Exercise Testing and Training: Secondary Cardiovascular and Pulmonary Dysfunction

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Chapter 25

Exercise Testing and Training

Secondary Cardiovascular and Pulmonary Dysfunction

Elizabeth Dean, Donna Frownfelter and Eduard Gappmaier

This chapter extends the general principles of exercise testing and training presented in Chapter 19 and describes special considerations concerning exercise testing and training for individuals with secondary cardiovascular and pulmonary dysfunction. These special considerations are also important when managing an individual with primary cardiovascular and pulmonary dysfunction who, in addition, has cardiovascular and pulmonary dysfunction secondary to other conditions. In that case, management is modified based on the combination of comorbidities. Individuals with progressive degenerative conditions are often older and debilitated; thus the combination of problems is common. Exercise testing and training is one component of the comprehensive physical therapy management of individuals with chronic, secondary cardiovascular and pulmonary dysfunction, which is described in Chapter 32.

Secondary cardiovascular and pulmonary dysfunction refers to dysfunction of the cardiovascular and pulmonary system that is a consequence of pathology other than primary chronic heart and lung disease. Examples of such secondary conditions are described in Chapter 6. These conditions include dysfunction of the musculoskeletal, connective tissue, neurological, gastrointestinal, hepatic, renal, hematological, endocrine, and immunological systems, or some combination thereof. Nutritional disorders, specifically obesity and starvation (anorexia nervosa), also have cardiovascular and pulmonary manifestations. Conditions leading to secondary cardiovascular and pulmonary dysfunction affect one or more steps in the oxygen transport pathway in such a way that the capacity for oxygen delivery is reduced, oxygen consumption is increased, or both.¹ Often oxygen delivery is further compromised by restricted mobility. Oxygen transport limitations resulting from secondary cardiovascular and pulmonary dysfunction can present subtly, yet have significant clinical implications. Exercise has a primary role in the management of these conditions, along with the elements of comprehensive multidisciplinary prevention and long-term rehabilitation programs.

Contemporary approaches to the rehabilitation of individuals with stroke serve as a prime example of conventional practice aligning with contemporary exercise physiology principles. Over the past 20 years, stroke rehabilitation has shifted from a focus on Bobath and Brunnstrom interventions to structured exercise training. Exercise training in the management of stroke has the potential for driving brain reorganization and exploiting the property of neuroplasticity to maximize functional capacity.² Exercise can take advantage of the potential for neural reorganization, optimize functional capacity, and address deconditioning. A focus on endurance and strengthening exercise, task-specific training, and treadmill walking in the rehabilitation of individuals with stroke, in addition to the conventional focus on cognitive engagement, sensorimotor integration, skill acquisition, and social readjustment has been an exciting advance in the rehabilitation of people with strokes.

Another prime example of exercise testing and training being prescribed for noncardiovascular and pulmonary conditions is their inclusion as a component of prehabilitation in preparation for surgery for a range of conditions. Before orthopedic surgical procedures, for example, improvements in functional capacity have been advocated to reduce perioperative complications and speed recovery.³ Such programs include warm-up, aerobic training, resistance training, flexibility, and daily functional activities.

As a handy reference for clinicians, key points in the assessment, evaluation, and exercise testing and prescription of patients with secondary cardiovascular and pulmonary conditions are summarized in Appendix D.

Assessment and Goals

Assessment

Knowledge of the cardiovascular and pulmonary consequences of conditions other than those of the cardiovascular and pulmonary systems enables the physical therapist to assess oxygen transport status, limitations, and risk factors in these individuals, in addition to ensuring their safety when undergoing physical activity and exercise. Such knowledge enables the physical therapist to prescribe exercise to optimize oxygen transport, maximize functional capacity and life participation, and maintain optimal long-term health.

Goals: Prevention

Many individuals with systemic conditions (see Chapter 6), the focus of this chapter, have manifestations of oxygen transport limitations or one or more risk factors. The risk factors must be identified and considered in a preventive management plan that includes exercise prescription to exploit the preventive effects of activity described in Chapters 18 and 19. Preventive goals for individuals with chronic, secondary cardiovascular and pulmonary conditions include optimizing central and peripheral adaptations to exercise, reducing biomechanical stress and strain (hence minimizing oxygen cost of exercise at submaximal work rates), optimizing fluid dynamics and hemodynamics, and optimizing lung health (e.g., alveolar ventilation, flow rates, mucociliary transport, and lymphatic drainage).

Another consideration with respect to prevention is the fact that many chronic conditions lead to deterioration over time, and this may be exacerbated further with aging and unhealthy lifestyles. Exercise training is modified over time to accommodate each individual’s needs and to help offset further deterioration and associated disability. Furthermore, optimal training effects will benefit the individual’s health overall and help prevent contracting illnesses whose effects may be more devastating than in the healthy population.

