Movement Analysis midterm

What is quantitative research?

Collects numerical data that can be measured and analyzed using statistics.

Researchers use quantitative methods to test hypotheses, measure outcomes, and examine relationships between variables.

For example, a researcher might measure the jump heights of 30 dancers before and after a six-week strength-training program.

The researcher can compare the average jump heights to determine whether performance changed.

What is qualitative research?

Focuses on understanding people's experiences, perspectives, feelings, and behaviors rather than primarily measuring numerical outcomes.

Researchers often collect data through interviews, observations, written responses, and personal accounts. They analyze the information to identify recurring themes and patterns.

For example, researchers might interview dancers recovering from injuries to understand their emotional experiences and challenges returning to performance.

Strengths: Provides detailed understanding, allows flexibility, and explores experiences that are difficult to measure numerically.

Weaknesses: Findings may be influenced by interpretation, and results may not generalize to a large population.

WHat is mixed-methods research?

Combines quantitative and qualitative approaches within the same study.

For example, researchers studying a new dance program for people with Parkinson's disease might:

Measure improvements in balance and walking speed (quantitative).

Interview participants about their confidence, mood, and enjoyment (qualitative).

Combining both methods provides a more complete understanding of the program's effects.

what is the abstract of a research paper?

a short summary of the entire research paper (all intro, methods, results, and discussion) meant to provide a quick overview, and used to quickly determine whether an article is relevant to their interests.

What is the introduction of a research paper?

explains the research problem, why it matters, and what previous research has discovered.

It identifies gaps in existing knowledge and presents the research question, aims, and often the hypothesis.

For example, a study might explain that dancers commonly use spotting during turns, but researchers do not fully understand whether spotting improves postural stability.

What is the methods section?

explains exactly how researchers conducted the study.

It includes participant recruitment, characteristics of the sample, equipment, experimental procedures, measurements, and data analysis.

The methods should be detailed enough that another researcher could replicate the study.

For example, researchers might explain that 34 dancers completed turning trials with and without spotting, then had their postural sway measured using a force plate.

What is the results section?

presents the findings of the study ONLY THE FACTS without extensively interpreting what they mean.

Results may include descriptive data, qualitative and quantitive analysis

For example, researchers might report that dancers experienced significantly less dizziness when using spotting.

What is the discussion section?

interprets the results and explains their significance.

Researchers compare their findings to previous studies, consider whether their hypothesis was supported, identify limitations, and suggest implications for practice or future research. conclusions reported as tentative

For example, researchers might discuss why spotting reduced dizziness but did not significantly improve stability after active turns.

What is the conclusion?

summarizes the study's major findings and explains their broader importance.

It may discuss practical applications, such as how dance teachers or physical therapists could use the findings.

Conclusions should remain appropriately cautious because one study rarely provides definitive proof.

What is the mean?

the arithmetic average of a group of numbers.

You calculate it by adding all the values and dividing by the number of observations.

What is the median?

the middle value when numbers are arranged from smallest to largest.

What is the mode?

the value that appears most frequently in a dataset.

What is the range?

measures the spread between the highest and lowest values.

What are the variance and standard deviation?

Both measure how spread out the data are around the mean.

1. Variance

Variance measures how much the values in a dataset differ from the mean, using squared differences.

High variance: The values are spread far apart.

Low variance: The values are clustered close to the mean.

2. Standard deviation

Standard deviation is the square root of the variance. It tells us approximately how spread out the values are around the mean, in the original units of measurement

A small standard deviation means values are clustered near the mean. A large standard deviation means values are more spread out.

What is a confidence interval?

a range of values used to estimate where the true population value (such as the population mean) might be.

It tells us how precise or uncertain our estimate is.

A 95% confidence interval means that if researchers repeated the sampling procedure many times, approximately 95% of the intervals calculated would contain the true population value.

What is a p-value?

measures how surprising the observed results, or more extreme results, would be if the null hypothesis were true.

null hypothesis - there is no significant effect, difference, or relationship between the variables being studied.

You conduct an experiment and calculate a p-value.

