Question 1

Which of the following best defines a motor unit?

Accepted Answer

One motor neuron and all the skeletal muscle fibers it innervates.

Question 2

During an EMG experiment, why does the integrated EMG value increase as clench force increases?

Accepted Answer

Because more motor units are recruited to generate greater force.

Question 3

What physiological process primarily explains the decline in muscle force during sustained maximal clench (fatigue)?

Accepted Answer

Depletion of ATP and reduced calcium release.

Question 4

If the maximum clench force recorded is $$20\ \mathrm{kg}$$, what is the value of 50% maximum clench force?

Accepted Answer

$$10\ \mathrm{kg}$$

Question 5

Which measurement tool in the Biopac Student Lab is used to determine the time between two points on a recording?

Accepted Answer

Delta T

Question 6

Why might males, on average, generate higher absolute clench forces than females in a classroom EMG experiment?

Accepted Answer

Males have greater muscle mass and higher testosterone levels, leading to more muscle protein synthesis.

Question 7

What is the primary purpose of using the I-beam cursor in the Biopac Student Lab EMG analysis?

Accepted Answer

To select specific regions of data for measurement and analysis.

Question 8

Which of the following best describes motor unit recruitment?

Accepted Answer

The activation of additional motor units to increase muscle contraction strength.

Question 9

During a sustained maximal clench, what happens to the force output as fatigue sets in?

Accepted Answer

Force output decreases due to physiological fatigue mechanisms.

Question 10

Which of the following is the correct definition of electromyography (EMG)?

Accepted Answer

A method for recording the electrical activity of skeletal muscle.

Question 11

If the time to fatigue (from maximum to 50% maximum clench force) is measured as $$30\ \mathrm{s}$$ for the dominant arm and $$20\ \mathrm{s}$$ for the nondominant arm, what can be inferred?

Accepted Answer

The dominant arm is more resistant to fatigue.

Question 12

Which scenario best illustrates the concept of motor unit rotation during a sustained submaximal contraction?

Accepted Answer

Some motor units take turns being active to prevent fatigue.

Question 13

What is the main function of dynamometry in the context of EMG experiments?

Accepted Answer

To measure the force produced by muscle contraction.

Question 14

A student selects a region on the EMG trace using the I-beam cursor and notes the mean value. What does this mean value represent?

Accepted Answer

The average amplitude of the EMG signal in the selected region.

Question 15

Which of the following best explains why the force output decreases during a continuous maximal clench, as seen in the Biopac data?

Accepted Answer

ATP stores are depleted and calcium release is reduced.

Question 16

If a student observes that the integrated EMG value is higher for the dominant arm compared to the nondominant arm during maximal clench, what is the most likely explanation?

Accepted Answer

The dominant arm has more muscle fibers and greater motor unit recruitment.

Question 17

Which of the following is NOT a plausible reason for differences in clench force between individuals?

Accepted Answer

Differences in skin pigmentation.

Question 18

In the Biopac Student Lab, what does the 'Value' measurement display when a single point is selected with the I-beam cursor?

Accepted Answer

The amplitude value at the selected point.

Question 19

A student is analyzing the time to fatigue for both arms. If the nondominant arm fatigues faster, which of the following is the most likely explanation?

Accepted Answer

The nondominant arm has less muscle mass and lower endurance.

Electromyography II: Motor Unit Recruitment and Fatigue – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards