EVALUATING FUNCTIONAL PERFORMANCE
By R. C. Schafer, DC, PhD, FICC
Manuscript Prepublication Copyright 1997
Copied with permission from ACAPress
The body can adapt to withstand a wide variety of threatening environmental
forces. This results in systems designed to work in harmony
during ever-changing internal and external stimuli. The nervous
system provides the necessary intricate coordination, and
physiologic measurements offer us data on the essential factors
involved in the integrated aspects of organic function. While
voluminous data can be gathered, our major concern in
rehabilitation involves those aimed at restoring and maintaining
an attribute of the human organism at its best. The development
of optimal physical fitness produces changes increasing physical
capacity and produces changes in altered metabolism at the
cellular level. A reduced level of fitness predisposes to injury,
its extent, and modifies its healing at both its macroscopic and
The degree of vascularity of the capillary network between
skeletal muscle fibers and in associated tissues depends greatly
on the type of habitual exercise. The quantity of interstitial
fat, most marked in atrophied muscle, is also determined by the
degree of exercise. Lymph vessels are not found within voluntary
Because every sport and every physical activity demands a
different combination of physiologic capabilities, an
individual's fitness must be specific for the task at hand. Even
if the potential exists to develop certain capabilities, the
decision to do so is a personal one.
human performance parameters are those of strength, endurance,
flexibility, speed, coordination, balance, and agility. Body type
could also be included here. Intelligence, creativity, and
motivation are other parameters. Clinicians must keep in mind
that the quality of one's strength, power, flexibility, speed,
coordination, balance, and agility are determined essentially by
The range of ability to perform motor activity is determined
by three essential aspects: (1) neuromuscular function (eg,
strength and skill), (2) energy output (eg, aerobic and anaerobic
processes), and (3) psychologic factors (eg, motivation,
perseverance). These aspects are involved in almost all types of
physical labor, though emphasis varies.
Performance is the result of central and peripheral
neuromuscular mechanisms, the energy yield of split compounds,
and profound psychologic effects. The methods of estimating
physical performance capacity can be classified into two major
groups: (1) physical fitness tests and (2) physiologic tests.
Typical examples of physical fitness tests in sports are sprints,
endurance runs, high jumps, long jumps, and throwing.
Determination of maximum oxygen intake and muscle strength
comprise the common physiologic types of tests as in (1)
determining the mechanical power developed on a bicycle ergometer
or staircase; (2) determining the time element necessary to run a
specified distance; (3) determining the duration of running on a
treadmill at varying degrees of speed and grade; and (4)
determining the distance run in a specified period.
Most studies used to evaluate physical performance have been
in the field of athletics. We can use this specialized
information by applying it to the nonathletic patient as it
involves daily activities. While the principles remain the same,
a concern is to remember that (1) the demands of the nonathlete
are much less strenuous, and (2) the factors considered in
physical fitness are not equal in all people who could be judged
be done to modify body type as much of the variables found in
body build and its individual physiology, especially in regard to
oxygen intake, are genetically determined. While skill has an
influence on efficiency, body type places a finite limit on
physical achievement goals. It is granted that a great deal of
practice time is allotted to the development of skill, but many
aspects of skill are inherited (eg, receptor organ sensitivity).
The potential "superstar" probably starts life with a peculiar
Because body type and receptor-organ sensitivity are
essentially governed genetically, training cannot turn an
antelope into an ox or vice versa. Depending on one's genetic
framework, training is an enhancement to potential expression.
But many variables are not trainable. Skill is the result
of practice, not training.
Practice tends to develop timing, accuracy, and conditioned
responses so that conscious faculties can be concentrated on
competitive strategies rather than on physical activities during
competition. The term "pressure practice" is practice under
highly competitive game conditions (eg, an intersquad
ATHLETIC TRAINING AND PRACTICE
"Training" and "practice" have different goals in sports. Training
refers to the improvement or maintenance of physical capacity
such as systematic endurance or strength exercises. Normally,
these are out of context with a particular sport. Practice
means repeating specific skill-developing techniques used in a
specific sport so that they may be executed at a higher level of
performance. During practice, a swimmer might practice his
push-off, a tennis player his forehand, a golfer his putting,
To complicate terminology, what would be called practice in
one sport might be called training in another. For example,
weight lifting is practice for the weight lifter, training for
the football tackle. Running is practice for the track athlete,
training for the boxer.
