Stretching
Concepts
Why do people have difficulty motivating themselves to stretch regularly?
Perhaps a primary reason is time constraints (Hedricks 1993). Another reason is people lack knowledge about proper stretching,
how it should be done, and its potential benefits. This chapter addresses several of these issues by examining a variety of
concepts related to stretching.
HOMEOSTASIS
Homeostasis is the maintenance of a steady state. Organisms have means of maintaining steady states
in their internal environments and also in their external environments. Stressful environmental factors (such as over
work) may alter the steady state of an organism. When an organism's ability to maintain homeostatic control is exceeded, injury
or death may result.
The concept of homeostasis can be extended to the cellular and even sub-cellular
level. Thus, within certain limits, the cell is capable of adjusting to varying demands. However, like the organism as a whole,
its adaptive capability may be exceeded, and cellular injury or death may follow.
One's response to
stress depends in part on one's ability to adapt oneself to new conditions. During or after stress, the functioning of the
homeostatic mechanism may change, and the individual may enter a new state. This process is called adaptation. Adaptive responses
for increased flexibility involve both functional and structural changes. Consequently, quantitative as well as qualitative
improvement in performance can be achieved. However, for such changes to occur, one's homeostatic state must be overloaded.
OVERSTRETCHING PRINCIPLE
Doherty (1985) suggests, "If we accept the word overloading as related to building strength in muscles, then overstretching
should be acceptable in building flexibility" (p. 425). This overstretching principle is the physiological principle
on which flexibility development depends. According to this principle, when the body is regularly stimulated by an increasingly
intense stretching program beyond the homeostatic level, it will respond with an increased ability to stretch. Conversely,
a decrease in the intensity of a stretching program lowers the ability to stretch. Therefore, the body adapts to the increasing
demands placed on it. "Overstretching" in this context does "not" mean stretching body parts that exceed
their safety limits and result in injury and impairment in function.
Flexibility is simply a result
of stretching. No other factor is more important in the development of flexibility in a healthy person. Stretching may be
applied either manually (i.e., by oneself or a partner) or by machine. Increased flexibility is achieved by implementing a
movement that exceeds the existing range of possible motion a ones 1975). Consequently, flexibility is best acquired by stretching
up to the edge of discomfort. However, discomfort is a subjective matter and will vary from person to person.
FLEXIBILITY-TRAINING METHODS
All flexibility-training methods that strive to develop optimum functional flexibility depend on two dominant factors, namely
structural conditioning and functional (central nervous and neuromuscular) conditioning. Consequently, flexibility training
may be categorized according to its major structural and functional aims relative to the importance of nervous system training
method. Table 12.1 is a simple chart demonstrating these aims.
RETENTION
OF FLEXIBILITY
A significant issue for concern is the retention of functional adaptation for a given period after
training has ceased. This topic is especially significant for therapists who give a home exercise program following discharge
from therapy (Willy et al. 2001). Unfortunately, the question of what happens to flexibility gains when a stretching
program
ceases has not received the attention that other aspects of stretching programs have received (Depino et al. 2000; Spernoga
et al. 2001; Zebas and Rivera 1985). Even less research has investigated the decreased training effect on stiffness and damping
capacity of various tissues. Stretching produces increases in joint ROM that are still evident 1 day or more after cessation
of treatment in people without clinically significant contractures (Harvey et al. 2002). However, these results should be
interpreted with caution because no studies of "high" quality have been conducted. Compounding matters, "it
is possible that both 'moderate' and 'poor' quality studies exaggerate the real size of the treatment effect".
Research in the area of retained flexibility falls into two categories: multiple-day stretching programs and single, same-day
acute stretches. Moller, Ekstrand et al. (1985) compared the retention of flexibility in several treated muscle groups 0,
30, 60, and 90 minutes after the stretching procedure. The increased flexibility remained for 90 minutes for most of the muscle
groups. Moller, Oberg et al. (1985, p. 52) subsequently found "the effect of stretching done at the start of the session
persists over the training session and up to 24 hours." Another study by Hubley et al. (1984) determined that "Fifteen
minutes of cycling or inactivity did not result in significant differences (p < .05) from the initial gains resulting from
the [static] stretching" (p. 104). Toft et al. (1989) investigated the use of contract-relax stretching performed twice
a day for 3 weeks. The stretches were repeated five times and measurements taken 90 minutes later. "There was no correlation
between: (1) flexibility and short-term effect of stretching, (2) flexibility and the long-term effect of stretching, or (3)
the short-term and long-term effects of stretching" (p. 489). However, a reduction of passive tension occurred after
3 weeks.
Magnusson et al. (1996a) applied a single 80-second stretch maneuver to the hamstrings of
10 male volunteers. The experiment produced an 18 % to 21 % decline in passive torque. However, 1 hour later no measurable
effect was seen. Zito et al. (1997) investigated the lasting effects of one bout of two 15 -second passive stretches on ankle
dorsiflexion ROM in 19 healthy volunteers. The study "found no statistically significant length gains using a single
bout of two IS-second stretches." Furthermore, the data of the study "did not provide evidence of lasting lengthening
at this duration" (p. 214).
DePino et al. (2000) investigated the duration of maintained flexibility
gains in knee-joint ROM after same-day static hamstring stretching. Subjects were warmed up and then performed four 30-second
static stretches separated by 15 -second rests. In contrast, they reported gains in stretching ability as a result of static
stretching are transient, lasting for only 3 minutes after cessation of the stretching protocol and then decreasing with time.
