Normal mobility is necessary for efficient movement. The terms range of motion (ROM), flexibility, and accessory joint motion are often listed as components of mobility. ROM refers to the distance and direction a joint can move. The direction in which a joint moves is described using terms like flexion, extension, abduction, adduction, internal rotation, and external rotation. Each specific joint has a normal ROM that is expressed in degrees. Within the field of physical therapy, goniometry is commonly used to measure the total amount of available motion at a specific joint. ROM of a joint may be limited by the shape of the articulating surfaces, adaptive shortening of the muscles, and capsular and ligamentous structures surrounding that joint. Under normal circumstances, it is the muscles that move the joints. The full range of extensibility of a muscle is called its functional excursion. The amount of excursion depends on the arrangement of the muscle fibers and whether the muscle is a one-joint or a multi-joint muscle (see later). Flexibility refers to the passive extensibility of connective tissue that provides the ability for a joint or series of joints to move through a full, nonrestricted, injury-free, and pain-free ROM. Flexibility is also dependent upon pain levels and neuromuscular control. Magnusson1 identified three factors that might contribute to improving flexibility: passive tissue properties, segmental reflex excitability, and tolerance of discomfort. When an injury occurs, there is almost always some associated loss of the ability to move normally due to the pain, swelling, muscle guarding, or spasm. The subsequent inactivity results in a shortening of connective tissue and muscle, loss of neuromuscular control, or a combination of these factors.2 Accessory joint motion. Accessory joint motion is the amount of the arthrokinematic glide that occurs at the joint surfaces, termed joint play (see Chapter 1). A number of anatomic factors can limit the ability of a joint to move through a full, unrestricted ROM, including the integrity of the joint surfaces, increasing age, and the mobility and pliability of the soft tissues that surround a joint. Before attempting to improve the arthrokinematic glide at a particular joint, the clinician must always consider the status of the neighboring joints in terms of their hypermobility or hypomobility (see Chapter 2). Joint mobilization is a technique that preserves or increases arthrokinematic motion. Techniques to enhance joint motion are described in Chapter 10. A decrease in accessory joint motion, ROM and/or in the flexibility of one joint can affect the mobility of the kinetic chain. For example, a decreased ROM or flexibility in the shoulder can impact the mobility of the entire arm. In order to provide treatment for a loss of mobility, the clinician must make the determination as to the specific cause, that is, loss of joint motion, ROM, or decreased flexibility. For example, is the specific cause due to joint effusion, adaptive shortening of connective tissue structures, a change in bony architecture, or malalignment of the articular surfaces? Attempting to perform ROM and flexibility techniques in the absence of normal arthrokinematic motion at the joint surface will not result in an improvement in the impaired mobility, but may instead increase the patient’s symptoms.
Normal mobility is necessary for efficient movement. The terms range of motion (ROM), flexibility, and accessory joint motion are often listed as components of mobility.
ROM refers to the distance and direction a joint can move. The direction in which a joint moves is described using terms like flexion, extension, abduction, adduction, internal rotation, and external rotation. Each specific joint has a normal ROM that is expressed in degrees. Within the field of physical therapy, goniometry is commonly used to measure the total amount of available motion at a specific joint. ROM of a joint may be limited by the shape of the articulating surfaces, adaptive shortening of the muscles, and capsular and ligamentous structures surrounding that joint. Under normal circumstances, it is the muscles that move the joints. The full range of extensibility of a muscle is called its functional excursion. The amount of excursion depends on the arrangement of the muscle fibers and whether the muscle is a one-joint or a multi-joint muscle (see later).