Mobility aids and devices may be indicated for people with progressive functional deterioration. These adjuncts are titrated to the individual’s needs to avoid their overuse. Overuse can lead to loss of remaining musculoskeletal function, which must be preserved as much as possible. Thus an individual can use these adjuncts to optimize functional performance throughout the day (e.g., use a wheelchair for activities in which symptoms are anticipated, or use an ankle foot orthosis in the afternoon when the tibial anterior muscle tends to be fatigued and needs support).

Goals: Short Term

When oxygen transport limitations occur, a regimen of physical activity and exercise can be prescribed to elicit the acute effects of exercise (see Chapter 18). Prescription of exercise to elicit its acute effects has a primary role in the management of individuals during acute episodes of illness and setbacks.

Goals: Long Term

When an individual has recovered from an acute episode, or an individual requires subacute and long-term management, a regimen of physical activity and exercise can be prescribed to elicit the long-term effects of exercise described in Chapter 18. The capacity of each individual to respond to an exercise stimulus and the individual’s oxygen transport reserve capacity are both assessed in detail. Knowledge of the reserve capacity is essential for optimal exercise prescription.

Individuals with Musculoskeletal Conditions

Exercise is prescribed for a broad range of conditions affecting the musculoskeletal system, with favorable outcomes and no documented deleterious effects. With increased understanding of exercise pathophysiology, physical therapists can prescribe therapeutic exercise that has the greatest benefit in terms of improved activities of daily living and life satisfaction with the least risk. Individuals with mitochondrial myopathies and nonmetabolic myopathies experience typical aerobic responses to low intensity training (i.e., improved aerobic capacity and reduced submaximal heart rate and blood lactate).⁴ The extent of these training effects, however, is less in individuals with nonmetabolic myopathies compared with those who have mitochondrial myopathies. Improved aerobic capacity is associated with improved self-reported functional status and quality of life in both groups.

Osteoporosis

Exercise is central to the prevention and management of osteopenia and osteoporosis. In addition to weight-bearing exercise, relatively intense exercise promotes bone density as well as a high volume of activity.⁵ Muscle stress across joints appears to be a critical component for osteogenesis; thus torsion around joints such as in racket sports is favorable provided risk for falling is minimized. Practicing tai chi may reduce bone loss in postmenopausal women and may have some role in the management of osteoporosis.⁶

Osteoarthritis

Osteoarthritis has an indirect impact on cardiovascular and pulmonary conditioning because of its effect on mobility. Aerobic exercise can improve functional aerobic capacity in individuals with osteoarthritis, but this effect is less pronounced with hydrotherapy programs.⁷ In response to a fitness walking program for obese people with osteoarthritis of the knee, self-efficacy tended to improve commensurate with improved functional capacity.⁸ When prescribing an increase in physical activity and exercise, the physical therapist needs to consider the person’s weight (not only in terms of the general health benefits of weight loss, but also in relation to the specific need to reduce weight bearing in obese patients). Given the fact that the majority of patients undergoing lower extremity joint replacement are overweight or obese,⁹ weight loss in conjunction with exercise is fundamental in the perioperative course of these patients with the expectation that some patients may avoid the need for surgery entirely. Even small amounts of weight gain have profound effects on joints and joint mechanics (hence, increased pain with exercise). In addition, most patients do not lose weight after their joint replacement surgery, so lifestyle changes need to be approached aggressively before, as well as after, surgery.¹⁰

Scoliosis

Individuals with idiopathic scoliosis and associated restrictive ventilatory disorder can improve pulmonary function with exercise.¹¹ Selected exercise can improve both vital capacity and chest wall expansion by almost 20%. The role of exercise for remediation of restrictive lung dysfunction associated with other spinal and chest wall deformities warrants further investigation. Correction of spinal defects in individuals with muscular dystrophy, for example, does not improve cardiac or pulmonary function and thus may not result in appreciably improved response to exercise.¹²

Individuals with Neuromuscular Conditions

Stroke

Because the pathoetiology of stroke involves atherosclerosis and hypertension, individuals with stroke need to be managed comparably to individuals with systemic atherosclerosis and circulatory dysfunction. Appropriate precautions must be taken when exercising these individuals or conducting other physical therapy interventions. Within weeks after a stroke, cardiorespiratory deconditioning complicates the clinical picture, along with muscle weakness, spasticity, incoordination, and abnormal gait.¹³ In the subacute stage of stroke, individuals who undergo aerobic training can improve aerobic and functional abilities;¹⁴ however, these benefits may not be reflected in the long-term by indexes such as the Frenchay Activities Index.^15,16 Although research is necessary to refine exercise testing and training procedures for individuals with stroke,¹⁷ there is no reason to believe that these patients would not respond to aerobic conditioning to counter the deconditioning that occurs after stroke or that this intervention would not augment gait reeducation and sensorimotor integration. Evidence supports that the application of a modified treadmill training protocol, based on exercise physiology principles, can be superior to conventional approaches to the rehabilitation of people with strokes.¹⁸

