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Summary Nutrition to support training adaptations (HMS4603)
Summary of all lectures
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Voorbeeld 4 van de 116 pagina's
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Door: lindesteinbusch • 2 jaar geleden
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SUMMARY OF LECTURESNUTRITION TO SUPPORT TRAINING ADAPTATION
PASCAL WISCHHOFF
,Muscle and muscle physiology
Topics:
Muscle function
Muscle tendon model
Motor unit
Muscle fiber recruitment
Muscle pennation angle
Fiber types
Sliding filament theory
mRNA transcription vs translation
Muscle stem cells
Myonuclear domain theory
What is the main function of skeletal muscles?
We need muscles to move, for posture, breathing and for the metabolism.
We are going to talk most about movement and metabolism.
When we think about skeletal muscle in the most general sense, the only thing it can do it
can actively shorten itself. It is the internal motor that allows us to pull on a certain joint. If
you have a origin and an insertion of a skeletal muscle its joint by the ligaments, by the
tendons. If you shorten yourself, e.g. your biceps pull on your elbow. It can not actively
lengthen itself, it can only if an antagonist is contracting itself again. It is important to
remember that muscles can also go across multiple joints (e.g. over the hip and knee). But
you can also have single joint muscles, they can shorten up to 70% of its resting length.
How muscles are able to transfer forces from the muscle contraction to the bone that
causes a rotation in the joint, we have to talk about the muscle-tendon model because there
are three different components that are basically helping to transfer forces that are being
produced by the skeletal muscle to allow us to have a rotation in the joint. You have the
contractile components, the series elastic component and the parallel elastic components.
Contractile component (CC): the CC in muscle is actin and myosin which is located in
sarcomeres. You have the sliding filaments and they are basically locking into each other
and they can produce force.
Active shortening of muscle through actin-myosin structures
Serial elastic components (SEC): tendons allows us to transfer forces towards the joint.
In series with the contractile component, reside in the cross-bridges between the actin and
myosin filaments and the tendons.
Parallel elastic component (PEC): It is elastic so it can store some elastic energy in the
muscle that is being released under muscle contraction. In the epimysium, perimysium we
can also store a lot of energy.
Parallel to contractile element of the muscle. Connective network residing in the
perimysium, epimysium and other connective tissues which surround the muscle fibers.
You need to be able to differentiate between these three so you can train these parts for
adaptation in different ways if you know where these are located as well.
,It is always a combination between these three. If you produce force it is not only that the
sarcomeres are shortening, it is also how strong are your tendons, how strong can you use
your PEC to transfer those forces towards those tendons.
Then you have the stretch-shortening cycle. That determines basically how you can produce
the force and how it can be transferred from the muscle towards the tendon and towards
the joint. Following a muscle contraction, basically what happens is that the PEC, SEC can
store energy (basically like an elastic band. If you stretch it and you release it, you release
some energy as well and it goes back to its original position). This is the same for your elastic
components, parallel and in series, same as with your tendons. They can store a little bit of
energy, that is first being released with a muscle contraction and this allows you to have a
higher force production.
The same as you can imagine when you jump from a standing position, you can jump less
high compared when you do a countermovement (you go down) you store energy in your
tendons and in your SEC when you jump up you will jump higher than from a standing
position itself.
You can also train this specifically parallel or in series (e.g. plyometrics or jump training). You
can specifically train someone in those components. That is the goal of this course, different
types of training that you need to do to see an improvement in performance.
Other tissue properties of skeletal muscle
Irritability: Responds to stimulation by a chemical neurotransmitter (Ach). An action
potential comes from the CNS, and it allows you for neurological input. This starts the
muscle contraction itself.
Contractibility: Ability to shorten (50-70%), usually limited by joint range of motion
Distensibility: Ability to stretch or lengthen the muscle itself, corresponds to stretching of
the perimysium, epimysium, and fascia that is surrounding the muscles.
Elasticity: Ability to return to normal state (after lengthening). If you stretch your muscle, it
will always go back to its original anatomical position. You train it you can change that a little
bit.
Motor units
, If you go towards muscle contractions you need neurological input, which is coming
from the motor unit. This is composed of a motor neuron (an alpha motor neuron that is
in the central nervous system) and all the muscle fibers that it innervates. You see the
alpha motor neuron; the exons go to the muscle and each motor neuron innervates
different muscle fibers. All that together is called the motor unit. Then you have
different motor units together, which innovate all together the entire muscle. Different
muscle groups have a different number of motor units as well. That will tell you
something about how well a muscle is able to perform specific force productions and
how well you can coordinate a certain movement in the muscle. If you for example have
your finger muscles, they have much more motor units because they need to be able to
make small adjustments in which muscle fibers need to contract compared to your thigh
muscles because they just need to extend your knee. Then you need less muscle fibers
per motor unit.
Each muscle has several motor units, that determines the precision. What happens for
example with aging? The number of motor units declines which is why coordination
mostly declines as well. That is also something that you can train. E.g., with strength
training looking at muscle mass. Your mass doesn’t go up in the first place, but your
strength does go up. That is because your motor units are training. You have more
neurological input, you have a better coordination of a certain exercise that you are
doing that is coming from how well you are able to coordinate your motor units and
maybe add motor units to an existing muscle. The less fibers per motor units, the more
precise the muscle.
Then you also need to consider how a muscle can control the force it can produce (how
much tension it will be able to produce). There is three different ways that it can do that.
The excitation is an all-or-nothing event, this can increase tension which can be
accomplished by
Increasing the number of motor units that you recruit.
The rate of coding (increasing the stimulation rate of the active motor units).
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