Flexibility refers to the passive extensibility of connective tissue that provides the ability for a joint or series of joints to move through a full, nonrestricted, injury-free, and pain-free ROM. Flexibility is also dependent upon pain levels and neuromuscular control. Magnusson1 identified three factors that might contribute to improving flexibility: passive tissue properties, segmental reflex excitability, and tolerance of discomfort. When an injury occurs, there is almost always some associated loss of the ability to move normally due to the pain, swelling, muscle guarding, or spasm. The subsequent inactivity results in a shortening of connective tissue and muscle, loss of neuromuscular control, or a combination of these factors.2
Accessory joint motion. Accessory joint motion is the amount of the arthrokinematic glide that occurs at the joint surfaces, termed joint play (see Chapter 1). A number of anatomic factors can limit the ability of a joint to move through a full, unrestricted ROM, including the integrity of the joint surfaces, increasing age, and the mobility and pliability of the soft tissues that surround a joint. Before attempting to improve the arthrokinematic glide at a particular joint, the clinician must always consider the status of the neighboring joints in terms of their hypermobility or hypomobility (see Chapter 2). Joint mobilization is a technique that preserves or increases arthrokinematic motion. Techniques to enhance joint motion are described in Chapter 10.
A decrease in accessory joint motion, ROM and/or in the flexibility of one joint can affect the mobility of the kinetic chain. For example, a decreased ROM or flexibility in the shoulder can impact the mobility of the entire arm. In order to provide treatment for a loss of mobility, the clinician must make the determination as to the specific cause, that is, loss of joint motion, ROM, or decreased flexibility. For example, is the specific cause due to joint effusion, adaptive shortening of connective tissue structures, a change in bony architecture, or malalignment of the articular surfaces? Attempting to perform ROM and flexibility techniques in the absence of normal arthrokinematic motion at the joint surface will not result in an improvement in the impaired mobility, but may instead increase the patient’s symptoms.
Flexibility is the ability to move a single joint or series of joints through an unrestricted and pain-free ROM. Flexibility depends on sound joint arthrokinematics, full ROM (normal osteokinematics), and soft-tissue extensibility. It also depends on the mechanical and neurophysiological properties of the tissues involved and how those tissues react to physical loading (see Chapters 1 and 2). Stretching techniques are designed to improve the extensibility of both contractile and noncontractile tissues, including neural tissues (see Chapter 11). Indications for stretching include those scenarios when ROM is limited due to a loss of extensibility in the soft tissues because of scar tissue formation, adhesions, and contractures that have resulted in functional limitations or participation restrictions. Contraindications for stretching include a bony end feel, an incomplete bony union, recent fracture, acute inflammatory or infectious process, sharp pain with joint movement, or in the presence of hypermobility.
When referring to flexibility, two types are recognized, static and dynamic.
Static flexibility. Static flexibility, also referred to as passive mobility, is defined as the range or motion available to a joint or series of joints.7,8 Increased static flexibility should not be confused with joint hypermobility, or laxity, which is a function of the joint capsule and ligaments. Decreased static flexibility indicates a loss of motion. The end-feel encountered may help the clinician differentiate the cause among adaptive shortening of the muscle (muscle stretch), a tight joint capsule (capsular), and an arthritic joint (hard). Static flexibility can be measured by a number of tests, such as the toe touch and the sit and reach, both of which have been found to be valid and reliable.9,10
Dynamic flexibility. Dynamic flexibility also referred to as active mobility, refers to the ease of movement within the obtainable ROM. Dynamic flexibility is measured actively. The important measurement in dynamic flexibility is stiffness, a mechanical term defined as the resistance of a structure to deformation.11,12 An increase in ROM around a joint does not necessarily equate to a decrease in the passive stiffness of a muscle.13–15 However, strength training, immobilization, and aging have been shown to increase stiffness.16–19 The converse of stiffness is pliability. When soft tissue demonstrates a decrease in pliability, it has usually undergone an adaptive shortening, or an increase in tone, termed hypertonus. There is growing research to suggest that the limiting factors in preventing increases in ROM are not only the connective tissues but are also the result of neurophysiological phenomena controlled by the higher centers of the CNS.20
In addition to those already mentioned, a number of other factors influence connective tissue deformation:
Sensory receptors. Two sensory receptors that monitor muscle activity, the muscle spindle, and Golgi tendon organs (GTOs) (see Chapter 3), play an important role when attempting to increase flexibility through stretching. These two receptors can activate both spinal reflexes and long-loop pathways involving supraspinal centers. When a muscle is stretched, both the muscle spindles and the GTOs immediately begin sending a stream of sensory impulses to the spinal cord. Initially, impulses coming from the muscle spindles notify the CNS 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.2 The GTOs respond to the change in length and the increasing tension by firing off sensory impulses of their own to the spinal cord and, if the stretch of the muscle continues for an extended period of time (at least 6 seconds), impulses from the GTOs begin to override muscle spindle impulses and cause a reflex relaxation of the antagonist muscle (autogenic inhibition).2
Tissue temperature. At temperatures above 37°C (98.6°F), the cross-links between collagen fibrils are broken more easily and more rapidly, with the most profound changes occurring between 40 and 45°C (104–113°F).21,22 A number of key points must be remembered by the clinician in order to effectively manipulate temperature:23
The amount of force required to attain/maintain a desired deformation decreases as temperature increases.
