|
|
Current Issues in Flexibility
Fitness
Recent research has clearly shown
that physical activity is one of the most important
factors related to maintaining good health (Corbin &
Pangrazi, 1993; USDHHS, 1996). Programmed physical
activity (exercise) and sport are forms of human movement
often used to achieve these positivie healt benefits.
Human movement is not possible without a certain amount
of the fitness component commonly called flexibility.
Most exercise and sports programs incorporate activities
for flexibility development because flexibility is thought
to be important for safe and effective movement.
Stretching exercises provide a training stimulus for
flexibility development. In the following sections
we will discuss several topics related to flexibility
fitness (1) Definitions of flexibility, (2) Normal static
flexibility, (3) The health-related benefits of flexibility,
(4) The performance-related benefits of flexibility,
and (5) Current recommendations for safe and effective
development of flexibility.
Definition of Flexibility
One problem in the literature is the
inconsistent use of terminology in flexibility, and
the related areas of stretching and joint range of motion.
Definitions of key terms are presented in Table 1. Sports
medicine professions sometimes use slightly different
terminology than in physical education, sport, and exercise
science professions. Common classifications of stretching
exercises also tend to use
|
Published quarterly by
the
President´s Council on
Physical Fitness and Sports
Washington, D.C.
Guest Authors:
Duane V. Knudson, Ph.D.
Department of Physical Education and Exercise
Science
California State University, Chico
Peter Magnusson, Ph.D.
Team Denmark Test Center,
Sports Medicine Research Unit,
Bispebjerg Hospital,
Copenhagen, Denmark
Malachy McHugh, Ph.D.
Nicholas Institute of Sports Medicine
and Athletic Trauma,
Lenox Hill Hospital, New York, NY
Co-Edited By:
Drs. Chuck Corbin and Bob Pangrazi
Arizona State University |
|
|
terminology that conflicts with
current biomechanical classifications of flexibility.
Even within a discipline there is potential for confusion
in terminology. For example, physical therapists often
distinguish between active range of motion (unassisted)
and passive range of motion (therapist assisted) in assessing
static flexibility. Therefore, when reporting a range
of motion for a flexibility test it is important to know
whether the test was active or passive. Flexibility tests
can also be confused with the joint laxity tests by which
orthopaedists and athletic trainers evaluate the small
accessory rotations and translations in joints (Corbin,
1984). Additionally, early flexibility research suggested
that there were both static and dynamic expressions of
flexibility (Fleishman, 1963), giving rise to the common
use of "static" and "dynamic" modifiers for two kinds
of flexibility (Anderson & Burke, 1991). However,
use of these "dynamic" flexibility tests stopped because
they involved ballistic movements that may be more related
to speed, coordination, and strength rather than flexibility.
Flexibility has been defined as "the
intrinsic property of body tissues, which determines
the range of motion achievable without injury at a joint
or group of joints." (Holt et al., 1996: 172).
This property of the musculoskeletal system can be examined
by two kinds of biomechanical measurements: static flexibility
and dynamic flexibility (Gleim & McHugh, 1997).
Static flexibility is a linear or angular measurement
of the actual limits of motion in a joint or complex
of joints. In other words, static flexibility is a clinical
measurement that defines the amount of motion at a joint
or group of joints. There are, however, several complications
in the interpretation of static flexibility measures.
First, the limits of the static flexibility tests are
subjectively defined by either the subject or the tester.
Physical therapists usually classify the limits of joint
motion according to various "end-feels" e.g. soft, firm
or hard (Norkin & White, 1995). The "end-feel" varies
depending on the type of tissue providing resistance
to movement. Generally, static flexibility tests measure
motions limited by the extensibility of the musculotendinous
units (MTU) surrounding the particular joint or joints.
For simplicity, the term "muscle" will be used in this
paper to mean the whole MTU. The straight leg raise
test is a static flexibility test thought to be limited
by the extensibility of the hamstring muscle group (McHugh
et al., 1998). However, ligamentous constraints and
bony congruencies can also limit motions depending on
the joint and the motion being tested. For most static
flexibility tests, the limits of motion are determined
by the subject's tolerance of the stretched position
(Halbertsma & Goeken, 1994; Magnusson et al., 1996c,
1997) and are therefore not truly objective measures.
Static flexibility measurements are somewhat limited
by the subjective nature of the assessment of the ends
of the range of motion. In contrast, measures of dynamic
flexibility do not depend on the subjective perceptions
of the end of the range of motion, and therefore, are
believed to be more objective measures (Gleim &
McHugh, 1997). Dynamic flexibility refers to the increase
in resistance with muscle elongation for a given range
of motion and can be quantified in terms of stiffness
[see Table 1] (Gleim & McHugh,
1997). So dynamic flexibility accounts for the resistance
to stretch throughout the range of motion. Tissue stiffness
is usually quantified according to the slope of the
load-deformation curve. The slope of the torque-range
of motion curve provides an equivalent for the in
vivo measurement of passive stiffness of muscle
groups (Gajdosik et al 1990, Magnusson et al 1997, McHugh
et al 1998). Dynamic flexibility measurements of relaxed
muscle are important because they essentially tell how
muscle passive tension increases at the limits of the
range of motion, and show that muscle has viscoelastic
behavior (force in stretching depends on elongation
and the rate of the stretch). Research has only begun
to document, in vivo, the short and long-term viscoelastic
responses of human muscles to stretching (Gajdosik,
Guiliani, & Bohannon, 1990; Goeken & Holt, 1993,
Magnusson, 1998; Magnusson et al., 1996a,1996b,1998;
McHugh et al. 1992). Consequently, little is currently
known about the clinical importance of dynamic flexibility.
