William E. Prentice, PhD, PT, ATC, FNATA
After reading this chapter,
the athletic training student should be able to:
- Define flexibility and describe its importance in injury rehabilitation.
- Identify factors that limit flexibility.
- Differentiate between active and passive range of motion.
- Explain the difference between ballistic, dynamic, static, and proprioceptive neuromuscular facilitation stretching.
- Discuss the neurophysiologic principles of stretching.
- Describe stretching exercises that may be used to improve flexibility at specific joints throughout the body.
- Compare and contrast the various manual therapy techniques including myofascial release, strain–counterstrain, positional release, Active Release Technique, massage, structural integration, and postural restoration, all of which may be used to improve mobility and range of motion.
When injury occurs, there is almost always some associated loss of the ability to move normally. Loss of motion may be a result of pain, swelling, muscle guarding, or spasm; inactivity resulting in shortening of connective tissue and muscle; loss of neuromuscular control; or some combination of these factors. Restoring normal range of motion (ROM) following injury is one of the primary goals in any rehabilitation program.66 Thus, the athletic trainer must routinely include interventions designed to restore normal ROM to regain normal function.
Flexibility has been defined as the ability to move a joint or series of joints through a full, nonrestricted, pain-free ROM.3,33,37,40,53 Flexibility is dependent on a combination of (a) joint ROM, which may be limited by the shape of the articulating surfaces and by capsular and ligamentous structures surrounding that joint; and (b) muscle flexibility, or the ability of the musculotendinous unit to lengthen.69
Flexibility involves the ability of the neuromuscular system to allow for efficient movement of a joint through a ROM.3,8,50 Flexibility can be discussed in relation to movement involving only one joint, such as the knees, or movement involving a whole series of joints, such as the spinal vertebral joints, that must all move together to allow smooth flexion, extension, side-bending, or rotation of the trunk.71 Lack of flexibility in one joint or movement can affect the entire kinetic chain. A person might have good ROM in the ankles, knees, hips, back, and one shoulder joint but lack normal movement in the other shoulder joint; this is a problem that needs to be corrected before the person can function normally.11
This chapter concentrates primarily on rehabilitative techniques used to increase the length of the musculotendinous unit and its associated fascia, as well as restricted neural tissue. In addition, a discussion of a variety of manual therapy techniques including myofascial release, strain/counterstrain, positional release therapy, soft tissue mobilization, massage, structural integration, and postural restoration (PRI) as they relate to improving mobility will be included. Joint mobilization and traction techniques used to address tightness in the joint capsule and surrounding ligaments are discussed in Chapter 13. Loss of the ability to control movement as a result of impairment in neuromuscular control was discussed in Chapter 6.
IMPORTANCE OF FLEXIBILITY TO THE PATIENT
Maintaining a full, nonrestricted ROM has long been recognized as essential to normal daily living. Lack of flexibility can also create uncoordinated or awkward movement patterns resulting from lost neuromuscular control. In most patients, functional activities require relatively “normal” amounts of flexibility.64 However, some sport activities such as gymnastics, ballet, diving, karate, and especially dance require increased flexibility for superior performance (Figure 8-1).70
For many years, stretching has been considered an essential part of the training regimen for both recreational and elite athletes and is used across all disciplines for warm-up, enhancing performance, and preventing injury.6
It is generally accepted that a period of warm-up exercises should take place before a training session begins, although a systematic review of the evidence-based literature reveals that there is insufficient evidence to endorse or discontinue a warm-up prior to exercise to prevent injuries, although the weight of the evidence favors a decreased risk of injury.30 Nevertheless, most athletic trainers would agree empirically that a warm-up period is a precaution against unnecessary musculoskeletal injuries and possible muscle soreness. Some evidence suggests that a good dynamic warm-up may also improve certain aspects of performance.31
The accepted technique was to perform a light jog followed by some static stretching. A more contemporary approach to the warm-up is to use an active, or dynamic, stretching to prepare for physical activity
A recent study found that neither short- or moderate-duration static nor dynamic stretching influence flexibility, sprint running, jumping, or agility performances following a preexercise warm-up routine.13 Further, it was shown that small-to-moderate reductions in muscle injury risk in running sports resulted from engaging in static stretching in a preexercise warm-up. It was added that there is a positive psychological effect from engaging in a warm-up that included static or dynamic stretching that allowed for individuals to feel more confident when subsequently participating in sport activities.