If p ≤ 0.05: Reject the null hypothesis. There is statistically significant evidence that fatigue affects jump height.

If p > 0.05: Fail to reject the null hypothesis. There isn't enough evidence to conclude that fatigue affects jump height.

What is internal validity?

concerns whether a study's design supports a trustworthy conclusion that the independent variable caused the observed change in the dependent variable.

For example, if researchers want to determine whether a new training program improves jump height, they must consider whether other factors, such as additional practice or previous experience, could explain the improvement.

Controlling confounding variables improves internal validity.

What is external validity?

refers to whether research findings can generalize beyond the participants and conditions studied.

For example, a study conducted with 15 elite ballet dancers may not necessarily apply to beginner hip-hop dancers.

Key distinction: Internal validity asks whether the causal conclusion is trustworthy. External validity asks whether the findings apply elsewhere.

What is correlation?

describes a relationship between variables.

Researchers use correlational studies to determine whether two variables change together.

For example, researchers might investigate whether dancers with more years of training tend to demonstrate better balance.

However, correlation does not prove causation. Other variables may explain the relationship.

What is a positive linear correlation?

correlation occurs when two variables tend to increase together.

For example, dancers with more years of training might generally have greater muscular strength.

As one variable increases, the other tends to increase.

What is a negative linear correlation?

correlation occurs when one variable tends to decrease as the other increases.

For example, greater fatigue might be associated with lower jump height.

As fatigue increases, jump height tends to decrease.

What is a parabolic relationship?

a curved relationship in which the direction of the association changes.

For example, increasing training intensity might initially improve performance, but extremely high intensity could eventually reduce performance because of fatigue.

The graph could resemble an upside-down U.

Unlike a straight-line correlation, a parabolic relationship cannot be fully described by a simple linear correlation coefficient.

What is R^2?

also called the coefficient of determination, measures the proportion of variance in one variable that can be explained by a statistical model. It tells us how well a model explains differences in the variable being studied. For example, if researchers examine the relationship between dancers' weekly practice hours and their jump heights and find that R² = 0.75, this means that 75% of the variation in jump height is explained by the model using practice hours, while the remaining 25% is unexplained by the model. The closer R² is to 1, the more variation the model explains; the closer it is to 0, the less variation it explains. However, R² does not prove causation. Even if practice hours explain much of the variation in jump height, this does not necessarily mean that practicing more causes dancers to jump higher.

what is a descriptive or cross sectional study?

Descriptive study: Describes characteristics of a population, such as the average flexibility of dancers.

Cross-sectional study: Collects data at one point in time and may describe characteristics or examine relationships between variables.

For example, researchers could survey 100 dancers about their weekly training hours and current injuries.

A purely descriptive study might report how common injuries are, while a cross-sectional analysis could examine whether training hours are associated with injury frequency.

Neither design alone establishes causation.

What is a case control study?

n observational research study that compares two groups of people: those who have a particular condition or outcome (cases) and those who do not (controls). Researchers then look backward to determine whether the groups differed in their exposure to certain risk factors.

For example, researchers identify two groups:

Dancers who have experienced ankle injuries.

Dancers who have not experienced ankle injuries.

They then investigate previous training schedules, jumping techniques, and other exposures.

What is a cohort study?

follows groups over time to determine whether different exposures are associated with different outcomes.

For example, researchers identify dancers using two different landing techniques and follow them for a year to see whether one group develops more injuries.

Unlike a case-control study, the researchers begin with the exposure and observe subsequent outcomes.

What is a quasi-experimental study?

a research study that examines the effect of an intervention or treatment without randomly assigning participants to groups. Researchers still compare outcomes between groups or before and after an intervention, but because participants are not randomly assigned, it is harder to determine whether the intervention directly caused the results.

Example from dance

Imagine researchers want to investigate whether a new balance-training program improves dancers' stability.

Group 1: A dance class that participates in the new balance-training program.

Group 2: A different dance class that continues its regular training.

What is single-subject research?

examines one person or a small number of individuals across different conditions or time periods.

The participant can serve as their own control.

