The type of exercise intervention will change according to the patient's clinical presentation. Interventions for various clinical stages are summarised in the table below.

Table 1: Interventions for clinically compensated acute inpatients

Table 2: Interventions for  clinically stabilising post-acute outpatients

Table 3: Interventions for clinically stable patients requiring maintenance

DVT = deep vein thrombosis; ICD = implantable cardioverter defibrillator

All individuals with cardiovascular disease should be encouraged to participate in an active lifestyle, incorporating recreational, domestic and vocational activities as their symptoms allow.

Patients recovering from a cardiac event, HF exacerbation or those who have stable disease but are sedentary, should gradually increase their level of physical activity to the recommended intensity. That is, aiming for 150 minutes of moderate intensity exercise per week, which equates to 30 minutes, most days of the week.  For those with good exercise tolerance, additional health benefits accrue from daily activity of up to 60 minutes. Those who find extended periods of continuous exercise difficult may tolerate breaking down exercise into smaller intervals such as 10 minute intervals.

For some individuals, attaining recommended levels of physical activity may be challenging. For these patients, encouragement and support to reduce sedentary behaviour and to replace this with light intensity activity, may prove an achievable starting point. Gradual progression of duration and intensity of activity may then be possible.

TIP: Pedometers are useful to help motivate patients and provide feedback on their amount of activity. Walking for 30 mins/day plus normal activity equates to 7000-10,000 steps on a pedometer.

An adequate warm-up and cool-down before and after each session reduces the risk of adverse events during exercise.

• Warm-ups aid the gradual transition from a state of rest to the increased physiological demand associated with exercise, encompassing increased skeletal muscle perfusion and thermoregulatory mechanisms. Warm-ups may reduce the likelihood of ST-segment depression, arrhythmias, and transient left ventricular dysfunction
• Cool-downs allow the HR and blood pressure to return to resting values. Cool downs reduce venous pooling of blood in the active musculature and reduce the risk of arrhythmias, post-exercise hypotension, dizziness and catecholamine surges

TIP: Adequate warm-up and cool-down periods are essential elements of a safe exercise prescription.

Walking performance on a six-minute walk test(6MWT) gives a good indication of exercise tolerance and helps guide initial exercise prescription for ground or treadmill walking.

Walking training intensity is calculated based on both the distance walked and the Rating of perceived exertion reached at the conclusion of the 6MWT.

Walking speed calculation:

• Rating of perceived exertion ≤11 (‘fairly light’); prescribe walking training at 100% of the walking speed during the 6MWT
• Rating of perceived exertion 12-14 (‘somewhat hard’); prescribe at 90% of the walking speed during the 6MWT
• Rating of perceived exertion ≥14 (‘hard’); prescribe at 80% of the walking speed during the 6MWT

This assumes an absence of ischaemic symptoms, peak HR <120 beats per minute and initial walking duration of 10-15 minutes.

6MWT average speed is calculated as shown below:

• 6MWT average speed = (6MWT distance x 10) ÷ 1000 km / hr

Table 1: Average 6MWT speed calculation

TIP: Set the initial treadmill speed 0.5-1.0 km/hr slower than calculated if the patient is unfamiliar with walking on a treadmill. Once the patient has become confident, increase to the calculated walking speed.

HF symptoms may vary from week to week. Assess at each attendance and adjust prescribed exercise accordingly.

Some exercise programs have both indoor and outdoor walking options. Indoor exercise, where monitoring and access to assistance is more rapidly accessible, is usually more appropriate for frailer patients and those at higher CV risk.

Aerobic exercise involves low-to-moderate intensity rhythmic movement of large muscle groups for an extended period of time. It includes activities such as walking and cycling. This is the best form of exercise for improving cardiorespiratory fitness.

Aerobic exercise should be encouraged on most days of the week. When prescribing aerobic exercise, the following should be considered:

• If there is a risk of ischaemia, the intensity and duration of exercise or the physiological demand (i.e., the muscle mass utilised at any given time) should be reduced.
• Maximal HR should be at least 5-10 beats per minute below the ischaemic threshold
• The symptoms that limit an individual’s exercise tolerance may vary according to the modality of exercise. For example, a rowing ergometer, which employs a large volume of muscle mass simultaneously, is likely to cause dyspnoea as the limiting symptom, while a cycle ergometer, which isolates the lower limb musculature, is more likely to induce localised muscle fatigue
• Exercise should be tailored to the individual. Orthopaedic limitations may dictate the type, frequency and duration of exercise in order to prevent exacerbation of symptoms
• Longer duration and more frequent rest periods may be required for those with frailty or severe symptoms
• The chosen mode of aerobic exercise should be one that an individual enjoys and tolerates without pain or residual fatigue. Regularity of physical activity is a significant part of attaining the cardiovascular benefits.

