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The Health Benefits of a 12-Week Home-Based Interval Training Cardiac Rehabilitation Program in Patients With Heart Failure
Accepted Manuscript The Health Benefits of a 12 Week Home-Based Interval Training Cardiac Rehabilitation Program in Patients with Heart Failure Hedieh Safiyari-Hafizi, MSc, Jack Taunton, MD, Andrew Ignaszewski, MD, Darren Warburton, PhD PII:
S0828-282X(16)00092-1
DOI:
10.1016/j.cjca.2016.01.031
Reference:
CJCA 2017
To appear in:
Canadian Journal of Cardiology
Received Date: 10 December 2015 Revised Date:
27 January 2016
Accepted Date: 27 January 2016
Please cite this article as: Safiyari-Hafizi H, Taunton J, Ignaszewski A, Warburton D, The Health Benefits of a 12 Week Home-Based Interval Training Cardiac Rehabilitation Program in Patients with Heart Failure, Canadian Journal of Cardiology (2016), doi: 10.1016/j.cjca.2016.01.031. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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The Health Benefits of a 12 Week Home-Based Interval Training Cardiac Rehabilitation Program in Patients with Heart Failure
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Hedieh Safiyari-Hafizi a,b, MSc, Jack Taunton b,d, MD, Andrew Ignaszewski b,c, MD, and
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Darren Warburton d,e, PhD a)
Copeman Healthcare Centre, Vancouver, British Columbia
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b)
Faculty of Medicine, University of British Columbia (UBC), Vancouver, British Columbia
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c)
Healthy Heart Program and Heart Function Clinic, St. Paul’s Hospital, Vancouver, British Columbia
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d)
Experimental Medicine Program, Faculty of Medicine, UBC, Vancouver, British Columbia
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e)
Physical Activity Promotion and Chronic Disease Prevention Unit, UBC, Vancouver, British Columbia
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Corresponding Author: Darren Warburton, 6018 Thunderbird Blvd, University of British Columbia, Vancouver, BC V6T1Z3
Summary
In a randomized controlled trial, we examined the safety and efficacy of a 12-week home-
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based rehabilitation program involving interval and resistance training in comparison to
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usual care. The novel training program was well tolerated and leading to improvements in
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cardiovascular fitness and Quality of Life in patients with heart failure. This research has
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important implications for cardiac rehabilitation and the treatment of heart failure.
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Abstract
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Background: Recently, high intensity interval training has been advocated for the
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rehabilitation of persons living with heart failure (HF). Home-based training is more
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convenient for many patients and could augment compliance. However, the safety and
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efficacy of home-based interval training remains unclear. Methods: We evaluated the safety
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and efficacy of a supervised home-based exercise program involving a combination of
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interval and resistance training. Measures of aerobic power, endurance capacity,
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ventilatory threshold, and Quality of Life in forty patients with heart failure (HF), were
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taken at baseline and after 12-weeks. Patients were matched and randomized to either
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control (CTL; n = 20) or experimental (EXP; n = 20) conditions. The EXP group underwent a
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12-week high intensity interval and resistance training program while the CTL maintained
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their usual activities of daily living. Results: In the EXP, we found a significant improvement
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in aerobic power, endurance capacity, ventilatory threshold, and Quality of Life. There were
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no significant changes in CTL. Conclusions: We have shown that a home-based cardiac
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rehabilitation program involving interval and resistance training is associated with
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improved aerobic capacity and Quality of Life in patients with HF. This research has
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important implications for the treatment of HF.
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Introduction Heart failure (HF) is a major public health problem in North America. It is associated with significant morbidity, mortality, frequent hospital admission, and marked health care
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costs. In Canada, approximately 3.5% of adults aged 40 or older have HF with an incidence
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rate of 511 per 100,000 1. There is a lifetime risk of one in five of developing HF with the
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majority of cases and related deaths being observed in those aged 65 or older 2.
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Despite gains in the treatment and prevention of cardiovascular disease, the
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prevalence of HF is anticipated to continue to rise as the result (in part) of an aging
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population, improvements in the treatment of acute HF, and improved survival in patients
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with hypertension and coronary artery disease 2. As such the burden of HF will continue to
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be of great concern including increased hospitalizations and re-hospitalizations, and
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increased costs to society and the individual 2.
