Motor Skills Classification

One-Dimensional Classification Systems

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In a one-dimensional classification system, the phenomena of interest are classified on a continuum between two polar opposites. For example, temperature can be classified on a continuum running between the polar opposites of hot and cold, mood between polar opposites of sad and happy, or political identity between polar opposites of liberal and conservative.

When applying a one-dimensional system to the classification of motor skills, three dimensions of performance or of the performance context are identified. These include:

1. the stability of the environment in which a skill is performed,
2. the temporal features of the skill relative to its beginning and ending, and
3. the precision of movement required in accomplishing the skill.

All motor skills can be classified along each of these three dimensions.

The Classification of Motor Skills Based upon the Stability of the Environment

One system for classifying motor skills is based upon the stability of the environment in which they are performed. Here, environment refers to the context in which a person performs, as well as any object or objects upon which the person acts. Motor skills are classified as either closed or open, depending upon the predictability of the environment.

If the environment in which a person performs remains relatively constant from one time the skill is performed until the next, we classify the skill as a closed motor skill.

Typing, for example, is a closed skill. The placement of the letters on a keyboard does not change from one keyboard to the next. Closed skills have the important feature that the environment or object acted upon waits, in effect, to be acted upon by the performer. You decide when to start typing, as well as when to stop and then start again. For this reason, closed motor skills are sometimes referred to as self-paced motor skills.

Examples of closed skills include target shooting, writing, using a knife and fork, shooting basketball free throws, pitching horseshoes, and painting a wall.

As opposed to closed skills, an open motor skill is performed in a changing, unstable, and unpredictable environment.

A person does not know from one attempt of a skill until the next how an object or the performance context may change and require modifications to the way in which the skill must be performed.

Although free-throw shooting is a closed motor skill in the sport of basketball, dribbling down court during a basketball game is an open skill. In this case, the basketball player must react to movements of opposing players, as well as those of teammates, all the while responding to constantly changing game situations.

Proper skill execution, or even whether a skill should or should not be executed, cannot be accurately predicted and planned for in advance. For this reason, open motor skills are also referred to as reactive motor skills. Examples of open motor skills include open-field running in football, driving in traffic, chasing a dog, downhill snow skiing, dodging water balloons, and surf boarding.

How would you classify bowling? Is it a closed or an open motor skill?

If you consider only the first ball in each frame, it is certainly closed because everything about the environment remains constant from one attempt to the next.

But what about the second ball of each frame?

For two kinds of bowlers, nothing changes: an expert bowler rolling a 300 game, and a beginner bowling all gutter balls. For both types of bowlers every attempt presents the same situation—all 10 pins are standing.

For most bowlers, however, the second ball of each frame will present a somewhat different situation than the initial ball. Some of the pins will have been knocked down, although not the same ones each time.

Sometimes nine pins will remain standing, and other times only a single pin; sometimes pins will remain standing on the right, sometimes on the left; and sometimes on both sides of the lane—a dreaded split!

In each case, something has changed about the environment. How, then, should we classify the second ball in a frame?

Although some features of the environment in our example of second balls within frames of bowling may change, it should be clear that many more remain predictable. The ball is still the same. The lane on which the ball is rolled does not change.

And even though the exact arrangement of pins may vary, they do not do so in a way that drastically alters the movement pattern required to successfully bowl the ball and knock down each changing pin arrangement.

In open motor skills performers must react to unpredictable and changing conditions (left), while closed motor skills are performed within stable and predictable environments (right).

More importantly, regardless of the number of pins standing, the skill is still self-paced—the performer can act when ready. So we can say that even a split presents a relatively closed environment where most features remain the same as for other balls thrown in the game.

Thus, considering skills on a continuum ranging between closed and open environmental features, the second ball of a bowling frame remains closer to the closed end of the continuum than to the open end. Regardless of the particular arrangemet of pins in the environment, bowling, in general, is considered a closed motor skill.

The closed-open classification system has been popular in instructional skill settings. An important reason is that it is relatively easy to classify skills in this fashion, and skills in each category follow common principles of instructiojn that teachers and therapists can readily apply. The closed–open distinction is also common in motor skills research, because findings relative to each category easily translate into real-world applications (see Figure 2.3).

Predictable performance context	Semi-predictable performance context	Unpredictable performance context
Basketball free throw	High jump	Mountain biking
Typing	Chopping wood	Wrestling
Springboard diving	Driving on a quiet road	Driving on a busy road
Painting a wall	Passing a basketball to a teammate in a game	Defending a goal in ice hockey
Figure 2.3 Classification of Skills as Closed or Open

The Classification of Motor Skills Based upon Temporal Predictability

A second way of classifying motor skills in a one-dimensional system is on the basis of the predictability of their beginning and ending points. Based upon these temporal features, motor skills are classified as being discrete, continuous, or serial.

Some skills, like hitting a baseball, have specific beginning and ending points. A batter must begin swinging as the ball approaches home plate, and once the swing is completed, all relevant action is over. Skills of this type, which have clearly identifiable beginning and ending points, are classified as discrete motor skills.