A review of the evidence-based information in the literature looking at the relationship between flexibility and improved performance is, at best, conflicting and inconclusive.8,28,46,74,79,86 Although many studies conducted through the years have suggested that stretching improves performance,8,11,22,46,63 several studies have found that stretching causes decreases in performance parameters such as strength, endurance, power, joint position sense, and reaction times.8,9,17,28,49,52,62,69,73,80,87
The same can be said when examining the relationship between flexibility and reducing the incidence of injury. Although it is generally accepted that good flexibility reduces the likelihood of injury, a true cause-and-effect relationship has not been clearly established in the literature.5,21,49,56,63
Clinical Decision-Making Exercise 8-1
A gymnast is out of practice for 2 weeks because of a stress fracture in her tibia. Why is it essential to incorporate flexibility into the rehabilitation program for this injury?
ANATOMIC FACTORS THAT LIMIT FLEXIBILITY
A number of anatomic factors can limit the ability of a joint to move through a full, unrestricted ROM.66 Muscles and their tendons, along with their surrounding fascial sheaths, are most often responsible for limiting ROM. When performing stretching exercises to improve flexibility about a particular joint, you are attempting to take advantage of the highly elastic properties of a muscle. Over time, it is possible to increase the elasticity, or the length that a given muscle can be stretched. Persons who have a good deal of movement at a particular joint tend to have highly elastic and flexible muscles.
Connective tissue surrounding the joint, such as ligaments on the joint capsule, can be subject to contractures. Ligaments and joint capsules have some elasticity; however, if a joint is immobilized for a period, these structures tend to lose some elasticity and actually shorten. This condition is most commonly seen after surgical repair of an unstable joint, but it can also result from long periods of inactivity.
It is also possible for a person to have relatively slack ligaments and joint capsules. These people are generally referred to as being loose jointed. Examples of this trait would be an elbow or knee that hyperextends beyond 180 degrees (Figure 8-2). Frequently, there is instability associated with loose jointedness that can present as great a problem in movement as ligamentous or capsular contractures.
Bony structure can restrict the end point in the range. An elbow that has been fractured through the joint might lay down excess calcium in the joint space, causing the joint to lose its ability to fully extend. However, in many instances, we rely on bony prominences to stop movements at normal end points in the range.
Fat can also limit the ability to move through a full ROM. A person who has a large amount of fat on the abdomen might have severely restricted trunk flexion when asked to bend forward and touch the toes. The fat can act as a wedge between 2 lever arms, restricting movement wherever it is found.
Skin might also be responsible for limiting movement. For example, a person who has had some type of injury or surgery involving a tearing incision or laceration of the skin, particularly over a joint, will have inelastic scar tissue formed at that site. This scar tissue is incapable of stretching with joint movement.
Over time, skin contractures caused by scarring of ligaments, joint capsules, and musculotendinous units are capable of improving elasticity to varying degrees through stretching. With the exception of bone structure, age, and gender, all the other factors that limit flexibility can be altered to increase range of joint motion.
Neural tissue tightness resulting from acute compression, chronic repetitive microtrauma, muscle imbalances, joint dysfunction, or poor posture can create morphologic changes in neural tissues. These changes might include intraneural edema, tissue hypoxia, chemical irritation, or microvascular stasis—all of which could stimulate nociceptors, creating pain. Pain causes muscle guarding and spasm to protect the inflamed neural structures, and this alters normal movement patterns. Eventually, neural fibrosis results, which decreases the elasticity of neural tissue and prevents normal movement within surrounding tissues.24
Clinical Decision-Making Exercise 8-2
Two days after an intense weight-lifting workout, a football player is complaining of quad pain. The athletic trainer determines that the athlete has delayed-onset muscle soreness. The soreness is preventing the athlete from getting a sufficient stretch. What can be done to optimize his stretching?