Studies show that dynamic flexibility accounts for about
44 to 66% of the variance of static flexibility (Magnusson
et al., 1997; McHugh et al., 1998). However, there is
insufficient research to determine whether static and
dynamic flexibility are two distinct properties or two
aspects of the same flexibility component. More research
on the relationship between static and dynamic flexibility
is needed, especially longitudinal studies of changes
in flexibility.
Although dynamic flexibility measurements
may provide a more objective measurement of flexibility,
there are problems with these flexibility variables.
The passive measurements mentioned can only estimate
the true mechanical stiffness of the individual muscles
(Latash & Zatsiorsky 1993). Some studies measure
the stiffness of activated muscle groups (Wilson, Wood,
& Elliott, 1991a). Additionally, differences in
scientific and lay terminology can result in misinterpretations.
For example, the use of the term "elasticity" can be
confusing. In biomechanics a greater elasticity implies
a higher stiffness, which means the tissue offers greater
resistance (stress) to elongation (strain). However,
for most individuals, greater elasticity implies less
resistance to elongation which is really compliance.
Table 1
Definitions of Key
Flexibility Terms
- Anklyosis – Pathologically
low joint range of motion.
- Ballistic Stretching – Fast,
momentum-assisted movements used to
stretch muscles.
- Compliance – A material that
is easily elongated with low levels
of force is compliant. Compliance is
the opposite of stiffness or elasticity.
- Dynamic Flexibility – The rate
of increase in tension in relaxed muscle
as it is stretched. The mechanical variable
that represents dynamic flexibility
is stiffness.
- Elasticity – The property of
a material to resist deformation from
a force and to quickly return to its
normal shape. The mechanical measure
of a materials elasticity is stiffness.
- Flexibility – "the intrinsic
property of body tissues which determines
the range of motion achievable without
injury at a joint or group of joints
(Holt et al., 1996; 172)."
- Hypermobility – Excessive joint
range of motion.
- PNF (Proprioceptive Neuromuscular
Facilitation) – Specialized stretching
routines that take advantage of reflexes
and neuro- muscular principles to relax
muscles being stretched.
- Static Flexibility – The measurement
of the range of motion in a joint or
group of joints.
- Static Stretching – Slowing
elongating a muscle group and holding
it in the stretched position.
- Stiffness – The measure of
a materials elasticity, defined as the
ratio of force to elongation.
- Viscoelastic – Complex mechanical
behavior of a material because the resistive
force in the material is depending on
elongation (elastic) and the rate (viscous)
at which the force is applied.
|
|
Normal Static Flexibility
Normal static flexibility occurs somewhere
between two pathologic extremes, anklyosis and hypermobility
[Table 1] (Russek, 1999). Studies
using animal models have shown that normal skeletal
muscle extensibility is a function of the number of
sarcomeres in series as well as the amount and organization
of intramuscular connective tissue (Williams & Goldspink,1978),
so muscles can increase or decrease their length to
accommodate the range of motion commonly used. The early
research demonstrated that static flexibility is not
a whole-body characteristic, but like fitness, is specific
to areas of the body (Cureton, 1941; Harris, 1969; Hoshizaki
& Bell, 1984). An individual may be quite flexible
in one joint motion but inflexible in another joint.
Furthermore, the same joint can be flexible in one anatomical
motion but inflexible in another motion. Additionally,
early work identified a trend for women to have greater
static flexibility than men (Harris, 1969), although
much of this effect may be related to anthropometric
differences (Corbin, 1984).
Several different bodies have established
normal ranges for static flexibility tests of the major
joints (AAOS, 1965; ACSM, 1995; AMA, 1988; Gerhardt
& Russe 1975). It is not known, however, if there
is an optimal or desirable level for static flexibility.
It is important to appreciate that some movements involve
a greater range of motion than others and therefore
require greater static flexibility. There have been
many reviews on flexibility and stretching (Alter, 1996;
Anderson & Burke, 1991; Clarke, 1975; Corbin 1984;
Corbin & Noble, 1980; Harris, 1969; Holland, 1968;
Hutton, 1993; Knapick et al., 1992; Knudson 1998, 1999;
Liebesman & Cafarelli, 1994; Magnusson, 1998; Spaega
et al., 1981; Wilkinson, 1992).
More recently, data have clearly demonstrated
that static flexibility changes across the lifespan.
Prior to primary school, children are quite flexible
because of limited calcification and development of
the joints. Static flexibility varies with physical
activity, but overall tends to remain the same or gradually
decrease to about age 12 and then increases to peak
between 15 and 18 years of age (Clarke, 1975). Research
has shown significant decreases in static flexibility
and increases in muscle stiffness with aging in adulthood
(Brown & Miller, 1998; Gajdosik, 1997; Gajdosik
et al., 1999; Vandervoot et al., 1992). However, the
decrease in static flexibility with aging is small relative
to the typical variation in flexibility between individuals
and the potential for improvement in flexibility with
stretching (Roach & Miles, 1991). Decreases in flexibility
are primarily due to changes in activity and arthritic
conditions (Adrian, 1981) rather than a specific effect
of aging. Therefore, stretching programs can be
effective for individuals of all ages.