Unlike batting in baseball, not all discrete motor skills have both a forced beginning and ending point. Some, like hitting a golf ball rather than a baseball, have arbitrary beginning points—the performer can wait until ready to hit the ball. The ending point to hitting a golf ball, however, is still forced by the completion of the swing and striking of the ball (this is, of course, the distinction between open and closed skills).

Discrete skills are also typically completed quickly, usually lasting from a fraction of a second to no more than a few seconds. A discrete skill is one that exhibits well-defined beginning and ending points, and is typically executed in a relatively brief period of time.

We can add that the beginning point is not always temporarily predictable, though the timing of the action is often rigidly fixed and highly predictable. Examples of discrete motor skills include serving a tennis ball, throwing darts, standing from a sitting position, ringing a doorbell, jumping over a fence, and flipping a coin.

A continuous motor skill is one in which both the beginning and ending are arbitrary and unpredictable.

Continuous skills are often (though not always) repetitive and rhythmic in nature—like walking and swimming, for example.

A different but important class of continuous skills includes tracking skills, such as steering an automobile or keeping a stylus in contact with the target on a rotary pursuit task, which require the performer to continuously monitor the external environment and correct actions in an ongoing fashion.

The point in either case is that the temporal dimensions of the tasks involved (beginning and, especially, ending points) are arbitrary and cannot be determined prior to the completion of an action.

The individual decides when to end a continuous skill, and frequently when it will begin, also. Examples of continuous skills include riding a bicycle, running, tracking a moving target on a computer screen using a joystick, stirring hot coffee with a spoon, and flying a kite.

An interesting problem confronts us when deciding upon classifying motor skills on the basis of temporal considerations. Consider the skill of typing, for example. It is clear when watching a beginning typist that the actions involved are discrete in nature. That is, the beginning typist deliberately strikes a single key at a time— “C” for example—stops to search for the next key and then produces another discrete action—striking “A” in this example—then pausing to search again before striking another key— “T” to complete the example “CAT”—and so on and on.

When observing those learning to type, it is clear that their actions represent a series of discrete acts. What about the same skill with an advanced typist?

The expert’s fingers seem to race effortlessly over the keyboard without pause. It is tempting to say the expert typist is performing a continuous skill.

The problem is that a skill cannot be classified as two different types of skill, in this case both discrete and continuous, depending on a performer’s skill level. (Remember that it is the skill itself, not the performer’s skill level, that is classified in one-dimensional systems).

The solution is a special classification for skills such as typing. Skills that require a series or sequence of discrete elements, like typing, are classified as serial motor skills.

Examples of serial skills include hammering a nail, shifting gears in an automobile, a dance routine, playing the piano, brushing your teeth, and dribbling a basketball.

It should be noted that some serial skills involve a simple repetitive or even rhythmic sequencing of the same action, such as dribbling a basketball or hammering a nail. Other serial skills involve the sequencing of different discrete skill elements in an exact order, such as typing or shifting gears in an automobile.

Although discrete skills have clearly predictable ending points, and the completion of continous skills is arbitrary, the temporal predictability of a serial skill’s ending point may be either predictable or arbitrary. For serial skills consisting of a series of different subskills, such as shifting gears in an automobile, the completion of the skill is highly predictable, whereas for highly repetitive actions like dribbling a basketball the performer decides upon the ending point (see Figure 2.4).

The Classification of Motor Skills Based upon Movement Precision

A third one-dimensional system for classifying motor skills is based on the precision of the movements required for completing the skill. (In defining this dimension, some writers prefer to focus upon the size of the primary musculature required in performing skills.) Within this one-dimensional system, motor skills are classified as being either fine or gross.

Skills such as threading a needle that place primary emphasis on the precision of movement, rather than upon muscular effort, are labeled fine motor skills.

Fine motor skills are typically accomplished by recruiting small muscle groups such as those of the fingers, hands, and forearms; may place a high premium on hand-eye coordination; and require little muscular force or energy to successfully accomplish.

Examples of fine motor skills include handwriting, sewing, using chopsticks, buttoning a shirt, repairing watches, using precision tools, and operating a rotary-pursuit apparatus in a motor learning laboratory. In all of these cases, it is the precision of the movement itself, and not how forcefully it is done, that results in successful performance of the skill.

Gross motor skills are those that require the use of relatively large musculature in producing an action. Fundamental motor skills such as walking, running, leaping, jumping, throwing, balancing, and climbing are gross motor skills.

Gross motor skills typically involve many muscle groups and, frequently, movement of the entire body. Although many sports skills classified as gross motor skills may require exquisite coordination to accomplish, the contributions of muscular force outweigh demands on movement precision in accomplishing the action. Examples of gross motor skills include standing from a chair, catching a football, doing sommersaults, performing a tour en l’air in a ballet program, blocking in volleyball, and climbing a ladder.

Fine and gross skills form a continuum marked by the gradual shift of importance placed on either movement precision or force production in accomplishing the goals of a skill (see Figure 2.5).

Knitting	Steering a car	Pole vaulting
Buttoning a shirt	Taping an athlete’s ankle	Changing a tire
Drawing	Putting in golf	Weight lifting
Repairing a watch	Shooting pool	Playing tug-o-war
Figure 2.5 Classification of Skills as Fine or Gross