Muscle Control & Recruitment - Lecture 28 Flashcards
How does Muscle Contraction work?
Action potential and resultant contraction
Multiple Impulses sent?
A wave summation occurs; multiple increasing frequencies of signal
What’s the result of multiple impulses
Increasing force of contraction with increase in signals
What happens when there’s a max amount of signals (Action Potential)
Fused tetanus; signal levels out and no more contractions.
Total Muscle Tension
Active + Passive Tension
Active Tension
Tension that the muscle creates itself from contraction
Passive Tension
Tension created by external force through stretch
How can the optimal strength (force production) of a sarcomere be produced
Depends on the resting length of the sarcomere; that produces the most force
75%
Muscles are too overlapped; actin cross bridges interfere
80-120%
Optimal length of the muscle, to allow to lift the most
170%
Forming cross bridges are hard to because they’re too stretched
Resting Length of Isometric
Resting length stays the same
Muscle tension of Isometric
Peak tension developed
Resting length of Concentric
Resting length shortens as muscle squeezes.
Increase in muscle tension in concentric caused by?
Before on set of movement
Resting length of Eccentric
Muscle Length elongates
What happens when resistance is greater than the force of contraction of the muscle
Muscle tear and significant damage
Relationship of force output and resistance
Being able to overcome a resistance produces a high force of contraction
What is a motor unit?
A neuron and all the muscle fibre that neuron innervates (supply with neurons)
Two types of muscle fibre?
Type 1 and Type 2
Same Neurons and Muscle Fibres
All muscle fibres innervated by the same motor neuron are same fibre (Must be Type 1 or Type 2 Neuron)
How do your muscle fibres generate more force?
Principle of Orderly Recruitment
Principle Of Orderly Recruitment
Motor Units are always recruited in the same order
What does recruitment in the same order mean?
i.e. all of motor units 1 will be recruited, and then if more force is needed, then all of motor unit 2 will be recruited and so on.
How does strength training affect recruitment?
Recruits a great amount of motor units, as well as improve speed of recruitment
2 main factors of strong muscle contractions
Frequency of impulses and recruitment of motor units
Muscle Fibre Continuum
A scale going from type 1 on one side, type IIa in the middle and Type IIb on the other end.
Based on contractile and metabolic properties
How muscle fibre types are identified
Type I
Oxidative (aerobic), Slow Twitch Muscles (slowly uses energy)
Type IIa
Glycolytic/Oxidative, Fast twitch Muscles
Type IIb
Glycolytic, Fast Twitch Muscles
Usual composition of Fibre Types
50-50 slow:fast
Why do people sometimes have more of one fibre type than the other?
Usually explained by predominant genes
Is it possible to fully change from one fibre type to another?
You can’t move from one to the other, but you can train to move across the continuum
How can muscle fibre composition be measured?
Muscle Biopsy; taking a piece of muscle and analyzing to see what muscle type they have
What do the muscle fibre types display under a microscope?
Different sizes and colour for each type. Some people have more of one muscle type over the other.
Reason for different colour fibre types?
Presence of myoglobin (O2 carrying) and RBC carrying compounds.
Primary fuel of Type I
Lipids
High capillary density
Type 1
How active is ATPase enzyme in Type I
Very low as it doesn’t need to produce a lot of ATP for short periods as Type I is longer periods.
Force of Type IIb?
Generates force much more quickly as this is associated with activities needing to produce a lot of force in a short amount of time
Anaerobic process and fatigues quicker
Type IIb
Major fuel of Type IIb
Creatine Phosphate
How active is ATPase enzyme in Type IIb
Very high as it needs to produce a lot of energy in a short amount of time
Major Fuel of Type IIa
Glycogen (stored sugar)
What does Type IIa possess that the other two don’t have simultaneously?
Aerobic and Anaerobic energy generating capabilities
How active is ATPase enzyme in Type IIa
Moderately active
