kine 301 exam

The three stages of the information processing model of the CNS – short answer

• Stimulus identification - recognizing and interpreting incoming sensory information

• Response selection - deciding what response to make

• Response programing - initiating and coordinating the movement response

Write an example (not the traffic light example) that illustrates the three stages of information processing – short answer

• Stimulus identification: sees the pitcher throw the ball

• Response selection: decides to swing based on the ball’s trajectory

• Response programming: initiated and executes the swing

s the integration of sensory information for postural control the same all the time, every time?

No integrating is not always the same, it adapts based on context, environment, and task demands (ex: vision is more important on uneven ground)

Stimulus Clarity, Stimulus Intensity, and Stimulus Modality

• Stimulus clarity: clear stimuli = faster response time

• Stimulus intensity: stronger stimuli = faster response 

• Stimulus modality: some senses (ex: vision) may be processes faster/slower depending on task

Examples of Good and Poor S-R Compatibility

Good s-r compatibility: the stimulus and response are well matched and easy to associate 

Ex: turning steering wheel left = car turns left

= faster reaction time, fewer errors 

Poor s-r compatibility: the stimulus and response are mismatched or unintuitive 

Ex: stove burner knob in a random order

= slower reaction time, more errors 

If uncertainty doubles, does reaction time increase by a near constant amount?

Yes, according to hicks law, reaction time increases by near constant amount when the number of choices (uncertainty) doubles

Ex: RT = a+b * log2(N), N = number of choices 

 What are the potential reasons that will decrease reaction time?

• Practice and experience

• Clear and intense stimuli (high clarity and intensity)

• Anticipation or cueing 

• Simple tasks or few choices

• Focused attention

• Optimal arousal level (not too tired or overstimulated

 Reaction time changes with and without a fore period

• With foreperiod (predictable cue/timing): RT is shorter and more consistent

• Without foreperiod (random timing): RT is longer and more variable

What is Response Time

• Response time = reaction time + movement time

• RT: time from stimulus to movement initiation

• MT: time from movement start to completion

The premotor and motor components of reaction time.

• Premotor time: stimulus onset -> muscle activation begins (planning and processing time)

• Motor time: muscle activation -> movement begins (time to generate movement force)

The factors that increase reaction time according to Hick’s Law

• More choices = longer RT

• Unfamiliar or complex responses 

• Low stimulus clarity or intensity

• Unexpected or random stimulus timing

The components of postural control are Postural Orientation, Postural Equilibrium, and Anticipatory Postural Adjustments.

• Postural orientation - alignment of the body with respect to gravity, the support surface, and environment (ex: upright standing posture)

• Postural equilibrium - the ability to maintain or return the balance during static or dynamic tasks

• Anticipatory postural adjustments (APAs) - muscle actions before voluntary movement to counteract expected disturbance (ex: tighten core before lifting leg)

 Define postural equilibrium

The ability to maintain balance by managing the relationship between center of mass and base support, especially in response to internal or external forces

Does the center of pressure measure postural sway?

Yes - center of pressure is used to quantify postural sway, tracking how often pressure shifts under the feet while maintaining balance

Vision’s role in the control of posture.

Vision helps determine body position relative to the movement, detects movement, and aids balance. Removing visual input (ex: eye closed) typically increase sway and reduces stability

Factors that increase postural sway

• Fatigue

• Aging

• Injury or neurological disorders

• Poor vision or eyes closed

• Unstable or uneven surfaces

• Distractions or dual tasking

Muscle recruitment patterns to correct postural perturbations, Distal or Proximal first?

Distal muscles activate first followed by proximal muscles. Ex: after a forward push, ankle muscles (distal) engage before hip/trunk muscles (proximal) to restore balance

The Theory of Optimal Control, Equilibrium Point Hypothesis, and Leading Joint Hypothesis

theory of optimal control:

• CNS selects the most efficient movement strategy based on minimizing effort, error, or time

• Movement is planned and controlled to optimize outcomes 

Equilibrium point hypothesis:

• CNS sets a final position (endpoint) and muscles behave like springs that naturally bring limbs to that positon

• Movement occurs by shifting the body’s equilibrium points

Leading joint hypothesis (LJH):

• One joint (the “leading joint”) initiates and generates the more torque, while subordinate joints adjust accordingly 

• Human limbs are linked segments, and movements are coordinated from leading to subordinate joints

What is the hypothesis that proposes that with multiple solutions to perform a movement, the selected movement solution is because the CNS programs the endpoint location

Equilibrium point hypothesis - CNS programs the final position, not the whole path

 Is there a hypothesis that describes our muscle function as springs?

