Exercise in rehabilitation



Exercise in rehabilitation


Duncan Mason



Introduction


Exercise is one of the cornerstones of rehabilitation, widely used by many types of health professionals to manage an even wider range of medical conditions. It could be defined as ‘using voluntary muscle activity produced by the integration of higher centres, cardiovascular, pulmonary and neuro-musculoskeletal components to rehabilitate these systems.’ The aims and reported effects of exercise are also numerous. Throughout this chapter we will see an evidence-based overview and rationale behind some of the more commonly encountered types of exercise.


Exercise is frequently used to enhance the recovery rate of all components of the movement control system, namely the musculoskeletal and central nervous system (CNS), to increase the range of motion, increase muscle strength, develop a higher level of proprioceptive feedback and develop an overall improvement in sensori-motor control. However, the list of benefits does not end here; exercise is used in rehabilitation of the cardiovascular and pulmonary systems (Rees et al. 2004), which are required to provide the raw fuels for the physiological processes involved in muscle contraction. Also, exercise has been shown to have beneficial effects on the higher centres, reducing the effects of some mental illnesses (Galper et al. 2006). This explains its invaluable use in this area of healthcare.


Exercise can be delivered in a variety of ways: in the clinical setting or by teaching home exercises; as an individual or in a group setting; on land or in water. All approaches need to be considered to select the most appropriate for the individual requirements of each patient. The way in which the exercise is taught or delivered to an individual is also important in the ultimate success of this modality. This, too, will be discussed in the course of this chapter.


To summarise, exercise is a widely used treatment modality, which has been shown to be effective in the management of many medical conditions when appropriately selected and applied.



Glossary of terms




Delayed-onset muscle soreness (DOMS) A dull, or frequently more severe, aching sensation that follows unaccustomed muscular exertion. It is often associated with athletic activity. Eccentric exercise activity is said to provoke symptoms more readily owing to microtrauma – minor damage as a result of strenuous exercise. Soreness usually peaks 24–48 hours after exercise (Cheung et al. 2003)


Kinetic chain exercise Closed kinetic chain is an exercise performed where the distal segment of the limb is fixed (e.g. knee squats with feet on the floor). Open kinetic chain is an exercise where the distal segment of the limb is able to move freely in space (e.g. a biceps curl with a free weight)


Muscle contracture The adaptive shortening of muscle or other soft tissues that cross a joint, which results in limitation of range of motion (Kisner and Colby 1996)


Muscle spasm A persistent muscle contraction that cannot be voluntarily released


Muscle spasticity A condition associated with hyperactivity of the stretch reflexes and tendon stretch receptors, due to loss of inhibitory influences on the alpha-motor neurones on the motor unit (Mense et al. 2001)


Muscle stiffness (also sometimes referred to as muscle tension) An increase in background resistance to passive movement of soft tissues over a joint. This is often necessary to enhance function and is not necessarily an undesirable occurrence


Muscle tone The resting activity level or tension of a muscle, clinically determined as resistance to passive movement or to deformation


Myalgia Pain felt within a muscle


Proprioception The specialised variation of the sensory modality of touch that encompasses the sensation of joint movement (kinaesthesia) and joint position (joint position sense) (Lephart et al. 1997)


Stretching Any therapeutic manoeuvre designed to lengthen pathologically shortened soft-tissue structures and thereby increase range of motion (Kisner and Colby 1996).



Strengthening exercises


Introduction


Strengthening exercises are aimed at increasing the torque- producing capacity or endurance of a specific muscle or muscle group.


Adequate muscle strength is necessary to perform many activities of daily living whether it is to achieve self-care, occupational tasks or elite athletic performance. As a result of many pathologies muscle strength can be lost, whether directly caused by a trauma resulting in a disruption in the motor control mechanism or indirectly, for example as a result of pain inhibition or disuse atrophy. Pathological disruption to the nerve supply will also directly affect motor unit recruitment and therefore strength.


An evaluation of muscle strength is usually performed as part of a patient’s objective examination. This should assist the therapist’s clinical reasoning and enable them to rationalise an appropriate point to start strengthening rehabilitation from.