Health Benefits of Flexibility
The primary theoretical reason for
the inclusion of static flexibility tests in health-related
fitness test batteries is that flexibility has been
associated with injury risk. While it is logical that
limited static flexibility will more likely result in
an overstretched muscle during vigorous activity, there
is little evidence that greater than normal levels of
static flexibility will decrease injury risk (Corbin
& Noble, 1980). If anything, people at both extremes
of static flexibility may be at a higher risk for musculoskeletal
injuries (Jones & Knapik, 1999; Knapik, Jones, Bauman,
& Harris, 1992). There is even less known about
the association between dynamic flexibility and injury
risk. Wilson, Wood and Elliott (1991a) hypothesized
that a less stiff musculature would be less susceptible
to muscle strain injury. There is very little research
in this area, but there is preliminary experimental
evidence that a stiffer muscle is more susceptible to
eccentric-induced muscle damage (McHugh et al., 1999).
With regard to specific injuries,
it seems logical that less flexible back muscles would
be related to the incidence of low-back pain, however,
the direct evidence for this link is not strong. Plowman
(1992) reviewed the literature and found that there
was limited support (mixed results) for an association
between lumbar/hamstring flexibility and occurrence
of low-back pain. In support of Plowman's conclusions,
a large prospective study has recently been unable to
demonstrate a relationship between static flexibility
and subsequent low-back pain in adults (Jackson et al.,
1998). Therefore, it appears that field tests of static
flexibility may not be useful in predicting future low-back
injury.
Although there is little scientific
evidence of an association between flexibility and muscular
injuries (Gleim & McHugh, 1997; Jones & Knapik,
1999; Knapik, Jones, Bauman, & Harris, 1992), there
is conflicting evidence on the effect of stretching
on injury. Recent prospective studies have shown no
effect of stretching on injury rate (Pope et al., 1998,
2000), while other studies have reported an effect for
stretching (Cross & Worrel, 1999; Hartig & Henderson,
1999). The studies with larger samples and better
controls (Pope et al., 1998, 2000), support the conclusion
that flexibility and stretching may be unrelated to
injury risk. Currently there is insufficient data to
support the common prescription of stretching programs
to modify flexibility based on the hypothesis of reducing
the risk of muscle injury.
Stretching is known to relax (inhibit
muscle activation) the muscle (Avela et al., 1999; Vujnovich
& Dawson, 1994) and has been advocated for the treatment
of various muscle problems (Clarke, 1975; Corbin &
Noble, 1980). Static stretching is clearly indicated
and commonly used for the acute relief of muscle cramps.
Similarly, stretching is commonly practiced to relieve
symptoms of delayed-onset muscle soreness (DOMS). However,
recent studies have shown that stretching before (Johansson
et al., 1999; Wessel & Wan, 1994) or after activity
(Buroker & Schwane 1989; Wessel & Wan, 1994)
has little or no effect on DOMS. Although light
stretching is a valuable activity to maintain static
flexibility, there is little evidence that it will decrease
symptoms of muscular overuse like DOMS.
While proper stretching remains a
safe physical activity, like all forms of training there
are potential risks to health and performance. Ballistic
or bounding stretches create large muscle forces that
may cause injury (Sapega et al., 1981) and certain stretching
exercises are contraindicated because of dangerous ligament
and tissue loading (Liemohn, Haydu, & Phillips,
1999; Lindsey & Corbin, 1989; Lubell, 1989). Less
is known about the joint stability-mobility paradox,
whereby increases in range of motion may come at the
cost of joint instability (Corbin & Noble, 1980;
Liebesman & Cafarelli, 1994).
In summary, the consensus of the literature
is that only normal levels of static flexibility are
needed for a low risk of injury in most vigorous physical
activities. Very high or low levels of static flexibility
may represent an increased risk of injury. Tests of
static flexibility in health-related fitness test batteries
are likely effective instruments for identifying people
at the extremes of the static flexibility distribution.
There is, however, little scientific evidence on which
to base precise flexibility prescriptions for these
individuals. In individuals with normal static flexibility
there is little evidence that stretching or increasing
static flexibility will lower injury rates. There is
also a lack of studies on how differences in dynamic
flexibility affect the risk of injury.
Performance Benefits of Flexibility
Since many sports require vigorous
joint rotations and often use extreme positions in the
range of motion, there is a common belief that static
flexibility is related to performance. While there is
considerable anthropomteric research showing static
flexibility differences between athletes from different
sports, the retrospective nature of most studies limits
our understanding of these differences (Clarke, 1975).
The scientific evidence for the performance benefits
of flexibility is not as strong as commonly believed
and the claims of benefits from stretching are often
exaggerated (Corbin & Noble, 1980; Gleim & McHugh,
1997). Depending on the nature of the movement, less
static flexibility may actually benefit performance.
For example, less static flexibility has been associated
with better running economy (Gleim et al.1990; Craib
& Mitchell, 1996).
