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Questionable Exercises
A Note from the Editors
The focus of virtually all previous
issues of the PCPFS Digest has been on the health-related
benefits of physical activity and other healthy lifestyles.
Too often we forget that while physical activity has
many benefits, when done improperly it can have negative
consequences. For this issue of the PCPFS Digest we
asked Wendell Liemohn and his colleagues to describe
some of the more common questionable exercises. The
intent is to describe how some exercises, especially
those designed to produce flexibility and muscle fitness,
can cause harm and to provide alternatives that are
safer.
Introduction
Any activity selected for an exercise
program should have some underlying value (e.g., improve
flexibility, strength, cardiovascular fitness). However,
even some exercises that have underlying value might
have elements that can make them inappropriate or even
contraindicated if done incorrectly. Thus, an exercise
for extremely physically fit individuals can be appropriate
because the quality of movement they display in doing
it meets the objectives for which the exercise was designed.
However, if the same exercise were done by individuals
with poor physical fitness (e.g., lack flexibility,
have weak abdominal muscles); their renditions of the
exercise could be deemed totally inappropriate (or even
contraindicated) because their quality of movement is
poor. The purpose of this issue is to present general
guidelines for exercise prescription that have an anatomical
basis but that also consider the exerciser's ability
to do the exercise correctly (i.e., show good quality
of movement). To aid the reader several important definitions
are included in highlighted boxes. The terms defined
are printed in bold in the text of the paper.
Parameters of Evaluation
Before discussing any exercise, anatomical
and biomechanical factors should be considered. For
example, knowing how much "safe movement" can occur
at a joint is of obvious relevance. After presenting
the anatomical/biomechanical characteristics of the
area of the body pertinent to the exercises to be addressed,
we will examine a few of the more "notorious" exercises
and discuss how movement quality and movement tempo
relate to their appraisal.
If you are having difficulty perceiving
the structure of an intervertebral disc,
just think of it as a thin jelly donut.
The donut part would represent the
annulus fibrosis and vertebral end
plates; the jelly would represent the
nucleus pulposus. Some neck and low
back problems relate to movement of
the nuclear "jelly" material from
its normal confines and into contact
with pain receptors in the annulus
fibrosis or adjacent tissues.
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The Spine
The spinal column consists of 7-cervical, 12-thoracic,
5-lumbar, and 5-fused-sacral vertebrae (i.e., the sacrum);
the latter transfers the weight of all structures above
it to the other bones of the pelvis. Any two vertebrae
and their intervening disc are called a motion segment
of the spinal column. A motion segment is the smallest
functional unit of the spine; the joints that comprise
it include the (a) anterior joints between the vertebral
bodies and the disc that separates them and (b) posterior
joints between the paired facets (i.e., junction of the
superior and inferior articular processes). Intervertebral
discs act as spacers and shock absorbers for the spinal
column; discs also permit movement between vertebrae.
The peripheral fibers of each disc (annulus fibrosis)
and its top and bottom (vertebral end-plates) enclose
the disc's fluid center (nucleus pulposus).
Spinal Movements:
Neck (Cervical) Area. Because
the cervical spine has an exceptional amount of movement
and is hard to depict pictorially, we will describe
cervical movement in terms of the degrees of range of
motion (ROM) from one end-point to another (e.g., end-ROM
in flexion to end-ROM in extension). Using these descriptors,
the cervical vertebrae have about (a) 145 degrees of
flexion and extension, (b) 90 degrees of lateral flexion
(e.g., 45 degrees to each side), and (c) 180 degrees
of axial rotation1. The greatest amount of rotation
occurs between the top two cervical vertebrae (C1 &
C2); approximately 9-11 degrees of motion exist between
the remaining motion segments of the cervical vertebrae.
Trunk Area. Figure 1 is an illustration
of trunk ROM showing ROM extremes from lumbosacral hyperextension
to lumbosacral flexion. Note that lumbar flexion is,
in essence, just a removal of the lordotic curve; people
really do not flex their lumbar spines. If, for example,
movement exceeds an individual's end-ROM for spine flexion
(or lateral flexion), there could be (a) compression
damage to discs, neural components, and vascular structures
on the side of the bending and (b) stretching of ligamentous
and other soft tissues on the opposite side. If end-ROM
in rotation is exceeded, the outer fibers of discs could
be torn. Although seemingly innocuous, movements such
as those listed may lead to repetitive microtrauma.