As a strengthening exercise programme is undertaken physiological changes occur within the muscle to increase its capacity to produce torque and sustain muscle contractions. This allows exercises to be progressed, in turn, to further overload and strengthen the muscle. Overload is an important component in an effective strengthening programme.


Therapists commonly employ several types of strengthening exercise



These will be discussed in further detail in the remainder of this section and will be used depending on the strength requirements of the individual.


Other factors such as the number of repetitions, how often they are performed, i.e. number of sets, frequency per day and the load applied are also important factors dependent on the intended outcomes.



Measurement of muscle strength



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It is important for a physiotherapist to measure muscle strength objectively when assessing an individual, to obtain a baseline level from which future improvements (or lack of them) can be gauged. This allows the therapist to devise an individual exercise plan and to evaluate the effectiveness of a prescribed exercise regimen.



Muscle strength can be evaluated in a number of ways: manually, functionally or mechanically.



The Oxford scale


The Oxford scale has been devised to manually assess muscle strength and is widely used by physiotherapists. According to the Oxford scale, muscle strength is graded 0 to 5. Table 13.1 summarises the grades.



There are limitations to the usefulness of the Oxford scale. These include:



Owing to these shortcomings, modified versions of the Oxford scale are commonly seen in clinical practice.




Isokinetic assessment


Isokinetic assessment has been used with increasing frequency since its inception in the 1970s. It involves the use of computerised evaluation of movement when exercising at a preset angular velocity on the isokinetic equipment (Figure 13.1).


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Figure 13.1 A typical isokinetic machine.

This means that the subject can push as hard or as little as desired and the machine will move only at the preset velocity. It is therefore the resistance provided by the machine that varies.


The use of isokinetics has functional relevance as it can evaluate both eccentric and concentric activity through range.



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Isokinetic machines are used for treatment, as well as assessment. They produce objective, reproducible and quantifiable data, and therefore have obvious advantages over other methods used in evaluating strength in the progression and monitoring of rehabilitation of strength deficits.




Drawbacks

The drawbacks of isokinetics relate to its function, as natural human movements rarely occur at fixed velocities. Also, the machine operates on a fixed axis of movement, which does not replicate the instantaneous axis of movement found in most normal joints. The equipment can also be time-consuming to set up and not all practitioners will have access to it.


Additional limitations have been acknowledged by Lieber (1992). These include the time required to recruit muscle fibres (50–200 ms), making this period of data obtained unusable. Another drawback is the limb striking the testing bar at the end of the movement, although some isokinetic units employ a damping mechanism to prevent this.



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While isokinetics can give the practitioner a good idea of any underlying deficiencies in the musculoskeletal system, there is no single tool to evaluate strength that is both totally functional and quantifiable.



Strength training


Benefits


Strength training can include free active exercise or resistance training, when the body must overcome this resistance to produce the movement. This may be simply by use of body weight or free weights, or by the use of other equipment such as exercise machines in a gymnasium. Resistance training can also be used to train submaximal and endurance work. All aspects of resistance training can be incorporated into various rehabilitation programmes. Some of the reported physiological benefits of resistance training are:



In order for a muscle or muscle group to develop sufficient strength gains it must be loaded progressively, otherwise strength improvements will be limited. This factor can often be overlooked when rehabilitating an individual and failure to progress exercise may result in a lack of improvement on the part of the patient.


Initial improvement in strength, when measured objectively, may be rapid without noticeable changes in physical characteristics. This is a result of enhanced neuromuscular coordination and utilisation of previously redundant motor units. More motor units are recruited within a given muscle and a stronger contraction of the muscle is therefore produced. This neural adaptation occurs before other physical and physiological changes that result from resistance training. It can be said, therefore, that there are two mechanisms that we aim to employ when applying strengthening exercises: firstly, the physiological adaptations occurring in the muscles, which take 6–8 weeks; and, secondly, the neural adaptations to facilitate more motor units within a muscle, which happens a lot sooner.



Further study


To gain deeper knowledge on the physiological processes involved in producing muscle contraction and the adaptations that occur, it is necessary to study your recommended physiology text. Study the sliding filament theory and formation of actin and myosin cross bridges.