The ROM gains returned to the baseline by 6 minutes after stretching. The significance of their findings was that "athletes
who statically stretch and then wait longer than 3 minutes before entering a game or practice can expect to lose the range
of motion gained" (p. 59). This discovery has implications for athletes who statically stretch and then attend a team
meeting or sit on the sideline for 30 minutes. The investigators recommend that future research should:
• determine whether intermittent stretching or activity alone is sufficient to maintain temporary increases in ROM obtained
from acute stretching bouts;
• determine the most efficient type of acute stretching to effect
same-day ROM increases;
• determine the optimal duration of stretch to pro duce long-term
or permanent changes; and
• perform comparisons between men and women, across age groups, and
between subjects with range restriction greater than 20% and less than 20% to determine whether these findings generalize
beyond young men with a 20% or greater restriction.
Spernoga et al. (2001) investigated the duration of hamstring
flexibility gains after a one-time modified hold-relax stretching protocol. Thirty male military cadets volunteered for the
study. All subjects performed six warm-up active knee extensions. The control group received in addition five modified hold-relax
stretches. The findings suggested, "that a sequence of five modified hold-relax stretches produced significantly increased
hamstring flexibility that lasted 6 minutes after the stretching protocol ended" (p. 44).
In
a review of the literature, Zebas and Rivera (1985) and Depino et al. (2000) determined that a number of studies have primarily
been focused on the hip joint, and in all cases, a significant amount of flexibility was retained in the hip joint. Specifically,
hip flexibility was retained after 3 weeks (Long 1971), 4 weeks (Tweitmeyer 1974), 8 weeks (McCue 1963), and several months
(Riddle 1956). Other significant flexibility retention was found in the neck joint (McCue 1963; Turner 1977) and back (McCue
1963). A retention of flexibility 4 weeks after cessation was also found by Zebas and Rivera (1985). However, they point out,
"even though flexibility was retained from the pre-testing period through the retention period, there were significant
losses of flexibility from the post testing period to 2 weeks after the cessation of exercise" (pp. 188-189). They also
addressed one major limitation of such longitudinal measures: The activities outside of the class could not be monitored or
controlled. However, Wallin et al. (1985) suggested that stretching once a week is frequent enough to maintain ROM gained
through a stretching program.
Willy et al. (2001) conducted a study to determine the effects of cessation
and resumption of a hamstring muscle stretching protocol on knee ROM. Eighteen subjects participated in a 16-week study. The
first 6 weeks consisted of the initial stretching period followed by 4 weeks of non-stretching and an additional 6 weeks of
stretching. The initia16-week hamstring static stretching regimen resulted in a significant gain in knee ROM. The ROM returned
to the baseline after the 4 weeks cessation period. Therefore, the gained ROM was not retained. The resumption of stretching
resulted in a significant gain in ROM. Thus, "the benefits of the stretching exercise will be lost relatively quickly
if stretching is not continued" (p. 143).
Why do individuals, both men and women, with very tight
hamstring muscles have a greater ROM gain after a stretching treatment than do individuals with just tight hamstring muscles?
Starring et al. (1988) speculate that differences lie in the connective tissue composition. A very "tight" (limited
ROM) muscle may have more connective tissue, and one of the main functions of connective tissue is to prevent muscle from
being overstretched. However, a shortened muscle requires even more protection to prevent even normal ROM. Furthermore, the
increased connective tissue results in a decrease in the elasticity and extensibility of the muscle tissue. With prolonged
stretching, plastic deformation of the soft tissue occurs, resulting in an increased ROM that is maintained after 1 week of
treatment. However, "in the individual with 'less tight' muscles, more elastic elements are present, and the muscle tissue
will return more easily to the original length" (p. 318).
REQUISITE KNOWLEDGE FOR STRETCHING
The methods of stretching
employed in athletics, dance, physical therapy, and yoga can vary considerably. However, certain knowledge is required in
all of these disciplines. A basic knowledge of the normal neuromuscular mechanism, including motor development, anatomy, neuroscience,
and kinesiology is very helpful, if not essential. Furthermore, whatever the method of stretching used, one should be thoroughly
familiar with the structure and function of the joint in question. One should know not only the degree of limitation of motion
but also which tissues are responsible for the limitations.
POTENTIAL FACTORS INFLUENCING FLEXIBILITY (ROM)
ROM is restricted
or impaired by a variety of factors:
• Lack of elasticity of connective tissues in muscles or
joints
• Skin disorder, including scleroderma or scarring from burns
• Muscle tension
• Contractures
• Reflexes
• Lack of coordination and strength in the case of active movement
• Paralysis
• Spasticity
• Length of ligaments and tendons
• Bone and joint
structure limitations
• Gender (e.g., pelvic structure)
• Hormones
(e.g., relaxin)
• Pregnancy (e.g., sit-and-reach test)
• Body fat/obesity
(e.g., sit-and-reach test) (acting as a wedge between two lever arms)
• Postural malalignment,
such as scoliosis or kyphosis
• Inflammation and effusion
• Pain
(stretch threshold or tolerance)
• Fear
• Immobilization in a cast
or splint
• The presence of any simultaneous movement in another direction
• Body mass (large biceps limit flexion)
• Temperature
• Age
• Ethnic origin
• Training
• Circadian
variations (time of day)
• Personal activity patterns (e.g., poor posture sitting)
• Vocation
• Medications
• A full bladder
• Warm-up
In general, to increase ROM at a joint, stretching and ancillary procedures must do at least one
of four things (when appropriate): (1) increase the extensibility of connective tissues in muscles or joints, (2) reduce muscular
tension and thus produce relaxation, (3) increase the coordination of the body segments and the strength of the agonistic
muscle group (see table 12.2), or (4) reduce inflammation, effusion, and pain. The caveat, "when appropriate" is
determined by the stretching technique employed. Loss of motion because of abnormal bone and joint structure is beyond the
scope of traditional stretching procedures.