Frequency

Evidence-based guidelines promote regular moderate physical activity for approximately 30 minutes on most (at least five) days of the week.

Commence with exercise 3-4 days a week (i.e., every second day), progressing to most days (at least 5 days) of the week.

Encourage independent exercise so that individuals have a mix of supervised and unsupervised sessions. Frequency will be guided by the patient's clinical status, motivation and commitment to exercise, and other commitments such as family and work.

Patients with very limited exercise tolerance may require multiple sessions of short-duration exercise (<10 minutes) to achieve the desired activity level.

Intensity

Exercise prescriptions should begin conservatively. For supervised programs, patients should be closely observed and their recovery reviewed at the next session.

Exercise intensity for patients with HF or CVD is often based on perceived exertion rather than target HRs because cardiac medications can affect HR. Few patients will have had maximal graded exercise testing prior to referral. Exercise should be prescribed at a Borg scale RPE of 11-13, and commence at a short duration (approximately 10 minutes).

Some individuals may be too frail to commence even this volume of exercise. For these patients, low- or moderate-intensity interval training may be more appropriate (e.g., using repeated cycles of 30 seconds of exercise followed by 1 minute of rest).

Exercise intensity may be progressed when the RPE or HR falls at the initial intensity. The new intensity can be adjusted to remain within the RPE and HR bands.

Higher intensities of exercise (up to 80% of VO₂ peak) may be conducted in hospitals or in exercise centres with equipment and personnel to manage advanced cardiac life support. Patients aspiring to higher-intensity exercise (up to 80% of VO₂ peak or RPE ≥14) should undergo a screening peak exercise test with 12-lead ECG monitoring under medical supervision.

The table below provides guidance on exercise intensity for patients with HF, according to the functional class status.

Table 4: Recommended exercise intensity for heart failure patients

NB: Exercise intensity is prescribed similarly for HFrEF and HFpEF

High-intensity interval training

High-intensity interval training (HIIT) is a new method of aerobic exercise training currently being trialled in patients with CVD. HIIT involves alternating short bouts (3-4 minutes) of high-intensity (>80-90% of maximum HR) and moderate-intensity (50-70% maximum HR) exercise.

Studies have reported that HIIT is more effective than moderate-intensity continuous exercise in improving aerobic capacity in patients with coronary artery disease[#rognmo-hetland-e-helgerud-j-et-al.-2004] and HF.[#wislff-u-stylen-a-loennechen-jp-et-al.-2007]

Additionally, in patients with HF, HIIT improved left ventricular end-diastolic (18%) and end-systolic volumes (25%), and ejection fraction (35%), whereas these changes are not observed following moderate-intensity training.[#wislff-u-stylen-a-loennechen-jp-et-al.-2007]

A recent meta-analysis also found that HIIT was more effective than moderate-intensity training in improving vascular endothelial function; an important indicator of vascular health.[#ramos-js-dalleck-lc-tjonna-ae-et-al.-2015] However, the rates of adverse cardiovascular responses during and immediately after HIIT training were approximately 5 times higher than in response to moderate-intensity exercise training in cardiac patients.[#rognmo-moholdt-t-bakken-h-et-al.-2012] Accordingly, caution and careful clinical judgement should be taken when considering HIIT prescription to patients with CVD until the safety of HIIT is more clearly determined.

Time (duration)

There is no set format for exercise duration progression. The duration of exercise is a function of the intensity that an individual is able to undertake.

Very frail individuals may commence exercising for only 1-10 minutes, accumulating 30 minutes with multiple short sessions and progressing as able. Other individuals may commence at the target intensity for a longer duration (e.g., 10-15 minutes) and progress more rapidly.

Recommendations suggest aiming for approximately 30 minutes on most (at least 5) days per week, although additional benefits accrue from activity of up to 60 minutes. For patients with very limited exercise tolerance, encourage any physical activity.

Type

The aerobic component of an exercise session should consist of a variety of activities targeting a range of large muscle groups. The choice of exercise is at the discretion of the clinician, however, both upper and lower limbs should be included with due consideration to co-morbidities.

Common examples of potentially suitable exercises include:

• Walking
• Treadmill
• Exercise bike
• Rowing machine
• Step ups
• Upper limb ergometry

There is no evidence that one modality of exercise yields a greater benefit than another if patients adhere to the prescribed recommended dose.

Progressing exercise

Once prolonged exercise is tolerated at a low intensity, the exercise intensity should be gradually intensified to the target level (see table below). After the target level is achieved, the duration may then require increasing. Improved exercise tolerance typically enables higher-intensity exercise at a similar or lower rating of perceived exertion.

Table 5: Example of staging exercise progression

*Very deconditioned patients may need to commence at a duration of less than 10 minutes.