Yes, equilibrium point hypothesis describes muscle function like springs, returning to equilibrium 

 Interaction torques – Good, Bad, or Ugly?

• Good: can assist movement, saving energy (ex: swinging a bat)

• Bad: can disrupt movement if not controlled, especially during movement if not controlled, especially during multi joint coordination

Ugly: if mismanaged due to injury or fatigue, can cause unstable or awkward movements

What torque is greatest at a leading joint?

The greatest torque at a leading joint is the muscle-generated torque, used to initiate and drive movement efficiently through the limb.

The characteristics of a leading joint in the Leading Joint Hypothesis?

• Initiates movement

• Generates largest torque

• Controls the overall movement pattern

• Influences motion at subordinate joints via interaction torques 

The LJH proposes that human limbs are linkages of several segments.

• Each limb consists of multiple joints (ex: shoulder, elbow, wrist) and segments (ex: upper arm, forearm, hand)

• Movements at one joint affect motion at others due to these physical linkages

• The leading joint initiates motion, while subordinate joints adjust their actions based on the forces (like interaction torques) generated by the leading joint’s movement

• This matters bc it emphasizes coordinated control of these linked segments to produce smooth, efficient, and purposeful movement

Know the term Degrees of Freedom

DOF refers to the number of independent ways a joint or system can move

• Each joint has a specific DOF based on its anatomical structure

• Movements can occur in different planes (ex: up down, side to side, rotation

  • Ex: shoulder joint: 3 DOF (flexion/extension, abduction/adduction, internal/external rotation)

• The cns must coordinate DOF to produce smooth and efficient movements

What is the function of subordinate joints?

subordinate joints play a supportive role in movement 

Key functions:

• Coordinate with the leading joint to ensure smooth, efficient movement 

• Adjust and compensate for the forces (ex: interaction torques) generates by the leading joint 

• Help achieve accuracy, stability, and fine control of the movement’s end goal

• Maintain balance and posture during dynamic actions

• Ex: reaching for an object

  • Shoulder (leading joint) initiates the reach

  • Elbow and wrist (subordinate joints) adjust to guide the hand precisely to the target

In the LJH, what happens when there is decreased control due to reduced neural processes?

Reduced neural input disrupts planned coordination, causing the limb segments to move less harmoniously, which negatively affects performance, accuracy, and safety. 

• Poor coordination between leading and subordinate joints

• Subordinate joints fail to properly compensate for interaction torques

• Movements become less efficient, more variable, and possibly unstable

• Inc energy cost and effort to complete tasks

• Greater risk of movement error or inability to accurately reach the intended goal

The LJH as it relates to running – short answer.

In running, the hip joint acts as the leading joint, generating the largest torque to initiate leg movement. The knee and ankle (subordinate joints) coordinate their actions in response to the hip’s motion, adjusting fro interaction torques to ensure efficient propulsion, balance, and stride control. Coordination allows for smooth, energy efficient running and proper force distribution through the limb

The difference between Feedforward Control and Feedback Control when catching a ball with eyes open and with eyes blocked.

• Feedforward control - movement is planning in advance, based on prediction, wo relying on real time sensory input

  • Ex: catching a ball w eyes blocked:

    • You rely on memory and predication of the ball’s speed, direction, and timing

    • No visual updates -> adjustments can be made midaction 

    • Accuracy depends on how well u anticipated the ball’s trajectory

• Feedback control - movement is adjusted in real time based on sensory input (ex:  vision, touch)

  • Ex: catching a ball with eyes open

    • You can see the ball and make on the fly corrections to your hand position 

    • Visual feedback helps improve accuracy and timing of the catch  

The problems to consider with multi-joint movements

• Coordination complexity

  • multiple joints must work tg precisely to achieve smooth, efficient movement

• Interaction torques

  • Movement at one joint can cause forces (torques) at other joints, which can assist or disrupt the intended motion

  • These torques must be anticipated and controlled

• Inc degrees of freedom (dof)

  • More joints = more dof, making it harder for the cns to control and stabilize the movement 

• Timing issues

  • Movement need correct sequencing (ex: leading joint first) for accuracy and balance 

• Energy efficiency

  • A smaller error at one joint can be magnified by downstream joints, affecting the end result

• Postural stability 

More moving joints can make it harder to maintain balance, esp during dynamic tasks

How is accuracy affected if you increase your bat/golf swing?