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Exercise training is a widely accepted intervention for HF leading to marked health
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benefits 3, 4. Most cardiac rehabilitation programs within Canada employ hospital-based,
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moderate intensity, continuous exercise training for 2 days/week for 12-16 weeks 5.
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Various research groups have recently advocated interval training for the rehabilitation of
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patients with cardiovascular disease including patients with HF 5-12. A growing body of
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evidence has examined the safety and efficacy of interval training in HF in medically
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supervised settings 6, 13-17. A recent meta-analysis 18 reported that interval training was
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more effective for improving peak aerobic power (VO2peak) versus traditional training
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patients with HF. Despite continuous aerobic training being the mainstay of rehabilitation,
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recommendations have increasingly incorporated messaging related to the potential health
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benefits of interval training. For instance, various agencies (including the Canadian
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Association of Cardiovascular Prevention and Rehabilitation, the American Association of
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Cardiovascular and Pulmonary Rehabilitation, the Canadian Cardiovascular Society, and
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the European Association for Cardiovascular Prevention and Rehabilitation) have included
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messaging on high intensity interval training for implementation within cardiac
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rehabilitation settings 5, 19.
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Researchers have begun to examine the effectiveness of interval training in homebased settings with patients living with coronary heart disease 11, 20, 21. This research has
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demonstrated the potential for long-term exercise adherence and the maintenance of
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VO2peak over a 1- yr period 21. Recently, home-based exercise interventions have also been
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advocated for the treatment of stable HF 22-25. However, the optimal home-based exercise
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intervention has yet to be clearly established.
To our knowledge, no study has examined the effectiveness of a high intensity
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home-based cardiac rehabilitation program in HF. Accordingly, the primary purpose of this
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research was to evaluate the effectiveness of a comprehensive home-based cardiac
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rehabilitation program involving interval training on the health status of patients with HF.
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We hypothesized that a novel home-based exercise intervention (involving high intensity
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interval training) would lead to significant improvements in aerobic power, exercise
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capacity, and overall Quality of Life in patients with HF in comparison to control.
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Methods
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Forty patients with HF were recruited, stratified (according to body mass, VO2peak,
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age, and New York Heart Association (NYHA) classification) and randomized to control
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(CTL; n = 20) or experimental (EXP; n = 20) conditions. Twenty-nine patients completed
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the trial (CTL = 15; EXP = 14) (see Supplementary Table S1 for inclusion and exclusion
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criteria). Ethical approval and written informed consent were obtained. Measures of VO2peak, cardiorespiratory responses at ventilatory threshold (V-slope
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method), endurance capacity (6-min walk test), and self-reported Quality of Life were
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assessed at baseline and following the 12-week training program. The EXP group
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underwent a 12-week high intensity interval aerobic and resistance training program. The
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CTL patients were asked to maintain usual activities of daily living; however, this was not
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documented.
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Measurements
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Exercise Capacity
Submaximal exercise capacity was estimated using the 6-min walk test 26. The 6-min
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walk test was performed on a flat, non-carpeted, unobstructed, indoor 20-m walking
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course. Participants were required to cover as much distance as possible during 6 min with
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no verbal encouragement. All participants were provided a practice session to minimize
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the learning effect. A tester that was blind to the treatment allocation of the participants
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performed all tests.
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Cardiopulmonary Stress Testing
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All patients performed an incremental exercise test using an electronically braked
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cycle ergometer with direct gas monitoring to assess VO2peak. The patients completed a
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symptom-limited incremental exercise protocol (10 W/min) with continuous 12-lead
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electrocardiography and the assessment of blood pressure and oxygen saturation every 2
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min. Criteria for terminating the exercise test included electrocardiogram changes
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associated with myocardial ischemia, volitional fatigue, a respiratory exchange ratio of
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>1.1, a levelling off in oxygen consumption, systolic blood pressure >200 mmHg, diastolic
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blood pressure >100 mmHg, dyspnea, or calf/thigh pain.