Since dynamic flexibility tests measure
the increase in resistance during muscle elongation,
it has been hypothesized to be more related to performance
than static flexibility (deVries, 1986). Several studies
have found that less stiff muscles are more effective
in utilizing elastic energy in stretch-shortening cycle
movements (Kubo et al., 1999, 2000; Walshe, Wilson,
& Murphy, 1996; Wilson, Elliott, & Wood, 1992;
Wilson, Wood, & Elliott, 1991b). Stiffer muscles
may have advantages in isometric and concentric movements
(Wilson, Murphy, & Pryor, 1994). Unfortunately,
these studies have used stiffness measurements of activated
muscle groups, so it is unknown if measures of passive
muscular stiffness have similar relationships to performance.
With advances in muscle imaging, much is being learned
about the elastic properties of human muscle in vivo
(Fukunaga et al., 1997; Kawakami et al., 1998; Ito et
al., 1998; Kubo et al., 1999). These kinds of studies
may advance our understanding of the effects of dynamic
flexibility on performance. In the future we may know
if stretching truly decreases muscle stiffness and consequently
improves the muscles capacity to perform in stretch-shortening
cycle actions. Whatever the eventual relationships,
it is likely that the effects of static or dynamic flexibility
on performance are very activity specific (Gleim &
McHugh, 1997).
Despite the universal practice of
pre-activity stretching exercises as part of a warm-up
routine, there is little evidence of a positive short-term
effect of stretching on performance. In fact, recent
research has shown that static stretching creates a
short-term decrease (up to 20%) in several kinds of
muscular performance (Avela, Kyrolainen, & Komi,
1999; Kokkonen, Nelson, & Cornwell, 1998; Rosenbaum
& Hennig, 1995). There is preliminary evidence of
a decrease in strength that can last up to 60 minutes
(Fowles & Sale, 1997). The possibility that stretching
prior to physical activities may create a short-term
decrease in performance warrants further investigation.
Recommendations for Flexibility
Development
Testing
Any recommendations for stretching
to improve flexibility should be based on a valid assessment
of flexibility using sound testing procedures. Currently,
testing of dynamic flexibility is still limited to the
research setting, because of problems related to expensive
equipment, insufficient standardization, and data to
establish norms. Static flexibility tests are based
on linear and angular measurements of the motion of
a joint or group of joints, and have been classified
as compound (multiple joints) or single joint tests
(Corbin & Noble, 1980). Single joint static flexibility
tests are common clinical measures in the medical professions
(AAOS, 1965; AMA, 1988; Gajdosik & Bohannon, 1987;
Norkin & White, 1995; Gerhardt & Russe 1975)
and usually involve angular measurements (goniometers
or inclinometers), rather than linear measurements common
in field tests of flexibility . Single joint tests are
considered better measurements of static flexibility
than compound tests because they better isolate specific
muscles and are less affected by anthropometric variation
(Cornbleet & Woolsey, 1996; Leighton, 1942). For
example, the straight leg raise (Goeken & Holf,
1993) and active knee extension (Gajdosik & Lusin,
1983) tests are the criterion hamstring static flexibility
tests used to validate field tests of hamstring flexibility
like the toe touch or sit-and-reach tests. Professionals
must remember, however, that the scores on these tests
are subjective and highly dependent on the subject's
tolerance of the high tensions (discomfort) during testing.
Most fitness professionals are familiar
with several compound static flexibility tests. The
most common health- related tests are the sit-and-reach,
shoulder lift, and trunk lift. There has been considerable
research on the sit-and-reach test resulting in quite
a number of test variations (Golding, 1997; Holt, Pelham,
& Burke, 1999). Fortunately, research on the
sit-and-reach test has shown it to be an moderately
valid measure of hamstring flexibility that is only
slightly affected by anthropometric variations (Hui
et al., 1999; Martin et al.,1998). Hamstring flexibility
accounts for most of the variance in the sit-and-reach
test. However, a recent study showed that 6% of children
falsely passed, and 12% falsely failed the sit-and-reach
test relative to the straight leg raise test (Cornbleet
& Woolsey, 1996). People failing the sit-and-reach
test should be retested with the straight leg test to
ensure they have limited hamstring static flexibility.
Current health-related norms for sit-and-reach tests
serve to identify individuals at the extremes who may
be at higher risk of muscle injuries. However, the sit-and-reach
test is not correlated with low-back flexibility (Martin
et al.,1998). A field test like the modified Schoeber
test that uses tape measurements of spine length (Norkin
& White, 1995) may be more useful in evaluating
lumbar flexibility.
Stretching
The following recommendations for
stretching procedures are based on recent reviews of
the viscoelasctic response of muscle to stretching (Knudson,
1998, 1999). These recommendations (Table
2) are designed for group exercise prescription
for normal subjects. Remember that flexibility testing
and subject-specific information may require small variations
in flexibility training. For best results, static stretching
or proprioceptive neuromuscular facilitation (PNF) stretching
should be performed at least three times per week, preferably
daily and preferably after moderate or vigorous physical
activity. Four to five stretches for each major muscle
group should be performed, usually during the cool-down
phase of a workout, with each stretch held for 15 to
30 seconds. The cool down is recommended because warmed-
up tissues are less likely to be injured and the placement
of stretching within the workout does not affect gains
in static flexibility (Cornelius, Hagemann, & Jackson,
1988). The intensity (force) of each stretch should
be minimized, slowly elongating and holding the stretched
position just before the point of discomfort.