Free active exercise


These strengthening exercises are performed when the only external resistance that is to be overcome is the resistance provided by the weight of the body part. These exercises are used when the individual is at grade two or three, or below, on the Oxford scale for the targeted muscle group. Certain strategies are employed when dealing with an individual with this level of disability. Exercising the muscle in its middle range is the most effective part of the range for facilitating muscle activity, followed by inner range and then outer range. In middle range there is optimum length for formation of actin and myosin cross bridges; in outer range there is less capacity than inner range, although having more overlap does not allow optimal cross bridge formation. The use of overflow can also facilitate muscle activity, for instance when applying a force at another muscle in the region which normally works functionally with the targeted muscle or by working the corresponding muscle on the other side of the body.


Muscle contractions can also be enhanced by use of afferent input to the CNS, touching the corresponding dermatome (area of skin sharing the same nerve root innervation). Vocal encouragement, visual feedback and the use of biofeedback units, such as electromyography, are all useful in facilitating activity in redundant motor units. The type of muscle contraction used can also have a bearing on the effectiveness of the exercise.



Muscle contractions

Muscles can contract in three different ways: concentrically, eccentrically and isometrically. The characteristics of these different types of contractions are summarised in Table 13.2.




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Sometimes the terminology isotonic shortening and isotonic lengthening may be seen instead of concentric and eccentric contraction. These terms are best avoided as they imply one contraction is an opposite of the other, whereas, physiologically, their characteristics vary greatly.


Individual muscles often exhibit more than one type of contraction at a time. Consider the muscle work occurring in the hamstring muscles in Figure 13.2.


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Figure 13.2 Concurrent dual contraction during a squat.

The proximal part of the muscle is lengthening (controlling hip flexion) and the distal part is shortening, controlling tibial movement.


The features of eccentric exercise when compared with concentric exercise are, on the positive side, that it is mechanically more efficient and metabolically more efficient, but, on the negative side, it is less resistant to fatigue and may result in DOMS micro-trauma inflammation between sarcomeres. See Table 13.3 for further examples of eccentric activity.



DOMS is a dull aching sensation that follows unaccustomed muscular exertion. It is a key characteristic occurring following eccentric muscle activity. DOMS should be differentiated from other types of muscle soreness that occur during, or soon after, exercise owing to metabolic factors, such as the build up of lactate.


DOMS is typically felt most acutely 48 hours after eccentric exercise has been completed (Howell et al. 1993; Rodenberg et al. 1993; Leger and Milner 2001). This commonly occurs in certain muscles of individuals undertaking a particular activity infrequently that has quite a high eccentric component. Examples include fell running (quadriceps in the downhill component) or playing squash (gluteus maximus when reaching for a low shot).


DOMS is effectively the occurrence of local micro-trauma within the muscle. A key site for this inflammation is between adjacent sarcomeres or within the Z bands. Evidence for this inflammatory reaction can be found in increased levels of creatine kinase (CK) in the blood following exercise. This enzyme is released into the bloodstream following a muscular injury. Occasionally, the high CK levels found following eccentric exercise can confuse the clinical picture of a patient in whom CK levels may be used as a means of informing clinical diagnosis (Gralton et al. 1998). Saxton et al. (1995) have also reported a decrease in proprioceptive function with high-level eccentric exercise.


Despite many suggestions of dietary, medicinal, massage and exercise remedies there is conflicting evidence as to how best to enhance recovery from DOMS (Bennett et al. 2005; Close et al. 2005; Racette et al. 2005; Rahnama et al. 2005).



Treatment with eccentric exercise

Eccentric exercise has been identified as a key treatment technique when rehabilitating tendon injuries, such as in the tendo-achilles. Stanish et al. (1985) proposed treatment protocols with eccentric exercise involving alteration in both load and speed.



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It is important to acknowledge that tendons function by storing elastic energy via elastic deformation and recoil. It may be that improved conditioning from isometric and eccentric exercise to the muscles (e.g. gastrocnemius and soleus) to which they are attached may also be a factor in studies reporting the positive benefits of eccentric exercises in tendon rehabilitation.