For example, a researcher might measure a dancer's jump height at baseline, introduce a training program, measure performance again, and then examine what happens when conditions change.

Repeated measurements help researchers investigate individual responses.

What is a randomized controlled trial (RCT)?

An RCT is an experimental study in which participants are randomly assigned to different groups or conditions.

For example, 40 dancers might be randomly assigned to either a new balance-training program or a comparison training program.

Random assignment helps reduce selection bias and distribute potential confounding factors across groups.

RCTs are often considered the gold standard for evaluating the causal effects of interventions, although their quality still depends on how well they are conducted.

What is a systematic review?

collects, evaluates, and synthesizes research studies addressing a specific question using a planned, transparent search and selection process.

For example, researchers might review all eligible studies examining whether dance improves balance in people with Parkinson's disease.

They evaluate the quality, consistency, and limitations of the available evidence.

What is meta-analysis?

statistically combines quantitative findings from multiple studies to estimate an overall effect.

For example, researchers could combine results from several comparable dance intervention studies to estimate the overall improvement in balance.

Difference: A systematic review synthesizes existing research; a meta-analysis mathematically pools results when appropriate.

What is the general hierarchy of research evidence?

ranks different types of research studies from weakest to strongest based on how reliably they can answer a research question, particularly whether an intervention causes an outcome.

1. animal laboratory studies - not involved with humanscase report or case series - narrative reviews, expert opinions, editorial no design then case report or case series - narrative reviews, expert opinion, editorials, no design.

2. Case-control studies: Provide slightly stronger evidence because they compare people with and without an outcome to identify possible risk factors, but cannot prove causation. Non experimental control studies. Retrospective - subjects have the outcome of interest

3. Cohort studies: Provide stronger evidence because they follow participants over time, allowing researchers to determine whether an exposure occurs before an outcome.. non experimental observational studies - prospective: cohort has been exposed to a risk.

6. Randomized controlled trials (RCTs): Provide strong evidence because random assignment reduces confounding variables, making it easier to establish cause and effect. - experimental

7. Clinical Practice guidelines - Systematic reviews and meta-analyses: Generally provide the strongest evidence when based on high-quality studies because they combine and evaluate findings from multiple studies to identify consistent results.

This is a useful exam framework, but study quality and the research question matter. For example, a rigorous cohort study can provide better evidence than a poorly conducted trial.

What is kinematics?

describes how movement occurs without focusing on the forces that cause it.

It examines variables such as position, distance, displacement, speed, velocity, and acceleration.

For example, when analyzing a grand jeté, kinematics could describe how far the dancer travels, how high they jump, and how quickly their position changes.

Kinematics can be linear (movement through space) or angular (rotation around an axis).

What is kinetics?

studies the forces and torques responsible for producing or changing movement.

It examines factors such as gravity, muscle forces, ground reaction forces, friction, and torque.

For example, kinetics could explain how a dancer pushes against the floor to generate enough force to jump.

What is the difference between linear and angular motion?

Linear motion describes movement through space, while angular motion describes rotation around an axis.

Linear motion can be straight or curved. Angular motion involves a change in orientation around an axis.

For example, when a dancer performs a pirouette, their body rotates around a vertical axis. When a dancer travels across the floor in a chassé, their center of mass moves through space.

These types of motion can happen simultaneously. The rotation of joints produces much of the linear movement involved in walking and dancing.

What is a scalar quantity?

has magnitude but no direction.

Examples include distance, speed, and mass.

For example, saying a dancer traveled 5 meters tells us the distance but not the direction.

What is a vector quantity?

has both magnitude and direction.

Examples include displacement, velocity, acceleration, force, and weight.

For example, saying a dancer traveled 5 meters to the right describes displacement because it includes direction.

What is the difference btween distance and displacement?

Distance measures the total length of the path traveled, while displacement measures the change in position from the starting point to the ending point.

For example, imagine a dancer travels 5 meters forward and then 5 meters backward.

Distance = 10 meters.

Displacement = 0 meters because the dancer finishes where they started.

Distance is a scalar; displacement is a vector.

What is the difference between speed and velocity?

peed measures how quickly distance is traveled, while velocity measures the rate of displacement, including direction.