As available time is also a concern, the relative degree of
emphasis between training and practice varies from sport to
sport. Training is minimal in tennis and golf, practice is
secondary to training in most explosive-strength sports, and most
highly skilled team sports require a careful blend of training
Coordination, Balance, and Agility
rdination may be defined as the ability to integrate separate abilities into a complex task.
Well-coordinated movement, usually involving the large muscles,
requires alert timing between the nervous and muscular systems,
as seen in bowling, gymnastics, badminton, throwing, jumping
hurdles, handball, tennis, ice hockey, baseball, golf, or
lance is a necessary attribute when one's base of
support is reduced yet body position must be maintained.
Ballet-like balance is required in such sports as tightrope
walking, handstanding, surfing, karate, hockey, skiing, and to
some varying degree in most ballplaying sports where movement is
required in an "off-balance" position.
ility, the ability to change positions in space,
involves speed with the addition of a sudden change in direction
or height such as in a defensive maneuver or a change in attack.
The number of positional changes available is obviously almost
endless, thus total agility is difficult to evaluate. Agility is
demanded in hockey players, running backs, gymnasts, infielders,
divers, boxers, karate enthusiasts, and wrestlers.
Mechanical Advantage and Bulk
advantage and disadvantage have distinct relationships with
performance. Pace varies with limb length, for example, thus long
limbs are an advantage in running, especially in long distance
events. A higher center of gravity is a disadvantage in that it
takes extra postural effort to maintain balance (eg, gymnastics,
skating), but it has its advantages in sports (eg, basketball)
where increased height places one closer to the goal.
Body bulk has both its advantages and disadvantages.
Muscle bulk, especially in contact sports, provides both force
inertia and protection for bones and joints. Body weight is of
less consideration in swimming sports because much weight is
supported, it offers some buoyancy advantages, or it provides
necessary insulation due to subcutaneous fat (eg, open-water
swimming). In contrast, due to gravitational pull, a heavy bulk
is a disadvantage in running sports as the weight must be raised
at each pace.
There are also disadvantages in that bulky hypertrophy
increases viscous resistance to movement, produces problems from
physical apposition, and increases the body mass to be moved.
Thus, to avoid mass accumulation in an irrelevant part of the
body, muscle training should be specific for the use desired, as
indiscriminate muscle hypertrophy is likely to impair performance
in endurance events.
nearly proportional to the quantity of body muscle. Muscle issue
constitutes about 43% of body weight in the well-developed adult
male and about 38% in the adult female. The average ratio between
muscle strength and an individual's weight has been computed to
be about 26:6. Thus, the aggregate strength of the muscles of a
150-lb male is about 4,000 lbs. Since only a portion of all
muscle can be employed for a specific task, only a small part of
one's total strength can be effectively used for a particular
As described previously, strength is developed in three
manners: (1) isotonically by exercises against resistance in such
a manner that body movements are allowed; (2) isometrically by
exercises done against resistance in such a manner that body
movements are restricted -sometimes offering a short cut to goals
of equivalent repetitive drudgery; and (3) isokinetically, by
exercises of a constant velocity against resistance that adapts
to the angle of a joint. Isokinetic exercises are employed
primarily to rehabilitate up to the point of normal strength,
after which other forms of exercise are used.
Application. Weight lifting is quite helpful in
enhancing strength and endurance when judiciously applied, but it
has little effect on developing flexibility or cardiorespiratory
endurance. With weights, sets of about a dozen repetitions per
bout are typical. A "bout" is one exercise series or program.
Training with weights has both its zealot adherents and
opponents, and both are well-armed with empiric evidence.
Most athletic movements are isotonic rather than isometric,
and most all sports present strength demands above those required
for normal living. Boxing, wrestling, judo, football, hockey,
soccer, lacrosse, and nearly all other contact sports require
above-average strength output, as do certain noncontact sports
such as mountain climbing, gymnastics, and rowing. Strength
development programs (eg, weight lifting, exercise equipment) are
now popular in a wide number of sports in which they were rarely
considered in times past (eg, tennis, swimming). Table 1.