ADDITIONAL
PRINCIPLES OF STRETCHING
A diversity of opinion concerning parameters and protocols in evaluating and developing optimum
ROM and stiffness may be attributed to the various disciplines and professions involved (e.g., athletics, contortionists,
dance, laypersons, rehabilitation, yoga). Therefore, guidelines should be tempered with a balance of philosophy, science,
and clinical experience. Following are some principles that should be observed when developing flexibility. These principles
are not necessarily the final word but do represent some of the more important points to remember when undertaking a flexibility-training
program.
Safety
Safety always comes first. The primary objective of any instructor
or health-care provider is to locate, analyze, and correct a student's or patient's stiffness or lack of optimal flexibility
in the safest and most efficient manner. Although the instructor or health-care provider is ultimately responsible for the
safety of those in their charge, these individuals must also be involved in the prevention of injury. However, more than the
health-care provider or instructor causing no harm assures patient or client safety. Safety is a multiple-stakeholder enterprise
that is only as successful as its weakest link. Consequently, safety requires attitudes, skills, and knowledge about the control
of potential hazards. The American Alliance for Health, Physical Education, and Recreation (1968) advocates a simple four-step
approach to safety issues: (1) know the hazards, (2) remove the hazards when feasible, (3) control the hazards that cannot
be removed, and (4) create no additional hazards.
Medical Examination
Ideally, a history should be obtained and a medical examination (assessment) should be performed before undertaking any exercise
program. Only by eliciting information relative to a person's health status can an instructor or health-care provider formulate
an appropriate protocol to achieve the desired goals. A case history IS necessary
• To determine
the overall health status of the athlete or patient
• To develop a better understanding of the
individual's concerns
• To detect any condition that may limit an athlete's participation
• To detect conditions that may predispose an athlete to injury during competition, such as past
or untreated injuries or illnesses, congenital or developmental problems, or lack of physical conditioning
• To meet legal or insurance requirements (Hunter 1994)
A medical examination may reveal that
certain types of stretching exercises are contraindicated. An examination may also lead the instructor or health-care provider
to modify his or her stretching regimen to ensure safety. A list of contraindications for therapeutic muscle stretching (TMS)
(i.e., specific muscle stretching performed, instructed, or supervised by a therapist in patients with dysfunctions of the
musculoskeletal system) has been developed by Mühlemann and Cimino (1990):
• Lack of stability.
TMS is contraindicated if joint integrity or stability is jeopardized or decreased by any (pathologic) process.
• Endangered vascular integrity. Pathologic processes or drugs (e.g., anticoagulants) can endanger vascular integrity
or facilitate bleeding.
• Inflammation or infection in and around the involved structures.
• Acute injury to the soft tissues and muscles. If per formed without sufficient time for healing,
TMS must be postponed until scar formation is sufficient for moderate tensile loads to be tolerated.
• Diseases of the soft tissues and muscles. Contraindications can be relative (i.e., TMS can or cannot be administered,
depending on the actual condition of the tissue, the operator's skills, the patient's cooperation, and so forth) or absolute
(as in conditions such as myositis ossificans).
• Lack of patient compliance and excessive pain
or reaction. Any therapeutic maneuver is contraindicated if the patient cannot or does not want to tolerate its application.
If the pain during TMS is not tolerated even though TMS is administered as skillfully and painlessly as possible, then TMS
maneuvers should not be used. Patients may be taught self-stretching exercises instead, the performance of which should be
supervised, and, later, controlled periodically.
• When common sense says "No." (p.
255)
Additional contraindications to the use of stretch include uncontrolled muscle cramping that occurs
when attempting to stretch, arterial insufficiency, local hematoma as a result of an overstretch injury, tendon repair, Dupuytren's
contracture, contracture (desired functional shortening) requiring stability to a joint capsule or ligament, or intentional
contracture to improve function (e.g., tenodesis of finger flexors to allow grasp in an individual with quadriplegia) (Fredette
2001; Hardy and Woodall 1998; Kisner and Colby 2000).
Identifiable Goals
One should establish his or her goals before beginning a flexibility program and have an idea of how much time is required
to reach the desired degree of flexibility. For example, the goal may be the ability to place the palms flat on the floor
with legs straight after 6 weeks of stretching. Whatever the goals are, they should be realistic.
Individualized
Program
Ideally, all exercises should be designed to fit an individual's specific needs.
However, one is often expected to fit into a group or team in a flexibility-training program. Should a coach, instructor,
or trainer insist that a given stretch be held for a specific time or encourage each athlete to sustain the stretch until
his or her individual threshold or objective is fulfilled?
The answer to this question depends on
a number of factors. Ideally, one should have already warmed up and stretched on one's own before participating in the team
stretch. However, doing so is not always possible or even desirable if the individual does not have the knowledge to warm
up and stretch safely. The team approach is usually the most appropriate course to follow. At least some stretching is guaranteed
if one participates in a group, and a team program fosters camaraderie and team spirit. At the end of the team workout, each
individual can concentrate on those muscles that need additional stretching.