Averagespeed=Distance/Time

Averagevelocity=Displacement/Time

For example, a dancer traveling 10 meters in 2 seconds has an average speed of 5 m/s.

If the dancer travels in a straight line toward the right, the average velocity is 5 m/s to the right.

What is acceleration?

Acceleration is the rate at which velocity changes over time.

Acceleration occurs when an object speeds up, slows down, or changes direction.

For example, a dancer accelerating into a run increases their velocity. A dancer decelerating before stopping changes velocity in the opposite direction.

Gravity produces an approximately constant downward acceleration of 9.8 m/s² near Earth's surface.

What is momentum?

the quantity of motion possessed by an object.

p=mv

Here, p is momentum, m is mass, and v is velocity.

A dancer moving faster has more momentum if their mass stays constant.

Momentum is important for connecting movements. For example, the momentum generated during a run can help carry a dancer into a leap.

what is the difference between mass and weight?

Mass is a measure of the amount of matter in an object and its resistance to acceleration.

Weight is the gravitational force acting on that mass.

W=mg

Mass is measured in kilograms (kg), while weight is measured in newtons (N).

A dancer's mass remains essentially the same regardless of location, but their weight changes if gravitational acceleration changes.

What is Newton's First Law — the Law of Inertia?

Newton's First Law states that an object remains at rest or continues moving at constant velocity unless acted upon by a net external force.

Inertia is an object's resistance to changes in motion.

For example, when a dancer is standing still, a net force is needed to accelerate them into motion. Once moving, a force is required to slow down, speed up, or change direction.

Important: A force is not required to maintain constant velocity when there is no net opposing force.

What is Newton's Second Law — the Law of Acceleration?

Newton's Second Law states that the net force acting on an object equals its mass multiplied by its acceleration.

Greater net force produces greater acceleration when mass remains constant.

For example, when a dancer performs a jump, the upward ground reaction force must exceed their weight during part of the takeoff to accelerate their center of mass upward.

What is Newton's Third Law — the Law of Action-Reaction?

Newton's Third Law states that whenever one object exerts a force on another object, the second object exerts an equal and opposite force on the first.

For example, when a dancer pushes downward against the floor, the floor pushes upward against the dancer.

These forces act on different objects, so they do not cancel each other on the dancer.

This explains how dancers generate ground reaction forces during jumps, running, and traveling movements.

What is a free body diagram?

A simplified drawing that represents an object or body as a single unit and uses arrows to show the magnitude and direction of all external forces acting on it.

For a dancer standing still, the main vertical forces are:

Conceptual illustration of opposing vertical forces; a formal free-body diagram would isolate the dancer as a single body.

When the dancer is standing without accelerating vertically, the upward ground reaction force equals the downward weight.

If the dancer accelerates upward, the net vertical force must be upward.

What is impulse?

the total effect of a force applied over a period of time.

For a constant force:

J=F (pryamid)t

Impulse equals the change in momentum:

J=(pryamid)p

This means dancers can increase impulse by applying a greater net force, applying it for a longer time, or both.

For example, using a deeper plié before a jump can allow more time and distance to generate upward momentum, potentially increasing takeoff velocity and jump height.

The important point is that a deeper plié does not automatically guarantee a higher jump; effective force production matters.

What is balance?

the ability to maintain or control the body's position relative to its base of support.

During quiet standing, balance generally requires keeping the vertical projection of the center of mass within the base of support.

For example, a dancer standing on two feet has a larger base of support than a dancer standing in passé on relevé.

What is the center of mass (COM)?

the point representing the average location of mass throughout the body.

It changes when body segments move.

For example, raising the arms, extending a leg, or leaning the torso can shift the body's center of mass.

The center of mass can even be located outside the physical boundaries of the body in certain positions.

What is the base of support (BOS)?

The base of support is the area formed by the body's points of contact with supporting surfaces.

A wider base of support generally makes balance easier because there is more room for the center of mass projection to move without crossing its boundaries.

For example, standing in second position generally provides a larger base of support than standing on one foot.

