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A good command of the language associated with forms of motion,
standard reference terminology, and joint movement terminology is
essential for being able to describe a qualitative analysis of human
movement. The ability to qualitatively assess human movement also
requires both knowledge of the movement characteristics desired
and the ability to observe and analyze whether a given performance
incorporates these characteristics (6). As introduced in Chapter 1, the word qualitative refers to a
description of quality without the use of numbers. Visual observation
is the most commonly used approach for qualitatively analyzing the
mechanics of human movement. Based on information gained from watching
an athlete perform a skill, a patient walk down a ramp, or a student
attempt a novel task, coaches, clinicians, and teachers make judgments
and recommendations on a daily basis. To be effective, however,
a qualitative analysis cannot be conducted haphazardly, but must
be carefully planned and conducted by an analyst with knowledge
of the biomechanics of the movement.
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Prerequisite
Knowledge for a Qualitative Analysis
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There are two main sources of information for the analyst diagnosing
a motor skill. The first is the kinematics or technique exhibited
by the performer, and the second is the performance outcome (12).
Evaluating performance outcome is of limited value, since the root
of optimal performance outcome is appropriate biomechanics.
++
To effectively analyze a motor skill, it is very helpful for
the analyst to understand the specific purpose of the skill from
a biomechanical perspective. The general goal of a volleyball player serving
a ball is to legally project the ball over the net and into the
opposite court. Specifically, this requires a coordinated summation
of forces produced by trunk rotation, shoulder extension, elbow
extension, and forward translation of the total-body center of gravity,
as well as contacting the ball at an appropriate height and angle.
Whereas the ultimate purpose of a competitive sprint cyclist is
to maximize speed while maintaining balance in order to cross the
finish line first, biomechanically this requires factors such as
maximizing perpendicular force production against the pedals and
maintaining a low body profile to minimize air resistance.
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Without knowledge of relevant biomechanical principles, analysts
may have difficulty in identifying the factors that contribute to
(or hinder) performance and may misinterpret the observations they
make. More specifically, to effectively analyze a motor skill, the
analyst must be able to identify the cause of
a technique error, as opposed to a symptom of the error, or a performance
idiosyncrasy. Inexperienced coaches of tennis or golf may focus
on getting the performer to display an appropriate follow-through
after hitting the ball. Inadequate follow-through, however, is merely
a symptom of the underlying performance error, which may be failure
to begin the stroke or swing with sufficient trunk rotation and
backswing, or failure to swing the racquet or club with sufficient
velocity. The ability to identify the cause of a performance error
is dependent on an understanding of the biomechanics of the motor
skill.
++
One potential source of knowledge about the biomechanics of a
motor skill is experience in performing the skill. A person who
performs a skill proficiently usually is better equipped to qualitatively
analyze that skill than is a person less familiar with the skill.
For example, research shows that experienced tennis players evaluate
arm and racquet motion during the serve, whereas novices focus on
the ball (5). Likewise, advanced batters demonstrate greater perceptual
decision making during a pitch than do intermediate batters, particularly
when the pitch is a curve ball (12). Research on physical education
student teachers also shows that when they analyze a movement, the
focus of attention differs with personal background experiences
(1). In most cases, a high level of familiarity with the skill or
movement being performed improves the analyst’s ability
to focus attention on the critical aspects of the event.
++
Direct experience in performing a motor skill, however, is not
the only or necessarily the best way to acquire expertise in analyzing
the skill. Skilled athletes often achieve success not because of the
form or technique they display, but in spite of it! Furthermore,
highly accomplished athletes do not always become the best coaches,
and highly successful coaches may have had little or no participatory
experience in the sports they coach.
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The conscientious coach, teacher, or clinician typically uses
several avenues to develop a knowledge base from which to evaluate
a motor skill. One is to read available materials from textbooks, scientific
journals, and lay (coaching) journals, despite the facts that not
all movement patterns and skills have been researched and that some
biomechanics literature is so esoteric that advanced training in
biomechanics is required to understand it. However, when selecting
reading material, it is important to distinguish between articles
supported by research and those based primarily on opinion, as “commonsense” approaches
to skill analyses may be flawed. There are also opportunities to
interact directly with individuals who have expert knowledge of
particular skills at conferences and workshops.