Static stretching will create a short-term increase
in range of motion and a decrease in passive tension
in the muscle at a particular joint angle due to stress
relaxation. The effect of stretching on muscle
stiffness is not clear (Knudson, 1999).
It is important for professionals
to remember that passive stretching does create large
tensile loads in the muscle, so it is possible to injure
and weaken muscle with vigorous stretching. Stretching
is like other training stimuli that result in temporary
weakening before the body accommodates to that activity.
Assisted stretching procedures like PNF should be performed
with care by trained subjects or sports medicine personnel.
The practice of having athletes passively stretch partners
is not recommended unless the athletes have been carefully
trained in correct procedures and understand the risk
of incorrect stretching.
The efficacy of stretching during
the warm-up phase for most physical activities is controversial.
A recent review of the literature (Knudson, 1999) noted
that stretching as part of a warm-up may have a detrimental
effect on performance. It was suggested that only activities
requiring high levels of static flexibility for aesthetic
or scoring purposes (e.g. dance, gymnastics, diving)
should include some static stretching following a general
warm-up. More research is clearly needed on the role
of stretching prior to performance.
Table
2
Stretching
Recommendations for
Group Excercise Prescription
Fitness Variable
Recommendation
Frequency
|
At lease 3 times per week,
preferable daily and aftere
moderate or vigorous physical
activity
|
Intensity
|
Slowly elongate muscle
and hold with low levels
of force
|
Time
|
Up to 4 to 5 stretches
held from 15 to 30 seconds.
Stretch normally during
the cool-down phase.
Be sure to stretch only
muscles that have been thoroughly
warmed-up from physical
activity. Warning:
Stretching in the warm-up
prior to physical activity
may weaken muscles and decrease
performance.
|
Type
|
Static or PNF stretches
for all major muscled groups
|
|
* Adapted
from Knudson (1998, 1999) |
|
Summary
Flexibility is a property
of the musculoskeletal system that determines the range
of motion achievable without injury to a joint or group
of joints (Holt, Holt, & Pelham, 1996). Static flexibility
tests measure the limits of the achievable motion but
these limits are subjective. Dynamic flexibility tests
are more objective and measure the stiffness of a passively
stretched muscle group; however, there are no recommended
field tests available at this time. Normal ranges of
static flexibility are well documented for most joints.
Major deviations (top or bottom 20% of the distribution)
from the norm may be associated with a higher incidence
of muscular injury. While there is a theoretical association
between flexibility and several musculoskeletal problems,
there are few prospective studies showing significant
associations. Currently, there is little scientific
evidence on which to base individual prescriptions for
static flexibility development beyond the maintenance
of normal levels. More longitudinal studies of dynamic
flexibility may provide a greater insight into the role
of flexibility in health and performance.
The President's Council on
Physical Fitness and Sports Research Digest
is now available on-line at http://www.indiana.edu/~preschal
Please note that the appropriate
language for the citation of this resource is:
The President's
Council on Physical Fitness and Sports Research Digest.
The
President's Council on Physical Fitness and Sports
The President's Council on
Physical Fitness and Sports (PCPFS) was established
in 1956 through an Executive Order by President
Dwight D. Eisenhower as part of a national campaign
to help shape up America's younger generation.
Today, the PCPFS serves as an advisory council
to the President and Secretary of the Department
of Health & Human Services on matters involving
physical activity, fitness and sports to enhance
and improve the health of Americans of all ages.
The PCPFS enlists the active
support and assistance of individual citizens,
civic groups, private enterprise, and voluntary
organizations to promote and improve the physical
activity and fitness of all Americans and to inform
the public of the important link which exists
between regular activity and good health.
Twenty (20) individuals from
the sports, fitness and health fields are appointed
by the President to serve as members of the Council.
They are:
- Lee Haney, Chairman
- Elizabeth Arendt, M.D., St. Paul, MN
- Billy Blanks, Sherman Oaks, CA
- Jeff Blatnick, Halfmoon, NY
- Ralph Boston, Knoxville, TN
- Don Casey, East Rutherford, NJ
- Timothy Finchem, Ponte Vedra Beach,
FL
- Rockne Freitas, Ed.D., Honolulu, HI
- Zina Garrison, Houston, TX
- Lauren Gregg, Charlottesville, VA
- Jimmie Heuga, Avon, CO
|
- Jim Kelly, Buffalo, NY
- Judith Pinero Kieffer, Los Angeles,
CA
- Deborah Slaner Larkin, Pelham, NY
- Nikki McCray, Washington, D.C.
- Albert Mead III, Atlanta, GA
- Jack Mills, Columbia, SC
- Ellen Hart Peña, Denver, CO
- Ken Preminger, Atherton, CA
- Amber Travsky, Laramie, WY
- Executive Director—Sandra Perlmutter
|
|
200 Independence Avenue, S.W., Washington,
DC 20201 • (202) 690-9000 • FAX (202) 690-5211
REFERENCES
Adrian, M.J. (1981). Flexibility
in the aging adult. In E.L. Smith & R.C. Serfass
(Eds.), Exercise and aging: the scientific basis. Hillside,
NJ: Enslow.
Alter, M.J. (1996). Science of
stretching (2nd ed.). Champaign, IL: Human Kinetics.
American College of Sports Medicine
(1995). ACSM's guidelines to exercise testing and prescription
5th ed. Baltimore: Williams & Wilkins.
