++
In any formal field of study, the task of analysis must proceed
along a logical and structured plan. This plan must be constructed
so that it is both appropriate to the activity and can be readily applied
by the practitioner. The teacher, therapist, trainer, athlete, and
coach all benefit from knowing how to conduct a kinesiological analysis
of a motor skill. The teaching of motor skills, whether it takes
place in the clinic, in the fitness facility, or on the playing
field, consists of presenting a skill and knowing what points to
emphasize. It also largely consists of diagnosing difficulties,
correcting errors, and eliminating actions that limit performance.
The specialist in motor skills must also be aware of the types of
injuries that are likely to occur during a particular activity and
how to prevent them. To accurately prescribe the movements necessary
for rehabilitation, the therapist or trainer must know joint structure
and exercise tolerances. An athlete in training must understand
the kinesiological factors involved in performance to optimize training
effects while guarding against deleterious actions. These tasks
that, on the surface, may seem simple can indeed be quite complex,
if for no other reason than that motor skills themselves are complex.
An effective aid in helping one understand the basic elements and
requirements of a motor skill is a systematic kinesiological analysis.
++
The tools needed for the execution of a detailed kinesiological
analysis will be introduced in subsequent chapters. The anatomical
components of human movements—the bones, joints, muscles, and
related portions of the nervous system—and the mechanical
bases for human motion will be presented. The basic movements of
the body segments will be described, and it will be shown how the
observation of both anatomical and mechanical principles contributes
to the efficient use of the body in the performance of motor skills.
A kinesiological analysis is the application of this information
to assessing the effectiveness of a given motor performance. It
consists of
++
The basic components for the kinesiological analysis of a motor
skill are outlined in Table 1.1. In this type of analysis the emphasis
is on a qualitative assessment of the performance, which may be conducted
with the assistance of videotapes, digital images, or the naked
eye. In any case the analyst must use a systematic approach in the
observation of the performance. Have someone demonstrate the movement
to be analyzed both before and at frequent intervals throughout
the analysis. In lieu of this, a video or digital recording is an
excellent substitute. If this is not available, a series of still
shots or even a single photograph or sketch is helpful. In the initial
stages of learning analysis procedures, movement may appear rapid
and confusing. With the aid of recording equipment and with much
practice, the analyst will gain the skills required for an accurate
and systematic approach to observation.
+++
Description
of the Motor Skill
++
The description of the motor skill being analyzed consists of
four elements that together help the analyst focus on the essential
nature of the skill.
+++
Primary Purpose
of a Motor Skill
++
The first step in the description phase of the analysis is to
identify the primary purpose of the movement. Without a clear understanding
of why the movement is being performed, it is virtually impossible
to evaluate its effectiveness. In this statement of purpose, applicable
references to speed, accuracy, form, and distance should be included.
For example, the purpose of the 50-meter backstroke is to cover
the course in the shortest amount of time. Speed is a major factor.
The purpose of swinging an ax is to split a piece of wood. Both
speed and accuracy are critical elements if the wood is to be safely
split into kindling. The purpose of the springboard dive is to execute
the motion according to a prescribed form. Neither speed nor accuracy
is stressed; success is measured on appearance alone. The purpose
of putting in golf is to sink the ball into the cup from a relatively
short distance away. The prime determinant of success in putting
is accuracy (Figure 1.1).
++
++
It is often beneficial to break down a motion into separate parts,
or “phases.” Often these phases are fairly obvious,
based on the motion. For example, a throw has a windup phase, a
throwing phase where the arm comes forward, and a follow-through
phase after release (Figure 1.2). In some skills, the phases are
not as obvious, but to make the analysis manageable, some sort of
division should be made.
++
++
It is critical that the appropriate starting and ending points
for each phase be identified. Two primary factors must be considered
in the choice of starting point. The first factor is to consider when in the motion the analysis should
begin. Many movement skills are discrete; that is, they have a very
definite beginning and ending. In such movements the starting point
for analysis is fairly obvious—at the beginning of the
first phase—as in a throwing skill, which starts with the
windup. Other skills are more continuous in nature, either because
they are done in a repetitive manner or because one movement flows
immediately into the next. Walking is a good example of a cyclical skill,
whereas many team sports include movements that change constantly.
