Heart failure (HF) is defined as “a complex clinical syndrome which may result from any structural or functional cardiac disorder which negatively impacts the filling or ejection of blood by the ventricle.”1 The 2 broad classifications of HF are (1) HF due to an impaired ability of the ventricle to contract adequately thus reducing its pumping efficiency (HF due to a reduced ejection fraction); and (2) HF due to the inability of the ventricle to relax adequately reducing its filling capacity (HF with preserved ejection fraction). The cardinal symptoms clinically associated with this syndrome are dyspnea, fatigue, and activity intolerance, which impair the functional abilities and quality of life of individuals.1 This physical activity intolerance, which develops secondary to symptoms, leads to further physical deconditioning, which compromises physical activity tolerance even more. As a result, individuals with HF make numerous lifestyle changes as a consequence of their decreased physical capacity and experience a diminished quality of life.
The overall medical management of individuals with HF continues to be a work in progress. However, the guidelines for optimal pharmacological therapy of individuals are now more clearly established.1,2 The use of angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin receptor blockers (ARB), β-blockers, and diuretic therapy, as indicated, is recommended as standard care of individuals with HF.1,2 However, the role of nonpharmacological interventions in the overall medical management of individuals with HF is an area of active investigation, particularly with regard to exercise training. Findings from the recently completed Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) study, a large multicenter randomized clinical trial, have now clearly demonstrated the efficacy and safety of aerobic exercise training for individuals with HF as well as its positive impact on quality of life.3,4 Furthermore, dynamic resistance exercise training, whether performed alone or in combination with an aerobic exercise program, has been shown to be beneficial and well tolerated and is assumed to be as safe as aerobic exercise training in stable patients with HF.5–7
The decrease in physical activity tolerance observed with individuals with HF has been attributed physiologically to a combination of central (decreased cardiac output) and peripheral factors (decreased skeletal muscle blood flow and early anaerobic metabolism in muscle).2,8–11 The peripheral alterations in skeletal muscle metabolism, blood flow, neuroendocrine activation, autonomic responses, inflammatory activation, and abnormal peripheral vasodilation are now recognized as extremely important contributory factors to exercise intolerance.12–17
Aerobic exercise training in patients with stable HF has shown many beneficial effects on physiological functional limitations or impairments. Diminished cardiac output was originally thought to be the primary determining factor associated with exercise capacity. However, resting left ventricular ejection fraction and hemodynamic measurements are poorly correlated with peak exercise performance and should not be used as a criterion for determining which individuals should or should not participate in exercise training programs.18 Although decreased cardiac output is obviously a contributory factor, skeletal muscle myopathy, metabolism, and abnormal peripheral vasodilation are now recognized not only as important contributory factors to exercise intolerance but factors modifiable with exercise training.12,13,19
Centrally, aerobic exercise training has been shown to have an effect on attenuating or reversing abnormal ventricular remodeling20,21 Peripherally, exercise training improves formation of endothelial nitric oxide, resulting in endothelial vasodilation22 and improved oxygen extraction and substrate delivery/utilization in skeletal muscle.23–26 Aerobic exercise training improves metabolism in skeletal muscle and has been shown to increase mitochondrial volume and density.24–26 In addition, resistance exercise training has been shown to improve skeletal muscle function, mass, strength, and endurance and decrease myocardial demands during daily activities.6,27,28 These physiologic changes contribute to the improved physical activity tolerance seen in individuals with HF following an exercise training program.
Clinically, exercise training has been shown to have a significant effect on improving functional capacity of individuals with HF. Positive increases in oxygen consumption, 6-minute walk test distances, symptoms, self-efficacy for exercise, and quality-of-life postexercise training are well established.29–33 Exercise training also appears to have a positive impact on reducing mortality and hospitalizations for individuals with HF.30,32,34,35 With the recognized benefits of exercise training for individuals with HF, current guidelines from national and international organizations all recommend exercise training in the management of individuals with stable HF.1,2,36–38 There is no evidence that exercise training should be limited to any particular subgroup of individuals with HF based on New York Heart Association (NYHA) class, etiology of HF, medications, or left ventricular ejection fraction.39,40 In addition, older adults with HF should be treated similarly to younger individuals with HF regarding treatment therapies, taking into account existing comorbidities.36 The following summarizes the current evidence regarding exercise parameters for aerobic exercise, resistance exercise, and inspiratory muscle training (IMT) for individuals with HF along with recommendations for monitoring and modifying exercise training programs.
