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EPHE 441 - Post Midterm > Fatigue > Flashcards

Fatigue Flashcards

1
Q

“a condition in which there is a loss in the capacity for developing force and velocity of a muscle resulting from muscle activity under load which is reversible by rest”

A

Fatigue!! Important part is that it is reversible by rest

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2
Q

Name at least 5 factors that influence development of muscular strength? (there are 11)

A 
Training Load
Speed of contrac.
Metabolic changes
Training to failure
Type of contrac.
Biomech. Adap.
Rest
Neural Adap.
Endocr. Influ.
Muscle Size
Training Vol.
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3
Q

Fatigue can occur during prolonged contractions of submaximal intensity without an apparent decrement in the ____ ____ targeted force

A

targeted force

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4
Q

Fatigue processes begin when?

A

immediately with the start of PA

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5
Q

What causes the temporary reduction in neuromuscular performance?

A

Peripheral (or muscle) factors or Central (or neural) factors

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6
Q

“mechanisms associated with excitation-contraction coupling as well as metabolic accumulation”

A

peripheral or muscle factors of fatigue

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7
Q

“Mechanisms including areas proximal (upstream) to the neuromuscular junction”

A

central or neural factors of fatigue

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8
Q

Fatigue depends on what 4 things?

A
  1. Type of exercise performed
  2. Fiber type of muscle involved
  3. Fitness status
  4. Nutritional status
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9
Q

What are the 4 potential sites of fatigue development? Are they central or peripheral?

A 
Central:
1. Brain
2. Spinal Cord
Peripheral:
3. Neuromuscular Junction
4. Muscle cells
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10
Q

Fatigue may be due to alterations in what 9 things?

A
  1. Activation of the PMC
  2. Propagation of command from CNS to MN
  3. Activation of MU and muscles
  4. Neuromuscular propagation (and NMJ)
  5. Excitation-contraction coupling
  6. Availability of metabolic substrates
  7. State of the intracellular medium
  8. Performance of the contractile apparatus
  9. Blood flow
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11
Q

Why would alterations in blood flow cause fatigue?

A

occluding blood flow means less O2 to the muscles and less clearing of metabolites

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12
Q

Three local factors of fatigue?

A
  1. Fiber Composition (FT vs ST) –> fuel availability
  2. Failure @ NMJ –> more common in type II
  3. Failure of contractile mechanism –> depletion of P stores, inc. acidity and temperature, and degradation of contractile proteins
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13
Q

8 muscle factors in development of local (peripheral) fatigue?

A
  1. Sarcolemma permeability
  2. Sarcolemma excitability/transmission of AP
  3. T-tubule propagation
  4. Ca++ release from SR
  5. Binding of Ca++ TnC
  6. Interaction of A+M (x-bridge)
  7. Metabolite accumulation (H+, Pi, ADP, heat)
  8. Substrate depletion (muscle glycogen, Cr, ATP)
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14
Q

What is the depletion hypothesis?

A

Fatigue within the muscle is due to a decrease in metabolites –> ATP, PC, and glycogen

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15
Q

What is the Accumulation hypothesis?

A

Fatigue within the muscle is due to the accumulation of metabolites known to impaire force generation –> lactate, H+ ions, NH3 and Pi

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16
Q

When H+ and lactate run amok, it causes what 5 bad things that lead ot fatigue?

A
  1. Decrease amt of Ca++ release
  2. Interferes with Ca++/Troponin binding
  3. Disrupts Na/K pump
  4. Inhibits PFK
  5. Interferes with actin/myosin interaction
17
Q

What are the two Neural (CNS) types of central fatigue?

A

Supraspinal and spinal

18
Q

What 3 neurotransmitters are involved in central fatigue?

A

Serotonin
Norepi
Dopamine

19
Q

What 4 neural factors inhibit force production?

A
  1. Supraspinal fatigue causes decreased cortical excitability
  2. Decreased MN discharge rate
  3. Inhibition from Renshaw cells
  4. Inhibition from muscle and tendinous afferents
20
Q

What is the TRY-5HT theory of central fatigue?

A

increases in free tryptophan –> 5-HT —> Serotonin
= relaxation, sleep, fatigue

Exercise = inc. FFA release = competition for albumin = bumping off tryptophan = inc free tryptophan = 5-HT synthesis = inc serotonin?

21
Q

What declines in motor neuronal output lead to central fatigue? (3)

A
  • Alpha MN affected/inhibited
  • Cutaneous fiber info (sensory output from periphery?)
  • Renshaw Cells activity enhanced (inhibitory interneurons)
22
Q

How does less action potentials lead to decreased force and therefore fatigue?

A

Less AP on sarcolemma = less Calcium released cause less ryanodine receptor action = less calcium binding to calcium = less troponin being pulled away = less contraction occurring, decreased force

DECREASE IN AP COMING DOWN MOTOR NEURON FROM THE INHIBITORY EFFECTS OF THE RENSHAW CELLS

23
Q
  • Excitatory input to cortex
  • descending drive from cortex
  • motor neuron excitability (altered threshold, ability to transmit repetitive signals)
  • antagonist activity (thinking about fatigue)
  • NMJ transmission

What do all of these things cause?

A

-Reduced firing frequency and recruitment
-ultimately fewer x-bridges formed
Therefore - imparted force production and fatigue due to failing central (neural) factors

24
Q

Fatigue is not all bad! What can fatigue contribute to in a positive way?

A

Initiates muscular adaptations in metabolic and structural areas

25
Q

6 training variables influencing peripheral fatigue?

A
  1. Training Status
  2. Rest interval
  3. Volume
  4. Intensity and load
  5. time under tension
  6. failure
26
Q

Fatigue during long term submaximal exercise?

A
  • Relies almost exclusively on SO fibers:
    ○ Depletion of glycogen stores
    ○ If FOG fibers recruit –> lactate and H+ buildup
    ○ Central fatigue (especially in warm environments)
27
Q

Static exercise and fatigue?

A
  • Depletion of PC in FG fibers
  • Accumulation of H+ –> inhibition of the CNS by afferent fibers (nociceptors)
    ○ Decrease in pH really affects afferent fibers –> goes back to nervous system with “owe owe owe” signal
  • Occlusion of blood flow (can be quite painful)
    ○ Inhibition of glycolysis
    ○ Decrease Ca++ release from SR
    ○ Interferes with Ca/troponin binding
    ○ La- interferes with cross-bridging
28
Q

Dynamic resistance exercise and fatigue?

A
  • PC depletion –> high load, low rep
  • H+, Pi, ADP accumulation –> high rep, low load
    ○ Inhibition of glycolysis
    ○ Decrease Ca++ release from SR
    ○ Interferes with Ca/troponin binding
    ○ La- interferes with cross-bridging
29
Q

Anaerobic (sprint) exercise and fatigue?

A 
- Depletion of PC stores and accumulation of H+
○ Inhibition of glycolysis
○ Decrease Ca++ release from SR
○ Interferes with Ca++/troponin binding
○ La- interferes with cross-bridging
30
Q

Sites of the sources of fatigue: 4 central and 2 peripheral?

A 
CENTRAL:
1. Afferent feedback
2. Motivation
3. MN excitability
4. Pre/post synapse at NMJ
PERIPHERAL
1. Fuel depletion
2. Waste accumulation
31
Q

Look at the “Origins of Localized Muscle Fatigue” slide = last slide of fatigue.

A

Should draw this and understand it :)

EPHE 441 - Post Midterm (5 decks)

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