ACTIVE AND PASSIVE RANGE OF MOTION
Active ROM, also called dynamic flexibility, refers to the degree to which a joint can be moved by a muscle contraction, usually through the midrange of movement. Dynamic flexibility is not necessarily a good indicator of the stiffness or looseness of a joint because it applies to the ability to move a joint efficiently, with little resistance to motion.50 Passive ROM, sometimes called static flexibility, refers to the degree to which a joint can be passively moved to the end points in the ROM. No muscle contraction is involved to move a joint through a passive range. When a muscle actively contracts, it produces a joint movement through a specific ROM.65 However, if passive pressure is applied to an extremity, it is capable of moving farther in the ROM. It is essential in sports activities that an extremity be capable of moving through a nonrestricted ROM.65 Passive ROM is important for injury prevention. There are many situations in physical activity in which a muscle is forced to stretch beyond its normal active limits. If the muscle does not have enough elasticity to compensate for this additional stretch, it is likely that the musculotendinous unit will be injured.
Assessment of Active and Passive Range of Motion
Accurate measurement of active and passive range of joint motion is difficult.71 Various devices have been designed to accommodate variations in the size of the joints, as well as the complexity of movements in articulations that involve more than one joint.71 Of these devices, the simplest and most widely used is the goniometer (Figure 8-3A).
A goniometer is a large protractor with measurements in degrees. By aligning the individual arms of the goniometer parallel to the longitudinal axis of the 2 segments involved in motion about a specific joint, it is possible to obtain reasonably accurate measurement of range of movement.65 To enhance reliability, standardization of measurement techniques and methods of recording active and passive ROMs are critical in individual clinics where successive measurements might be taken by different clinicians to assess progress.35 Table 8-1 provides a list of what would be considered normal active ranges for movements at various joints.
The goniometer has an important place in a rehabilitation setting, where it is essential to assess improvement in joint flexibility to modify injury rehabilitation programs.
In some clinics a digital inclinometer is used instead of a goniometer (Figure 8-3B). An inclinometer is a more precise measuring instrument with high reliability that has most often been used in research settings. Digital inclinometers are affordable and can easily be used to accurately measure ROM of all joints of the body from complex movements of the spine and large joints of the extremities to the small joints of fingers and toes.
STRETCHING TO IMPROVE MOBILITY
The goal of any effective stretching program should be to improve the ROM at a given articulation by altering the extensibility of the neuromusculotendinous units that produce movement at that joint. It is well documented that exercises that stretch these neuromusculotendinous units and their fascia over time will increase the range of movement possible about a given joint.8
For many years, the efficacy of stretching in improving ROM has been theoretically attributed to neurophysiologic phenomena involving the stretch reflex. However, an extensive review of the existing literature suggests that improvements in ROM resulting from stretching must be explained by mechanisms other than the stretch reflex.21 Studies reviewed indicate that changes in the ability to tolerate stretch and/or the viscoelastic properties of the stretched muscle are possible mechanisms. The vast majority of the theories relative to muscle lengthening resulting from stretching attribute the increases to mechanical changes. A more recent theory attributes muscle lengthening to an alteration of sensation that changes the patients perception of when stretching elicits pain, allowing the muscle to be stretched to a greater length.91
NEUROPHYSIOLOGIC BASIS OF STRETCHING
Every muscle in the body contains various types of mechanoreceptors that, when stimulated, inform the central nervous system of what is happening with that muscle.38 Two of these mechanoreceptors are important in the stretch reflex: the muscle spindle and the Golgi tendon organ. Both types of receptors are sensitive to changes in muscle length. The Golgi tendon organs are also affected by changes in muscle tension.38
When a muscle is stretched, both the muscle spindles and the Golgi tendon organs immediately begin sending a volley of sensory impulses to the spinal cord. Initially, impulses coming from the muscle spindles inform the central nervous system that the muscle is being stretched. Impulses return to the muscle from the spinal cord, causing the muscle to reflexively contract, thus resisting the stretch.38 The Golgi tendon organs respond to the change in length and the increase in tension by firing off sensory impulses of their own to the spinal cord. If the stretch of the muscle continues for an extended period (at least 6 seconds), impulses from the Golgi tendon organs begin to override muscle spindle impulses. The impulses from the Golgi tendon organs, unlike the signals from the muscle spindle, cause a reflex relaxation of the antagonist muscle.21 This reflex relaxation serves as a protective mechanism that will allow the muscle to stretch through relaxation without exceeding the extensibility limits, which could damage the muscle fibers.21 This relaxation of the antagonist muscle during contractions is referred to as autogenic inhibition.