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Quality of Life Quality of Life was assessed via self-report using the Minnesota Living with Heart
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Failure Questionnaire 27. This validated questionnaire contains 21 questions related to
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physical, socioeconomic, and psychological impairments. It is scored on a 6-point Likert
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scale (0-5) with total scores ranging from 0 to 105 with higher scores reflecting greater
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impairment.
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Exercise Program
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The EXP group was enrolled in a 12-week supervised home-based walking program that was individualized according to the stress test, medications, and activity level.
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Participants exercised using bouts of high intensity work phases (80-85% VO2peak)
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followed by periods of active recovery (40-50 % VO2peak). The duration of each interval
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varied and was carefully individualized for each patient depending on their functional
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capacity to ensure the safety and efficacy of the program. The patients’ intensity, frequency
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and time were adjusted on a regular basis according to the capacity of the patient and
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according to changes in the heart rate response to exercise (Supplementary Table S2) 8, 30.
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Patients were provided portable heart rate monitors and pedometers to keep track of their
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workouts. In addition, patients in EXP were also instructed on a series of strengthening
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exercises owing to its additive health benefits 31 (Supplementary Table S2).
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To ensure compliance and safety, the qualified exercise professional also contacted
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each patient within EXP initially for three times a week for the first month, twice a week for
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the second month, and once a week for the third month. The CTL was not provided any
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formal exercise prescription and follow-ups. They were simply encouraged to continue
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exercising moderately on a regular basis by the nurse at the intake clinic without being
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given any specific guidelines (as per usual clinical practice).
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Statistical Analyses
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Descriptive and inferential statistical analyses of all data were conducted using Statistica 6 and reported as mean ± SD. The alpha level set a priori at p < 0.05. A two
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(Group) x two (Time) mixed model ANOVA was used to evaluate significant changes in each
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dependent variable in CTL versus EXP over the 12 wk. Tukey post hoc comparisons were
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used to determine where differences existed. Independent t-tests were used to establish
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group differences for baseline characteristics.
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Results
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At baseline, patients from both groups were well matched based on age, body mass index, initial VO2peak and NYHA functional class (Supplementary Table S3). There was a
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significant interaction effect for VO2peak representing an improvement in EXP and a
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reduction in CTL over the intervention (Figure 1A). There were no significant
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improvements in peak power output, oxygen pulse, and minute ventilation in EXP group
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compared to the CTL group (Supplementary Table S4). There was a significant interaction
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effect for Quality of Life as reflected by fewer adverse symptoms in the EXP in comparison
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to the CTL who exhibited a slight increase in adverse symptoms (Figure 1B). There was a
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significant interaction effect for the 6 min walk test reflecting an improvement in EXP and a
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decline in CTL (Figure 1C). There was a significant improvement in power output and VO2
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at ventilatory threshold in EXP versus CTL (Table 1). There were no adverse exercise-
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related events in EXP and CTL and the adherence to the exercise prescription was high in
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EXP (77 ± 20%).
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Discussion The major new finding of this investigation was that supervised home-based cardiac
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rehabilitation including a combination of high intensity interval and resistance training
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resulted in a significant improvement in VO2peak in patients with HF. Furthermore, we
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showed a significant improvement in exercise capacity, Quality of Life, and the oxygen
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consumption at ventilatory threshold. These findings have significant implications for the
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health status and overall Quality of Life in HF. Given the important role aerobic power and
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functional status plays in morbidity and mortality in HF 32, 33, these findings may also have
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potentially important implications for improving survival in HF and reducing
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hospitalizations and the health care costs associated with treating HF.
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High intensity exercise training has been advocated as a safe and effective means of
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cardiac rehabilitation providing a viable option to traditional programming for patients
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living with cardiovascular disease 6, 13-17. Previously, we 8 revealed that interval training led
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to similar changes in VO2peak and greater improvements in strenuous exercise capacity in
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comparison to traditional continuous training. A compelling body of literature has also
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demonstrated the safety and efficacy of high intensity interval training in HF in medically
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supervised settings 6, 13-17. For instance, two recent systematic reviews 18, 34 established the
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potential health benefits and limited risks associated with interval training in HF. For
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instance, Haykowsky et al. 18 examined seven randomized controlled trials in patients with
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HF and found that there were significantly greater increases in VO2peak with interval
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training in comparison to traditional cardiac rehabilitation (weighted mean = 2.14
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mL/kg/min). There was no difference after training in resting left ventricular ejection
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fraction. Similarly, Ismail and colleagues 34 examined 74 studies of different exercise
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intensity training programs in patients living with HF. The authors reported that high
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intensity training increased VO2peak by 3.3 mL/kg/min (23%) in comparison to control.
