L4

Question 1

what is surface EMG

Answer 1

uses electrodes adhered to the skin which picks up electrical activity of the muscle underneath

Question 2

why would we be interested in recording from one MU

Answer 2

???

Question 3

what are three ways discharge pattern can be altered that affect force production

Answer 3

• double discharge
• synchrony
• fatigue (muscle wisdom?)

Question 4

what is double discharge and an example of when it could occur

Answer 4

a second discharge is injected after only 10ms, to produce a jump in force production
- could occur at the onset of a rapid movement (ballistic movements)

Question 5

pros and cons of double discharge

Answer 5

pro: increase in the rate of force development
con: loss of fine motor control

Question 6

why do we get more force with double discharge

Answer 6

• more calcium floods out onto the cell
• not enough tune to all be re-sequestered and therefore more cross bridges can be formed
  cooperative recruitment = not all myosin heads have an affinity for actin at the start of a contraction (the mechanical pull activates more myosin heads making them available to bind)

Question 7

what is synchrony

Answer 7

the degree to which two different motor units fire simultaneously

Question 8

when does synchrony occur

Answer 8

• large contractions
• fatigue!!!
• coordination between muscles

Question 9

T or F: Synchrony is greatest in skill-trained individuals and least in strength trained

Answer 9

F: greatest in strength trained individuals