However, if one is stretching
in a class at a fitness or health club, one should listen to one's own body and either participate with the class or hold
the stretch as individually appropriate. Such a class may have a wider range of abilities, and stretching beyond one's safety
limit is a real possibility, especially for beginners. Instructors should educate class members about which and to what degree
exercises should be attempted. In addition, instructors should tell their students that stopping and resting in the middle
of a class session or modifying an exercise is allowed. Adaptation is particularly appropriate in the case of fatigue, pain,
or excessive difficulty with a given exercise. The instructor must constantly monitor all members of the class during the
workout for potential complications.
Keep Accurate Records
A well-planned
program is also a recorded one. Records should include the date and time of exercise; types of exercises performed; exercise
intensity, duration, and frequency; and self-evaluation before, during, and after the program. A variety of devices are available
for measuring and evaluating ROM, ranging from the sophisticated and expensive to the simple and inexpensive. They include
radiography, photography, videofluroscopy, schematography, spine motion analyzers, grids, outline tracing, goniometers or
protractors, electrogoniometers, single/double inclinometers (mechanical, electronic, or fluid-filled), tape measures, performance
charts, and visual observations. Regardless of the method chosen for measuring ROM, a standardized procedure for warm-up before
testing should be established (Maud and Cortez-Cooper 1995).
Record keeping is prudent for a variety
of reasons (American Medical Association 1993; Hubley-Kozey 1991; Protas 2001; Rondinelli and Katz 2000). (1) Analytical information
can be gained concerning the ROM. (2) Information may reveal positive or negative patterns in the training program. (3) Recorded
evaluations could also identify areas that may be associated with poor performance of a skill or with possible risk of injury.
(4) Collected data could assess the rehabilitation procedure after injury and assist in determining the suitability of the
individual to return to play. (5) The accumulation of normative values for various population's could enhance the interpretation
of flexibility testing. (6) Record keeping can serve as a motivational tool and (7) can also provide valuable information
in the event of legal challenges to the care provided.
Measuring and evaluating pain or stiffness
is a specific concern for physical therapists, rheumatologists and heath-care providers, either primary or allied. Joint stiffness
can be evaluated on a subjective basis. How ever, these evaluations may be unreliable. Wright and Johns (1960) developed
a technique (arthrography) that permitted quantitative and qualitative measurements of joint stiffness in precise physical
terms (Lung et al. 1996). Since then, several pressure gauge methods of objectively assessing soft-tissue consistency or compliance
have been developed. Pressure-pain threshold measurement is referred to as algometry. Regardless of the methodology, measuring
the rheological properties of joints or soft tissues presents many challenges (Bovens et al. 1990; Gifford 1994; Helliwell
1993) such as age, gender, circadian variations, anti-inflammatory drugs, disease, and stiffness. Measurements must be made
in reference to the equilibrium point of the joint.
The reliability of ROM measurements is subject
to a host of factors (intraobserver reliability, instrument reliability, subject cooperation and effort). According to Rondelli
and Katz (2000), "these conditions can make it quite easy for measurements to vary by 5% or more, which could have a
significant effect on an impairment rating" (p. 56). Thus, one may diligently record the measured results; however, this
diligence does not guarantee the measured results are in fact accurate. Accordingly, Gajdosik and Bohannon (1987) advise,
"As a rule, ROM of measurements are just that, not measurements of muscle 'tightness,' the length of specific structures,
or other factors that may affect ROM" (p. 1872). Technology and research continue to progress at a rapid rate. Therefore,
those concerned with measuring ROM or stiffness should keep abreast of the newest innovations that can afford optimum means
for gaining this information.
Expect Gradual Progress
The development
of flexibility takes time. Therefore, set realistic goals and begin with easy exercises before advancing to more difficult
ones. Plateaus, or periods of no apparent progress, are part of the learning process.
Comparing and Competing
Do not compare yourself with others. Improvement and progress are important, not competition with someone
who may be at a different level of ability. No two people are alike: Some may develop flexibility rapidly; others may take
longer to reach the same level.
Clothing and Positioning
Wear loose
and comfortable clothes when working out. Because a warmed muscle is believed to be more flexible and pliant, people often
wear sweat suits and wool socks. Position yourself as comfortably as possible to reduce muscle tension and make the stretching
more enjoyable.
Attitude and Mind-Set
A positive mental attitude is important. The mental,
physical, and spiritual aspects of life are inseparable from one another. Without a positive mind-set, the best of all possible
results will never be achieved. Another important and deleterious consideration is that some athletes and performers believe
perfection of their discipline takes precedence over their physical condition (Weisler et al. 1996). This attitude can potentially
result in chronic or acute injuries. An example is a ballet dancer who attempts to force the turn-out position by employing
the dangerous technique called "screwing the knee."
Relaxation
In
certain types of stretching exercises (passive stretching) relaxation may be beneficial. On the other hand, in specific types
of stretching exercises (functional stretching; PNF) developing or maintaining a certain amount of tension might in fact be
safer and more efficient. Relaxation is the opposite of tension. Inappropriate tension originating in contracted muscles can
result in inflexibility, an insufficient oxygen supply, and fatigue. Therefore, the ability to relax can be important because
it decreases tension and its negative consequences, thus allowing one to function more effectively and efficiently. In general,
stretching slowly and exhaling gently at the moment of maximum stretch can often facilitate stretching. However, exhaling
during the stretching phases of a movement is not always beneficial or conducive for safe and efficient stretching.
Breathing
Most publications devoted to stretching, athletic training, physical therapy, and rehabilitation recommend
that participants should either never hold their breath when stretching or exhale during the effort phase. Siff and Verkhoshansky
(1999), in their text Super training, warn not to follow this popular advice as applied to resistance or strength training.