In a continuous movement situation, the analyst must carefully choose
a starting point that will give adequate information about the movement
of interest while not ignoring the resultant effects of the previous
movement. In walking, many analysts start the first phase of the
analysis as the toe leaves the ground and end the last phase when
that same toe is about to leave the ground in the next step cycle;
others start the phase as the heel strikes the floor and end with
the subsequent heel strike.
+++
Classification
of the Motor Skills
++
Motor skills take many forms and are used for many purposes.
The therapist is interested in using physical skills and exercise
to rehabilitate individuals for independent living or work; the
teacher uses motor skills for health, learning, and play; the athlete
and coach strive to produce near-perfect performance. Each practitioner
requires an understanding of the body and mechanical laws that govern
motion. A classification scheme is important because it permits
the variety of potential movement skills to be organized into a
manageable grouping. This manner of organization facilitates the
recognition of commonalities across movements. It also fosters increased
understanding by enabling one to focus on either differences or
similarities in movement patterns, as the situation demands. Classification
of movement patterns and skills provides further clues as to the
nature of both the anatomical and mechanical requirements of a particular
group of skills.
++
The following system for classifying motor skills takes into
account the objective of the skill, the medium in which the skill
occurs, and the nature of the motion.
+++
System for Classification
of Motor Skills
++
- I. Maintaining erect posture
- II. Movement for exercise and fitness
- III. Giving motion
- A. To external objects
- 1. Pushing and pulling
- a. Lifting and
carrying
- b. Punching
- 2. Throwing, striking, and kicking
- B. To one’s own body
- 1. Supported
by the ground or other resistant surface
- a. Locomotion
on foot
- b. Locomotion on wheels, blades, and runners
- c. Rotary locomotion
- 2. Suspended and free of support
- a. Swinging
activities on trapeze, flying rings, or similar equipment
- b. Hand traveling on traveling rings or horizontal ladder
- c. Unsupported—i.e., projected into or falling through
the air
- d. Weightlessness
- 3. Supported by water
- a. Swimming
- b. Aquatic stunts
- c. Boating
- IV. Receiving impact
- A. From one’s
own body in landing from a jump or fall
- B. From external objects in catching, trapping, spotting,
or intercepting
++
The four major headings in this outline are maintaining erect
posture, movement for exercise and fitness, giving motion, and receiving
impact. Some may question the reason for treating the maintenance
of erect posture as a major category instead of including it under
giving motion to one’s own body. The rationale for this
decision is that the emphasis here is on adjusting to the immediate
environment rather than on making a movement in the sense that one
usually interprets this concept. With one exception, the adjustments
are made from a stationary position, the exception being a shift
in stance necessitated by standing on a moving base. This action
does not involve moving from one place to another but only widening
the stance and facing in a different direction to maintain balance.
The erect posture then becomes the foundation and starting point
for subsequent dynamic postures and motions.
++
The initial step in the classification of movement is to determine
in which major category the skill belongs, and then in which secondary,
and possibly tertiary, category. A forehand drive in tennis, for
instance, belongs in the primary category of giving motion to an
external object and in the secondary one of striking. Turning a
cartwheel is a form of giving motion to one’s own body
while it is supported by the ground and is classified further as
rotary locomotion.
++
In addition to pinpointing the exact categories to which the
skill belongs, a number of other factors should be considered. Many
skills consist of a series of phases that cut across different categories,
and these must be considered separately. The tennis serve, like
the forehand drive, is a form of striking, but it also involves
tossing the ball, a push pattern skill that should not be overlooked.
Vaults over a gymnasium box or horse consist of the approach, the
placement of the hands, the momentary support by the hands, and
the push-off from the box, followed by the projection of the body
together with the necessary adjustments of the bodily segments,
and finally the landing, which involves movements of the upper extremities
and trunk as well as of the lower extremities. In pole vaulting
and rock climbing, there is a smooth transition from pulling to
pushing. In hurdling, repeated alternation occurs between the run
and the hurdles without any break in rhythm. In many basketball
shots for the basket, the shot is accompanied by a jump. All phases
of the skill should be included in the analysis.