Although individuals with physical impairment secondary to stroke present methodological challenges during exercise testing and training, submaximal oxygen consumption () has good agreement with maximum () when the test is tightly standardized.¹⁹ The high degree of reliability of these tests supports their use as outcome measures in this population. Metabolic assessment during short, submaximal tests, such as a five-minute walk, can provide supplemental information for evaluating gait in individuals with stroke.²⁰ Individuals with mild-to-moderate impairment from chronic stroke who require hand rail support on the treadmill also have been reported to have good reliability with respect to heart rate and oxygen pulse in peak-effort treadmill testing.²¹ However, hand rail support is an important variable that can increase or decrease work intensity and thus must be described and recorded to facilitate comparison of exercise results across tests. Hand rail support can be described on the data sheet with respect to side or front support, one or two hands, finger support or grasp support, and heavy or light support.

Treadmill training has proven to be a useful means of improving fitness and offsetting deconditioning in individuals with stroke. Individuals with impaired gait can improve their oxygen transport reserve capacity with a regular program of treadmill walking.²² Peak and walking workload are increased, and the energy cost associated with abnormal gait is reduced. For individuals with stroke, these changes may help to enhance functional capacity comparable to those achieved in individuals with other neurological deficits.

Treadmill training and weight support with a body harness for walking after stroke are showing promise in terms of conditioning strategy and gait reeducation.²³ Patients with severe impairments after stroke who retrain their gait with a portion of their body weight (up to 40%) supported during exercise have better outcomes after training than those who carry their full weight.²⁴ Older individuals and those with the most impairment show the greatest benefits. These individuals walk more symmetrically on a treadmill compared with ground walking, and they walk with less spasticity and improved movement economy.²⁵ Furthermore, improvement in treadmill walking speed in these individuals generalizes to balance, trunk control, functional activities, and ground locomotion.^24,26 Training at speeds comparable to an individual’s normal velocity over ground is more effective than training at speeds above or below that velocity.²⁷ Also, when different treadmill walking protocols are compared, structured speed-dependent treadmill training, as performed in sports training, improves walking ability more than either modified progressive treadmill training or conventional gait training.¹⁸

Despite the compelling results of studies on partial body weight support in the rehabilitation of individuals with stroke, these and related studies often fail to address the principles of physical therapy for management of individuals with systemic atherosclerosis, which include hemodynamic monitoring and possibly electrocardiogram (ECG) screening. One exception was a study by Eng et al (2002)²⁸ that recommended that actual exertion (defined as a physiology measure; specifically, rate pressure product or heart rate) be measured in conjunction with walking distance in functional walk tests when testing people with stroke. When performance on several functional walk tests was compared, performance was associated with level of impairment rather than perceived exertion or intensity as measured by rate pressure product or heart rate. Thus debility may limit aerobic training capacity.

Aerobic exercise may have a preventive effect for stroke mediated by endothelium-dependent vasodilation in the cerebral arterioles.²⁹ Several risk factors are associated with impairment of this mechanism. Exercise stimulates the expression of endothelial nitric oxide synthase, which promotes vascular dilation and thereby exercise’s potential protective and preventive effect.

Community ambulation is a meaningful outcome for people with stroke.³⁰ A discrepancy exists, however, between mobility outcomes on standardized measures of community-based individuals and the extent to which they actually get out in the community. Gait velocity is an important variable in determining community ambulation capacity.

Resistance muscle training has been of interest as a component of physical therapy management of individuals with stroke. Strength training augments the benefits of aerobic exercise with respect to functional strength ³¹ without reinforcing abnormal movement patterns.³² One study, however, reported no difference between leg exercise training programs with and without resistance.³³ Inadequate exercise prescription to explain the absence of an effect of resistance training cannot be ruled out.

When prescribing exercise for individuals with stroke, it must be remembered that stroke results from a hemodynamic insult—usually high blood pressure. Aerobic exercise and resistance muscle training elicit unique hemodynamic responses; thus the hemodynamic status of individuals with stroke must be assessed in the initial baseline review, considered carefully in the exercise prescription, and assessed in the outcomes of these programs. If blood pressure is being pharmacologically managed, then an objective of exercise will be to augment oxygen transport efficiency and normalize blood pressure. Medications must be followed so that these can be reduced or withdrawn in response to an overall effect of a comprehensive exercise and management program.