What is stability?

the ability to resist a disturbance or return toward equilibrium after being displaced.

A stable dancer can maintain or recover their balance when something changes.

For example, if a dancer is gently pushed while standing on one leg, stability determines how effectively they can recover their position.

Stability is influenced by the base of support, center of mass, muscular control, and sensory information.

What is posture?

refers to the orientation and alignment of body segments relative to one another and gravity.

Posture is not limited to standing still. Dancers must regulate posture during turns, jumps, traveling movements, and floor work.

What is postural control?

the process of achieving, maintaining, and regulating body orientation and stability during static positions and dynamic movements.

The nervous system combines visual, vestibular, and somatosensory information to make adjustments.

For example, when a dancer balances in arabesque, their nervous system continuously adjusts muscular activity to maintain orientation.

What is postural sway?

refers to the small movements or deviations that occur while someone attempts to maintain a stable position.

Even when a dancer appears perfectly still, their body makes subtle adjustments.

Researchers can measure sway to investigate postural control.

What is the center of pressure? COP

the point at which the resultant ground reaction force acts on the supporting surface.

point n which the total sum of pressure acts thorugh a body causing the force to act through that point

Researchers often measure COP using a force plate.

As a dancer makes adjustments to maintain balance, the COP shifts.

Greater COP movement can indicate greater postural activity or sway, but it does not always mean poorer balance because some movement may represent effective corrective strategies.

What is the difference bwteen COM and COP?

The center of mass describes the distribution of the body's mass, while the center of pressure describes where the resultant ground reaction force acts.

COM represents the body's overall mass position. COP reflects the interaction between the body and its supporting surface.

The nervous system adjusts COP to help regulate COM and maintain balance.

What is projectile motion?

Describes the movement of an object through the air under the influence of gravity, neglecting air resistance.

When a dancer jumps, their center of mass follows a trajectory determined largely by takeoff velocity, takeoff angle, initial height, and gravity.

Once the dancer leaves the ground, they cannot substantially change the trajectory of their center of mass without an external force, although they can reposition body segments.

What three components influence a projectile's trajectory?

Angle of projection: The direction in which the dancer takes off.

Speed of projection: How quickly the dancer is moving at takeoff.

Height of projection: The height of the center of mass when the dancer leaves the ground.

For example, a grand jeté requires both vertical and horizontal takeoff velocity to create height and travel.

What influences the vertical component of projectile motion?

The vertical component is influenced by the initial vertical velocity and the downward acceleration of gravity.

Gravity causes upward velocity to decrease as the dancer rises, reach zero at the apex, and then become downward velocity during descent.

vy=v0y-gt

At the highest point of the jump, vertical velocity is momentarily zero, but vertical acceleration is still downward.

What influences the horizontal component of projectile motion?

Neglecting air resistance, horizontal velocity remains constant during flight because there is no horizontal acceleration. Horizontal travel depends on horizontal takeoff velocity and the amount of time spent in the air.

For example, a dancer who takes off with greater horizontal speed will generally travel farther during the same flight time.

Why do two balls dropped from the same height land at the same time if one is projected horizontally?

If both balls begin with zero vertical velocity and air resistance is ignored, they experience the same downward gravitational acceleration.

Horizontal motion does not change how quickly an object falls vertically.

Therefore, both balls land at the same time, even though one travels horizontally. gravity only acts. vertically not horizontally

what is kinetic energy?

Kinetic energy is the energy an object possesses because it is moving.

KE=1/2 mv2

Kinetic energy depends on mass and the square of speed.

For example, a dancer running across the floor has kinetic energy.

Because speed is squared, doubling speed produces four times the kinetic energy when mass remains constant.

What is potential energy?

stored energy associated with an object's position, configuration, or condition.

Two important types for dancers are gravitational potential energy and elastic potential energy.

Gravitational potential energy:

PE=mgh

A dancer at the top of a jump has more gravitational potential energy than at a lower height.

Elastic potential energy is stored when elastic structures are stretched or compressed.

How do kinetic and potential energy change during a jump?