In any synergistic muscle group, a contraction of the agonist causes a reflex relaxation in the antagonist muscle, allowing it to stretch and protecting it from injury. This phenomenon is referred to as reciprocal inhibition94 (see Figure 12-32).
EFFECTS OF STRETCHING ON THE PHYSICAL AND MECHANICAL PROPERTIES OF MUSCLE
The neurophysiologic mechanisms of both autogenic and reciprocal inhibition result in reflex relaxation with subsequent lengthening of a muscle. Thus, the mechanical properties of that muscle that physically allow lengthening to occur are dictated via neural input.
Both muscle and tendon are composed largely of noncontractile collagen and elastin fibers. Collagen enables a tissue to resist mechanical forces and deformation, whereas elastin composes highly elastic tissues that assist in recovery from deformation.48
Collagen has several mechanical and physical properties that allow it to respond to loading and deformation, permitting it to withstand high tensile stress.29 The mechanical properties of collagen include elasticity, which is the capability to recover normal length after elongation; viscoelasticity, which allows for a slow return to normal length and shape after deformation; and plasticity, which allows for permanent change or deformation.29 The physical properties include force-relaxation, which indicates the decrease in the amount of force needed to maintain a tissue at a set amount of displacement or deformation over time; the creep response, which is the ability of a tissue to deform over time while a constant load is imposed; and hysteresis, which is the amount of relaxation a tissue has undergone during deformation and displacement. If the mechanical and physical limitations of connective tissue are exceeded, injury results.29
Unlike tendon, muscle also has active contractile components that are the actin and myosin myofilaments. Collectively, the contractile and noncontractile elements determine the muscle’s capability of deforming and recovering from deformation.29
Both the contractile and noncontractile components appear to resist deformation when a muscle is stretched or lengthened. The percentage of their individual contribution to resisting deformation depends on the degree to which the muscle is stretched or deformed and on the velocity of deformation. The noncontractile elements are primarily resistant to the degree of lengthening, while the contractile elements limit high-velocity deformation. The greater the stretch, the more the noncontractile components contribute.29
Lengthening of a muscle via stretching allows for viscoelastic and plastic changes to occur in the collagen and elastin fibers. The viscoelastic changes that allow slow deformation with imperfect recovery are not permanent. However, plastic changes, although difficult to achieve, result in residual or permanent change in length due to deformation created by long periods of stretching.29
The greater the velocity of deformation, the greater the chance for exceeding that tissue’s capability to undergo viscoelastic and plastic change.29
EFFECTS OF STRETCHING ON THE KINETIC CHAIN
Joint hypomobility is one of the most frequently treated causes of pain. However, the etiology can usually be traced to faulty posture, muscular imbalances, and abnormal neuromuscular control.24 Once a particular joint has lost its normal arthrokinematics, the muscles around that joint attempt to minimize the stress at that involved segment. Certain muscles become tight and hypertonic to prevent additional joint translation. If one muscle becomes tight or changes its degree of activation, then synergists, stabilizers, and neutralizers have to compensate, leading to the formation of complex neuromusculoskeletal dysfunctions.