Table 1. Comparison of Various Exercises to Develop Strength
Specific to sport
Certain exercises should be discouraged. For instance,
deep-knee bends and the duck-waddle, both used for many years
with several sports, exert severe stress on the cruciate
ligaments of the knee, far outweighing any benefit to the
Guided Progression. Care must be taken in any exercise
program for logical progression. Regardless of a patient's
enthusiasm, the beginning level should be comfortably below that
which may cause injury. Progression at any stage should be to a
comfortable point requiring moderate effort. Stress should be
felt, but pain should not be. The rationale is for the patient to
work to full capacity against an orderly ever-increasing
Progression means to permit a small but increasing overload to
tissues to spur adaptation of bones, tendons, muscles, ligaments,
and capsules. Failure to increase demands will stymie further
development. Imposing an increase in loading too quickly produces
reinjury. The objective is to slightly overload, not overwhelm,
the musculature. Correct procedure, state Wallis/Logan, is to
balance these two extremes by applying the Specific Adaptation to
Imposed Demands (SAID) principle. Wilmore says this implies that
the body responds to a given orderly demand with a specific and
predictable adaptation. More simply, function improves with
Harrelson points out that it is not a prerequisite that full
pain-free active ranges of motion are attained before beginning
active resistive exercise. The patient may begin isometric manual
resistance or active resistive exercise in a limited range of
motion as long as the healing process is not jeopardized. This is
usually achieved by light-load high repetitions, not a few
An ideal program should be balanced and conducted on a daily
basis with varying intensity on alternate days, depending on how
often and when the athlete competes. An intense workout the day
before competition or hard labor is usually not wise.
Types of Strength
For discussion, strength can be
divided into dynamic (isotonic), explosive, and static
1. Dynamic strength is the ability to lift, move, and
support body weight, calling on endurance when functions are
strenuously repeated; ie, explosive movements repeated in rapid
succession (eg, pull-ups, sprinting). Limits are imposed by speed
resisting factors and the quantity and quality of energy-exchange
factors. If extreme pain, breathlessness, or weakness comes at
the end of an effort, a gain in active muscle strength will do
much to improve performance.
2. Explosive strength is the ability to
release maximum power in the fastest possible time (eg, standing
long jump). Single violent efforts are commonly seen in
sprinting, jumping, and throwing where speed factors are combined
with force/velocity features of active muscle. Response is
determined by mechanical leverage (influenced by body type),
immediate energy resources from tissue chemical coupling
(influenced by glycogen and mineral ion levels), the quantity of
actin and myosin filaments per fiber (influenced by training
hypertrophy), and the number of fibers activated (influenced by
learning experiences). The performance result of these forces is
determined largely by the degree of dynamic viscosity.
3. Static strength, a separate factor of physical
fitness, is exertion of a maximum force for a brief period of
time against a difficult to move object (eg, handgrip or arm-pull
dynamometer). The importance of static strength is brought out in
such activities as weight lifting. Such strength depends on the
total number of active muscle fibers involved in a specific
activity; ie, the functional (gross muscle less fat and
connective tissue) cross-section of the muscle exerting the
force, under control of the nervous system, with some assistance
from the type of contraction and mechanical advantage in play.
Lessening of central inhibition and greater relaxation of
antagonists also play a part in the performance effect. Limits
are imposed by exhaustion, motivation, Valsalva effects, pain,
and quickly diminishing endurance. Muscles required to contract
against increasing resistance become progressively stronger and
usually, but not inevitably, hypertrophied; ie, women need not
fear that weight lifting with good style will bring gross
Effects of Strength on Circulation. Either progressing
central or local fatigue adversely affects skill: diminished
skill is commonly associated with approaching exhaustion. As
muscle perfusion is greater in a strong muscle as compared with
that of a weak muscle, fatigue, to a great extent, is due to
inadequate perfusion. However, the overt signs of pallor and the
energy-wasting poor coordination, confusion, and staggering gait
are to be blamed on inadequate blood flow to the
posture-regulating center. Strength also has an effect on
recovery in that strength tends to minimize the microtrauma
secondary to oxygen lack and local weakness.
General Health. There is a close correlation to one's
degree of strength and endurance and one's degree of health
because of the relationship to a greater capacity for physical
work and the lessened functional response to the challenges of
stress. In this regard, the absence of disease would not indicate
rate of doing work, is determined by the rate at which energy can
be released within muscle. While the type of contraction (ie,
isometric, eccentric, or concentric), resistance, duration,
quantity of repetitions, and number of exercise bouts are
important in any exercise program, the most important factor
appears to be that the contraction force developed by a muscle
must be close to maximum if improved change is to be expected.
It has been well established that low-repetition
high-resistance exercises develop power; high-repetition
low-resistance exercises develop endurance. Many
authorities believe that strength is the only training variable
in enhancing the speed of muscle contraction and that tissue
viscosity is relatively constant. This is only true, however,
when strengthening actions mimic movements used in customary
the capacity to maintain strenuous activity of a large number of
muscle groups for a duration sufficient to prolonged resistance
to progressing fatigue and oxygen demands. It is essentially
oxygen dependent and a manifestation of cardiovascular and
respiratory function (both aerobic and anaerobic capacity).