The benefits of using eccentric exercise programmes for tendon injuries are thought to include:



Knowledge of the types of contraction whether eccentric, concentric or isometric, is required when planning strengthening exercises. Eccentric contractions are capable of producing more torque than isometric, which, in turn, are stronger than concentric contractions. Isometric exercises are particularly useful when an area is immobilised, for instance when a joint is immobilised in Plaster of Paris, provided the contraction does not further damage soft tissues or destabilise fracture sites as active movement would be more likely to. It is useful to apply eccentric and concentric exercises in a functional context during rehabilitation. The functions of eccentric exercise being the deceleration of limb part, for example hamstrings braking knee extension when kicking a football, the absorption of force, for example when landing from a jump, or controlling a movement with the recoil of resistance or with gravity, for example during sit to stand (Figure 13.3).


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Figure 13.3 Eccentric training of the hamstrings.


Open-chain and closed-chain kinetic strengthening

The emphasis on closed kinetic chain exercises has developed since the onset of accelerated protocols for anterior cruciate ligament (ACL) rehabilitation and rehabilitation of anterior knee pain pathologies. A closed kinetic chain exercise occurs when the distal part of the limb (upper or lower) is fixed on a firm surface. Squatting is a commonly quoted example of a closed chain kinetic exercise, but performing a leg press exercise with the feet in contact with a metal footplate is also an example. Contemporary postoperative management of ACL reconstruction currently involves a combination of open and closed kinetic chain exercise; this reflects the mixture of open and closed kinetic functions in the knee and the lower limb as a whole in everyday functional activities.


The following are some of the proposed benefits of closed chain exercises in the lower limb:



Closed kinetic chain exercises are not just a valuable part of lower limb rehabilitation, they are also widely used to good effect in the upper limb, particularly when addressing scapular or glenohumeral stability problems.



Resisted exercise


Resisted exercise is a more progressive form of strengthening exercise used in the more advanced stages of rehabilitation to achieve grade 5 on the Oxford scale. It is also an essential component of the training regimes of athletes aimed at enhancing performance and preventing the onset of injuries. As the name suggests, it is an activity during which an external resistance must be overcome to complete the exercise. This external resistance could be provided by the therapist during treatment, but, more commonly, is provided by equipment. The conventional means for this is by application of weight training with the use of free weights or weight training equipment as found in gymnasia. However, other equipment, such as medicine balls, elastic tubing or wrist and ankle weights, can be equally effective if used selectively. As larger weights are applied in this type of training it is essential to ensure that the patient has been progressively advanced to this stage of rehabilitation and must be closely supervised during the exercise, particularly whenever the loads are progressed. This type of training can be used to promote power or endurance in muscles and will be discussed in more detail in the following sections.



Types of muscle fibre

There are three main types of muscle fibre, usually called I, IIa and IIb, but newer subdivisions are now being described, such as Ic, IIc and IIab (Scott et al. 2001). Individual muscles are composed from all types, but have different proportions of each. Some of the differences in the physiological make-up of these muscle fibres are illustrated in Table 13.4.



The exact proportion of different fibre types is not consistent between muscles or between individuals. These characteristics are generally thought to be partly genetically determined and are part of the reason for the natural selection that sees individuals excel in different sports or play in different positions within a team. They are also influenced by training applied to the muscle (Scott et al. 2001). However, some general points can be made.




Number of repetitions

The number of repetitions performed of a particular exercise, along with load applied determines the type of muscle training effect. Resistance training includes pure strength work, as well as endurance work and, as a consequence, the number of repetitions will be based on the required outcome.


There is little clear evidence on the number of repetitions that should be used, but there are many protocols that can be used or adapted. A group of repetitions is known as a set, with three or four sets of an exercise usually being performed. This allows physiological recovery of the muscle to occur and delays the effects of fatigue.


Instructing a patient to perform ten repetitions may be the most appropriate number to prescribe for the particular weight and exercise, but there needs to be a method of determining the weight required for these repetitions. It is important not to lose sight of the purpose of resistance training (particularly strength training) – one of progressive overload to increase muscle strength and improve function. Progressive overload will not occur with repetitions of a weight that is too light and, as a consequence, recovery will be slower.


