Fatigue

Question 1

what is an ok definition of fatigue

Answer 1

failure to maintain the required force or expected force

Question 2

what is a better than ok definition of fatigue

Answer 2

loss of max or potential performance

Question 3

what are the main questions for fatigue research

Answer 3

what is the breaking point?
which part of the contractile machinery has failed?
what is the mechanism for failure?

Question 4

what are 2 ways we manifest fatigue?

Answer 4

• inability to achieve max force
• slowing of contractile response

Question 5

What is the motor command pathway

Answer 5

motivation
motor cortex
spinal cord
motorneuron
peripheral nerve
NMJ
surface membrane
T tubules
Ca+ release from SR
Ca+ bind to troponin
Cross-bridge
Consequence of contraction = force, metabolites, heat

Question 6

how do we remove the motivation complication from the motor command pathway?

Answer 6

electrical stimulation to a peripheral nerve

Question 7

potential causes for central fatigue

Answer 7

• emotions/lack of motivation
• psychological perception of the sense of effort
• unfamiliarity of task
• CNS function

Question 8

in a situation where force applied is gradually decreasing while eyes are closed, but suddenly increase to normal when eyes are opened, is this an example of central or peripheral fatigue

Answer 8

peripheral
*if muscles were truly fatigued (central) you wouldn’t see a rapid recovery

Question 9

What are 2 kinds of peripheral fatigue

Answer 9

high and low frequency fatigue

Question 10

high frequency peripheral fatigue

Answer 10

can be painful, unable to maintain force

Question 11

low frequency peripheral fatigue

Answer 11

series of contractions, associated with eccentric exercise

Question 12

potential sites of peripheral fatigue

Answer 12

• NMJ
• sarcolemma
• E-C coupling (Ca+ release and removal)
• cross-bridge cycling

Question 13

potential mechanisms of peripheral fatigue

Answer 13

• slowed resynthesis of ACh
• electrical properties of the fiber (Na influx/K efflux)
• reductions in Ca release and uptake
• acidosis - pH changes
• temp is probably not an issue

Question 14

is recovery from fatigue fast or slow

Answer 14

fast

Question 15

What does all this information about fatigue mean for training/PT?

Answer 15

• motivation is an issue
• take breaks
• novel interventions may increase fatigue
• every pt is different

Question 16

what does all this information about fatigue mean for injury occurrence and prevention?

Answer 16

• more injuries occur when fatigued!
• it takes time to get to fatigue (advocate for longer pt sessions) but also you should train them while they are fatigued to decrease chance of injury