Exam 3 (final)

Question 1

what is happening at the molecular level during muscle fatigue

Answer 1

lower amount of cross-bridges able to form means we ultimately decrease force production

Question 2

how does the EMG signal usually change with force from muscles that are NOT fatigued?

Answer 2

As the force goes up so does the EMG and vice versa. If you are holding a constant force, the EMG is constant as well.

Question 3

when a muscle is fatigued - what happens to the central drive from the brain to the motor neurons ?

Answer 3

we increase the central drive to the muscle to increase motor unit recruitment OR increase firing rate of current active motor units. This is all done to compensate for the failure occurring in the muscle (failure in the muscle fibers)

Question 4

what is muscle fatigue?

Answer 4

activity-related impairment of the physiologic processes that are involved in the production of muscle force.

Question 5

during what type of contractions can be study muscle fatigue? (four total)

Answer 5

1. sustained max
2. repetitive max
3. sustained sub-max
4. repetitive sub-max

Question 6

what are the sites in the neuromuscular system which fatigue can occur?

Answer 6

a.Central drive to the motor neurons
b.Activation of motor units and muscles
c.Neuromuscular propagation
d.Excitation-contraction coupling
e.Availability of energy substrates
f.The intracellular environment
g.Contractile apparatus
h.Blood flow to the muscle

Question 7

what is the EMG signal actually showing us?

Answer 7

gross command from the brain to the muscle

Question 8

what happens to MU as fatigue occurs?

Answer 8

discharge of MU decreases as fatigue increases. Think about the force-frequency relationship (higher frequency is greater force) so with decreased frequency of discharge we ultimately have decreased force production