Summary Class notes - Maximal Neuromuscular Performance

Course
- Maximal Neuromuscular Performance
- Yannick Mahieu
- 2017 - 2018
- VU
- _TEACHER_GENERAL_
199 Flashcards & Notes
1 Students
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Summary - Class notes - Maximal Neuromuscular Performance

  • 1504216800 Voorbereiding Totaal

  • Name the basic anatomy of a skeletal muscle cell:
    • epimysium
    • basal lamina
    • sarcolemma
    • myofibrills
    • sarcomere
    • actin
    • myosin
  • What do the 'bands' in sarcomeres stand for?
    Z band: the connection between sarcomeres
    M band: the tissue that connects myosin filaments in the middle of a sarcomere
    I band: zone of actin filaments that do NOT overlap with myosin filaments
    A band: the entire length of myosin filaments
    H band: the zone of myosin filaments that does NOT overlap actin filaments
  • Describe the contraction of a muscle fiber:
    • Actiepotentiaal
    • Voortgeleiding via T-tubuli
    • Vrijkomen Ca2+ uit het sarcoplasmatisch reticulum
    • Binden Ca2+ aan Tn-C
    • Vrijkomen aankoppelpunt op actine door wegdraaien tropomyosine
    • Koppelen S1 aan actine
    • Powerstroke
    • Ontkoppelen van S1 door binden ATP aan S1
  • What is the optimum muscle length?
    2.2um
  • What does the Force-Velocity relationship explain?
    relatively high forces are attained at relatively low contractile velocities
  • Considering the Force-Velocity relationship, when is maximal Power attained?
    At 30% of the maximal contractile velocity.
  • Explain the crossbridge kinetics during 1 powerstroke:
    1. ATP binds myosin head
    2. Myosin head is released from actin
    3. ATP is phosphorylated into ADP and Pi
    4. Myosin head binds actin
    5. Powerstroke
    6. ADP leaves the myosin head
  • What is a muscle twitch?
    A composed actionpotential (M-wave) that induces a short burst of Force.
  • What is a Tetanus?
    A series of twitches that follow in rapid succession.
  • Explain the Stimulation frequency - Force relationship
    Calcium is key here, electrical stimulation enables an action potential to release Ca2+ from the SR. The Ca2+ induces a contraction. The more often you stimulate the Ca2+ release, the more contractions up till the point the Ca2+ cannot be cleared fast enough which results in a plateau of the generated Force.
  • 1504303200 Artikelen College 1

  • What was the aim of the study on box jumps?
    To study the relation between two common force modifications in skeletal muscle:

    •   prolonged force depression induced by unaccustomed eccentric contractions
    • residual force depression observed immediately after active shortening
  • What did the authors on box jumps hypothesize?
    • the residual force depression orginates from (1) distortions within the sarcomere and (2) correlates to force and work during shortening
  • How was the residual force depression defined and studied?
    By electrical stimulation of the knee extensor muscles.

    rFD was defined as the reduction in isometric torque after active shortening as compared to the torque in a purely isometric contraction
  • How were the eccentric contractions of the extensor muscles performed?
    By doing 50 repeated drop jumps.
  • 1504562400 College 1

  • What is the difference in elektrical stimulation between nerve stimulation and surface stimulation?
    Nerve = all muscle fibers 
    Surface =  distal nerve ends, not all muscle fibers are in
  • Why does the muscle force decline when you have a certain shortening velocity?
    The Force-Velocity tells us that a higher speed gives less power because the myosin heads attach less AND can, at certain speeds, not dettach in time, which will lead to force in the wrong direction.
  • How can a muscle exert the same force at a different length when isometrically stimulated?
    Only if the length is at a certain length that elicits the same forms as seen in the Length - Force relationship.
  • How can you see if a force is tetanic?
    A force plateau. Or a riple.
  • What stimulation frequency is usually used to elicit a maximal tetanic contraction?
    50Hz
  • Explain the first force increase in slide 18L Class 1
    Passive resistance force of the muscle/tendons/joints
  • Explain the exponential force decrease in slide 18L Class 1
    First phase (exponentially): the tendons are maximally stretched, which means the shortening of the CE is less because of high tendon recoil. It's exponential because of the exponential shortening of the elastic elements.
  • How come the Force - Length relationship of the m. Abductor Pollicis is rather flat?
    The m. Abductor Pollicis has several bundles which can have their own Force-Length relationships which can be added up.
  • What increases the force deficit after active shortening?
    The time component and the total amount of work done
  • What can be concluded about the rFD considering work done?
    The rFD is greater the more work (force and displacement) has been done.
  • Explain the influence of fatigue on the residual force deficit (rFD).
    The fatigue induces an increase in rFD with the same amount of work performed in a fresh state! The relationship shifted to the left.
  • What are the explanations given for the shortening induced rFD?
    1. accumulation of metabolites over time
    2. sarcomere damage over time
    3. reduced Ca2+ affinity
    4. stress-induced inhibition of cross bridge attachment
  • What is the most plausible explanation given for the shortening induced rFD?
    stress-induced inhibition of cross bridge attachment
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Why does the EMG/Force ratio decrease during the first 60 contractions?
Well... Potentiation.
Why does the ratio remain constant below the fatigue threshold?
Well... EMG does not go up... he thinks.
What can be concluded from the signal of the VM in the short fatigue task?
The small rise in mVO2 at 45% indicated fatigue.
Explain the inflow of arterial blood during 30% MTC at some point in time
Blood pressure levels rise until they overcome the pressure of the muscle
What is a practical conclusion of metabolic use in hiking?
Blood flow occlusion may contribute more to fatiguability than the knee angle.
name some explanation about the metabolic use during 30 deg and 90 deg?
at 90 deg the tendons are more stretched than at 30 deg, there will be changes in overlap between actin and myosin when not maximally activated (less tendon stretch).
What does de Ruiter conclude from the results about the oxygen consumption at different knee angles?
Oxygen consumption is lower at relative Force production compared to both 60 deg and 90 deg, but he actually does not know.
How to compare muscles fatiguability at different lengths with eachothers?
By normalizing the MVC to the MTC and compare the relative percentages.
What did the authors on box jumps hypothesize?
  • the residual force depression orginates from (1) distortions within the sarcomere and (2) correlates to force and work during shortening
What was the aim of the study on box jumps?
To study the relation between two common force modifications in skeletal muscle:

  •   prolonged force depression induced by unaccustomed eccentric contractions
  • residual force depression observed immediately after active shortening