AEROBIC EXERCISE TRAINING
Aerobic exercise training protocols used with individuals with HF have varied in terms of setting and presence of supervision, type of exercise and equipment used, intensity of exercise, frequency or number of days per week, and the length of the program. Although studies on exercise training have primarily been conducted in formal rehabilitation settings under supervision,41–48 some have allowed patients to complete the exercise training at home49–51 and others have used a combination of supervised exercise training and home-based exercise.3,9,16 Interestingly, despite the variability in settings and supervision, a variety of positive benefits have been shown with aerobic training. Current recommendations are for a symptom-limited graded exercise test to be performed before an individual with HF begins an exercise training program.2,38
The type or mode of aerobic exercise training has predominately included walking and cycle ergometry programs;3,16,25,26,43,47,49,50,52 however, arm ergometry,10,53 stair climbing,44,54 endurance leg training,45,46 and multimodal regimens with cycles, treadmills, rowers, and weights,41,42,48,54 have also been successfully utilized. Therefore, specificity of training needs to be taken into account by clinicians, along with patient preference, in selecting the mode or modes of aerobic training for a particular individual to achieve the functional outcomes desired.
Current guidelines recommend moderate intensity aerobic exercise for individuals with HF whether using continuous or interval training. However, there is no one established gold standard for how to prescribe exercise intensity as various methods have been employed to achieve positive benefits. These methods include a percentage of peak oxygen consumption (%
2peak), percentage of maximal heart rate (%HRmax), percentage of heart rate reserve (%HRR), and rating of perceived exertion (RPE). Exercise intensity protocols based on %
2peak have ranged from 40% to 80%
2peak, with the most frequently used moderate intensity training range being 70% to 80% of
2peak.13 Studies using intensities based on %HRmax have ranged from 45% to 90% of HRmax, with the most common moderate intensity range being 60% to 80% of HRmax.13,55,56 For the %HRR method, a range of 55% to 80% HRR is commonly recommended.34 Consistent with this recommended range was the HF-ACTION trial, which used a moderate training intensity of 60% to 70% of HRR.3 In addition, the HRR method has been shown to be a robust and reliable technique to use with individuals on β-blocker therapy.57 RPE ranges of 11 to 15, on the Borg 6–20 category scale, have been used to guide moderate intensity training with a RPE range of 12 to 14 being most consistent.13,52,58 RPE is especially useful if a recent graded exercise test is not available, an individual has a change in medications, or if the individual is in chronic atrial fibrillation. In HF-ACTION, the prescribed training intensity range was targeted at 60% to 70% of HRR, modified as needed to achieve a RPE between 12 and 14.34 To use %
2peak, %HRmax, or %HRR to guide the exercise training intensity of an individual, a cardiopulmonary exercise test must be performed to accurately obtain the individual's
2peak and HRmax. Age-predicted maximum heart rate formulae must not be used to calculate a HRmax to determine a %HRmax or %HRR training range for individuals with HF due to alterations in HRR capacity and the common use of β-blocker therapy in this population.
Duration of the aerobic exercise is typically 20 to 45 minutes per session but has been reported to vary from 10 to 60 minutes per session.1,3,16,24,50,52,58,59 For individuals with HF having a functional capacity less than 5 METs (1 MET = 1 metabolic equivalent, corresponding to 3.5 mLO2/kg/min), it is recommended that multiple short exercise sessions from 5 to 15 minutes be used initially, then duration progressed as tolerated.58 Each training session should include an adequate warm-up period of 10 to 15 minutes and a cool down period.13 The goal should be for the individual with HF to train for at least 20 to 30 minutes at their prescribed moderate exercise intensity level.