The majority of protocols that are in existence for strength training are based upon what are known as the ‘one repetition maximum’ (1RM) and the ‘ten repetition maximum’ (10RM). The 1RM is the weight that can be lifted once and only once in an exercise, with further completed effort being prevented by fatigue (Cahill et al. 1997). Determining the 1RM therefore prevents a challenge in the clinical environment and perhaps explains the sometimes arbitrary nature of repetitions given. The 10 RM is calculated similarly, i.e. the weight that can be lifted ten times. Once the 1RM or 10RM are established, weight training protocols can be calculated using percentages of this figure.



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Sets consisting of ten repetitions are commonplace within exercise prescription. However, this is often just an arbitrary number. Avoid giving ‘sets of ten’ without any underlying rationale. It is often better when prescribing and teaching an exercise to observe for signs of fatigue and substitution to give a number of repetitions in a set. It may happen to be ten, but more often than not this will not be the case.


The number of repetitions prescribed is determined by the objective of the exercise. If the aim is to increase power then relatively few repetitions will be required, with long rests between sets, to achieve gains provided a high load is applied. Muscles with a higher proportion of type IIa and IIb muscle fibres with a mobiliser function will respond to this type of regime. If the aim is to increase endurance then lower loads will be required, but longer holds and higher frequencies of repetitions will be necessary for suitable gains. These exercises will be suitable for muscles with stability or postural function and a relatively higher proportion of type I fibres.



Further study


For more detail on exact protocols consult a strength and conditioning text.



Resistance training in different populations




Mobilising exercises


Introduction


These are exercises aimed at moving a targeted anatomical structure a precise amount in order to gain a treatment effect.


Soft tissue extensibility is a prerequisite for normal functioning. Unfortunately, following injury, inflammation, prolonged abnormal postures and other factors, such as exercise history, age and gender, this extensibility can be lost.


Therapists regularly encounter people who have well-established limitation of movement and need to be able to recognise this presentation and act accordingly to restore the length of the soft tissues involved. It is also important that the therapist is able to identify the muscles and soft tissues that are most prone to shorten and lose extensibility. The following sections of this chapter discuss the key concepts in the use of mobilising exercises in management of soft tissue conditions.


Mobilising exercises are a fundamental component of the rehabilitation process as they enhance normal tissue healing and are necessary to load the soft tissues progressively. Ultimately, the resultant scar tissue is stronger (Melis et al. 2002) and this enables it to more effectively withstand the stresses and strains it encounters during normal functional use (Hunter 1998).


Mobilising exercises can be used to maintain or increase range of movement, when restricted, for which the causes are numerous. These causes include:



Physiotherapists often use mobilising exercises in conjunction with other treatment modalities such as passive movements, heat, electrotherapy and soft-tissue techniques, depending on the presenting symptoms of the client.


For the purposes of this chapter, exercises are divided into the following classes:




Classes of mobilising exercise


Passive exercises


Passive exercises can be defined as exercises by which movement is produced entirely by an external force with the absence of voluntary muscle activity on behalf of the patient. This external force may be supplied by the therapist (as is the case with passive movements) or by a machine. For example, continuous passive motion (CPM) units might be used following total knee arthroplasty or other knee surgical procedures, or in stroke rehabilitation (Lynch et al. 2005) to enhance recovery of the shoulder.


Passive exercises are typically employed in the early stages of rehabilitation after the onset of trauma, provided that affected structures are stable enough to sustain movement without vulnerability to further injury, and provided that the exercise is not unduly painful. They may also be used to maintain range of movement in soft tissues during periods of joint inactivity. They are commonly utilised in conjunction with stretching exercises to further increase the ranges achieved.



Active-assisted exercises


These are exercises in which the movement is produced in part by an external force, but is completed by use of voluntary muscle contraction. These exercises are of obvious value when strengthening a weakened muscle, but with the assistance given by the external force they can also be used to increase range of movement while allowing the individual to maintain control of the exercise.



Equipment


All manner of equipment is used to facilitate active-assisted exercises. Common examples are pulleys, slings and pole exercises for shoulders, re-education boards for knees and elbows, as well as many other external adjuncts. The physiotherapist should be as innovative as required.