++
In many skills, especially those involving either the giving
or the receiving of a force of appreciable magnitude, the ability
to maintain balance is an all-important feature. Maintaining balance effectively
means observing the principles of balance and posture adjustment
as well as those relating to the specific form of giving motion
or receiving impact. Lifting a heavy weight from the floor or down
from a shelf is a good example of a motion-giving activity that
depends in large part for its effectiveness on the maintenance of
a posture that favors lifting.
++
The standing long jump shown in Figure 1.3 is a skill that belongs
in the major category of giving motion to one’s own body.
The initial phases prior to the takeoff, landing, and recovery phases belong
in the secondary category of movement on a solid base, whereas the
flight phase is an activity of the unsupported category.
++
+++
Simultaneous-Sequential
Nature of the Motion
++
Comprised of joints and levers, the body can move in a wonderful
variety of ways. To simplify the complexities of such a wide range
of possibilities, it is important to understand that when motions
are combined, bodily movements may be classified as occurring on
a continuum ranging from the simultaneous to
the sequential use of the body segments.
The simultaneous use of the body segments, where the various segments
move as one, is exemplified by motions such as pushing, pulling,
or lifting objects. In a simultaneous movement pattern, all of the
movement is directed along a straight line. Simultaneous use of
body segments is the only way it is anatomically possible to move
the hand or foot in a straight line. This straight-line application
of force by the hand or foot is the most advantageous method to
use when overcoming heavy or large objects or external forces such
as those encountered in pushing file cabinets and lifting weights.
In addition, when accuracy is important, such as in putting in golf,
lunging in fencing (movement of the arm and weapon), and punching,
it is more effective to involve the segments in a simultaneous fashion.
++
When it is important to have maximum speed at impact or release,
a sequential use of the body segments is appropriate. The use of
the segments in an orderly sequence so that subsequent segments
are accelerated at the appropriate time to create the highest possible
speed is critical in activities exemplified by throwing, striking
movements such as batting or the golf drive, and kicking. Sequential
movements produce forces applied so that the final segment moves
along a curved path. The farther this curved path is from the center
of the motion, the greater will be the speed of the throwing, striking,
or kicking segment.
++
Motions may occur anywhere along this simultaneous-sequential
continuum or may combine the two basic forms (Figure 1.4). The skill
of putting the shot, for example, involves the sequential use of
the lower extremities and trunk followed by the simultaneous use
of the upper extremity to safely move the relatively large weight
of the shot. For our purposes, simultaneous motions and those combination
motions that occur at the simultaneous end of the continuum will
be classified as push-pull motions, and those at the other end,
the sequential end, will be classified as throwing, striking, and
kicking patterns.
++
++
To clarify the nature of the motion at any given point in the
performance, it is desirable to break down the total movement into
phases for analysis. Using the standing long jump (see Figure 1.3) as
an example, an analysis of the nature of the motion might be as
follows:
++
- 1. Preparatory phase—simultaneous motion of the
joints of the lower extremity, into a semisquat position.
- 2. Execution (force) phase—simultaneous extension
of the segments in a forward-upward direction.
- 3. Flight (unsupported) phase—sequential motion of
the lower body to “whip” the legs forward.
- 4. Landing phase—simultaneous flexion of the lower
extremity to take up the shock of the landing forces.
++
Having now described the motor skill by clarifying the primary
purpose, classifying the skill and establishing the simultaneous-sequential
nature of the skill, analysis of the
performance is the next, and very critical, step. In evaluating
the motion from the starting point, the analyst must then consider
to what extent the performer conforms to the anatomical and mechanical
requirements necessary to achieve the stated purpose of the motion.
Failure to perform in accordance with the principles that govern
motion will produce a less than optimal performance. For this reason
the analyst should be conversant with the anatomical and mechanical principles
that are critical for the movement skill in question.