Studies have used exercise training frequencies varying from as infrequent as 2 days per week to as frequent as 7 days per week.53,60 Most often training frequencies of 3 to 5 days per week have been used, which is consistent with most current recommendations.1,2,13,37,58 However, the training frequency will be dependent upon the intensity and duration. If an individual requires a lower intensity or shorter duration, then more frequent sessions, possibly 5 to 7 days a week, would be required to achieve optimal benefits. Training programs have varied in length from 8 to 24 weeks, with gains in cardiorespiratory function plateauing at about 16 to 23 weeks.52 It is recommended that once an individual is established on an exercise program participation in it should continue indefinitely.13
Since agreement on a universal exercise prescription for this population does not exist, and the variability in clinical presentation and exercise tolerance in individuals with HF is large, an individualized approach to developing an exercise program is recommended.13,33,36,37,61 It should be emphasized that, when beginning an exercise training program for individuals with HF who are not accustomed to aerobic activity, the program should be initiated at a lower intensity, with interval training (periods of rest), and progressed as tolerated to the appropriate intensity level for that individual. A summary of recommendations for aerobic exercise training is provided in Table 1.
RESISTANCE EXERCISE TRAINING
In the past, resistance training was discouraged for individuals with HF due to concerns over potential adverse remodeling effects on the heart and reduced ventricular function associated with an increase in afterload. However, these concerns are now tempered by studies demonstrating that the hemodynamic demands associated with performing moderate resistance training are no greater than those imposed by aerobic exercise.58,62 Furthermore, moderate intensity resistance exercise training appears to be supported from a safety perspective for appropriate individuals with stable HF.27,63
Individuals with HF should be carefully evaluated and monitored during the initial sessions of resistance training. Although resistance exercise in individuals with HF has been shown to increase the rate pressure product, no significant changes in systemic vascular resistance or cardiac output have been reported.7 Various modes of resistance training using free weights, stacked weight machines, hydraulic machines, pneumatic resistance equipment, wall pulleys, and elastic bands have all been used successfully to create an adequate stimulus for achieving a training effect. The intensity of resistance used in various studies has ranged from 40% to 90% of maximum voluntary contraction (MVC) or 1-RM (1-repetition maximum), or have employed an RPE of 10 to 15. Generally, 1 set of 10 to 15 repetitions is recommended, 2 to 3 times per week, although studies have varied on the number of sets (1–4), numbers of repetitions (8–20), and frequency (1–5 d/wk). The American Heart Association and American College of Sports Medicine recommend 1 set of 10 to 15 repetitions, 2 to 3 times per week to include 8 to 10 exercises encompassing both the upper and lower body.61,63 Clinically, the determination of exercise intensity by a 1-RM test may be unsuitable for individuals with HF because it can lead to a Valsalva maneuver.37 Therefore, an alternative approach would be using the load-repetition relationship for resistance training, performing 10 to 15 repetitions to volitional fatigue, which would correspond to an intensity of approximately 65% to 75% 1-RM.63
Regardless of age, health status or fitness level, moderate-intensity resistance training should not be initiated until an individual has acclimated to more modest levels of resistance training.63 Initial resistance training should begin with a lower intensity load and with proper instruction on lifting technique and breathing. Individuals should be advised to raise and lower the load with slow, controlled movements through their full range of motion while maintaining a normal breathing pattern and avoiding straining, breath holding or performing a Valsalva maneuver.37,61 Intensity should be increased as tolerated to the 40% to 60% MVC level for moderate risk individuals and toward the 60% to 80% MVC level for low risk individuals. At this time, the guidelines recommend dynamic resistance training to be included as an adjunct to aerobic training, not a substitute for aerobic training. Using a combination of aerobic and dynamic resistance training in individuals with HF has been shown to positively impact muscular strength and endurance, in addition to exercise capacity, symptoms (fatigue and dyspnea), 6-minute walk distance, and quality of life.6,28,31,51,64–66 Static or isometric resistance exercises are not recommended for individuals with HF. Table 2 summarizes the recommended parameters for a resistance exercise prescription based on current guidelines.
