement patterns?
to maintain COG over BOS
-failure to maintain this results in falling/injury
Closed kinetic chain
a movement chain where you push against an object but can’t move it
ex. squat or pushup on the floor
Open kinetic chain
the chain is open if you overcome resistance and move the weights
6 fundamental movement patterns
- Squat
- Hip Hinge
- Lunge
- Push
- Pull
- Rotation
Coaching movement skills
what pete told me:
verbal cues are good but sometimes you need to physically move their body to cue them (etc. retracting scapula down and back)
–> people tend to learn by association; meaning learning through things they are already good at
Coaching movement skills: creating an optimal learning environment
-make client feel comfortable
-objective communication; explain the benefit for them
-educate client about the learning process
-challenge them w variations of the movement to keep them focused
Coaching: optimize instructions
-cues can be verbal or visual
-no more than 2 cues
-don’t use don’t!
-give a good demonstration
Coaching: feedback
-be positive and specific
-praise w technical pointers
-give feedback once in a while not too often
Is it always good to have previous knowledge of a sport?
no because learning may actually be harder if there are corrections to be made
Misconceptions in movement: analysis of the squat
-Rectus femoris, hamstrings and gastrocnemius are biarticulate muscles and they contract to stabilize the knee, hip and ankle (they are dynamic stabilizers)
-The quadriceps and hamstrings are antagonistic but they contract at the same time (this is called Lambrado’s paradox)
-Hip and knee flexion occurs in the downward phase–> assumption is that they contract to cause the motion
–> gravity causes hip and knee flexion without the need for muscle contraction
–> hip and knee extensors are eccentrically contracting during downward motion to slow speed of descent
–> if muscles were contracting eccentrically, you would accelerate downward very fast
The Valsalva Manouevre (VM)
-The VM is a forced exhalation against a closed glottis (which prevent exhalation)
-VM increases intra-abdominal pressure (IAP) which helps stabilize the spine
-there are some safety concerns
–> pushing in all directions in chest= increased BP (should not be done by anyone w heart problems), the body also has a reflex after detecting high BP to quickly decrease BP and can cause fainting etc.