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They also revealed a direct relationship between exercise training intensity and the
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magnitude of improvement in aerobic fitness, with very low risks for adverse exercise-
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related events (i.e., no exercise-related deaths occurred). Based on the current literature,
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interval training has gained more acceptance in traditional, medically supervised, cardiac
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rehabilitation settings including specific messaging from major international cardiac
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rehabilitation agencies 5, 19. However, its implementation within traditional rehabilitation
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settings has been remarkably slow 5.
Despite a relatively limited uptake in traditional rehabilitation environment, the
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research in the area has translated directly into an increased evaluation of high intensity
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interval training in home-based settings. This research has been largely confined to
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patients living with coronary heart disease demonstrating improvements in aerobic fitness,
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high exercise adherence rates, and the maintenance of aerobic/functional capacity over
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prolonged periods 11, 20, 21. To the best of our knowledge, this is the first study to examine
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the health benefits of a home-based walking program using an interval training method
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combined with resistance training. We revealed that this closely monitored home-based
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cardiac rehabilitation program (employing high intensity interval and resistance training)
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resulted in significant improvements in physiological well-being and overall Quality of Life.
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This is consistent with other trials of HF management that support the use of home-based
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aerobic training programs that include close monitoring and interaction with patients via
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follow-ups 23, 35. We demonstrated an average 11.4 ± 18.4% (approximately 2 mL/kg/min)
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change in VO2peak in our patients after a 3-month home-based program. Our findings
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compare quite well to other large clinical trials employing traditional cardiac rehabilitation
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(i.e., moderate intensity, continuous exercise training). For instance, the HF-ACTION 36 and
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EXERT 25 trials demonstrated 4 and 10% increase in VO2peak, respectively, after 3 months
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of traditional cardiac rehabilitation, while Belardinelli and coworkers 37 revealed 18%
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increases in VO2peak after 2 months of traditional cardiac rehabilitation (3 times a week
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for 8 weeks at 60% of VO2peak) with little change over a 1 year period of supervised
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training (2 times per week). Our findings also compare well to the findings from the
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systematic reviews 18, 34 that demonstrated mean changes of 2-3 mL/kg/min after interval
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training in medically supervised environments with patients living with HF. This speaks
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directly to the applicability and efficacy of home-based interval training in persons living
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with HF. There were no exercise-related adverse events in the patients assigned to interval
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training.
The changes observed in aerobic power have important implications for the overall
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health and well-being of patients with HF. For instance, the mean 11% improvement in
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VO2peak (13 ± 4 to 15 ± 3 mL/kg/min) has important prognostic implications 32. Moreover,
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this aerobic power level has significant implications for the ability to complete activities of
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daily living and functional dependence. For instance, Myers and colleagues 38 recently
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developed age-specific exercise capacity thresholds (i.e., 8-9, 7-8, 6-7, and 5-6 METs for
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<50, 50-59, 60-69, and ≥70 yr, respectively) for mortality risk in males 38. Mortality risk
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was progressively higher in those individuals with a peak MET level below each threshold.
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The authors revealed that for every 1-MET increase in exercise capacity, mortality risk was
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12% lower for the entire cohort, 15% for those <60 yr, and 11% for those ≥60 yr. Similarly,
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Paterson and colleagues 39 revealed that the minimum level of aerobic power compatible
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with an independent life at age 85 yr was approximately 18 and 15 mL/kg/min in men and
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women, respectively. As such, many patients with HF live at or below the functional
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threshold for dependence 4, 40. The significant improvement in aerobic power is important
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for improving the functional reserve of the patients with HF and reducing the risk for
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disability/functional dependence and premature mortality 4. Similarly, our improvements
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in 6 min walk time have important health implications. For instance, Bittner and colleagues
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revealed that those individuals with HF in the lowest 6 min walk performance level had the
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greatest chance of dying prematurely, while those with the highest score had the lowest
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risk (10 vs. 3%, respectively) 33. Similar findings were also recently observed in another
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clinical trial 41. During a 3-yr follow-up, the authors revealed that the shorter the distance
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covered the greater the 1- and 3-yr morality risk. Also, the distance covered was inversely
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related with hospitalization rates in HF 41.