++
The anatomical analysis of a movement should include an examination
of the skeletal joint action, a description of segment motion, an
account of the muscle participation, and an identification of the
neuromuscular mechanisms involved. Anatomical analysis involves
analysis of a process rather than a product. That is, it is a review
of how the body accomplishes the task rather than an in-depth examination
of the results. It should attempt to give specific answers to the
following questions:
++
- 1. Which joints are involved, and what are their exact
movements in the motor skill?
- For each phase of
the technique and for each joint participating in the phase, the
precise joint action and segment being moved should be identified
and recorded as was done for the sample analysis of the force phase
of the standing long jump shown in Table 1.2.
- 2. Are any of the joints used to the limit of their range
of motion?
- 3. Which muscles are responsible for the joint actions, and
what is the nature of their contraction?
- The muscular
action is identified for each joint movement and recorded next to
the joint actions in Table 1.2. This implies identifying not only
the muscles that are contracting but also their precise function
in the movement and the kind of contraction they are undergoing.
Identification of the force causing the motion facilitates the subsequent
identification of the muscle and type of contraction involved.
- 4. Which neuromuscular mechanisms are likely to help or hinder
the action, and what is the nature of their involvement?
- The muscle-response patterns of well-learned motor skills
involve the integrated action of many reflexes and the inhibition
of others. After repeated viewing of the performance “live” or
on a recording, the student should name and discuss the reflexes
that could be acting at various points in each phase.
- 5. Which anatomical principles contribute to maximal efficiency
and accuracy in the performance of the motor skill?
- 6. Which principles are directly related to the avoidance
of injury?
- In any analysis, a set of anatomical
principles governing the safe and effective performance of the movement
skill must be considered. These principles take into account the
structure and function of the human body, human tolerance of both
internal and external stresses, and the efficiency of movement patterns.
Hudson (1995) has also suggested that it is critical to examine
such core concepts as range of motion, the number of body parts
involved, the nature of the body parts involved, and the coordination
of the movement. In addition, it is important to look at the alignment
of the body, and the reflexes that might be utilized. Anatomical
principles of motion then stipulate the way in which each of these
core concepts apply to a specific movement. In particular, anatomical
principles speak to the qualities associated with each of these
concepts.
++
In performing a mechanical analysis of a motor skill, the human
body is often viewed as a “machine,” subject to
the same laws and mechanical principles that govern the actions
of any other machine. The mechanical analysis of human performance
involves the identification of laws and principles that help explain
the most appropriate form for the execution of the activity and
identify the mechanical reasons for success or failure. To assess
the mechanical nature of a technique and use this information in
helping performers choose movements that will result in skillful motion,
the analyzer should attempt to identify those principles and laws
that verify the actions as desirable. Once the movement is classified
according to an outline such as that in System for Classification of Motor Skills, the analyst
should determine exactly how and when the movements of the performance
do or do not satisfy the standards of good performance as explained
by the laws and principles of mechanics. Once this process is accomplished,
a greater depth of understanding of the skill is achieved, and the
basis for making change is founded on sound knowledge and understanding
of the reasons “why.”
++
+++
Underlying Mechanics
Objective
++
To explain the mechanical factors that contribute most to performance,
it is first necessary to define clearly the purpose or objective
of the motion involved. The focus of the statement of mechanical
objective will be on the desired outcome of the motion, which is
necessary to measure effectiveness. Several systems have been proposed
for the classification of mechanical objectives of human movement.
A synthesis of many of those systems is presented here as a simplified
set of objectives.
++
The underlying objective of a motion may be
++
- 1. Balance
- a. Regain stability
- b. Attain mobility
- 2. Locomotion
- a. Travel from point to point
- b. Travel a prescribed distance
- c. Travel a prescribed pattern
- 3. Projection
- a. For maximum height
- b. For maximum range
- c. For maximum accuracy
- d. For optimum speed and accuracy
- 4. Manipulation
- a. Of objects
- b. To reproduce a pattern
- c. Of a resistance
- 5. Maximum effort
- a. Maximum speed
- b. Maximum power
- c. Maximum force
++
Each of these underlying mechanical objectives requires consideration
of different but overlapping sets of mechanical factors. The standing
long jump, for instance, has the underlying mechanical objective
of projection of the body for maximum range (distance). The question
now becomes one of determining what must be done in mechanical terms
to produce the maximum distance. Because the distance traveled is
in the air, the body becomes a projectile, and those factors that cause
the projectile to travel the farthest are those that must be considered.