The time required to deform collagen to the point of failure is inversely related to temperature.
The higher the temperature, the greater the load collagen is able to tolerate before failure.
The higher the temperature, the greater the amount of deformation possible before failure.
It is important to make a distinction between stretching and warm-up as the two are not synonymous but are often confused by the layman. While stretching places neuromusculotendinous units and their fascia under tension, a warm-up requires the performance of an activity that raises total body and muscle temperatures to prepare the body for exercise.24 Research has shown that warm-up prior to stretching results in significant changes in joint ROM.25 Anecdotally, it would make sense not to perform stretching at the beginning of the warm-up routine because the tissue temperatures are too low for optimal muscle–tendon function, and are less compliant and less prepared for activity. Some advocate stretching after an exercise session, citing that the increased musculotendinous extensibility leads to the potential for improved joint flexibility.26 In one study, static stretching was done before, after, and both before and after each workout. All produced significant increases in ROM.27
The amount of force used. Viscoelastic changes are not permanent, whereas plasticity changes, which are more difficult to achieve, result in a residual or permanent change in length. The key factor for any change in connective tissue length is the deforming force, in particular, the magnitude and velocity applied. The application of low-load, long duration forces is recommended, although a muscle may require a greater stretching force initially, possibly to break up adhesions or cross-linkages, and to allow for viscoelastic and plastic changes to occur in the collagen and elastin fibers.28
The direction of the stretch. To stretch a muscle appropriately, the stretch must be applied parallel to the muscle fibers. The orientation of the fibers can be determined by palpation. Typically, in the extremities, the muscle fibers run parallel to the bone.
The duration and frequency of the stretch. The duration refers to how long the clinician applies the stretching force. The frequency refers to the number of times or repetitions the stretch is performed. There continues to remain a lack of agreement on the ideal combination of either the duration of a single stretch or the number of repetitions of a stretch in a single session that is necessary to achieve the best results. Researchers have reported that techniques utilizing cyclic and sustained stretching for 15 minutes on 5 consecutive days increased hamstring muscle length and that a significant percentage of the increased length was retained 1 week posttreatment.29 Other researchers have reported that after using four consecutive knee flexor static stretches of 30 seconds, the new knee ROM was maintained for 3 minutes but had returned to prestretch levels after 6 minutes.30 A similar study using a sequence of five modified hold–relax stretches reported producing significantly increased hamstring flexibility that lasted 6 minutes after the stretching protocol ended.31 Frequent stretching ensures that the lengthening is maintained before the muscle has the opportunity to recoil to its shortened state.32 Frequency of stretching needs to occur at a minimum of two times per week.33,34 In contrast, it has been determined that 80% of the length changes occur in the first four stretches of 30 seconds each.26 It is important for the clinician to remember that any gains in flexibility and ROM achieved from a stretching program are only temporary.35 Thus, it is important to integrate functional activities such as reaching, bending, squatting, twisting, and pushing into the patient’s exercise program that utilize the regained range on a regular basis.