Resistance exercise involves exerting muscular force to move a body segment or an external resistance, such as a weight or resistance band. This is the best form of exercise for maintaining and improving muscle strength; it contributes to joint health and maintains lean body mass. Resistance exercise training complements aerobic training by addressing muscle strength and improving local muscle endurance. It also improves the capacity for routine daily living activities that involve a strength component, such as carrying groceries, gardening and cleaning.

In HF patients, muscle atrophy and weakness are common, especially in the elderly and those with more advanced disease and frailty. Earlier concerns regarding the detrimental effect of resistance training on ventricular function and potential acceleration of remodelling have not been confirmed. In addition, haemodynamic responses to resistance exercise at moderate intensities are comparable to similar intensities of aerobic exercise.[#mckelvie-rs-mccartney-n-tomlinson-c-et-al.-1995]

Muscle strength (especially leg strength) and total muscle cross-sectional area are independent predictors of exercise tolerance, clinical prognosis and long-term survival in patients with HF.[#braith-rw-beck-dt.-2008] For this reason, resistance training is now recommended practice for patients with HF.

Availability of equipment will often guide program design.

Equipment may include:

• Body weight/body segments
• Free weights
• Machine stacks
• Isokinetic machines
• Thera-Bands

The minimum frequency to improve strength is a single set performed twice a week.[#williams-m-haskell-w-ades-p-et-al.-2007] As training progresses, patients may need to train more frequently and increase the number of sets. Resistance exercise should complement rather than replace aerobic exercise, so it is important to ensure the time required to undertake all exercise is consistent with the patient’s level of commitment and health status.

Resistance exercise is particularly useful when:

• The patient is prone to myocardial ischaemia – resistance exercise utilising small muscle groups is associated with lower myocardial oxygen demand than large muscle group aerobic activities such as cycling or walking
• Orthopaedic complaints limit aerobic exercise
• Maintaining or promoting strength-related activities of daily living
• Dyspnoea significantly limits aerobic exercise
• Climatic conditions limit the patient's ability to perform outdoor aerobic exercise.

When prescribing resistance exercise, it is important to:

• Initiate resistance training under supervision
• Initiate resistance loads conservatively to ensure good technique
• Encourage appropriate breathing techniques (exhale while lifting the weight and inhale while lowering) to avoid Valsalva manoeuvre
• Aim initially for 12-25 reps at low intensity (RPE 12-13) to increase muscle endurance with reps before progressing the intensity
• When the patient is confident, progress to higher intensities (RPE < 15) at 8-15 reps, emphasising increased muscle mass
• Avoid isometric exercises
• Include 8-10 exercises to engage major functional muscle groups of the upper and lower body
• For patients with advanced CVD, prescribe exercises that involve single joints and isolate smaller areas of muscle
• After about 4 weeks of low intensity exercise, employ strength testing to individualise resistance exercise at 50-70% of the one-repetition maximum strength.[#piepoli-mf-conraads-v-corra-u-et-al.-2011]

TIP: A comprehensive exercise program should include both aerobic and resistance exercise. Including both exercise modalities improves the time efficiency of exercise sessions and yields greater physiological outcomes.

Some patients, particularly the elderly and frail, should undertake balance and flexibility exercises, which aim to challenge the individual’s balance system.

A stretching regimen may be incorporated into the warm-up or cool-down, or be included as a specific component of the individualised exercise program. Muscles commonly targeted are the hamstrings, quadriceps, calves and pectoralis major, however, this will vary significantly according to individual requirements.

Respiratory (inspiratory) muscle training is particularly useful for people who have respiratory muscle weakness. A mouthpiece (inspiratory muscle trainer), as shown below, provides resistance as the individual breathes in, thereby training the respiratory muscles. Specific protocols determine the appropriate level of resistance. A recent meta-analysis of respiratory muscle training in patients with HF, identified additional gains in 6MWT and VO₂ peak in those with respiratory muscle weakness.[#montemezzo-d-fregonezi-ga-pereira-da-et-al.-2014]

Figure 1: ‘Powerbreathe’ inspiratory muscle trainer

Reproduced with permission from Powerbreathe International

Functional electrical stimulation (FES) is an adjunct to exercise training for patients who are extremely unwell or deconditioned (i.e., NYHA class III or IV). FES is a passive therapy, where a small electrical current is passed through a targeted muscle (usually quadriceps), stimulating a muscle contraction. The effect is improved muscle function similar to that which occurs after exercise training.

FES may help maintain fitness during periods of severe HF decompensation and subsequently assist in returning a patient to a level of function that allows the recommencement of a low-intensity cycling or walking exercise. FES may be contraindicated in those with a cardiac device.

Figure 2: Example of functional electrical stimulation (FES) machine

Reproduced with permission from Astir Australia