INSPIRATORY MUSCLE TRAINING
Decreased respiratory muscle strength and endurance are common findings in individuals with HF and have been associated with being contributory to the dyspnea and fatigue experienced with this syndrome.67 This becomes evident in individuals with mild-to-moderate disease, with a greater reduction noted in individuals with more severe disease. These findings are consistent with the peripheral skeletal myopathy seen in HF.67 Although aerobic and resistance exercise produce significant physiologic and clinical benefits in individuals with HF and have been shown to improve respiratory muscle endurance,68 there is a small but growing body of evidence suggesting specific IMT offers additional benefits when performed alone or in conjunction with aerobic training.69–72 Although there are various methods for performing IMT, many studies have utilized a targeted inspiratory resistance device, such as the Threshold® Inspiratory Muscle Trainer, in which the resistance can be adjusted as an individual progresses. Improvements in maximal inspiratory pressure (PImax), 6-minute walk test distance, dyspnea, and quality of life have been reported following training; however, those individuals with documented inspiratory muscle weakness (<70% predicted PImax) at the outset seem to derive the most benefit from IMT.69–71,73,74
IMT protocols have ranged from 20% to 60% PImax, for 5 to 30 minutes, 1 to 3 times per day, 3 to 7 days per week for 6 to 12 weeks.69–72,74,75 In general, beginning an IMT program at an intensity of 15% PImax and progressing to at least 30% PImax, and up to 60% of sustained PImax, is consistent with the literature. The protocol should be performed for a duration of 15 to 30 minutes, 1 to 2 times a day at a frequency of 3 to 7 days per week for 8 to 12 weeks. A summary of the guidelines for IMT is provided in Table 3.
MONITORING OF INDIVIDUALS DURING EXERCISE
The guidelines described and the recommendations offered by expert panels regarding exercise training with individuals with HF are directed at those individuals with stable HF in NYHA classes I to III.1,2,36–38,61 There is limited information and no specific guidelines available on individuals with NYHA class IV. If an individual is not stable or becomes unstable, they should not be participating in an exercise training program until they are stable. It is important that when developing and managing exercise programs for individuals with stable HF that they be challenged with an adequate intensity of exercise to gain the most benefits for their time investment. Therefore, when working with individuals with HF, practitioners need to be diligent in monitoring individuals' responses to exercise and apply sound clinical judgment in tailoring programs on an individualized basis.
Indications for Modifying or Terminating Exercise Training36,58,76
Dyspnea and fatigue are common symptoms of individuals with HF that need to be taken into account when developing or progressing an exercise program. However, in and of themselves, they are not adequate reasons for not exercising individuals with HF. However, undue dyspnea or a progressively worsening of dyspnea and marked fatigue are reasons for modifying an exercise program, such as providing longer rest periods between sessions (eg, every other day), or possibly terminating the program if you suspect a change in an individual's HF status or the individual is becoming unstable. Other common signs and symptoms to monitor include angina, mental confusion, dizziness, ataxia, pallor, diaphoresis, claudication, musculoskeletal discomfort, peripheral edema, and weight gain of 3 lb or more in a single day.
A weight gain of 3 or more pounds in a day is generally indicative of fluid retention, which will require adjusting the intensity of the exercise program, or possibly holding the exercise program, as the fluid increase places a greater workload on the heart. It is also important to monitor the individual's compliance to medications and diet as the weight gain may be suggestive of missed medications or excess sodium intake. If this occurs consistently, or weight continues to steadily increase, the individual's exercise program may need to be held until the individual is reevaluated for possible adjustments in medications, diet, and HF status. In older adults, acute and fluctuating cognitive impairment, or delirium, may be signs brought on by decompensated HF and should be discussed with the individual's physician.
Respiration rate (RR) normally increases with increasing intensity of exercise. During exercise, individuals with HF should have a RR of less than 40 breaths/min. If RR is more than 40 breaths/min, this would necessitate decreasing the exercise intensity.
Heart rate should also increase linearly in relationship to intensity of exercise. Since most individuals are on β-blocker therapy, the magnitude of change will be blunted but should still demonstrate an adaptive response (an increase with increasing workload, a decrease with decreasing workload). A decrease of 10 beats/min (bpm) from resting HR or no change in HR with increasing workload would indicate a nonadaptive response and would warrant discontinuing exercise until the individual's HF status is reassessed. An atypical elevation in HR during a session may indicate the individual missed or stopped taking their β-blocker; this would need to be discussed with the individual.