The speed of the stretch. Two common stretching techniques, static and ballistic, use different speed parameters. The static stretch allows for a steady speed to allow lengthening of the entire myotendinous unit, and a hold or delay at the end of the available motion.36 The ballistic stretch uses various speeds of singular or repetitive bouncing at the end of motion to stretch a particular muscle. The muscle is stretched by the momentum created from the bouncing movements supplying the tensile force used for the stretch.26 The patient quickly relaxes the muscle when reaching the end of ROM. This is performed in a cyclical bouncing motion and repeated several times, thus engaging a neurological component called active resistance—the contraction of muscles that resist elongation in the form of muscle reflex activity.26,37 In comparisons of the ballistic and static methods, two studies38,39 have found that both produce similar improvements in flexibility. However, the ballistic method appears to cause more residual muscle soreness or muscle strain, than those techniques that incorporate relaxation into the technique and are therefore not appropriate for elderly or sedentary individuals.39,40 Instead, the application of any stretch should be applied and released gradually to minimize muscle activation and injury to tissues.
Positioning and stabilization of the structure being stretched. As described in Chapter 10, when performing any manual technique, correct positioning of the patient is essential both to help the patient relax and to ensure safe body mechanics from the clinician. For example, when stretching the hip musculature, it is important to protect the lumbar spine by maintaining it in a neutral position. When patients feel relaxed, their muscle activity is decreased, reducing the amount of resistance encountered during the technique. Accurate hand placement is essential for efficient stabilization and for the accurate transmission of force. The clinician can stabilize either the proximal or distal attachment site of the muscle tendon unit being stretched, although it is more common to stabilize the proximal attachment and move the distal segment.
The type of stretch. The type of stretch refers to the method by which the stretch is imparted. Stretching can be applied manually or mechanically.
A variety of stretching techniques can be used to increase the extensibility of the soft tissues.
Static stretching involves the application of a steady force for a sustained period. The stretch should be performed at the point just shy of the pain, although some discomfort may be necessary to achieve results.28 Small loads applied for long periods produce greater residual lengthening than heavy loads applied for short periods.41 Restoration of the normal length of the muscles may be accomplished using the guidelines outlined in Table 13-1. Weighted traction or pulley systems may be used for this type of stretching. It is important for the patient to realize that the initial session of stretching may increase symptoms.42 However, this increase in symptoms should be temporary, lasting for a couple of hours, at most.32,43
Heat should be applied to increase intramuscular temperature prior to, and during, stretching.a–d This heat can be achieved with either through low-intensity warm-up exercise, or through the use of thermal modalities. The application of a cold pack following the stretch is used to take advantage of the thermal characteristics of connective tissue, by lowering its temperature and thereby theoretically prolonging the length changes—the elasticity of a muscle diminishes with cooling.a–d
Effective stretching, in the early phase, should be performed every hour, but with each session lasting only a few minutes.
With true muscle shortness, stronger resistance is used to activate the maximum number of motor units, followed by vigorous stretching of the muscle.
Stretching should be performed at least two times a week using:
Low force, avoiding pain
Rapid cooling of the muscle while it is maintained in the stretched position
aAssmussen E, Bonde-Peterson F. Storage of elastic energy in skeletal muscle in man. Acta Physiol Scand. 1974;91:385–392.
bBosco C, Komi PV. Potentiation of the mechanical behavior of the human skeletal muscle through prestretching. Acta Physiol Scand. 1979;106:467–472.
cCavagna GA, Saibene FP, Margaria R. Effect of negative work on the amount of positive work performed by an isolated muscle. J Appl Physiol. 1965;20:157–158.
dCavagna GA, Disman B, Margarai R. Positive work done by a previously stretched muscle. J Appl Physiol. 1968;24:21–32.