American Academy of Orthopaedic
Surgeons (1965). Joint motion: method of measuring and
recording. Chicago, IL: American Academy of Orthopaedic
Surgeons.
American Medical Association
(1988). Guides to the evaluation of permanent impairment.
Chicago, IL: American Medical Association.
Anderson, B., & Burke, E.R.
(1991). Scientific, medical, and practical aspects of
stretching. Clinics in Sports Medicine, 10, 63-86.
Avela, J., Kyrolainen, H., &
Komi, P.V. (1999). Altered reflex sensitivity after
repeated and prolonged passive muscle stretching. Journal
of Applied Physiology, 86, 1283-1291.
Brown, D.A, & Miller, W.C.
(1998). Normative data for strength and flexibility
of women throughout life. European Journal of Applied
Physiology, 78, 77-82.
Buroker, K.C., & Schwane,
J.A. (1989). Does postexercise static stretching alleviate
delayed muscle soreness? Physician and Sportsmedicine,
17(6), 65-83.
Clarke, H.H. (1975). Joint and
body range of movement. Physical Fitness Research Digest,
5(4), 1-23.
Corbin, C.B. (1984). Flexibility.
Clinics in Sports Medicine, 3, 101-117.
Corbin, C.B., & Noble, L.
(1980). Flexibility: a major component of physical fitness.
JOPER, 51(6), 23-24, 57-60.
Corbin, C., & Pangrazi, B.
(1993). The health benefits of physical activity. Physical
Activity and Fitness Research Digest. 1(1), 1-7.
Cornbleet, S.L., & Woolsey,
N.B. (1996). Assessment of hamstring muscle length in
school-aged children using the sit-and- reach test and
the inclinometer measure of hip joint angle. Physical
Therapy, 76, 850-855.
Cornelius, W.L., Hagemann, R.W.,
& Jackson, A.W. (1988). A study on placement of
stretching within a workout. Journal of Sports Medicine
and Physical Fitness, 28, 234-236.
Craib, M.W., Mitchell, V.A.,
(1996). The association between flexibility and running
economy in sub-elite male distance runners. Medicine
and Science in Sports and Exercise, 28, 737-743.
Cross, K.M., & Worrell, T.W.
(1999). Effects of a static stretching program on the
incidence of lower extremity musculotendinous strains.
Journal of Athletic Training, 34, 11-14.
Cureton, T.K. (1941). Flexibility
as an aspect of physical fitness. Research Quarterly,
12, 381-390.
deVries, H.A. (1986). Physiology
of exercise for physical education and athletics 4th
ed. Dubuque, IA: W.C. Brown.
Fleishman, E.A. (1963). Factor
analysis of physical fitness tests. Educational and
Psychological Measurement, 23, 647-661.
Fowles, J.R., & Sale, D.G.
(1997). Time course of strength deficit after maximal
passive stretch in humans. (Abstract) Medicine and Science
in Sports and Exercise, 29, S26.
Fukunaga, T., Ichinose, Y., Ito,
M., Kawakami, Y., & Fukashiro, S. (1997). Determination
of fascicle
length and pennation in a contracting human muscle in
vivo. Journal of Applied Physiology, 82, 354-358.
Gajdosik, R.L. (1997). Influence
of age on calf muscle length and passive stiffness variables
at different stretch velocities. Isokinetics and Exercise
Science, 6, 163-174.
Gajdosik, R.L, Guiliani, C.A.,
& Bohannon, R.W. (1990). Passive compliance and
length of the hamstring muscles of healthy men and women.
Clinical Biomechanics, 5, 23-29.
Gajdosik, R., & Lusin, G.
(1983). Hamstring muscle tightness: reliability of an
active-knee extension test. Physical Therapy, 63, 1085-1088.
Gajdosik, R.L., Vander Linden,
D.W., & Williams, A.K. (1999). Influence of age
on length and passive elastic stiffness characteristics
of the calf muscle-tendon unit of women. Physical Therapy,
79, 827-838.
Gerhardt, J.J., & Russe,
O.A. (1975). International SFTR method of measuring
and recording joint motion. Bern: Hans Huber.
Gleim, G.W., & McHugh, M.P.
(1997). Flexibility and its effects on sports injury
and performance. Sports
Medicine, 24, 289-299.
Gleim, G.W., Stachenfeld, N.S.,
& Nicholas, J.A. (1990). The influence of flexibility
on the economy of walking and jogging. Journal of Orthopaedic
Research, 8, 814-823.
Goeken, L.N., & Holf, A.L.
(1993). Instrumental straight-leg raising: results in
healthy subjects. Archives of Physical Medicine and
Rehabilitation, 74, 194-203.
Golding, L.A. (1997). Flexibility,
stretching, and flexibility testing. ACSM's Health and
Fitness Journal, 1(2), 17-20, 37-38.
Halbertsma, J.P.K, & Goeken,
L.N.H. (1994). Stretching exercises: effect on passive
extensibility and stiffness in short hamstrings of healthy
subjects. Archives of Physical Medicine and Rehabilitation,
75, 976-981.
Harris, M.L. (1969). Flexibility.
Physical Therapy, 49, 591-601.
Hartig, D.E., & Henderson,
J. M. (1999). Increasing hamstring flexibility decreases
lower extremity overuse injuries in military basic trainees.
American Journal of Sports Medicine, 27, 173-176.