During a jump, kinetic energy is converted into gravitational potential energy as the body rises. At the highest point, potential energy is greatest and kinetic energy is lowest. As the body falls, potential energy is converted back into kinetic energy.

As the dancer rises, upward kinetic energy decreases while gravitational potential energy increases.

At the apex, the vertical component of velocity is zero, although the dancer may still possess horizontal kinetic energy.

As the dancer descends, gravitational potential energy decreases while kinetic energy increases.

Muscles contribute energy during takeoff, and some mechanical energy is transferred into heat and other forms during landing.

What is static friction?

the frictional force that prevents two surfaces in contact from sliding relative to each other.

For example, when a dancer pushes against the floor to begin a leap, static friction provides traction so the foot does not slip.

What is kinetic friction?

acts when two surfaces slide relative to each other.

For example, when a dancer intentionally slides their foot across the floor, kinetic friction opposes the sliding motion.

Main difference: Static friction prevents slipping; kinetic friction resists sliding that is already happening.

What are the angular equivalents of linear motion variables?

The angular equivalents of linear motion variables describe rotational movement instead of movement in a straight line.

Linear velocity: A dancer travels across the floor.

Angular velocity: A dancer spins during a pirouette.

Linear acceleration: A dancer increases speed while running.

Angular acceleration: A dancer begins turning faster.

Moment of inertia: A dancer brings their arms closer to their body, decreasing their moment of inertia and allowing them to spin faster if angular momentum is conserved.

What is angular displacement?

the change in an object's rotational position.

It is measured in radians or degrees.

For example, a dancer completing one full pirouette rotates through 360 degrees, or 2 radians.

What is angular velocity?

describes how quickly angular position changes over time.

For example, a dancer who completes two full rotations in two seconds has an average angular speed of one revolution per second.

What is moment of inertia?

a dancer's natural resistance to changes in motion (linear inertia) or changes in spinning speed (rotational inertia)

It depends on both the object's mass and how that mass is distributed relative to the axis of rotation.

When mass is closer to the axis, moment of inertia is smaller.

When mass is farther from the axis, moment of inertia is larger.

For example, during chaîné turns or pirouettes, bringing the arms closer to the body reduces moment of inertia, allowing faster rotation when angular momentum is approximately conserved.

What is torque?

the turning effect of a force around an axis.

Here, r is the perpendicular moment arm.

Torque increases when either the force or perpendicular moment arm increases.

For example, muscles produce torque around joints to move body segments.

What is a moment arm?

is the shortest perpendicular distance between the axis of rotation and the line of action of a force.

A longer moment arm creates greater torque for the same applied force.

For example, holding the arms extended horizontally creates a larger gravitational torque around the shoulder than keeping them close to the body.

What is the relationship between torque and angular acceleration?

The angular equivalent of Newton's Second Law for rotation around a fixed axis is:

A greater net torque produces greater angular acceleration if moment of inertia remains constant.

A larger moment of inertia requires greater torque to produce the same angular acceleration.

What is angular momentum?

describes the quantity of rotational motion.

For rotation about a fixed principal axis:

Angular momentum depends on moment of inertia and angular velocity.

For example, a dancer rotating with their arms extended has a larger moment of inertia than when their arms are close to their body.

What is conservation of angular momentum?

states that an object's angular momentum remains constant when there is no net external torque acting on the system.

If moment of inertia decreases, angular velocity increases to maintain angular momentum.

For example, a dancer can accelerate a turn by bringing their arms inward, reducing moment of inertia.

If they extend their arms outward, moment of inertia increases and rotational speed decreases.

What is angular impulse?

the total effect of torque applied over time.

Angularimpulse=t

For constant torque, angular impulse equals the change in angular momentum:

For example, applying torque against the floor during the preparation for a pirouette creates angular impulse and helps generate angular momentum.

A greater torque or longer duration of torque can produce a greater change in angular momentum.

What is lever?

a rigid structure that rotates around a fixed point called a fulcrum or axis.

In the body, bones act as levers, joints act as fulcrums, and muscles provide the effort force.

The load or resistance may come from body weight, another body segment, or an external object.