Dynamic stretching involves stretching by a muscular contraction to increase or decrease the joint angle where the muscle crosses, thereby elongating the musculotendinous unit as the end ROM is obtained26 Dynamic stretching is a specific warm-up using activity-specific movements to prepare the muscles by taking them through the movements used in a particular sport.26 Dynamic stretching does not incorporate end-range ballistic movements, as in ballistic stretching, but rather the use of controlled movements through a normal ROM.26
There is some debate as to whether the static or dynamic method is better to stretch a muscle. Static stretching is considered the gold standard in flexibility training.44 However, recent studies have found that static stretching is not an effective way to reduce injury rates,45,46 and may actually inhibit athletic performance.6 This is likely because the nature of static stretching is passive and does nothing to warm a muscle.47 More dynamic methods of stretching involve either a contraction of the antagonist muscle group, thus allowing the agonist to elongate naturally in a relaxed state, or eccentrically training a muscle through its full ROM.44 The latter method would appear to address the problem that most injuries occur during the eccentric phase of activity.45 A study by Nelson44 that compared the immediate effect of static stretching, eccentric training, and no stretching/training on hamstring flexibility in high school and college athletes (75 subjects) found the flexibility gains in the eccentric training group to be significantly greater than the static stretch group.
This type of stretching refers to the use of techniques that rely on the neurophysiological changes that occur in contractile tissues. The goal of these techniques is to reduce the sensory-motor feedback and thereby increase relaxation. Such techniques include proprioceptive neuromuscular facilitation (PNF) and muscle energy (see Chapter 10). The majority of studies have shown the PNF techniques to be the most effective for increasing ROM through muscle lengthening when compared to the static or slow sustained, and the ballistic or bounce techniques,48–58 although one study found it to be not necessarily better.59
The PNF techniques of contract–relax (CR), hold–relax (HR), an agonist contraction (AC), or a hold–relax–agonist contraction sequence (HR–AC) can be used to actively stretch the soft tissues:2
CR and HR. HR and CR stretching techniques begin as per the static stretching techniques in that the clinician supports the patient and brings a limb (and the targeted muscle to be stretched) to the end of ROM until gentle stretching is felt. At that point, the clinician asks the patient to provide a prestretch, end range, isometric contraction of the muscle being stretched for approximately 5 seconds after which the patient is asked to relax the muscle. The clinician then moves the limb passively into the new range until a limitation is again felt and repeats the procedure two to four times. The only difference between the HR technique and the CR technique is that in the former technique the prestretch isometric contraction occurs in all muscles of the diagonal pattern, whereas in the latter technique the rotators of the limb contract concentrically while all of the muscle groups of the diagonal pattern contracts isometrically during the prestretch phase of the procedure.60
AC. AC stretching uses the principle of reciprocal inhibition, and the term agonist refers to the muscles opposite the range limiting target muscle, which can be confusing. The clinician moves the limb to the position of gentle stretch and asks the patient for a contraction of the muscle opposite the muscle being stretched (the antagonist) for about 5 seconds, and for the patient to hold the end range position for another 5 seconds. For example, when stretching the hamstring muscles, a simultaneous contraction of the quadriceps muscles can facilitate the stretch of the hamstrings. The technique is repeated two to four times.
HR–AC. This technique, also referred to as the CR–AC or slow reversal HR technique, combines the HR and AC procedures. The clinician takes the limb to the point of gentle stretch and performs a CR sequence (i.e., resistance applied against the muscle being stretched). After contracting the muscle being stretched, the patient is asked to relax this muscle while contracting the opposing muscle group (antagonist), thus facilitating the stretch. For example, when stretching the hamstring muscles, the hamstrings are brought to a stretched position, the hamstrings are then contracted against resistance, and then relaxed, and then the quadriceps are contracted. Each contraction is held for approximately 5 seconds, and the technique is repeated two to four times.
Other techniques that can assist in lengthening of contractile tissue through relaxation include the following:
The application of heat, which increases the extensibility of the shortened tissues, will allow the muscles to relax in length and more easily, reducing the discomfort of stretching. Heat without stretching has little or no effect on long-term improvement in muscle flexibility, whereas the combination of heat and stretching produces greater long-term gains in tissue length than stretching alone.
