week 5: The muscular system: Acute muscular responses to exercises:fatigue

Question 1

muscular fatigue

Answer 1

reduction in muscle force (or power) below expected/ required level of force

( a decline in force with repeated contractions)

reversible and temporary

Question 2

mechanism of muscle fatigue

Answer 2

central and peripheral

Question 3

sites of limitations of peripheral fatigue

Answer 3

1. action potential-reduction causes lower force outputs
2. release of calcium
3. calcium bind to troponin C - H+ due to acidosis can effect
4. myosin power storke
5. force proudction

Question 4

as muscle contractions are repeated, SR’s ability to release calcium

Answer 4

becomes impaired

Question 5

cytoplasmic [Ca2+] with fatigue

Answer 5

reduced

Question 6

effect of caffeine on SR Ca2+ release

Answer 6

if muscle is incubated with caffeine, allows increased release of SR stored Ca2+

caffein elevates cytosolic levels of Ca2+
results in direct increase of force production

evidence that impairments in Ca2+ cycling are contributing to fatigue process in muscle

Question 7

metabolites implicated in fatigue process

Answer 7

increase H+
increase in inorganic P
increase ADP
increase Mg2+
increase reactive oxygen species

Question 8

how does increase in H+ and Pi induce fatigue

Answer 8

H+:
competes with binding of Ca2+ to troponin C
H+ and Pi:
effects cross bridge

Question 9

why is power reduced with increasing sprint number
(PCr)

Answer 9

progressive reduction in Pcr stores with greater sprints
incomplete PCr resynthesis
(4 mins needed to replenish stores via CK reaction)

PCr + H+ + ADP > ATP + Cr

Question 10

why is power reduced with increasing sprint number
( anaerobic glycolysis)

Answer 10

impaired rates of anaerobic glycolysis, linked to glycogen depletion and increase in - modulators of this pathway (H+)

Question 11

why is power reduced with increasing sprint number (metabolites)

Answer 11

inability to maintain cellular homeostasis that impacts force generation
e.g build up fatigue inducing metbaolites