Muscle tightness and hypertonicity have a significant impact on neuromuscular control. Muscle tightness affects the normal length–tension relationships. When one muscle in a force-couple becomes tight or hypertonic, it alters the normal arthrokinematics of the involved joint. This affects the synergistic function of the entire kinetic chain, leading to abnormal joint stress, soft tissue dysfunction, neural compromise, and vascular/lymphatic stasis. These result in alterations in recruitment strategies and stabilization strength. Such compensations and adaptations affect neuromuscular efficiency throughout the kinetic chain. Decreased neuromuscular control alters the activation sequence or firing order of different muscles involved, and a specific movement is disturbed. Prime movers may be slow to activate, while synergists, stabilizers, and neutralizers substitute and become overactive. When this is the case, new joint stresses will be encountered.24 For example, if the psoas is tight or hyperactive, then the gluteus maximus will have decreased neural drive. If the gluteus maximus (prime mover during hip extension) has decreased neural drive, then synergists (hamstrings), stabilizers (erector spinae), and neutralizers (piriformis) substitute and become overactive (synergistic dominance). This creates abnormal joint stress and decreased neuromuscular control during functional movements.
Muscle tightness also causes reciprocal inhibition. Increased muscle spindle activity in a specific muscle will cause decreased neural drive to that muscle’s functional antagonist. This alters the normal force-couple activity, which, in turn, affects the normal arthrokinematics of the involved segment. For example, if a patient has tightness or hypertonicity in the psoas, then the functional antagonist (gluteus maximus) can be inhibited (decreased neural drive), causing decreased neuromuscular control. This, in turn, leads to synergistic dominance—the neuromuscular phenomenon that occurs when synergists compensate for a weak and/or inhibited muscle to maintain force production capabilities.24 This process alters the normal force-couple relationships, which, in turn, creates a chain reaction.
IMPORTANCE OF INCREASING MUSCLE TEMPERATURE PRIOR TO STRETCHING
To most effectively stretch a muscle during a program of rehabilitation, intramuscular temperature should be increased prior to stretching.55 Increasing the temperature has a positive effect on the ability of the collagen and elastin components within the musculotendinous unit to deform. Also, the capability of the Golgi tendon organs to reflexively relax the muscle through autogenic inhibition is enhanced when the muscle is heated. It appears that the optimal temperature of muscle to achieve these beneficial effects is 39°C (103°F). This increase in intramuscular temperature can be achieved either through low-intensity warm-up–type exercise or through the use of various therapeutic modalities.15 It is recommended that exercise be used as the primary means for increasing intramuscular temperature.
The use of cold prior to stretching also has been recommended.15 Cold appears to be most useful when there is some muscle guarding associated with delayed-onset muscle soreness.14 However, it has been demonstrated that cryotherapy induces an increase in muscle stiffness and, thus, muscle mechanical properties may lower the amount of stretch that the muscle tissue is able to sustain without subsequent injury.67
Clinical Decision-Making Exercise 8-3
Following anterior cruciate ligament surgery, one of the first goals of rehabilitation is to regain full ROM. How can improvements in knee extension be quantified for day-to-day record keeping?