The word "endurance" is generally used to denote the ability
of skeletal muscle to continue contractions relative to
contraction length (time), contraction quantity (per unit of
time), and contraction quality (force). During vigorous muscle
effort, the endurance factor is determined by the initial
glycogen content of muscle fibers (influenced by diet and
Endurance increases as the result of enhanced muscle
hypertrophy, glycogen reserves, myoglobin, and increased
vasculature. Local endurance is an effect of muscle strength. We
witness this in the power of serves in a long tennis match and
the final paces of the runner. In such instances, repetitions of
isotonic overload exercises enhance local endurance. Both
quantity of movements and the time duration involved are
reflections of endurance; eg, the number of push-ups or pull-ups,
time to run a mile. Endurance exhibits in a variety of ways in
sports, especially gymnastics, crew, cross-country skiing,
mountain climbing, wrestling, marathon runs, and swims.
Circuit Training. Circuit training is frequently used
to develop endurance and strength both locally and generally in
athletes. A series of exercises (eg, 8-10) is done in sequence. A
battery of stretching curls, push-ups, sit-ups, pull-ups, and
shuttle runs may be completed. These exercises are added to those
primarily designed for a specific activity. During the first
circuit program, each participant is judged on each exercise for
the maximum number of repetitions. This maximum may be determined
either by time or by the point of exhaustion.
The score obtained is divided by three to arrive at the
individual's training rate for each exercise. At subsequent
sessions, the participant completes three circuits of the
prescribed exercises as fast as possible at the training rate. As
training progresses, the time necessary to complete the three
circuits will gradually decrease. Then adjustments can be made by
increasing the number of repetitions. An alternative method to
continually retesting the maximum level is to set three
progressively difficult grades of performance, but this largely
ignores individual differences.
Cardiovascular-Respiratory Training. Circuit training
can be modified to be appropriate for even youth and the elderly
showing signs of dysfunctional cardiovascular-respiratory
efficiency. Careful monitoring and supervision are mandatory to
avoid overstress. With progression keyed to adaptive changes,
such training can lead to increased respiratory volume, increased
blood volume and cardiac output, improved heart rate and stroke
volume, and an increase in total hemoglobin. Shands also reports
benefits in improved blood supply to active musculature have also
highly correlated with muscle power and difficult to isolate.
Speed (fastness) can refer to running time or reaction time. It
can refer to the legs of a racer, the fists of a boxer, the arms
of a goalie, the eyes of a skeet shooter. As inertia is
proportional to mass, total speed considers three aspects:
time/distance in initiating body movement (explosive force of
active muscles); time/distance rate of acceleration to maximum;
and time/distance loss of acceleration as the event is prolonged.
During the last stage of a run, the reducing metabolic energy
must cope with continuing resistances in air flow, tissue
viscosity, surface friction, and other energy losses.
Great speed is obviously essential in runners, tennis players,
and football backs and ends. Like a heavy truck, it is difficult
for a bulky body frame to accelerate quickly to maximum speed.
The ideal physique of a sprinter would be one with powerful legs
and little weight elsewhere. In sprinting, performance is
enhanced by a preliminary warm-up that raises intramuscular
temperature. A slight increase in temperature enhances
muscle-tissue viscosity and use of energy resources influencing
Reaction Speed. Reaction speed is determined by the
interval between when stimuli are received by receptor organs
(eg, eyes, ears, hands, soles) and when the muscles react. A fast
reaction time is necessary for high efficiency in such events as
table tennis, dashes, and boxing.
are exercises that link speed of motion and strength to cause an
explosive reactive-type motion. They are helpful in developing
speed, power, and locomotor skill. This is achieved by maximizing
the myotactic (stretch) reflex. Muscles are fully stretched by
eccentric contractions immediately before a concentric
contraction. The greater the stretch on the muscle from its
resting length, the greater the load the concentric contraction
Application is commonly done with large rubber bands (eg,
Thera-Bands) or surgical tubing. The subject muscles are
stretched against the resistance of the band or tube, then the
patient moves the part or limb as fast as possible through all
normal ranges of motion.