Holland, G.J. (1968). The physiology
of flexibility: a review of the literature. Kinesiology
Review, 1, 49-62.
Holt, L.E., Pelham, T.W., &
Burke, D.G. (1999). Modifications to the standard sit-and-reach
flexibility protocol. Journal of Athletic Training,
34, 43-47.
Holt, J., Holt, L.E., & Pelham,
T.W. (1996). Flexibility redefined. In T. Bauer (Ed.),
Biomechanics in Sports
XIII, pp. 170-174. Thunder Bay, Ontario: Lakehead University.
Hoshizaki, T.B., & Bell,
R.D. (1984). Factor analysis of seventeen joint flexibility
measures. Journal of Sports
Sciences, 2, 97-103.
Hui, S.C., Yuen, P.Y., Morrow,
J.R., & Jackson, A.W. (1999). Comparison of the
criterion-related validity of sit-and-reach tests with
and without limb length adjustment in Asian adults.
Research Quarterly for Exercise and Sport, 70, 401-406.
Hutton, R.S. (1993). Neuromuscular
basis of stretching exercise. In P. Komi (Ed.). Strength
and Power in Sports (pp. 29-38). Oxford: Blackwell Scientific
Publications.
Ito, M., Kawakami, Y., Ichinose,
Y., Fukashiro, S., & Fukunaga, T. (1998). Nonisometric
behavior of fascicles during isometric contractions
of a human muscle. Journal of Applied Physiology, 85,
1230-1235.
Jackson, A.W., Morrow, J.R.,
Brill, P.A., Kohl, H.W., Gordon, N.R., & Blair,
S.N. (1998). Relation of sit-up and sit-and-reach tests
to lower back pain in adults. Journal of Orthopaedic
and Sports Physical Therapy, 27, 22-26.
Johansson, P.H., Lindstrom, L.,
Sundelin, G., & Lindstrom, B. (1999). The effects
of preexercise stretching on muscular soreness, tenderness
and force loss following heavy eccentric exercise. Scandinavian
Journal of Medicine and Science in Sports, 9, 219-225.
Jones, B.H., & Knapik, J.J.
(1999). Physical training and exercise-related injuries.
Sports Medicine, 27, 111-125.
Kawakami, Y., Ichinose, Y., &
Fukunaga, T. (1998). Architectural and functional features
of human triceps surae muscles during contraction. Journal
of Applied Physiology, 85, 398-404.
Knapik, J.J., Jones, B.H., Bauman,
C.L., & Harris, J. (1992). Strength, flexibility,
and athletic injuries. Sports Medicine, 14, 277-288.
Knudson, D. (1998) Stretching:
science to practice. JOPERD, 69(3), 38-42.
Knudson, D. (1999). Stretching
during warm-up: do we have enough evidence? JOPERD,
70(7), 24-27, 51.
Kokkonen, J., Nelson, A.G., &
Cornwell, A. (1998). Acute muscle stretching inhibits
maximal strength performance. Research Quarterly for
Exercise and Sport, 69, 411-415.
Kubo, K., Kanehisa, H., Kawakami,
Y., & Fukunaga, T. (2000). Elastic properties of
muscle-tendon complex in long-distance runners. European
Journal of Applied Physiology, 81, 181-187.
Kubo, K., Kawakami, Y., &
Fukunaga, T. (1999). Influence of elastic properties
of tendon structures on jump performance in humans.
Journal of Applied Physiology, 87, 2090-2096.
Latash, M.L., & Zatsiorski,
V.M. (1993). Joint stiffness: myth or reality? Human
Movement Science, 12, 653-692.
Leighton, J.R. (1942). A simple
objective and reliable measure of flexibility. Research
Quarterly, 13, 205-216.
Liebesman, J. & Cafarelli,
E. (1994). Physiology of range of motion in human joints:
a critical review. Critical Reviews in Physical and
Rehabilitative Medicine, 6, 131-160.
Liemohn, W., Haydu, T., &
Phillips, D. (1999). Questionable exercises. President's
Council on Physical Fitness and Sports Research Digest,
3(8), 1-8.
Lindsey, R., & Corbin, D.
(1989). Questionable exercises—some safer alternatives.
Journal of Physical Education, Recreation and Dance,
60(8), 26-32.
Lubell, A. (1989). Potentially
dangerous exercises: are they harmful to all? Physician
and Sportsmedicine, 17(1), 187-192.
Magnusson, S.P. (1998). Passive
properties of human skeletal muscle during stretch maneuvers:
a review. Scandinavian Journal of Medicine and Science
in Sports, 8, 65-77.
Magnusson, S.P., Simonsen, E.B.,
Aagaard, P., Buesen, J. Johannson, F. & Kjaer, M.
(1997). Determinants of musculoskeletal flexibility:
viscoelastic properties, cross-sectional area, EMG and
stretch tolerance. Scandinavian Journal of Medicine,
Science and Sports, 7, 195-202.
Magnusson, S.P., Simonsen, E.B.,
Aagaard, P., Dyhre-Poulsen, P., McHugh, M.P., &
Kjaer, M. (1996a). Mechanical and physiological responses
to stretching with and without preisometric contraction
in human skeletal muscle. Archives of Physical Medicine
and Rehabilitation, 77, 373-378.