Blood pressure (BP) should be monitored at rest and during exercise to assess for an adaptive response (systolic BP should increase with increasing workload, decrease with decreasing workload). Nonadaptive BP responses to exercise would be a decrease in systolic BP ≥ 10 mm Hg or an increase in diastolic BP to 110 mm Hg or greater. If an individual demonstrates a drop or hypotensive response in systolic BP with exercise, the clinician may need to consider adjusting the timing of the exercise session to the individual's medication schedule. Since many individuals will be on an ACE-I or ARB and β-blocker, the vasodilatory effect of exercise, at a time when the medications are having a peak effect, may result in an abnormal drop in BP response during exercise. If individuals are taking an ACE-I or ARB and β-blocker at the same time of day and become hypotensive with exercise, see whether it is possible for the individual to separate the timing of these 2 medications so as to avoid or minimize the potential synergistic hypotensive response with exercise.
Auscultation of the heart and lung sounds at rest and immediately postexercise may also provide information to the clinician regarding the individual's tolerance to the exercise program. The development of an S3 heart sound or crackles postexercise would indicate that the exercise program intensity needs modification. The development of an S3 would suggest an excessive increase in workload on the heart, and crackles indicative of increased central edema, either of which would warrant modification of the intensity or duration of the exercise program. If an individual has crackles at rest, close monitoring for an increase in crackles with exercise is warranted to assess whether adjustments in the exercise program need to be made.
Pulse oximetry (SpO2) to assess oxygen saturation, especially in those individuals with more severe HF, is important as an indicator of oxygen loading ability. A SpO2 ≥ 90% is recommended during exercise. If the individual is on supplemental O2, it should be titrated to keep the SpO2 ≥ 90% or exercise intensity may need to be decreased to keep the SpO2 ≥ 90%. This is particularly important to monitor when individuals are retaining fluid or have an underlying comorbid pulmonary disease. It is recommended that individuals with HF initially be monitored electrocardiographically to assess the electrical stability of the heart during exercise. When not available, such as in the home setting, monitoring changes in pulse with exercise may provide some indication of significant rhythm alterations, which warrant further evaluation. For example, the development of an irregularly irregular pulse may be suggestive of atrial fibrillation, which would result in a decrease in cardiac output.
Although HF can occur at any age, it is considered to be primarily a condition associated with the older population, with approximately 80% of individuals admitted to the hospital with a diagnosis of HF being over the age of 65 years.1 With the “aging of the population” in the United States, the incidence of HF is expected to continue to rise. Therefore, many of the older individuals seen by physical therapists for an array of conditions will have HF as a primary diagnosis or comorbidity, which needs to be addressed in developing their plan of care. Current evidence supports the safety and efficacy of exercise training as a component in the overall medical management of individuals with stable HF regardless of age. Exercise training should be used as an adjunct therapy to the pharmacological management of individuals, which may necessitate coordination of exercise and medication schedules. Prior to beginning an exercise training program, individuals with HF need a thorough medical evaluation to establish the stability of their HF status, and once established, can and should participate in exercise training. Aerobic, resistance, and IMT exercises must be individualized based on each individual's tolerance, signs and symptoms, severity of HF, and comorbidities. It is the role of the clinician to use sound clinical judgment and expertise in applying evidence-based practice on an individual basis. It is well established that physical activity is superior to inactivity in the management of individuals with HF, and at this point in time the evidence supports progressing exercise training to the moderate intensity level for achieving optimal benefits. On-going monitoring of individuals participating in exercise training is essential and prudent to evaluate their responses to exercise and adapt the training program appropriately.
The primary aims of this white paper were to review the benefits associated with exercise training in individuals with HF and present the current recommendations for aerobic, resistance, and inspiratory muscle exercise training. A secondary aim was to emphasize to physical therapists the need to adequately challenge individuals with HF with appropriate exercise intensities, while closely monitoring their patients, to achieve optimal functional benefits and quality of life.
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