What is a first-class lever?

has the fulcrum positioned between the effort and the resistance.

An example is the head balancing on the neck, where the atlanto-occipital joint serves as the fulcrum.

A seesaw is another example.

What is a second class lever?

has the resistance positioned between the fulcrum and the effort.

A common example is rising onto the balls of the feet.

The toes act as the fulcrum, body weight provides the resistance, and the calf muscles generate the effort through the Achilles tendon.

Second-class levers can provide a mechanical advantage for producing force.

What is a third class lever?

has the effort positioned between the fulcrum and the resistance.

An example is elbow flexion using the biceps.

The elbow is the fulcrum, the biceps applies force near the elbow, and the resistance acts farther along the forearm.

Third-class levers are the most common in the human body.

They favor speed and range of motion rather than force advantage.

How can you remember the three classes of lever?

Remember what is in the middle.

First-class: Axis in the middle.

Second-class: Resistance in the middle.

Third-class: Effort in the middle.

What is motor learning?

the process through which practice and experience produce relatively permanent changes in a person's ability to perform a motor skill.

For example, when a dancer practices pirouettes over several weeks and develops better coordination, balance, and consistency, motor learning has occurred.

Important: Learning cannot be observed directly. We infer it from lasting changes in performance.

What is motor control?

refers to how the nervous system and body organize, coordinate, and regulate movement.

It explains how we produce movements and adjust them in response to sensory information.

For example, when a dancer begins losing balance during an arabesque and automatically adjusts their supporting ankle and torso, motor control is occurring.

What is motor development?

refers to changes in movement abilities throughout the lifespan.

These changes result from interactions among growth, maturation, experience, practice, and the environment.

For example, infants gradually develop abilities such as reaching, crawling, standing, and walking.

What are three factors that shape motor performance?

Motor performance emerges from interactions among the person, task, and environment.

Person: Individual characteristics such as strength, flexibility, coordination, experience, fatigue, and motivation.

Task: The movement goal and its requirements, such as completing a double pirouette or landing inside a designated circle.

Environment: External conditions such as the floor, music, lighting, available space, and other dancers.

For example, performing a leap depends on the dancer's strength, the required leap distance, and the surface on which they are dancing.

What is the difference between a skill, an action, and a movement?

A skill is a learned ability to achieve a particular goal with consistency and efficiency.

An action is a goal-directed activity performed by a person.

A movement is the actual motion of the body or body segments used to perform the action.

For example, executing a pirouette is a motor skill. Completing the turn is the action goal. The movements include bending the knees, pushing against the floor, rotating the torso, and coordinating the arms.

Different movements can accomplish the same action.

What is Bernstein's main idea about motor control?

Bernstein argued that movement is not simply the result of the brain sending exact instructions to individual muscles.

Instead, movement emerges through the coordination of the nervous system, muscles, joints, sensory feedback, and environment.

The body must organize many possible movements to accomplish meaningful goals.

For example, a dancer does not consciously control every individual muscle during a leap. The nervous system organizes the entire body into a coordinated movement.

What does Bernstein mean when he says we solve meaningful motor problems?

Bernstein believed that movements are organized around goals or problems that the person is trying to solve.

For example, if a dancer wants to leap across a particular distance, the problem is figuring out how to coordinate the body to reach the target.

The goal is not necessarily to repeat identical joint angles every time. The goal is to successfully accomplish the task.

Different movement patterns can produce the same successful outcome.

How does the central nervous system develop representations of the world through action?

Bernstein argued that the nervous system learns about the environment by interacting with it.

Each movement provides sensory information about the body and surroundings.

The nervous system uses successful and unsuccessful attempts to improve its understanding of how actions work.

For example, when a dancer leaps toward a target and lands short, they learn something about the relationship between takeoff force, distance, and landing position.

On the next attempt, they can modify their movement based on that experience.

What is the degrees of freedom problem?

The degrees of freedom problem refers to the challenge of coordinating the enormous number of possible movements available to the human body.

A degree of freedom represents an independent way a joint or body segment can move.

For example, during a pirouette, the dancer must coordinate the head, arms, torso, hips, knees, ankles, and feet.