Magnusson, S.P., Simonsen, E.B.,
Aagaard, P., & Kjaer, M. (1996b). Biomechanical
responses to repeated stretches in human hamstring muscle
in vivo. American Journal of Sports Medicine, 24, 622-628.
Magnusson, S.P., Simonsen, E.B.,
Aagaard, P., Sorensen, H., & Kajer, M. (1996c).
A mechanism for
altered flexibility in human skeletal muscle. Journal
of Physiology, 487, 291-298.
Martin, S.B., Jackson, A.W.,
Morrow, J.R., & Liemohn, W.P. (1998). The rationale
for the sit and reach test revisited. Measurement in
Physical Education and Exercise Science, 2, 85-92.
McHugh, M.P., Connolly, D.A.J.,
Eston, R.G., Kremenic, I.J., Nicolas, S.J., & Gleim,
G.W. (1999). The role of passive muscle stiffness in
symptoms of exercise-induced muscle damage. American
Journal of Sports Medicine, 27, 594-599.
McHugh, M.P., Kremenic, I.J.,
Fox, M.B., & Gleim, G.W. (1998). The role of mechanical
and neural restrains to joint range of motion during
passive stretch. Medicine and Science in Sports and
Exercise, 30, 928-932.
McHugh, M.P., Magnusson, S.P.,
Gleim, G.W., & Nicholas, J.A. (1992). Viscoelastic
stress relaxation in human skeletal muscle. Medicine
and Science in Sports and Exercise, 24, 1375-1382.
Norkin C.C., & White, D.J.
(1995). Measurement of joint motion: a guide to goniometry
2nd ed. Philadelphia: F.A. Davis.
Plowman, S.A. (1992). Physical
activity, physical fitness, and low-back pain. Exercise
and Sport Sciences Reviews, 20, 221-242.
Pope, R.P., Herbert, R.D., &
Kirwan, J.D. (1998). Effects of flexibility and stretching
on injury risk in
army recruits. Australian Journal of Physiotherapy,
44, 165-172.
Pope, R.P., Herbert, R.D., Kirwan,
J.D., & Graham, B.J. (2000). A randomized trial
of preexercise
stretching for prevention of lower-limb injury. Medicine
and Science in Sports and Exercise, 32, 271-277.
Roach, K.E., & Miles, T.P.
(1991). Normal hip and knee active range of motion:
the relationship with age. Physical Therapy, 71, 656-665.
Rosenbaum & Hennig (1995).
The influence of stretching and warm-up exercises on
achilles tendon reflex activity. Journal of Sports Sciences,
13, 481-490.
Russek, L.N. (1999). Hypermobility
syndrome. Physical Therapy, 79, 591-599.
Sapega, A.A., Quedenfeld, T.C.,
Moyer, R.A., & Butler, R.A. (1981). Biophysical
factors in range-of-motion exercise. Physician and Sportsmedicine,
12(9), 57-65.
U.S. Department of Health and
Human Services. Physical Activity and Health: A Report
of the Surgeon General. Atlanta, GA: U.S. Department
of Health and Human Services, Centers for Disease Control
and Prevention, National Center for Chronic Disease
Prevention and Health Promotion, 1996.
Vandervoot, A.A., Chesworth,
B.M., Cunningham, D.A., Patterson, D.H., Rechnitzer,
P.A., & Koval, J.J. (1992). Age and sex effects
on mobility of the human ankle. Journal of Gerontology:
Medical Sciences, 47M, 17-21.
Vujnovich, A.L., & Dawson,
N.J. (1994). The effect of therapeutic muscle stretch
on neural processing. Journal of Orthopaedic and Sports
Physical Therapy, 20, 145-153.
Walshe, A.D., Wilson, G.J., &
Murphy, A.J. (1996). The validity and reliability of
a test of lower body musculotendinous stiffness. European
Journal of Applied Physiology, 73, 332-339.
Wessel, J. & Wan, A. (1994).
Effect of stretching on the intensity of delayed-onset
muscle soreness. Clinical Journal of Sports Medicine,
4, 83-87.
Williams, P.E., & Goldspink,
G. (1978). Changes in sarcomere length and physiological
properties in immobilized muscle. Journal of Anatomy,
127, 459-468.
Wilkinson, A. (1992). Stretching
the truth. A review of the literature on muscle stretching.
Australian Physiotherapy, 38, 283-287.
Wilson, G.J., Elliott, B.C.,
& Wood, G.A. (1992). Stretch shorten cycle performance
enhancement through flexibility training. Medicine and
Science in Sports and Exercise, 24, 116-123.
Wilson, G.J., Murphy, A.J., &
Pryor, J.F. (1994). Musculotendinous stiffness: its
relationship to eccentric, isometric, and concentric
performance. Journal of Applied Physiology, 76, 2714-2719.
Wilson, G.J., Wood, G.A., &
Elliott, B.C. (1991a). The relationship between stiffness
of the musculature and static flexibility: an alternative
explanation for the occurrence of muscular injury. International
Journal of Sports Medicine, 12, 403-407.
Wilson, G.J., Wood, G.A., &
Elliott, B.C. (1991b). Optimal stiffness of series elastic
component in a stretch-shorten cycle activity. Journal
of Applied Physiology, 70, 825-833. Indiana University
PRESIDENT'S CHALLENGE
Poplar's Research Center
400 East 7th Street
Bloomington, IN 47405 41-454-02
Back
to top
|