When you inc the speed or force of your bat or golf swing accuracy typically dec

• Fast movements introduce more variability in motor output 

• There is less time to make corrections 

• Force variability inc at lower to moderate force levels, making it harder to control the exact movement path

Key concepts: this reflects the speed-accuracy trade off as movement speed inc, accuracy dec, esp in task requiring precise targeting

In Fitts’ Law, movement time vs index of difficulty is plotted. The slope corresponds to what?

The movement time (MT) is plotted against the index of difficulty (ID) in fitts law, the slope corresponds to the performer's information processing rate

• It reflects how much movement time incs as task difficulty incs

• Steeper slope = slower processing (more time needed for harder tasks)

• Shallower slope =  faster processing (less time inc per unit of difficulty)

Fitts law equation: MT = a + b * ID

• A = y intercept (baseline movement time for simple tasks

• B = slope (info processing time per unit of difficulty)

As the amount of force required increases, at what percent of maximum force does the variability of force begin to decrease?

Variability of force begins to dec at around 70% of maximum force

Explanation:

• Low to moderate force levels, force variability inc as force inc

• But once the force exceeds abt 70% of mac, the variability starts to dec due to 

  • Greater recruitment of high threshold motor unit

  • More consistent firing patterns from motor neurons

• Summary: 

  • <70% max force -> more variability 

  • >70% max force -> less variability (force output becomes more stable)

 In the Fitts’ Law equation, what does the y-intercept signify?

MT (movement time) = a + b * ID (index difficulty)

• Y intercept (a) = baseline movement time when ID is zero - meaning the task is rlly each (ex: very large target at a short distance)

• Y intercept means the minimal time it takes to initiate and execute a simple movement

• Reflects non difficulty related delays like reaction time, motor initiation, and basic movement preparation

 Factors that Are and Are Not part of the Fitts’ Law calculation.

Fitts law is based on the relationship between:

• Distance to the target (D) - how far u need to move

• Target width (w) - how big or small the target is

These 2 factors determine the index of difficulty (ID): ID = log2(2D/W)

NOT part of fitts law calculation:

• Force required to move

• Muscle fatigue

• Stimulus clarity or intensity

• Reaction time

• Environmental conditions

• Individual experience of skill level (though it may affect slope/intercept, not the formula)

• Type of feedback (visual auditory)

Examples of Feedforward and Feedback tasks

Feedforward (planned movements wo real time adjustments)

• Throwing a dart at a dartboard

• Swinging a bat at a pitched ball

• Jumping to catch a ball w eyes closed

• Typing on a keyboard wo looking 

Feedback (movements adjusted using sensory input during the task)

• Balancing on an unstable surface (using vision and proprioception)

• Catching a ball w eyes open (adjusting hand position)

• Diving an steering around curves

• Walking on uneven ground (adjusting steps in real time)

Define Feedback Control.

Feedback control - process of adjusting movements during or after an action based on real time sensory info (ex: vision, touch)

Key points:

• Allows for corrections if something unexpected happens

• Involves a sensory loop: stimulus -> response -> sensory feedback -> adjustment

• Slower than feedforward control due to processing time for the feedback

Ex: catching a ball w eyes open - u adjust your hand’s position based on visual feedback of the ball’s trajectory

Define Impedance Control.

Impedance control - regulation of muscle stiffness, damping and resistance to external forces to maintain stability and control movement 

Key points:

• Helps the body adapt to unpredictable forces (ex: someone bumping into you)

• Involves adjusting muscle tone to make joint more rigid or more flexible depending on the task

• Essential for fine motor control, postural stability, and interacting w the environment safely 

Ex: holding a cup of coffee while someone brushes past u, your muscles adjust stiffness to resist spilling the coffee wo overreacting

The function of reflexes for eye control while the head is moving

Reflex involved is the vestibulo ocular reflex (vor)

Function:

• Stabilizes your gaze by producing eye movements that are equal in magnitude but opposite in direction to head movements

• Allows you to maintain clear vision (keep objects in focus) even while your head is moving

Ex: when you turn your head to the right, the vor moves your eyes to the left at the same speed, so you can keep your gaze fixed on an object 

Summary: reflexes like the vor are essential for eye stability, balance, and visual clarity during movement 

The logarithmic relationship between movement speed and timing on accuracy.