Because there are so many possible combinations, the nervous system must find a way to organize them into a coordinated action.

What is the difference between redundancy and abundance?

Redundancy views the body's many degrees of freedom as a problem because there are more movement possibilities than necessary to complete a task, making it challenging for the nervous system to coordinate them. For example, a dancer can raise their arm using different combinations of shoulder, elbow, and torso movements, so the nervous system must determine which combination to use.

Abundance views the body's many degrees of freedom as an advantage because they allow flexibility and adaptation. For example, if a dancer loses balance during an arabesque, they can adjust their arms, torso, or ankle to regain stability while maintaining the position.

What does freezing degrees of freedom mean?

Freezing degrees of freedom means temporarily restricting or limiting movement possibilities to simplify coordination.

Bernstein suggested that beginners often reduce the number of independently moving body segments when learning a new skill.

For example, a beginner learning a turn may keep their arms and torso rigid to reduce the number of movements they must coordinate.

As the dancer improves, they can gradually free those degrees of freedom, allowing smoother, more flexible, and more efficient movement.

How does freezing degrees of freedom relate to learning?

Freezing degrees of freedom can help beginners manage the complexity of a new skill.

However, remaining too rigid can limit movement efficiency and adaptability.

With practice, learners gradually free and coordinate more degrees of freedom.

For example, in your class walking exercise, walking with the same arm and leg limited normal coordination and felt unnatural.

Allowing the arms and legs to swing more freely produced smoother movement.

This demonstrates the transition from restricted coordination toward more flexible movement.

What does Bernstein mean by coordination as a self-regulating system?

Bernstein described motor control as a system that continually compares actual movement with desired movement.

The nervous system receives sensory information about what is happening and uses it to detect and correct errors.

For example:

A dancer intends to land in the center of a circle.

The dancer leaps and lands slightly short.

Sensory and visual information reveal the difference between the intended and actual landing.

The dancer adjusts takeoff force on the next attempt.

This is a feedback-based process.

What does "repetition without repetition" mean?

Bernstein's idea of repetition without repetition means that effective motor learning does not require reproducing exactly the same movement every time.

Instead, the learner repeatedly solves the same motor problem while making adjustments and refining their movement.

For example, a dancer practicing leaps across the floor may adjust takeoff force, arm placement, and timing on different attempts while pursuing the same goal.

Each repetition becomes an opportunity to discover a more effective solution.

Important: The goal is repeated, but the exact movement solution may change.

What is Adams' closed-loop theory?

Adams' closed-loop theory proposes that motor learning occurs through practice and the refinement of sensory feedback processes.

The performer compares incoming sensory information with a stored reference of correct movement.

If there is a difference between the actual and desired movement, the nervous system uses feedback to make corrections.

For example, a gymnast balancing on a beam continuously uses sensory information to detect changes in body position and make adjustments.

What is a memory trace?

In Adams' theory, the memory trace is responsible for initiating movement.

It helps determine the initial direction and early organization of the action.

For example, when a dancer begins a pirouette, the memory trace helps initiate the learned movement pattern.

What is perceptual trace?

a stored reference representing what a correct movement should feel like.

It develops through previous movement experiences and feedback.

During performance, the nervous system compares incoming sensory feedback with the perceptual trace.

For example, a dancer who has practiced balancing in passé many times develops a stronger sensory reference for the correct position.

When their balance changes, they can detect the difference and make corrections.

What role does practice play in Adam's theory?

Practice strengthens the perceptual trace by providing repeated experiences of the correct movement.

The more consistently someone practices a particular skill and receives useful feedback, the stronger their reference for successful performance becomes.

For example, repeatedly practicing a balance in the same position can help a dancer develop a reliable sense of the correct alignment.

What is knowledge of results (KR) in Adams' theory?

Knowledge of results is feedback about the outcome of a movement.

For example, a teacher might tell a dancer, "You completed two rotations," or "You landed 10 centimeters short of the target."

This feedback helps the learner understand whether the movement achieved its goal.

Adams believed knowledge of results contributed to developing a stronger perceptual trace.