The first few times normal ROM of a joint is exceeded,
perhaps only a few bands of collagen (a constituent
of connective tissue seen in ligaments, discs, and in
other soft-tissue structures) is damaged. However, repetitive
microtrauma can eventually lead to serious damage of
tissues.
Some exercise leaders suggest that
any spine hyperextension should be avoided. However,
hyperextension is a natural movement and it is in the
best interest of the biomechanics of one's spine to
maintain this mobility. If such mobility is not maintained
it will be lost2, 3. Nevertheless, it is
acknowledged that uncontrolled or ballistic-hyperextension
movements of the spine are totally inappropriate because
they can stress and damage the posterior aspects of
one or more motion segments. But, "slow and controlled"
hyperextension movements are appropriate for inclusion
in exercise programs; in fact they are a prime element
in the very popular McKenzie exercise therapy program
for individuals with neck or low back pain4-6.
Nonetheless, it is important that spine movements are
carefully taught and monitored by exercise leaders,
for some individuals do not have a very good awareness
(kinesthetic sense) of how they move and position their
body parts when they exercise.
Excessive and uncontrolled rotation
movements of the spine (e.g., as in a "no" headshake)
are of utmost concern. As previously indicated, the
greatest rotation exists between the first and second
cervical vertebrae; however, there are about 9-11 degrees
of rotation between the other motion segments of the
cervical vertebrae. In the lumbar region only 1-3 degrees
of motion exist between each vertebra; here the restriction
is due to the structure of the posterior portions of
the motion segments (i.e., the facet joint). If spinal
rotation exceeds a joint's physiological limits, the
excessive stress may be placed on intervertebral discs,
their supporting ligaments, and their neural and vascular
tissue.
Pelvic Area. The muscles crossing
the hip joint can be viewed as "guy wires" that control
pelvic positioning; if any of these guy wires are too
tight, the affected individual will have difficulty
controlling pelvic position with the trunk musculature.
The posterior-lateral wall of the pelvis includes the
five fused sacral vertebrae (i.e., sacrum and ilia).
Because these joints (i.e., the sacroiliac) permit so
little movement, the pelvis in essence becomes the foundation
of the spinal column. Therefore, tightness in any muscle
crossing the hip joint can affect the biomechanics of
the spine. It is for this reason that ROM at the hip
joint is often measured and its improvement is often
an objective of exercise programs. The normal ROM for
the hip joint in forward and backward bending is 135
degrees; this includes 10 degrees of hip extension and
125 degrees of hip flexion7. Besides the joint capsule,
hip joint extension can be limited by tightness of the
hip flexor muscles (e.g., iliopsoas muscle). When the
knee-joint is extended, hip-joint flexion can be limited
by the hamstring muscle group that crosses both hip
and knee joints. Although other hip-joint muscles are
also important, the flexors and extensors of the hip
joint have greater roles in exercise considerations
than do the other muscles, and thus they are the only
ones that we will discuss for this area.
Exercise Concerns:
Cervical Spine ROM. The yoga plough
is done by extending the legs overhead and backwards
behind the head and neck; this movement involves transferring
the weight of the body over the cervical spine (see
Fig. 2). The purpose of this exercise is to stretch
the lower back; however, the extreme amount of flexion
of the neck that occurs in doing the exercise can be
problematic. This exercise would be particularly inappropriate
for individuals with either arthritis or osteoporosis
of the spine, or amenorrheic women8, 9. However,
this exercise may not pose a problem for healthy youngsters8.
On the other hand, exercises involving
neck hyperextension (e.g., as seen in neck circles)
are considered potentially dangerous if done forcefully
and quickly. This type of exercise is inappropriate
because it may result in the compression of neural and
vascular structures at the base of the skull8,
10, and potentially damage discs and other
soft tissue structures. Obviously neck hyperextension
can be dangerous for individuals with degenerative joint
disease, osteoporosis, or who have suffered whiplash
injuries. However, hyperextension movements can be considered
safe if done slowly and with controlled movement in
the normal range of motion4, 8. Conversely,
much less support exists for bridging as done by wrestlers
and football players to strengthen the neck; bridging
is inappropriate for most everyone because of the extreme
pressure it places on cervical discs8.