Massage and other soft-tissue techniques (see Chapter 10), which increase local circulation to the muscle and reduce muscle spasm and stiffness.
Biofeedback, which teaches the patient to reduce the amount of tension in a muscle.
Following each stretching session, the stretched tissues must be allowed to cool in a lengthened position. This can be facilitated by using cold packs. Once gains in motion have been achieved, it is important for the patient to gain neuromuscular control of the agonists in the new range. This can be accomplished with low load resistance exercises throughout the newly acquired range. For example, after having stretched the hamstrings to reduce a knee flexion contracture, the patient is encouraged to activate the quadriceps in the new range. Once the ROM approaches what is normal for the patient, the muscles that were shortened and then stretched must also be strengthened.
Range of Motion
Any given muscle, crossing a single joint, is normally capable of shortening sufficiently to permit a full ROM at that joint. The functional excursion of a one-joint muscle is limited by the ROM at the joint it crosses. For example, the hip abductors are limited by the range available at the hip joint. For two-joint or multi-joint muscles, the functional excursion goes beyond the limits of any one joint that they cross. For example, the sartorius muscle can flex, abduct, and externally rotate the hip as well as being able to flex the knee. The absolute amount by which any muscle can shorten depends on:
- The length of, and arrangement of, the fibers
- Structure and design of the joint.
- The number of joints traversed.
- Resistance of antagonist muscle or muscles
- The presence of any load that opposes the muscle.
If a muscle that crosses two or more joints produces simultaneous movement at all of the joints that it crosses, it soon reaches a length at which it can no longer generate a functional amount of tension. This is referred to as active insufficiency (e.g., attempting to achieve maximal hip flexion with the knee fully extended). In contrast, when the full ROM at any joint, or joints, that the muscle crosses is limited by the muscle’s own length, it is referred to as passive insufficiency (e.g., attempting to fully extend the elbow, while simultaneously pronating the forearm and extending the shoulder places the brachialis muscle in a position of passive insufficiency).
From a rehabilitation viewpoint, to maintain or improve the amount of ROM at a joint or kinematic chain, each joint must be moved through its available ROM at regular intervals. Continuous immobilization of skeletal muscle tissues can cause some undesirable consequences, including weakness or atrophy of the muscles.61 Muscle atrophy is an imbalance between protein synthesis and degradation. After modest trauma, there is a decrease in whole-body protein synthesis62 rather than increased breakdown. With more severe trauma, major surgery, or multiple organ failures, both synthesis and degradation increase, the latter being more enhanced.63,64
When referring to ROM techniques used in rehabilitation, three major movements are recognized:2
Passive range of motion (PROM). PROM refers to the degree to which a joint can be passively moved to the endpoint in the ROM. PROM exercises are performed by the clinician, family member, caregiver without any muscular activation by the patient. In some cases, the patient is able to perform PROM on one part of their body using another part (using the left arm to flex the right elbow). In addition, pulleys, continuous passive motion (CPM) devices, or various household objects, such as a counter or chair, can be used to assist in the performance of PROM. PROM is indicated when the patient’s own muscle force is inadequate to produce sufficient motion at a joint, when active contraction of the muscle would be harmful, or as a means of educating a patient about a particular movement. PROM is contraindicated during any stage of tissue healing in which motion could prevent or inhibit tissue repair, in the presence of muscle guarding, or in the presence of increasing pain. Factors that can limit PROM about a joint include the joint capsule, periarticular connective tissue, adaptive shortening of the musculotendinous unit, bone on bone approximation, loose bodies, pain, and scarring of the overlying skin. If overpressure is applied at the end of the available PROM, a stretching force is imparted, and the clinician can determine the end feel. Patient handling and positioning are critical to allow the patient to relax during treatment by decreasing apprehension. For example, adequate stabilization and the use of a smooth and steady pace. Although PROM is important to enhance vascular dynamic and synovial diffusion, maintain joint motion, ROM, and flexibility, it does not prevent muscle atrophy, increase strength or endurance, or assist circulation to the same extent that active, voluntary muscle contraction does.