+++
Nature of the
Forces Causing or Impeding Motion
++
To accurately analyze the efficiency with which a motor skill
is performed, the analyst must be aware of the kind of motion being
performed (classification and simultaneous-sequential nature) and
the forces that are acting to cause, modify, or prevent that motion.
Pushing and pulling forces, weight and resistance, twisting and
turning forces must all be identified, and their effects noted. Muscle
force applied through the joints’ range of motion to propel
the body through the air for maximum distance is a force-causing
motion. A force resisting motion is the resistance force offered
by the weight of the jumper. Impact with the ground at the end of
the jump will produce a force-stopping motion. Other impeding forces
might be produced by lack of strength or limited range of motion.
+++
Mechanical Principles
++
The identification of the mechanical principles related to the
execution of the skill is a first step in establishing the causes
of error in the performance of the skill. Focusing on these principles
and how they relate to the skill suggests the potential sources
of error. Each movement phase must be considered in turn. The core
concepts from which these principles are derived include considerations
of the speed of the movement, the forces involved in the movement,
balance, direction, and timing, and the pressure of air or water.
If the motion involves projecting something into the air, the concepts
of extension at release (or contact), path of the object, and spin
must also be considered. Once again, the primary concern is the
quality of each of these factors that is required for an optimum
performance. In deriving mechanical principles, one might discuss
how much speed or how much force, as well as the direction of the
force. It might become important to know how much air pressure is
acting or what angle produces the best path of a thrown object.
+++
Violation of
Mechanical Principles
++
Diagnosing the cause of an error is difficult because the cause
may be far removed from the observed effect. The purpose in identifying
the mechanical principles is to locate potential sources for error.
Given the purpose of the skill, which of the principles, if violated,
has the greatest potential for limiting performance? How? These
are the most troublesome questions to answer. Without quantitative
data it is difficult to make any selection with certainty. And even
with the support of such data, which indeed can provide us with
much useful information, we still cannot be certain. At this time
no general method is available to identify and establish the order
of importance for those factors that limit performance. One must
rely primarily on knowledge of the technique and the principles
of mechanics that apply.
++
Again, using the example of the standing long jump, we know that speed and direction are
the two most important factors in performance. The direction is
governed by the direction of the jumper’s takeoff. It appears,
then, that direction might be a good place to start to look for errors.
++
The speed of the jump depends on the speed and force of the push
against the ground. The faster the legs can move, the greater will
be the push off the ground.
+++
Prescription
for Improvement of Performance
++
After the performance has been described in anatomical and mechanical
detail and the causes for error have been identified, the analyst
must decide on the appropriate strategy for effecting change in
the performance so that it conforms to the anatomical and mechanical
ideal. Now the analyst becomes an instructor who must decide not
only what must be done but how best to communicate that information
to the performer in a manner that will make sense. The task is not unlike
that of a physician who uses vast medical knowledge to prescribe
bed rest as the best cure for an ailment. The cure may be simple,
but the complexities attached to knowing what to do, and why, and
then making that information understandable to the patient are far
from simple. The instructor of motor skills needs to develop ability
as a prescriber as well as an analyst. Both talents will improve
with practice. As more systematic analyses are performed, the analyst
will become aware of characteristics common to groups of skills.
Common errors and their causes will emerge for related skills as
well as similar or common prescriptions appropriate for correcting
the errors. The important thing to remember is to concentrate on
the causes of errors, not on the resultant symptoms. Before the
physician can prescribe for a limping gait, the cause must be known
and the viable options for treatment identified. Before an instructor
of motor skills can prescribe for improvement of a standing long
jump or any other motor performance, the cause(s) for the error must
be known and the valid options for correction determined.