Fig.
1. This figure presents the limits of
lumbar spine ROM in the sagittal plane
(i.e., extremes from backward to
forward bending). If the individual were
to reach towards his/her toes from
the forward position, the additional
movement would occur at the hip
joint. (Adapted from White and Panjabbi3)
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Repetitive Microtrauma (also called repetitive
motion injury). If one bends a paper clip
a couple of times, it is still strong
but its molecular makeup has been changed
forever. With continued bending it will
eventually break. This is similar to what
happens in a repetitive microtrauma injury
to soft tissue structures such as
ligaments and intervertebral discs. The
minor damage is not noted initially;
however, by the time it reaches
pain threshold it has become serious.
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Ballistic Rotation. Ballistic rotation
movements of the spine that are quick
and with little control have been cited
as being a major cause of neck as well
as low back problems because of the stress
that they place on discs and other structures
of the spine. This movement is truly contraindicated.
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Fig.
2. The Yoga Plough Exercise. Although
this exercise can stretch the low back
(e.g., if the legs were bent and brought
to the mat), it can place an undue amount
of the body weight on the cervical and
thoracic spine. It is for this reason
that it would be inappropriate for
individuals with either arthritis or osteoporosis
of the spine, or for amenorrheic young
women.
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Hip-Joint Flexion ROM. The movements
inherent in both the fingertips-to-floor (FTF) and the
sit-and-reach (SR) exercises and tests have been questioned
with respect to endangerment of the spine11-13.
If either activity is done repeatedly, and if the exerciser
has tight hamstrings, the limited excursion at the hip
joint can transfer the stress to the connective-tissue
structures of the spine12, 14. However, if
the exerciser has good hip-joint flexibility, the activity
is more apt to achieve what it is intended to do, namely
stretch the hamstrings. If the tempo of the activity
were increased markedly by one with tight hamstrings,
the torso would have greater momentum (i.e., more ballistic
in nature), and there would be a greater chance that
the posterior ligaments of the vertebral column could
be sprained11.
An important point to remember in
administering either the finger-tip-to-floor or the
sit and reach is that the quality of the movement may
be more important than the number of centimeters reached.
A major quality point to check is the angle of the sacrum;
in the sit and reach it should be 80 or more degrees
with the floor; a book or small object with a 90-degree
angle placed next to the sacrum provides a good criterion7.
If this angle were less than 80 degrees (see Fig. 3)
and the individual practiced this activity (or the comparable
finger-tip-to-floor), the stress in stretching would
be more apt to occur in the connective tissue structures
of the spine rather than in the hamstrings12, 15.
Ideally the spine should make a smooth arc; there should
neither be a flattening or an excessive curve in any
area.
Hip-Joint/Trunk (Extension Strength).
In the previous discussion on spine extension ROM,
we mentioned that the movement is often done without
active contraction of the muscles of the spine; therefore
hyperextension movements are appropriate as long as
they are done slowly and under total control (i.e.,
not done ballistically). On the other hand, if strengthening
the lumbar spine musculature is the objective, the rules
change. If there is active contraction of these muscles
(e.g., spine muscles in a Roman-Chair-type activity),
a good rule of thumb to follow is to limit extension
to the extent of one's normal standing lumbar lordosis
(i.e., do not hyperextend)24.
Trunk/Hip-Joint (Flexion Strength).