++
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Planning a Qualitative
Analysis
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Even the simplest qualitative analysis may yield inadequate or
faulty information if approached haphazardly. As the complexity
of the skill and/or the level of desired analytical detail
increases, so does the level of required planning.
++
The first step in any analysis is to identify the major question
or questions of interest. Often, these questions have already been
formulated by the analyst, or they serve as the original purpose
for the observation. For example, has a post–knee surgery
patient’s gait returned to normal? Why is a volleyball
player having difficulty hitting cross-court? What might be causing
a secretary’s wrist pain? Or simply, is a given skill being
performed as effectively as possible? Having one or more particular
questions or problems in mind helps to focus the analysis. Preparing
a criteria sheet or a checklist prior to performing an analysis
is a useful way to help focus attention on the critical elements
of the movement being evaluated (11). Of course, the ability to
identify appropriate analysis questions and formulate a checklist
is dependent on the analyst’s knowledge of the biomechanics
of the movement. When an analyst is observing a skill that is less
than familiar, it can be helpful to recall that many motor skills
have commonalties. For example, serves in tennis and volleyball
and the badminton overhead clear might all be considered part of
the “overarm throw family” (15).
++
The analyst should next determine the optimal perspective(s)
from which to view the movement. If the major movements are primarily
planar, as with the legs during cycling or the pitching arm during
a softball pitch, a single viewing perspective such as a side view
or a rear view may be sufficient. If the movement occurs in more
than one plane, as with the motions of the arms and legs during
the breaststroke or the arm motion during a baseball batter’s
swing, the observer may need to view the movement from more than
one perspective to see all critical aspects of interest. For example,
a rear view, a side view, and a top view of a martial artist’s
kick all yield different information about the movement (Figure
2-19).
++
++
Even when a movement is primarily planar, using more than a single
viewing perspective may be useful. Sometimes, for example, observing
the performer’s eye movements yields valuable information.
A common error among beginning tennis players is looking across
the net to where they expect to hit the ball rather than visually
tracking enough of the oncoming ball’s trajectory to establish
racket contact with it. In fencing, focusing the eyes on the rapidly
moving tip of an opponent’s blade can be a drastic performance
error, facilitating the effectiveness of the opponent’s
feints (16).
++
The analyst’s viewing distance from the performer should
also be selected thoughtfully (Figure 2-20). If the analyst wishes
to observe subtalar pronation and supination in a patient walking
on a treadmill, a close-up rear view of the lower legs and feet
is necessary. Analyzing where a particular volleyball player moves
on the court during a series of plays under rapidly changing game conditions
is best accomplished from a reasonably distant, elevated position.
++
++
Another consideration is the number of trials or executions of
the movement that should be observed in the course of formulating
an analysis. A skilled athlete may display movement kinematics that
deviate only slightly across performances, but a child learning
to run may take no two steps alike. Basing an analysis on observation
of a single performance is usually unwise. The greater the inconsistency
in the performer’s kinematics, the larger the number of
observations that should be made.
++
Other factors that potentially influence the quality of observations
of human movement are the performer’s attire and the nature
of the surrounding environment. When biomechanic researchers study
the kinematics of a particular movement, the subjects typically
wear minimal attire so that movements of body segments will not
be obscured. Although there are many situations, such as instructional
classes, competitive events, and team practices, for which this
may not be practical, analysts should be aware that loose clothing
can obscure subtle motions. Adequate lighting and a nondistracting
background of contrasting color also improve the visibility of the
observed movement.