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survival and lower hospital admission and overall cost associated with HF 28, and some are
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still examining the importance of formal exercise training over a general exercise
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recommendation with no guidance 29. Despite this growing body of evidence, relatively
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limited HF clinics offer closely monitored and structured home-based exercise programs.
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Unique to this investigation, we requested that the patients to follow a home-based interval
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training routine (in combination with resistance training) rather than low to moderate
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intensity aerobic training at a continuous pace that is currently used in traditional cardiac
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rehabilitation settings.
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Unlike previous investigations of interval training (including our own work 8), the current investigation utilized an individualized interval training program rather than a
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single (generic) pre-set training intensity. This is quite distinct from most previous studies.
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For instance in our previous work with patients with coronary artery disease 8 we utilized
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2-min, high-intensity work phases at 90% of heart rate reserve (range 85% to 95%)
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followed by 2 min recovery bouts at 40% of heart rate reserve (range 35% to 45%).
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Another study with HF used four 4-min walking intervals at 90-95% of peak heart rate
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interspersed with 3-min active recovery stages (50-70% of peak heart rate) 6. Others have
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advocated shorter bouts of work/recovery phases such as 15s/60s and 10s/60s with 70%
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and 80% of maximum short-term exercise capacity 42, and others demonstrated use of
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short work/recovery phases (30s/ 60s), by using a lower intensity of 50% of maximum
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short-term exercise capacity for work phases 43. Thus, there is widespread variability in the
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recommended intensity and work to rest ratio for interval training in patients with
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cardiovascular disease and HF. For the present investigation, we decided that an
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individualized approach to interval training was the best for the home-based setting,
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particularly from an exercise adherence perspective. The high exercise adherence rate and
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no adverse exercise-related events are evidence of the success of this intervention.
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The improvements in subjective indicators of Quality of Life have important
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implications for the health and overall well-being of our patients. In our investigation, there
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were significantly fewer adverse symptoms in the EXP in comparison to the CTL who
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exhibited a slight increase in adverse symptoms. These findings are similar to those of
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Belardinelli et al. 37 who reported that Quality of Life improved in parallel to VO2peak after
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a traditional cardiac rehabilitation program. Our findings are also consistent (albeit more
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pronounced) than the findings from the HF-ACTION trial that demonstrated modest, but
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statistically significant improvements in Quality of Life after traditional rehabilitation. Our
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results also compare well to other home-based interval training programs in patients with
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coronary heart disease 11.
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Limitations
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We recognize that our small sample size may have limited our ability to detect significant differences in some of our secondary outcome measures. Moreover, our
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participants generally consisted of male patients with HF that were less than 75 yr,
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potentially limiting the generalizability to other patients.
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Conclusions
In conclusion, the findings of our investigation support strongly the hypothesis that
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an individualized and closely supervised (by consistent follow-ups) home-based interval
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exercise program is an effective means of functionally rehabilitating patients with HF.
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These findings have important implications for the treatment of HF, particularly for
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outpatients who do not have accessibility to hospital-based cardiac rehabilitation. Further
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research is warranted to determine whether this program can reduce the health care costs,
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morbidity, and premature mortality associated with HF.
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Acknowledgements
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This study was supported by BC Sports Medicine Research Foundation Grant.