Can this advice be expanded to include stretching exercises? Their argument is that during resistance or strength training,
"breath-holding plays a vital role in increasing the intra-abdominal pressure to support and stabilise the lumbar spine
during heavy lifting" and "exhalation during lifting increases the risk of lumbar injury" (p. 170). Thus, without
breath-holding, far greater pressure is exerted on vulnerable structures of the lumbar spine, in particular the intervertebral
discs and ligaments.
Obviously, in cases of passive stretching or static stretching where maximal
force and spinal stabilization are not produced, exhalation is often advantageous. Many of the advantages of exhalation were
explored in chapter 8. However, two specific situations bear special consideration. During several types of PNF maneuvers,
holding breath and not exhaling may in fact be highly advantageous for stabilizing the body and facilitating maximal or near
maximal contractions. During active or functional stretching, the constant interplay of mobility and stability must not be
lost. If for example, when a ballerina or gymnast is training to master a technique that must be maintained for several seconds,
exhalation may in fact make lifting and holding the leg in the desired position more difficult. Clearly, ideal training must
include neuromuscular interactions in the execution of all skills. Thus, "appropriate techniques of breathing should
always be combined with all phases of movement to enhance mobility, stability and relaxation" (Siff and Verkhoshansky
1999, p. 186).
Warm-Up and Cool-Down
Warm-up and cool-down exercises improve performance
and reduce the chances of injury. The most important advantages of both active and passive warm-ups are increased muscle temperature,
reduced muscular viscosity, decreased muscular tension, and more extensible tissue. A stretching program is used as an adjunct
to warm-up or cool-down to increase flexibility. Stretching is not a warm-up procedure.
Isolate the Muscle and
Connective Tissues
Ten important caveats must be kept in mind when attempting to "isolate"
a muscle, muscle group, or its respective connective tissues. First, "the real function of muscles/muscle groups must
always be taken into account" (Evjenth and Hamberg 1989, p. 7). Second, a targeted muscle or muscle group cannot be truly
isolated. Adapting the words (in reference to strength training) of Siff and Verkhoshansky (1999, p. 407), the concept of
muscle isolation training when stretching incorrectly implies that only one specific muscle group is being stretched by a
given procedure. This idea is very misleading. Movements of parts of the human body are interconnected and not isolated from
the whole. In the case of active stretching or functional flexibility (ROM), movements are a combined result of the appropriate
contribution of agonists (prime movers), antagonists, stabilizers, synergists, and neutralizers. "This is why it is vital
to remember that all human movement involves the intricate orchestration of concurrent and sequential contractions of movers
and stabilizers" (p. 407). Third, as a joint progresses through a ROM (i.e., during non-static stretching) different
portions of muscle groups and their respective connective tissues are stressed more than other portions at each joint position
as a consequence of simple geometry (Martin et al. 1998). Therefore, once again, the concept of "isolation" is in
fact a misnomer. Fourth, muscles often cross more than one joint. Consequently, using just one single stretch may not result
in an optimum stretch or "isolation". Fifth, several important functional ROMs are not limited to a single joint,
but result from a combination of movements by multiple joints (Protas 2001). For example, the ability to bend over and tie
one's shoe requires adequate ROM in the trunk, hip, and shoulders. Sixth, in the case of active stretching with large loads
(i.e., a resistance as in PNF stretching), isolation becomes virtually impossible because stabilizing muscles become involved
to ensure that the body or specific joints remain stable, while the prime movers attempt to cope with the load (Siff and Verkhoshansky
1999, p. 241). Seventh, when attempting to identify a specific stretch for a specific muscle or muscle group, "the reverse
of any action to contract a given muscle group becomes a stretch for that same muscle group" (Siff and Verkhoshansky
1999, p. 186). For instance, the biceps brachii flexes the elbow and supinates the forearm. Therefore, elbow extension and
pronation result in stretch to that muscle. Eighth, for stretching to be most beneficial, the proper muscle group and its
respective connective tissues must be the target to develop the optimum tensile force. Undesired compensation by other muscles
and structures (e.g., the spine) may facilitate a reduction in the desired tensile force. For example, the anterior tilt position
is more important than stretching technique (PNF or static stretching) for increasing hamstring muscle length (Sullivan et
al. 1992). Ninth, if two stretching procedures result in significant gains in flexibility, the safest and most effective procedure
should be the one employed. Tenth, the concept of multi-directional stretching may at first appear contradictory to the idea
of isolating the muscle. "Multi-directional stretching is important, since the structural orientation of the fibers is
different for the different collagenous tissues and is specifically suited to the functions of each tissue" (Siff 1993
b, p. 128).
Starting Position
For stretching to be safe and effective, the starting
position must be stable. That is, you can "support, control and relieve your muscles throughout the exercise" (Evjenth
and Hamberg 1989, p. 11). Caution must be observed when attempting stretches balanced on one leg, sitting on a chair, or employing
a raised platform. Additional stabilization may be provided by the use of equipment such as belts or splints. These devices
may help avoid substitute motions when stretching or assist in maintaining support and control. Another important factor when
stretching is the stabilization of one attachment site of the muscle (usually proximal) or limb during stretching (Brody 1999).
For example, to optimally stretch the hamstrings, the pelvis must be tilted. "Failure to stabilize proximally results
in lumbar spine flexion, posterior pelvic tilt, and movement of the hamstring origin closer to the insertion, thereby minimizing
the stretch" (p. 100).