++
A final consideration is whether to rely on visual observation
alone or to use a video camera. As the speed of the movement of
interest increases, it becomes progressively less practical to rely
on visual observation. The human eye cannot resolve events that
occur in less than approximately one-fifth of a second (5). Consequently,
even the most careful observer may miss important aspects of a rapidly
executed movement. Video also enables the performer to view the
movement, as well as allowing repeated viewing of the movement by
analyst and performer, enabling performance feedback that can enhance
the learning of a motor skill (4). Better-quality playback units also
enable slow-motion viewing and single-picture advance that facilitate
isolation of the critical aspects of a movement.
++
The analyst should be aware, however, that there is a potential
drawback to the use of video. The subject’s awareness of
the presence of a camera sometimes results in changes in performance. Movement
analysts should be aware that subjects may be distracted or unconsciously
modify their techniques when a recording device is used.
++
++
++
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Conducting a
Qualitative Analysis
++
Despite careful planning of a qualitative analysis, new questions
occasionally emerge during the course of collecting observations.
Movement modifications may be taking place with each performance
as learning occurs, especially when the performer is unskilled.
Even when this is not the case, the observations made may suggest
new questions of interest. For example, what is causing the inconsistencies
in a golfer’s swing? What technique changes are occurring
over the 30–40 m range in a 100 m sprint? A careful analysis
is not strictly preprogrammed, but often involves identifying new
questions to answer or problems to solve. The teacher, clinician,
or coach often is involved in a continuous process of formulating
an analysis, collecting additional observations, and formulating
an updated analysis (Figure 2-21).
++
++
Answering questions that have been identified requires that the
analyst be able to focus on the critical aspects of the movement.
Once a biomechanical error has been generally identified, it is often
useful for the analyst to watch the performer over several trials
and to progressively zero in on the specific problem. Evaluating
a softball pitcher’s technique might begin with observation
of insufficient ball speed, progress to an evaluation of upper-extremity
kinematics, and end with an identification of insufficient wrist
snap at ball release.
++
The analyst should also be aware that every performance of a
motor skill is affected by the characteristics of the performer.
These include the performer’s age, gender, and anthropometry;
the developmental and skill levels at which the performer is operating;
and any special physical or personality traits that may impact performance.
Providing a novice, preschool-aged performer with cues for a skilled,
mature performance may be counterproductive, since young children
do not have the same motor capabilities as adults. Likewise, although
training can ameliorate loss of muscular strength and joint range
of motion once thought to be inevitably associated with aging, human
movement analysts need increased knowledge of and sensitivity to
the special needs of older adults who wish to develop new motor
skills. Analysts should also be aware that although gender has traditionally
been regarded as a basis for performance differences, research has
shown that before puberty most gender-associated performance differences
are probably culturally derived rather than biologically determined
(13). Young girls are usually not expected to be as skilled or even
as active as young boys. Unfortunately, in many settings, these
expectations extend beyond childhood into adolescence and adulthood.
The belief that an activity is not gender appropriate has been shown
to negatively affect college-aged women’s ability to learn
a new motor skill (2). Analysts of female performers should not
reinforce this cultural misunderstanding by lowering their expectations
of girls or women based on gender. Analysts should also be sensitive
to other factors that can influence performance. Has the performer
experienced a recent emotional upset? Is the sun in his eyes? Is
she tired? Being an effective observer requires full awareness of
the surrounding environment (3).
++
To supplement visual observation, the analyst should be aware
that nonvisual forms of information can also sometimes be useful
during a movement analysis. For example, auditory information can
provide clues about the way in which a movement was executed. Proper
contact of a golf club with a ball sounds distinctly different from
when a golfer “tops” the ball. Similarly, the
crack of a baseball bat hitting a ball indicates that the contact
was direct rather than glancing. The sound of a double contact of
a volleyball player’s arms with the ball may identify an
illegal hit. The sound of a patient’s gait usually reveals
whether an asymmetry is present.
++
Another potential source of information is feedback from the
performer (Sample Application 2.1). A performer who is experienced
enough to recognize the way a particular movement feels as compared
to the way a slight modification of the same movement feels is a
useful source of information. However, not all performers are sufficiently
kinesthetically attuned to provide meaningful subjective feedback
of this nature. The performer being analyzed may also assist in
other ways. As Hoffman (6) has pointed out, performance deficiencies
may result from errors in technique, perception, or decision making.
