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PHA 511 > 2. EMG and Muscle Physiology > Flashcards

2. EMG and Muscle Physiology Flashcards

1
Q

Electromyography

A

Measure of changes in electrical potential on the surface of the skin by muscle action potentials being conducted along nearby muscle fibers when a muscle contracts

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2
Q

Hand Dynamometry

A

Test measuring pure motor ability

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3
Q

Strength of Preferred (dominant) Hand

A

5-10% stronger than non preferred hand

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4
Q

Strength

A

Capacity for gross muscular effort

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5
Q

Power

A

Effort at high speed

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6
Q

Electromyograph

A

Differences in amplitude of EMG recording reflects differences in number and size of active motor units

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7
Q

Number of Motor Units

A

Brain uses sensory receptors in muscles and tendons to determine

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8
Q

Isometric Contraction

A

Muscle is activated and held at constant length

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9
Q

Graded Response

A

Increased amplitude resulting from recruiting additional motor units

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10
Q

Tonus

A

Small amount of electrical activity between major pulses

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11
Q

Size Principle

A

Motor units will be recruited in order of size (smallest to largest) depending on intensity

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12
Q

Max Grip Strength (demographic differences)

A 
Gender
-size of muscle fibers
-testosterone
Age
Height/weight
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13
Q

When holding an object does the number of motor units remain the same?

A

Yes

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14
Q

Are the same motor units used for the duration of holding that object?

A

No, different motor units are used in order to delay fatigue in specific motor units

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15
Q

Fast Twitch (aka Type II (glycolytic)) Fibers

A

Activated with max clench

Rapid fatigue

Energy source: glycogen

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16
Q

Slow Twitch (aka Type I (oxidative)) Fibers

A

Activated with moderate clench

Slow fatigue

Energy source: aerobic respiration

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17
Q

Fibers of any one motor unit are always…

A

of one type

18
Q

Slow Oxidative

A

Red muscle (lots of myoglobin)

Type I

Slow twitch

Oxidative (lots of mitochondria)

Well supplied with capillaries

19
Q

Fast Glycolytic

A

White

Type IIx (IIb)

Fast twitch

Anaerobic

Dependent on glycolysis

Larger in diameter than SO

High glycogen content

20
Q

Fast Oxidative Glycolytic

A

Type IIa

Not abundant in humans

Fast twitch

21
Q

Differentiation of Skeletal Muscle Fibers

A

Differentiated on basis of structural, contractile, biochemical properties

22
Q

Speed of Contraction

A

Dependent on rate of ATP usage by myosin

23
Q

Causes of Muscle Fatigue

A
  • Reduced Ach
  • Poor ATP supply
  • Decrease in pH
  • Accumulation of extracellular K
  • Accumulation of lactic acid
  • Decrease in glycogen
  • Dehydration
  • Hypoglycemia
24
Q

Integrated EMG

A

Activity level of muscle (overall muscle effort)

Linear relationship between force produced by muscle and amount of iEMG

25
Q

Non Exercise vs Exercise (1)

A

After strength training: same amount of muscle force requires less iEMG (think of trained rowers)

Non exercise: require more overall effort to perform work (think of untrained rowers)

26
Q

Non Exercise vs Exercise (2)

A

CNS, neural adaptation, motor learning

Better synchronization of motor unit activation (use less force to produce a movement)

27
Q

3 Sources of ATP

A

Creatine phosphate

Glycogen

Cellular respiration

28
Q

Creatine Phosphate

A

Donates phosphate to make ATP

Fast but doesn’t last long (2-7 seconds)

29
Q

Glycogen

A

Limited source

Comes from glucose stored in muscle and liver

Important under anaerobic conditions

2 ATP

30
Q

Cellular Respiration

A

Required for prolonged activity

Lots of mitochondria

36 ATP

31
Q

Slow Twitch Fibers (Type 1)

A

Red (lots of myoglobin)

Small fiber size

Small force

Slow contraction speed

High oxidative capacity

Fatigue resistant

Usage: posture, endurance

32
Q

Fast Fatigable (Type IIB)

A

White (not as much myoglobin)

Large fiber size

Large force

Fast contraction speed

Low oxidative capacity

Easily fatigable

Usage: gallop, jump, rapid movement

Lots of power, strength

33
Q

Fast Fatigue Resistant (Type IIA)

A

White (not as much myoglobin)

Large (not as much as IIB)

Intermediate force

Fast contraction speed

Moderate to high oxidative capacity

Fatigue resistant (less than I)

Usage: run

34
Q

Motor Unit

A

Motor neuron and all the muscle fibers it innervates

35
Q

One motor neuron per muscle fiber

A

Many muscle fibers per motor neuron

36
Q

All muscle fibers innervated by a given motor unit will be…

A

Of the same type

37
Q

Recruitment

A

Progressive activation of additional motor units

38
Q

Order of Recruitment

A

Starting with smallest motor units, progressively larger unites are recruited with increasing strength of muscle contraction

First: Smaller motor units (Type 1)

I –> IIa –> IIb

39
Q

More units activated…

A

Greater force of muscle contraction

40
Q

All or None Phenomenon

A

Neuronal AP induces all the fibers of the motor unit to contract simultaneously

PHA 511 (7 decks)

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