Stretching techniques for improving flexibility have evolved over the years.4 The oldest technique for stretching is ballistic stretching, which makes use of repetitive bouncing motions. A second technique, known as static stretching, involves stretching a muscle to the point of discomfort and then holding it at that point for an extended time. This technique has been used for many years. Another group of stretching techniques, known collectively as proprioceptive neuromuscular facilitation (PNF) techniques, involving alternating contractions and stretches, also has been recommended.45,89 Although dynamic stretching is the newest of the 4 stretching techniques, in the athletic population, it has become the stretching technique of choice. Dynamic stretching uses controlled functional movements to stretch muscles. Most recently, emphasis has been on the contribution of stretching myofascial tissue, as well as stretching tight neural tissue, in enhancing the ability of the neuromuscular system to efficiently control movement through a full ROM. Researchers have had considerable discussion about which of these techniques is most effective for improving ROM, and no clear-cut consensus currently exists.8,11,56,89
Agonist vs Antagonist Muscles
Before discussing the different stretching techniques, it is essential to define the terms agonist muscle and antagonist muscle. Most joints in the body are capable of more than one movement. The knee joint, for example, is capable of flexion and extension. Contraction of the quadriceps group of muscles on the front of the thigh causes knee extension, whereas contraction of the hamstring muscles on the back of the thigh produces knee flexion.
To achieve knee extension, the quadriceps group contracts while the hamstring muscles relax and stretch. Muscles that work in concert with one another in this manner are called synergistic muscle groups.37 The muscle that contracts to produce a movement (in this case, the quadriceps) is referred to as the agonist muscle. The muscle being stretched in response to contraction of the agonist muscle is called the antagonist muscle.37 In this example of knee extension, the antagonist muscle would be the hamstring group. Some degree of balance in strength must exist between agonist and antagonist muscle groups. This balance is necessary for normal, smooth, coordinated movement, as well as for reducing the likelihood of muscle strain caused by muscular imbalance. Comprehension of this synergistic muscle action is essential to understanding the various techniques of stretching.
Over the years, many fitness experts have questioned the safety of the ballistic stretching technique. Their concerns have been primarily based on the idea that ballistic stretching creates somewhat uncontrolled forces within the muscle that can exceed the extensibility limits of the muscle fiber, thus producing small microtears within the musculotendinous unit.35,74,112 Certainly, this might be true in sedentary individuals or perhaps in individuals who have sustained muscle injuries.48
Successive, forceful contractions of the agonist muscle that result in stretching of the antagonist muscle may cause muscle soreness. For example, forcefully kicking a soccer ball 50 times may result in muscle soreness of the hamstrings (antagonist muscle) as a result of eccentric contraction of the hamstrings to control the dynamic movement of the quadriceps (agonist muscle). Stretching that is controlled usually does not cause muscle soreness.9 This is the difference between ballistic stretching and dynamic stretching. The argument has been that dynamic stretching exercises are more closely related to the types of activities that athletes engage in and should be considered more functional.9,17,50 Thus, dynamic stretching exercises are routinely recommended for athletes prior to beginning an activity (Figure 8-4).
A progressive velocity flexibility program has been proposed that takes the patient through a series of stretching exercises where the velocity of the stretch and the range of lengthening are progressively controlled.8 The stretching exercises progress from slow static stretching to slow, short, end-range stretching, to slow, full-range stretching, to fast, short, end-range stretching, and to fast, full-range stretching.8 This program allows the patient to control both the range and the speed with no assistance from an athletic trainer.
Clinical Decision-Making Exercise 8-4
During a preseason screening, you observe that a rower has only 120 degrees of knee flexion. What are some of the things that might be limiting this motion?
The static stretching technique is another extremely effective and widely used technique of stretching.8 This technique involves stretching a given antagonist muscle passively by placing it in a maximal position of stretch and holding it there for an extended time. Recommendations for the optimal time for holding this stretched position vary, ranging from as short as 3 seconds to as long as 60 seconds.50 Several studies indicate that holding a stretch for 15 to 30 seconds is the most effective for increasing muscle flexibility.8,46,58,62 Stretches lasting longer than 30 seconds seem to be uncomfortable. A static stretch of each muscle should be repeated 3 or 4 times. A static stretch can be accomplished by using a contraction of the agonist muscle to place the antagonist muscle in a position of stretch. A passive static stretch requires the use of body weight, assistance from an athletic trainer or partner, or use of a T-bar, primarily for stretching the upper extremity.