Application of the SAID Principle
According to Wallis and Logan (1964), strength, endurance, and flexibility training should be based on the principle of specific
adaptation to imposed demands (SAID). That is, one should stretch at a velocity not less than 75% of the maximum velocity
through the exact plane of motion, through the exact ROM, and at the precise joint angles used while performing skills in
a specific activity (e.g., high leg kicks emulate punting a football). For movements performed at rapid velocity, a slow stretch
should precede the application of the SAID principle.
Application of the "Overstretching"
Principle: Stretching Duration, Frequency, Timing, and Intensity
The physiological principle on which
strength development depends is the overload principle. Its analogue for flexibility is the "overstretching" principle.
The difference between the two is that the latter uses stretch, whereas the former uses resistance, usually weight. Many individuals
seek an established number of exercises to perform similar to the recommended dietary allowance for vitamins and minerals
(Shrier and Gossal 2000) or a universal stretching dosage or recipe. Individuals want to know the exact duration, frequency,
timing, nature, and intensity of the stretch to achieve their desired goal. Unfortunately, recommendations for these variables
have sparked much debate and little consensus. Stretching protocols need to take into consideration variations and differences
between healthy and injured tissues. Perhaps, the most important consideration is the purpose of the flexibility-training
session. Specifically, is the purpose of the program development, maintenance, or rehabilitation of flexibility (Alter 1998)?
Stretching Duration
The utilization of specific stretching procedures such
as static, dynamic, or PNF in part determines the duration of a stretch. Many programs recommend holding each stretch for
6 to 12 seconds. However, 10 to 30 seconds is also commonly recommended. The problem with holding stretches for longer than
30 seconds is that stretching programs might last longer than many workouts (Alter 1998). Magnusson, Aagaard, and Nielson
(2000) reiterate, "multiple repetitions of sustained static stretches for a single muscle group can be very rigorous,
time consuming, and hence an unrealistic stretching program" (p. 1160). Several impinging determinants for the time to
maintain each stretch include the number of muscle groups or joints targeted and the number of repetitions and sets of each
stretch (Alter 1998; Brody 1999; Knudson 1998). According to Prentice (1999), stretches lasting for longer than 30 seconds
seem to be uncomfortable for some athletes. An additional mitigating factor could include fatigue.
Bandy and Irion (1994) compared the effectiveness of 15, 30, and 60 seconds of static stretching of the hamstrings. Their
study revealed that 30 and 60 seconds of stretching were more effective at increasing hamstring flexibility than stretching
for 15 seconds or no stretching at all. "In addition, no significant difference existed between stretching 30 seconds
and for 1 minute, indicating that 30 seconds of stretching the hamstring muscles was as effective as the longer duration of
1 minute" (p. 845). Later, this finding was again substantiated (Bandy et al. 1997). Consequently, this study reiterated
the use of increased duration, and frequency beyond one 30 second stretch per day cannot be supported. Grady and Saxena
(1991) also found that a 30-second stretch of the gastrocnemius is adequate to improve flexibility, with minimal additional
gains when the stretch is extended to 2 or 5 minutes. Cipriani et al. (2003) found no difference between a 10-second stretch
repeated six times for a total of 1 minute or a 30-second stretch repeated two times for a total of 1 minute. In both groups,
stretching of the hamstrings was performed twice daily for a total of 2 minutes each day for 6 weeks.
Walter et al. (1996) determined that 30 seconds of passive stretch of the hamstrings was superior to 10 seconds at 85% and
100% intensity. The investigators suggested, a minimum threshold seems to exist for intensity and duration to be effective
in improving ROM. In contrast, Madding et al. (1987) compared the effectiveness of a IS-second, 45-second, and 2-minute passive
stretch to increase hip abduction ROM in 72 male subjects. No significant mean difference between the three groups was demonstrated.
Based on these data, the authors concluded that it was "reasonable to stretch 15 seconds in athletic settings where immediate
increases in abduction ROM are desired" (p. 416). In a study of people 65 years of age or older (Feland et al. 2001),
the straight-Ieg-raising technique for the hamstrings was compared. Subjects were randomly assigned into groups that stretched
five times per week for 6 weeks for 15, 30 and 60 seconds. Stretches were repeated four times with a 10-second rest between
stretches. The 60-second stretch produced a greater rate of gains in ROM and more sustained increase in ROM. These results
differed from those of Bandy and Irion (1994). The investigators speculated the longer duration of stretch "may have
been more beneficial than shorter durations in overcoming the increased muscle stiffness and collagen deposition that accompany
the aging process" (p. 1116).
Borms et al. (1987) compared the effects of 10, 20, and 30 seconds
of active static stretching on active coxofemoral flexibility. The program consisted of two sessions per week lasting for
10 weeks. Their findings suggested that a duration of 10 seconds for static stretching is sufficient for improving hip joint
flexibility. Roberts and "Wilson (1999) suggested, "that holding stretches for 15 seconds, as opposed to five seconds,
may result in greater improvements in active ROM" (p. 259). However, Apostolopoulos (2001) and Bates (1971) are of the
opinion that 60 seconds of maintained stretch is optimal for increasing and retaining flexibility. A stretch normally takes
about 30 seconds to progress from the middle of the muscle belly to the tendons. Therefore, "a token 10 [to] 15 -second
stretch may be beneficial to the muscle belly but will have minimal influence on the ligaments, tendons, and fascia that are
largely responsible for range of motion and flexibility" (p. 54). However, Proske and Morgan (1987, 1999) point out that
"when a passive muscle and its tendons are stretched, initially most of the movement is taken up by the tendon and only
when tension begins to rise are the muscle fibres themselves stretched" (1999, p. 434). In contrast, the American College
of Sports Medicine Position Stand (1998) proposes that static stretches should be held for 10 to 30 seconds, whereas PNF techniques
should include a 6-second contraction followed by 10-second to 30-second assisted stretch. Similarly, Krivickas (1999) advocates
holdings stretches for 15 to 30 seconds. Anderson (2000) suggests beginning with an easy stretch for 10 to 15 seconds followed
by a "developmental" stretch for an additional 10 to 15 seconds. At the lowest end of the time spectrum, Mattes
(1990) and Wharton and Wharton (1996) also promote a I-second to 2-second lengthening strategy as an integral part of the
Active Isolated Stretching protocol. Weider (1995), a world-renowned body trainer and publisher, also recommends holding each
stretch for 2 seconds. His rationale is that after 2 seconds "the muscular response is to tighten up the area to prevent
injury, which not only defeats the purpose of stretching but can also lead to microtrauma and soreness" (p. 139). In
contrast, Brody (1999) recommends a patient or an athlete hold a stretch based on his or her perceived need or comfort level.