In Figure 3 the reader is reminded that (a) the amount
of lumbosacral flexion is in essence limited to the
removal of the lordotic curve and (b) any subsequent
flexion occurs at the hip-. Because the abdominal muscles
do not cross the hip joint, they obviously cannot produce
flexion at this joint. However, individuals with weak
abdominal muscles often do full-sit-up-type exercises
entirely with their hip flexors7; the role
of the hip flexors in this type of sit-up becomes even
more dominant if the feet are held25. The
full sit-up (either with legs bent or straight) has
been criticized for a number of years7, 13, 26,
27; moreover, Saal and Saal28 believe
that this exercise can cause low-back injury. This possibility
is supported by two recent studies that have shown that
either the straight-leg or bent-leg sit-up can place
extremely high compressive forces on intervertebral
discs29, 30. Although the timed full-sit-up
is now only used in a few settings31, the
tempo of the movement can add to its drawbacks. For
example, too much flexion may occur at the neck if the
hands are placed behind the head. If done too quickly,
movement quality diminishes; however, if an individual
with strong abdominal muscles does this exercise at
a cadence of 20 repetitions per minute, movement quality
is apt to be good. Nevertheless, even this cadence would
probably be questionable for those deficient in abdominal
muscle strength. Other Nuances of Abdominal Strength.
A safe "crunch-type" test was recently developed at
Georgia Tech University32; the only critical
review of this test raised minor statistical points33.
Of more importance, although the test appears safe,
its biggest drawback is that it only permits evaluation
of the strength of the rectus abdominis. If functional
spinal integrity is of concern, the strength of the
obliques and the transversus abdominis (i.e., lateral
abdominal muscles) should be evaluated24, 34.
The Knee
Besides being the largest joint in
the body, the knee joint is very complex because it
includes articulations between the (a) tibia and femur
(tibiofemoral joint) and (b) patella and femur (patellofemoral
joint). The knee is particularly susceptible to injury
because of the high forces it sustains due to its location
between the body's two longest lever arms (femur and
tibia)35. Poor technique or uncontrolled
movement during exercises increases the risk of injury
to the knee.
Exercise Concerns:
The medial structures of the knee
(i.e., medial collateral ligament & medial meniscus)
are put at risk for injury when individuals perform
flexibility exercises (such as the standing quadricep/hip-flexor
stretch) in which the hip is abducted during the stretch36
(Fig. 4). One way to avoid this possibility is to use
the contralateral hand to hold the ankle.
The hurdler stretch is unique because
it can be used for either stretching the hamstrings
or quadriceps, dependent upon whether body lean is forward
or backward (See Fig. 5). When used for stretching the
hamstrings, the individual leans forward. In this position
a considerable stress is placed on the medial structures
of the bent leg; strain or discomfort in the hip and
groin area may also occur because the femur of the bent
leg is placed in extreme rotation. A safer alternative
is to bend the knee in front of the body rather than
to the side. This is the stretch originally recommended
by Cailliet12 and subsequently adapted for
use in a testing protocol by The Cooper Institute for
Aerobics Research37.
If the individual in Figure 5 were
to lean backward, the quadriceps would be stretched;
however this movement too has its drawbacks because
the position of the bent leg does not allow the pelvis
to rotate as the trunk is brought backward. This results
in a hyperextension stress being placed on the lumbar
spine. Furthermore, the rotation of the tibia relative
to the femur may damage the soft tissue structures of
the knee. Also questionable are exercises that
involve knee hyperflexion (e.g., 120 degrees or more)
because they increase forces markedly at the patellofemoral
joint. In weight-supporting activities, for example,
these forces have been documented to be 2-3 times a
person's body weight when the knee is flexed at 90 degrees35.
Exercises that involve deeper squatting (i.e., more
hyperflexion) or that are performed with added weight
would increase the patellofemoral forces even further.
The supportive structures of the knee are placed in
a vulnerable position in these activities; therefore,
they should be avoided by individuals who have a history
of knee injury38. Sports such as weight
or power lifting, ballet, and gymnastics sometimes require
movements that place the knee in a hyperflexed position
of more than 90 degrees. Although elite athletes in
these sports may be capable of performing knee hyperflexion
exercises without any problem, other types of individuals
may benefit less from them because of the risks of injury8,
39.
In general, high impact exercises
are common injury mechanisms for the hip, knee, ankle
and foot. Particularly questionable are jumping or bouncing
type movements in which the exerciser lands on one foot;
research has shown that vertical ground reaction forces
for such movements can be 5-6 times the vertical force
experienced in walking40. High impact aerobic
dance movements that require bouncing in the same spot
can increase the risk of shin pain, compartment syndrome,
and stress fractures of the tibia and fibula41.
