Accuracy, kinematics and EMG

Question 1

measure of accuracy (discrete task)

Answer 1

Constant Error (Σ(X₁ - T)/N): the average signed error score providing a measure of bias (i.e. under-or undershooting)

Variable Error (SQRT(Σ(X₁ - T)²/N): a measure of consistency (or variability) across a series of trials (standard deviation)

Absolute Error (Σ lX₁ - Tl /N): average unsigned error score (measure of error magnitude)

Question 2

measures of accuracy (continuous task)

Answer 2

root mean squared error: the average unsigned error for a continuous task

difference between performance and criteria at different points in time

• average measure of error

Question 3

describing the movement

Answer 3

A. Qualitative description

• verbal descriptions, time-lapse photography

B. Movement Kinematics

1. displacement - spatial position of effector (i.e. arm) during movement
2. velocity - rate of change of an objects position (i.e. arm) with respect to time
   - slightly right skewed (at beginning of movement, of reaching out for glass, arm moves fast, then slows down to become accurate)
3. acceleration - change in velocity of an object (i.e. arm) during movement
   - velocity and acceleration are scaled by increasing displacement

Question 4

apraxia vs normal movement

Answer 4

Apraxic patient has problems with timing when to flex and relax, inter-joint coordination

normal person has smooth movement, with coordinated flexion and relaxation

Question 5

measuring CNS activity

Answer 5

electromyography (EMG)

• electrical activity associated with muscle contration
• provides info regarding the temporal and intensity characteristics
• provide info regarding maximal contraction and fatigue

(bicep and tricep, represent when an alpha motor neurons fires

Question 6

tonic and phasic contraction

Answer 6

tonic contraction

• external muscle stimulation
• synchronous (all muscles fire at the sametime)

phasic contraction

• voluntary muscle activity
• asynchronous (extrafusal muscle fibers not firing at sametime)

Question 7

co-contraction

Answer 7

• activation of two or more muscles about a joint
• can serve to stabilize (hold book inplace)
• can impair movement (spasiticity) following upper-motorneuron injury

all the muscles of the patient contracted at the sametime, even antagonists