Such drills, states Harrelson, were once confined to
off-season strength training programs but have now become part of
therapeutic rehabilitation in the late stages. Application two or
three times weekly is sufficient when combined with other
regimens. Judicious use of plyometrics is important because
overuse injuries easily occur when supervision is not alert.
performance assessment is often studied in an isolated
compartmentalized fashion (eg, strength, endurance,
aerobic-anaerobic capacity, etc) by the exercise physiologist,
care must be taken to avoid oversimplified specific-muscle
training that does not enhance overall performance. For example,
the development of isometric strength does not assure an
improvement in dynamic performance. Multiple intrinsic and
extrinsic factors and adaptations affect performance on any one
day. A "star" is more than the sum of his parts.
performance during youth is greatly determined by body size, body
type, the degree of maturation of the nervous system, and the
degree of sexual maturation (more important in males than
females). Added to this under conditions of good nutrition, the
body of both the immature and mature thrives on use, and use
encourages adaptation to maintain a functional reserve of about
25% greater than demand.
REFERENCES AND BIBLIOGRAPHY:
American College of Sports Medicine: Resource Manual for Guidelines for
Exercise Testing and Prescription Philadelphia, Lea &
Andreoli G: Neurological Implications of Sports Injuries.
New England Journal of Chiropractic, Winter 1979.
Atha J: Physical Fitness Measurements, Fitness, Health, and
Work Capacity New York, Macmillan, 1974, Part VII.
Doherty JK: Modern Track and Field London, Bailey
Brothers and Swinfen, 1963.
Elftman H: Biomechanics of muscle. Journal of Bone and
Joint Surgery, 48A:363-377, 1966.
Esch D, Lepley M: Musculoskeletal Function: An Anatomy and
Kinesiology Laboratory Manual Minneapolis, University of
Minnesota Press, 1974.
Fletcher GF, et al: Rehabilitative Medicine: Contempory
Clinical Perspectives. Baltimore, Lea & Febiger,
Gordon AM, Rosse C: Skeletal Muscle. In Rosse C, Clawson DK:
The Musculoskeletal System in Health & Disease
Hagerstown, PA, Harper & Row, 1980.
Gould J, Davies G: Orthopaedic and Sports Physical
Therapy St. Louis, C.V. Mosby, 1985.
Harrelson GL: Introduction to Rehabilitation. In Andrews RA,
Harrelson GL: Physical Rehabilitation of the Injured
Athlete Philadelphia, W.B. Saunders, 1991, pp 165-196.
Harrelson GL: Physiologic Factors of Rehabilitation. In
Andrews RA, Harrelson GL: Physical Rehabilitation of the
Injured Athlete Philadelphia, W.B. Saunders, 1991, pp
Hettinga DL: Normal Joint Structures and Their Reaction to
Injury. Journal of Orthopaedic Sports Physical Therapy,
Hirschberg GG, et al: Rehabilitation Philadelphia,
J.B. Lippincott, 1964.
Karpovich PV, Sinning WE: Physiology of Muscular
Activity Philadelphia, W.B. Saunders, 1971.
Kraus H: Evaluation and Treatment of Muscle Function in
Athletic Injury. American Journal of Surgery, Vol 98,
Laubach LL: Comparative Muscular Strength of Men and Women: A
Review of the Literature. Aviation Space Environment
Medicine, 47:534-542, 1976.
Lee M, Wagner MM: Fundamentals of Body Mechanics and
Conditioning. Philadelphia, W.B. Saunders, 1949.
Middleton K: Range of Motion and Flexibility. In Andrews RA,
Harrelson GL: Physical Rehabilitation of the Injured
Athlete. Philadelphia, W.B. Saunders, pp 141-196.
Morehouse LE, Gross L: Maximum-Performance. New York,
Simon and Schuster, 1977.
Muller EA: The Regulation of Muscular Strength. Journal of
the Association of Physical Medicine and Rehabilitation, Vol
Rasch PJ, Morehouse LE: Effect of Static and Dynamic Exercises
on Muscular Strength and Hypertrophy. Journal of Applied
Physiology, 11:29, 1957.
Schafer RC: Chiropractic Physical and Spinal Diagnosis
Oklahoma City, American Chiropractic Academic Press, 1980.
Schafer RC: Clinical Biomechanics: Musculoskeletal Actions
and Reactions, ed 1. Baltimore, Williams & Wilkins,
Schafer RC: Symptomatology and Differential Diagnosis
Arlington, Virginia, American Chiropractic Association, 1986, pp
Shands C: Chiropractic Rehabilitation, ed 2. Danville,
California, Life at Its Peak, 1991, pp 4-14.
Wilmore JH: Athletic Training and Physical Fitness
Boston, Allynn & Bacon, 1976.
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