However, "when in doubt, a stretch should be held for a longer period rather than a shorter period" (p. 103).
Another avenue to determine the optimum duration of a stretch is the use of animal models. Experiments
on rabbit extensor digitorum longus and tibialis anterior muscle-tendon units by Taylor et al. (1990) suggests that the greatest
amount of stress relaxation muscle elongation occurs during the first 12 to 18 seconds of a static stretch.
Given that
time constraints limit ideal stretching during a workout session, athletes and performers must stretch on their own time.
For some, serious stretching can be concentrated on off days, whereas others, particularly highly specialized athletes and
performers, will need to stretch religiously on a daily basis. Empirical evidence would probably reveal a significant improvement
in flexibility occurs when stretching is done on personal time. Later, this flexibility is transformed into finely coordinated
and skilled movement.
Stretching Repetitions and Sets
Differences of opinion are apparent regarding
the most effective frequency or number of repetitions (Smith 1994). Repetitions can refer to the number of times a stretch
is performed within a set (i.e., the completion of one "turn" or a consecutive series or repetitions), the number
of sets in a workout, the number of workouts in a session, or the number of sessions in a week. The number of sets and repetitions
depends on the frequency and the number of exercises performed (Brody 1999). Their number is also determined by the objective
of the stretching and one's state of health (healthy, rehabilitation for an injury). The American College of Sports Medicine
(1998, 2000) recommends at least four repetitions per muscle should be completed for a minimum of 2 to 3 days a week. Weider
(1995) advocates stretching for only 2 seconds but performing 3 to 4 or even more sets of micro-stretches for as often as
needed. In contrast, Apostolopoulos (2001) recommends stretching once or twice a day three times per muscle group per session.
Taylor et al. (1990) experimented using rabbit extensor digitorum longus and tibialis anterior muscle
and tendon units. The greatest change (80%) in muscle and tendon length occurred in the first four static stretches in a series
of 10. Further stretching did not result in significant increases in length. In addition, "relaxation curves of the first
two stretches demonstrated statistically significant differences from the other curves. There were no significant differences
in curves 4 through 10." Taylor et al. (1990) state, "the magnitude of the stretching force or the duration of hold
time may have an influence on the ideal number of stretches". The research by Taylor et al. (1990) is admirable and commendable.
However, Carborn et al. (2001) point out that "the study did not account for the added difficulty of stretching muscles
that act across multiple joints, the components of functional muscle groups that present divergent sites of insertion, or
the learning of proper technique". In addition, the development of flexibility is multifaceted, and extrapolating research
carried out on animals to finely conditioned athletes has limitations.
Stretching Frequency
In general, the frequency of the stretching program is often inversely related to the intensity and duration
(Brody 1999). Therefore, stretch exercises of high intensity and duration are performed less frequently and vice versa. Generally,
one should stretch at least once a day for maintenance of flexibility. Such daily workouts are feasible if interest and motivation
can be maintained (Rasch and Burke 1989). However, empirical evidence suggests that stretching at least twice a day is preferable.
Perhaps the best time to stretch is when one feels as if one wants to.
Placement and Timing
of the Stretching Program
Many texts and articles recommend stretching in the morning or
in the evening. The common subjective feeling of "stiffness" or "tightness" in the lower and upper torso
is caused by the change in fluid content of the vertebral disks (Adams et al. 1987). Consequently, the lumbar disks and ligaments
are at greater risk for injury in the early morning (Adams et al. 1987). Another issue is the placement of stretching exercises
in a workout.
Several options are possible for the placement of the stretching program within a workout.
Opinions on the specific placement of stretching exercise are usually based on an intuition. Several researchers and writers
have recommended stretching at the end of the workout. Their rationale is:
• tissue temperatures are elevated;
• the time to perform your developmental stretching (meaning to actually increase your functional
flexibility) is at the end of your workout, when you are totally warmed up and loose;
• stretching
a muscle may temporarily decrease its force production capacity; and
• stretching at the beginning of
the workout takes time from the overall workout.
What about stretching throughout a workout session? The recommendation
that stretching should be conducted at the end of a workout should not be construed to mean that one should not stretch during
a workout. To the contrary, one may in fact need to stretch during a work out, especially if a tight muscle group (i.e.,
hamstrings) is negatively affecting one's technique. However, most people seem careful to not go overboard and spend an excessive
amount of time stretching if the total workout is short. Office workers (e.g., secretaries, people working at computer terminals,
nurses) are now being advised to take small stretch breaks to reduce the risk of injury.