However, a resilient exercise surface would lessen the
chances of injuries.
Summary
It should be noted that all questionable
exercises have not been covered in this brief discussion.
However, a point that has been stressed is that certain
exercises that are appropriate for some individuals
may be totally inappropriate for others. The quality
of the exerciser's movements is a most critical variable
when evaluating exercises for inclusion in a conditioning
program; we also suggest that readers consider the following
criteria when judging either an exercise or an exerciser:
- Does the exercise have an underlying
value that is apt to benefit the target population?
- Does the exercise present an element
that could make it inappropriate for some individuals?
- Do the benefits of doing the exercise
outweigh the drawbacks?
- Do the exercisers do the exercise
in a manner that makes it beneficial?
Fig.
3. Sit-and-Reach (SR). In the individual depicted
the angle of the sacrum is about 50 degrees with
the floor; this angle should be a
minimum of 80 degrees7. If this individual
with very tight hamstrings were to use this as
a stretching activity, most of the stress would
be absorbed by the soft tissue structures of the
lumbar spine; thus the exercise would be most
inappropriate.
Sit and Reach Modifications. Cailliet12
contends that his protective hamstring stretch
with only one leg extended instead of two places
less stress on the lumbosacral area. Although
we did not find a significant stress reduction
when we studied this issue16, we recommend his
stretch. Also, the one-leg extended
version of the sit and reach permits checking
for symmetry, an important fitness element. It
should be mentioned that if the finger-tips-to-floor
test, or any of the sit-and-reach ests
described, is used, hamstring length is the factor
being easured, not low back flexibility17-21.
Tests have also been developed that partial out
the effect of (a) disproportionate arm/leg length
ratios22 and (b) tightness of the soft
tissue structures behind the knee23.
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Fig.
4. Standing Quadricep/Hip-Flexor Stretch. In doing
this stretch the leg should be pulled straight back
rather than back and to the side as shown. As depicted,
excessive stress is placed on the medial soft-tissue
structures of the bent leg; a simple way to
avoid this stress is to hold the ankle with the
opposite hand. (Note that the exerciser is leaning
forward at the hip joint; although this is a common
mistake and the posture is safe, increases in hip-joint
flexion decrease the chance that the hip flexors
are being stretched.) |
Fig.
5. Hurdler Stretch. This exercise is inappropriate
for stretching either the (a) quadriceps (leaning
backward) or (b) hamstrings (leaning forward). If
this individual were to place his/her right
foot adjacent to his/her left knee, it would be
a beneficial hamstring stretch12.
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Published quarterly by the
President's Council on
Physical Fitness and Sports
Washington, D.C.
Guest Authors:
Wendell Liemohn, Ph.D.
Professor, Exercise
Science
University of Tennessee, Knoxville
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Traci Haydu, M.S.
Ph.D.Candidate, Exercise Science
University of Tennessee, Knoxville
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Dawn Phillips, M.S.
Fitness Instructor, Fort
Sanders
Health and Fitness Center, Knoxville
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Co-Edited By:
Drs. Chuck Corbin and Bob Pangrazi
Arizona State University
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Movement Quality. Typically individuals
who are physically fit and have good body awareness,
can do an exercise precisely as it should be done; thus,
their quality of movement is usually good. However,
individuals lacking in these variables may attempt the
same exercise and produce such incorrect movements that
for them the exercise is inappropriate. Movement Tempo.
If some exercise activities are done too quickly and
without good body control, the momentum of the
body part being moved may be so great that the movement
exceeds the physiologic limits of a joint. This would
be an example of a ballistic movement; a movement initiated
by forceful muscle contraction followed by an inertial
or coasting movement of the body part.
References
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Physical Activity
and
Fitness Quote
"When choosing
an exercise, be sure that it is appropriate for you—that
means doing it will help you achieve a fitness goal
and that you can do the exercise in a safe manner.
The microtrauma that can occur from repeatedly doing
exercises that are unsafe for you can have long term
health and injury
consequences." Wendell Liemohn, Ph.D. Professor, Exercise
Science University of Tennessee, Knoxville
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