Identification of perceptual and decision-making errors by the performer
often requires more than visual observation of the performance.
In these cases, asking meaningful questions of the performer may
be useful. However, the analyst should consider subjective input
from the performer in conjunction with more objective observations.
++
Another potential way to enhance the thoroughness of an analysis
is to involve more than one analyst. This reduces the likelihood
of oversight. Students in the process of learning a new motor skill
may also benefit from teaming up to analyze each other’s
performances under appropriate teacher direction.
++
Finally, analysts must remember that observation skills improve
with practice. Research indicates that training in both general
analysis protocol and visual discrimination of critical features
of a specific motor skill can dramatically improve an analyst’s
ability (9, 14). As analysts gain experience, the analysis process
becomes more natural, and the analyses conducted are likely to become more
effective and informative. The expert analyst is better able to
both identify and diagnose errors than the novice (10). Novice analysts
should take every opportunity to practice movement analysis in carefully
planned and structured settings, as such practice has been shown
to improve the ability to focus attention on the critical aspects
of performance (7).
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Sample Application 2.1
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Problem: Sally, a powerful outside
hitter on a high school volleyball team, has been out for two weeks
with mild shoulder bursitis, but has recently received her physician’s
clearance to return to practice. Joan, Sally’s coach, notices
that Sally’s spikes are traveling at a slow speed and are
being easily handled by the defensive players.
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Planning the Analysis
+
1. What specific problems need to be solved or questions
need to be answered regarding the movement? Joan first questions
Sally to make sure that the shoulder is not painful. She then reasons
that a technique error is present.
2. From what angle(s) and distance(s) can problematic
aspects of the movement best be observed? Is more than one view
needed? Although a volleyball spike involves transverse plane rotation
of the trunk, the arm movement is primarily in the sagittal plane.
Joan therefore decides to begin by observing a sagittal view from
the side of Sally’s hitting arm.
3. How many movement performances should be observed?
Since Sally is a skilled player and her spikes are consistently
being executed at reduced velocity, Joan reasons that only a few
observations may be needed.
4. Is special subject attire, lighting, or background
environment needed to facilitate observation? The gym where the
team works out is well lit and the players wear sleeveless tops.
Therefore, no special accommodations for the analysis seem necessary.
5. Will a video recording of the movement be necessary
or useful? A volleyball spike is a relatively fast movement, but
there are definite checkpoints that the knowledgeable observer can watch
in real time. Is the jump primarily vertical, and is it high enough
for the player to contact the ball above the net? Is the hitting
arm positioned with the upper arm in maximal horizontal abduction
prior to arm swing to allow a full range of arm motion? Is the hitting
movement initiated by trunk rotation followed by shoulder flexion,
then elbow extension, then snaplike wrist flexion? Is the movement
being executed in a coordinated fashion to enable imparting a large force
to the ball?
+++
Conducting the Analysis
+
1. Review, and sometimes reformulate, specific questions
of focus. After watching Sally execute two spikes, Joan observes
that her arm range of motion appears to be relatively small.
2. Repeatedly view movements to gradually zero in on
causes of performance errors. After watching Sally spike three more
times, Joan suspects that Sally is not positioning her upper arm
in maximal horizontal abduction in preparation for the hit.
3. Be aware of the influence of performer characteristics.
Joan talks to Sally on the sideline and asks her to put her arm
in the preparatory position for a hit. She asks Sally if this position
is painful, and Sally responds that it is not.
4. Pay attention to nonvisual cues. (None are apparent
in this situation.)
5. When appropriate, ask the performer to self-analyze.
Joan tells Sally that she suspects Sally has been protecting the
shoulder by not rotating her arm back far enough in preparation
for spikes. She can correct the problem. Sally’s next few
spikes are executed at much faster velocity.
6. Consider involving other analysts to assist. Joan
asks her assistant coach to watch Sally for the remainder of practice
to determine whether the problem has been corrected.