Cornelius et al. (1988) investigated
the placement of stretching exercises in a workout and discovered that adherence to a static flexibility program will produce
gains in joint ROM regardless of the placement of the flexibility routine. Their findings refute claims that specific placement
of stretching exercises within a workout session makes a difference in increasing ROM. Placement is more relevant for "other
objectives such as increasing tissue temperature and reducing tissue discomfort that might be affected by specific placement
of stretching".
Post-workout Stretching
Some investigators (Anderson 2003a; Bledsoe 2003) suggest that post-workout stretching is more advantageous than
pre-workout stretching. They cite research by Vandenburgh and Kaufman (1983) that demonstrates stretching-related stimulation
of the passage of amino acids into muscle cells, accelerate synthesis inside the cells, and inhibit protein degradation rates.
Consequently, post-workout stretching should theoretically help muscle cells repair themselves and synthesize energy-producing
enzymes and structures, which enhance overall fitness. Thus, these effects may be the reason athletes who stretch after workout
are injured less often.
Stretching Intensity
The correct target intensity of stretching is extremely
significant because, like any form of training, it can provide a potentially traumatic stimulus to the muscle-tendon unit
(Knudson 1998). Like other forms of training, acute stretching programs can result in the structural weakening of the muscle-tendon
unit and increase the risk of injury (Noonan et al. 1994; Sapega et al. 1981; Taylor et al. 1990). Stretching has also been
documented in certain situations to produce a short-term strength deficit.
The intensity of stretch
affects the increase in ROM (Walter et al. 1996). Their research suggested 85% to 100% intensities resulted in significantly
greater flexibility than 60%. However, they cautioned "there may be an intensity that produces maximal gains in flexibility
lower than 85% but greater than 60% of a maximal stretch" (p. 43). In contrast, Apostolopoulos (2001) advocates stretching
should always be performed at a low-intensity level of approximately 30% to 40% of perceived exertion.
The dilemma regarding stretching intensity is three fold. First, intensity is subjective. Second, stretching intensity
is most often conducted under conditions in which the intensity cannot be quantified. Third, vigorous stretching is important
for optimum progress (i.e., for athletes and highly trained performers); however, stretching intensity beyond the adaptability
of the respective tissues capacity could result in injury.
In general, the intensity of the stretch
should also be up to you. Although stretch may produce some discomfort (especially for beginners), it should not be so great
a discomfort as to cause pain. If your muscle begins to quiver and vibrate, if pain persists, or if ROM decreases, you have
stretched too much, and either the force or the duration of the stretch should be decreased. Discomfort and pain are subjective
matters, so no absolute answer about where to draw the line can be given. The best advice is "Train, don't strain."
Mechanics
The individual must use proper mechanics and techniques when stretching to achieve optimal results. Applying proper
mechanics involves identifying and "isolating" those muscle groups and tissues to be stretched and using the appropriate
exercise to fulfill that goal. Correct technique reduces the risk of injury and the impairment of performance.
Reflex
A variety of reflexes can influence ROM. Perhaps, the best known and commonly cited is the stretch
reflex. In general, laypeople, the sedentary, and the elderly should use slow or static methods of stretch because sudden
or painful movements may elicit a stretch response, causing the muscle to simultaneously contract (see chapter 6). Therefore,
ballistic stretching for these populations should be avoided, especially during the early stages of a program. On the other
hand, most sports and disciplines necessitate some ballistic stretching as a part of their training program. Flexibility training
encompasses both structural conditioning and functional (central nervous and neuromuscular) conditioning. Individuals engaged
in those sports or activities should first warm up thoroughly, then progress from passive or static stretching to dynamic
sports-related movements. Other potential reflexes impacting on ROM during stretching include reciprocal innervation and the
positive support reaction reflex.
Anticipation and Communication
During passive stretching
or specific PNF stretching exercises, partners should communicate with each other. The person being stretched should inform
the partner when the stretch becomes unpleasant or painful. The person applying the stretch should anticipate how much overstretch
should be employed. This activity is a two way process.
Appropriate Injury Management
If injured, one should determine to the best of one's knowledge the extent of the damage. As a general rule, rest, apply ice
and pressure, and elevate the injured part
of the body, then seek appropriate medical care. The sooner an injury is treated,
the earlier rehabilitation can begin and the faster the recovery will be. Again, use common sense.
Reversibility
Muscle and connective tissue respond to disuse and immobilization. Consequently, these tissues
will "detrain" if not constantly trained toward a set goal (Bischoff and Perrin 1999). Maintenance of flexibility
is a continuous process. Here, the relevant axiom is "Use it or lose it."
Enjoyment
Stretching should be enjoyable and satisfying and create a sense of well-being. Enjoyment and pleasure are a matter of satisfying
one's motives. However, stretching has the potential to involve varying degrees of pleasantness or unpleasantness. \When stretching
ceases to be enjoyable, it can become self-defeating.
SUMMARY
Homeostasis is maintenance of a steady state.
To develop flexibility, one's homeostatic state must be exceeded by added stress to enter a new state, in a process called
adaptation. Overstretching is the physiological principle on which flexibility development depends: \When one properly stretches
regularly, the body will respond with an increased ability to stretch. For stretching to be successful, a movement must actually
exceed the existing ROM. However, "overstretching" in this context does not mean stretching body parts that exceed
their safety limits and result in injury and impairment in function.
Before engaging in a stretching
program, one should have some knowledge about anatomy, physiology, and the structure and functions of joints. In addition,
a number of important principles must be observed when developing flexibility: safety always comes first; expect gradual progress;
warm-up and cool down; and use appropriate medical treatment in case of injury.
FROM: Science of Flexibility by Michael J. Alter