Relationship describes by fitts law which shows that as movement speed inc, accuracy dec, in a logarithmic fashion

Key ideas:

• When tasks require greater speed, they become less accurate - esp for small or distant targets

• Conversely, to maintain high accuracy,  you must slow down your movement

• Speed inc = accuracy dec

• Small inc in difficulty lead to progressively greater inc in movement time to maintain accuracy 

Formula: movement time (MT) = a + b * log2 (2D/W)

• D = distance to target 

• W = width (size) of target 

• The logarithmic part (log2 (2D/W)) represents index of difficulty (ID)

·  What is the relationship between target size and reaction time?

  As target size dec, rection time in - meaning smaller targets lead to longer reaction times

• Smaller targets require more precision, so the brain takes more time to plan the movement accurately 

• Tied to fitts law, where smaller targets inc task difficulty, leading to slower reaction and movement times 

• Smaller target -> larger reaction time

• Larger target -> shorter reaction time

What defines the beginning of the Stance Phase?

The beginning of the stance phase is defined by initial contact, also known as heel strike - the movement when the heel of the foots first touches the ground during walking or running

• Start stance phase = heel contract w the ground

Marks the transition from the swing phase (foot in the air) to stance phase (foot on the ground)

What defines the end of the Stance Phase?

The end of the stance phase defined by toe-off, called pre-swing - the moment when the toes of the foot leave the ground, transitioning into the swing phase

• End stance phase = toe leaves the ground (toe off)

• Marks the start of the swing phase, where the leg moves forward through the air  

·  Stance phase comprises what percent of the total gait cycle (1 stride)?

The stance phase makes up approx 60% of the total gait cycle (1 full stride)

Breakdown:

• Stance phase: ~60% (foot is on the gound)

• Swing phase: ~40% (foot is in the air)

Is gait velocity related to stride length?

Yes, gait velocity is directly related to stride length

• Stride length inc, gait velocity (walking speed) generally inc - assuming cadence (steps per minute) also stays the same or inc

• Faster walking or running usually involves longer strides and higher step freq

• Formula: gait velocity = stride length * cadence

During exercise, your muscles may fatigue, so what should you expect to observe?

• Dec force production 

  • Muscles generate less force, making movements feel harder

• Slower contractions and movements

  • Reaction time and movement speed may slow down

• Inc muscle tremors or shaking

  • Due to motor unit firing variability and less coordinated muscle activity 

• Poorer coordination and accuracy

  • Movements become less precise and more variable 

• Inc effort perception

  • Tasks feel more difficult, even if they ar the same intensity

• Changes in posture or technique 

  • Fatigue may cause compensations ore form breakdown

Long sustained muscle contractions may cause shaking.  What is the reason for this?

Shaking during prolonged muscle contractions happen due to motor unit fatigue and firing variability 

• Motor unit fatigue 

  • As motor units tire, the body recruits additional units irregularly to maintain force

  • This leads to uncoordinated contractions, causing visible shaking

• Firing rate variability

  • Inconsistent firing patterns to motor neurons as they try to sustain force lead to tremors or twitches 

• Impaired synchronization

  • Motor unit fire in a coordinated rhythm, but fatigue disrupts this, resulting in jerky, unstable force output

Muscle shaking = fatigue induced variability in motor unit activation as the body struggles to maintain force

Do supraspinal structures that control voluntary movement contribute to decreased muscle force during fatigue?

Yes, supraspinal structures (brain regions above the spinal cord, like the motor cortex) do contribute to dec muscle force during fatigue

• Reduced motor cortex excitability

  • Fatigue can cause less effective activation of motor neurons from the brain

• Altered motor command output

  • The brain sends weaker or fewer signals to muscles, reducing voluntary force

• Inc perception of effort

  • Fatigue may cause the brain to “limit output” to avoid overexertion, further reducing force

Supraspinal fatigue = brain level fatigue that reduces voluntary muscle force by dec the quality of motor signals sent to muscles

Are there changes in the motor cortex as you fatigue?

Yes, there are changes in the motor cortex during fatigue, and these changes contribute reduced muscle performance 

• Dec excitability

  • The motor cortex becomes less responsive, making it harder to activate motor neurons effectively

• Altered signal output

  • Strength and precision of signals to muscles decline, leading to weaker contractions

• Inc effort perception

  • The brain perceives tasks more difficult which can limit voluntary drive to the muscles 

• Slower reaction times

  • Neural processing and response initiation slow down, affecting timing and coordination

Fatigue alters motor cortex function, reducing its ability to effectively drive muscle contractions, which leads to weaker, less coordinated movements

response time