Another important factor to be considered is gravity. If the exercise is performed with assistance from gravity, this may increase its effect on mobilising the targeted structure (Figure 13.4).


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Figure 13.4 (a–c) Active-assisted shoulder elevation demonstrating the use of gravity and the other arm (via a pole) to gain range of movement.



Active exercises


Also known as free active exercises, these are activities in which the movement is produced solely by use of the individual’s voluntary muscle action. They can be used as either strengthening for grade 2 and above on the Oxford scale (see previous) or to mobilise structures – as is the case with dynamic stretching exercises.



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With any exercise the correct choice of starting position is important. For example, for a mobilising exercise aimed at increasing range of movement, gravity may well need to be counterbalanced or the body part positioned so that gravity assists the movement. If an exercise is performed against gravity it will have more emphasis towards strengthening.


A clinically useful feature of active exercises is that they can be performed without the use of equipment, so they can be practised anywhere and can easily form the basis of a home exercise programme.



Stretching exercises


If performed appropriately, stretching exercises may be a simple, yet very effective, form of treatment. For example, in the elderly a loss of hip extension during walking implies the presence of functionally significant hip flexor tightness (Kerrigan et al. 2001) and predisposes individuals to falls and subsequent femoral neck fractures. Overcoming hip tightness with specific stretching exercises as a simple intervention shows some improvement in walking performance and possibly fall prevention in the elderly (Kerrigan et al. 2003).


Stretching is commonly employed within the athletic population. Increasing the range of motion available at a joint has obvious advantages in increasing function and performance. It is suggested that regular stretching improves force, jump height and speed, although there is no evidence that it improves running economy (Shrier 2004). It has also been suggested that it contributes to injury prevention, although research does not suggest that stretching reduces risk of injury or reduces the effects of DOMS at present (Herbert and Gabriel 2002).



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Stretching exercises are normally used to mobilise neural and muscle tissue to the limits of the available range. There are many forms of stretching exercise and techniques commonly used in combination, therefore a consensus as to their effects is difficult to ascertain within the published evidence. Stretching will result in a temporarily increased change in length but prior to sporting activity, as part of a warm-up, it may be more appropriate to use a technique that activates muscles, as stretching may result in a reduction of muscle tone.


Stretching exercises are performed with the target structure moving towards a lengthened position. The stretching exercise will involve further movement in this direction so as to further lengthen the structure. Collagen fibres realign rapidly as a result of stretching forces and become aligned (and therefore stronger) in the direction of the stretching force (Melis et al. 2002). The limiting factors to further movement, such as the degree of pain experienced, will govern the extent to which any further movement is possible. Stretches are commonly used to increase range of movement by mobilising restrictions within soft tissue (e.g. scar tissue) and are specifically used in the lengthening of tight muscles.


The time at which stretching is commenced after an injury needs careful consideration. After any soft tissue injury, the length of the immobilisation depends on the grade of injury and must be optimised so that the scar can withstand the longitudinal forces operating on it without re-rupture. Mobilisation of soft tissues by stretching will aid reabsorption of the connective tissue scar and recapillarisation of the damaged area (Kujala et al. 1997).


Stretching may also be used as a preventative measure, for example to prevent joint contractures. However, while the primary intervention for the treatment and prevention of contracture is to regularly stretch the soft tissues, and the rationale behind this intervention appears sound, the effectiveness of stretching has not been verified with well-designed clinical trials on subjects who have sustained soft tissue injury (Shrier and Gossall 2000). One such trial (Malliarapolous et al. 2004) looked at the frequency of stretching protocols in athletes with hamstring injuries and found a significant difference in rate of recovery when the protocol was applied three times daily compared with once a day. However, a lack of control group limits our insight into the effectiveness of this modality and a lack of longer-term surveillance limits insight into its effect on reinjury rates.


Stretches may be applied in one of two ways: either dynamically or statically (Table 13.5).


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Jan 7, 2017 | Posted by in PHYSICAL MEDICINE & REHABILITATION | Comments Off on Exercise in rehabilitation

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