Proprioceptive Neuromuscular Facilitation Stretching
PNF techniques were first used by physical therapists for treating patients who had various neuromuscular disorders.32,45 More recently, PNF stretching exercises have increasingly been used as a stretching technique for improving flexibility.36,45,47,48,52,59,81,89
There are 3 different PNF techniques used for stretching: contract-relax, hold-relax, and slow reversal-hold-relax.45 All 3 techniques involve some combination of alternating isometric or isotonic contractions and relaxation of both agonist and antagonist muscles (eg, a 10-second pushing phase followed by a 10-second relaxing phase).
Contract-relax is a stretching technique that moves the body part passively into the agonist pattern. The patient is instructed to push by contracting the antagonist (the muscle that will be stretched) isotonically against the resistance of the athletic trainer. The patient then relaxes the antagonist while the athletic trainer moves the part passively through as much range as possible to the point where limitation is again felt. This contract-relax technique is beneficial when ROM is limited by muscle tightness.
Hold-relax is very similar to the contract-relax technique.1 It begins with an isometric contraction of the antagonist (the muscle that will be stretched) against resistance, combined with light pressure from the therapist to produce maximal stretch of the antagonist. This technique is appropriate when there is muscle tension on one side of a joint and may be used with either the agonist or the antagonist. This technique is also referred to as a muscle energy technique and will be discussed in Chapter 12.19
Slow reversal-hold-relax, also occasionally referred to as the contract-relax-agonist-contraction technique, begins with an isotonic contraction of the agonist, which often limits ROM in the agonist pattern, followed by an isometric contraction of the antagonist (the muscle that will be stretched) during the push phase. During the relax phase, the antagonists are relaxed while the agonists are contracting, causing movement in the direction of the agonist pattern and thus stretching the antagonist. This technique, like the contract-relax and hold-relax, is useful for increasing ROM when the primary limiting factor is the antagonistic muscle group. PNF stretching techniques can be used to stretch any muscle in the body.11,25,36
PNF stretching techniques are perhaps best performed with a partner, although they may also be done using a wall as resistance.
Comparing Stretching Techniques
Although all 4 stretching techniques discussed to this point have been demonstrated to effectively improve flexibility, there is still considerable debate as to which technique produces the greatest increases in range of movement.8,17,48,50,72 The ballistic technique is often used by individuals involved in dynamic activity, despite its potential for causing muscle soreness in the sedentary individual. In physically active individuals, it is unlikely that ballistic stretching will result in muscle soreness.
Static stretching is perhaps the most widely used technique.8 It is a simple technique and does not require a partner. A fully nonrestricted ROM can be attained through static stretching over time.
Much research has been done comparing ballistic and static stretching techniques for the improvement of flexibility.12,48 Static and ballistic stretching appear to be equally effective in increasing flexibility, and there is no significant difference between the two.48 However, much of the literature states that, with static stretching, there is less danger of exceeding the extensibility limits of the involved joints because the stretch is more controlled. Most of the literature indicates that ballistic stretching is apt to cause muscular soreness, especially in sedentary individuals, whereas static stretching generally does not cause soreness and is commonly used in injury rehabilitation of sore or strained muscles.48,56,96 Static stretching is likely a much safer stretching technique, especially for sedentary individuals. However, because many physical activities involve dynamic movement, stretching in a warm-up should begin with static stretching followed by dynamic stretching, which more closely resembles the dynamic activity.55 Several studies have shown that dynamic stretching is effective for improving ROM,9,42 but there does not appear to be any difference between static and dynamic stretching for preventing injury.95 Dynamic stretching in the cool-down period has been recommended for increasing joint ROM as well as reducing muscle injuries with no significant effects on subsequent athletic performance.8 PNF stretching techniques are capable of producing dramatic increases in ROM during one stretching session.92 Studies comparing static and PNF stretching suggest that PNF stretching is capable of producing greater improvement in flexibility over an extended training period.33,59 The major disadvantage of PNF stretching is that a partner is usually required to assist with the stretch, although stretching with an athletic trainer or partner can have some motivational advantages.