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Table 1: Cardiovascular responses at ventilatory threshold in control and experimental group over the 12-week intervention. Baseline
Post
p
Power Output (W) Experimental
Variable
56 ± 21
62 ± 25
0.010*
Control
54 ± 21
43 ± 15
Experimental
10.1 ± 3.1
11.2 ± 2.9
Control
10.1 ± 2.8
9.4 ± 2.4
RER Experimental
1.00 ± 0.04
Control
1.01 ± 0.07
0.99 ± 0.10
VE (L/min) Experimental
33.0 ± 8.0
35.3 ± 12.9
Control
32.9 ± 9.7
30.4 ± 6.8
92 ± 12
95 ± 22
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Heart Rate (bpm) Experimental Control Heart Rate (% max) Experimental
86 ± 24
60 ± 12
63 ± 19
65 ± 24
62 ± 19
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0.040*
0.758
0.082
0.069
0.475
Oxygen Pulse (mL O2/beat)
Control
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9.8 ± 4.2
10.5 ± 3.1
9.3 ± 3.8
9.0 ± 2.9
0.266
VE, minute ventilation; RER, respiratory exchange ratio; VO2, oxygen consumption. Values are means ± SD; the p values for the interactions effect are shown. * significant interaction effect (p < 0.05).
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Figure Legend
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walk distance (C) over the 12-week intervention. * Significant interaction effect
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reflecting an improvement in the experimental group and no change in the control
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group.
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Figure 1: Changes in peak aerobic power (VO2peak; A), Quality of Life (B), and 6 min
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Chrysohoou C, Tsitsinakis G, Vogiatzis I, et al. High intensity, interval exercise
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Haykowsky MJ, Timmons MP, Kruger C, McNeely M, Taylor DA, Clark AM. Meta-
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Mezzani A, Hamm LF, Jones AM, et al. Aerobic exercise intensity assessment and prescription in cardiac rehabilitation: a joint position statement of the European
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Association of Cardiac Rehabilitation. Eur J Prev Cardiol. 2013;20:442-467.
intensity interval training in cardiac rehabilitation: a randomized study. Eur J Prev
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Aamot IL, Forbord SH, Gustad K, et al. Home-based versus hospital-based high-
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Chien CL, Lee CM, Wu YW, Chen TA, Wu YT. Home-based exercise increases exercise
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capacity but not quality of life in people with chronic heart failure: a systematic
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review. Aust J Physiother. 2008;54:87-93. 23.
Fayazi S, Zarea K, Abbasi A, Ahmadi F. Effect of home-based walking on performance
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cardiac rehabilitation. Cochrane Database Syst Rev. 2010:CD007130.
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Taylor RS, Dalal H, Jolly K, Moxham T, Zawada A. Home-based versus centre-based
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McKelvie RS, Teo KK, Roberts R, et al. Effects of exercise training in patients with
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Burr JF, Bredin SS, Faktor MD, Warburton DE. The 6-minute walk test as a predictor of objectively measured aerobic fitness in healthy working-aged adults. Phys
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Rector TS, Kubo SH, Cohn JN. Validity of the Minnesota Living with Heart Failure questionnaire as a measure of therapeutic response to enalapril or placebo. Am. J.
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Cardiol. 1993;71:1106-1107. 28.
Piepoli MF, Davos C, Francis DP, Coats AJ, ExTra MC. Exercise training meta-analysis of trials in patients with chronic heart failure (ExTraMATCH). B.M.J. 2004;328:189.
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Whellan DJ, O'Connor CM, Lee KL, et al. Heart failure and a controlled trial
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Warburton DE, Haykowsky MJ, Quinney HA, et al. Blood volume expansion and
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cardiorespiratory function: effects of training modality. Med. Sci. Sports Exerc.
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Delagardelle C, Feiereisen P, Autier P, Shita R, Krecke R, Beissel J.
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Strength/endurance training versus endurance training in congestive heart failure.
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Myers J, Gullestad L, Vagelos R, et al. Cardiopulmonary exercise testing and
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prognosis in severe heart failure: 14 mL/kg/min revisited. Am. Heart. J.
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Bittner V, Weiner DH, Yusuf S, et al. Prediction of mortality and morbidity with a 6-
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minute walk test in patients with left ventricular dysfunction. SOLVD Investigators.
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JAMA. 1993;270:1702-1707. 34.
Ismail H, McFarlane JR, Nojoumian AH, Dieberg G, Smart NA. Clinical outcomes and
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cardiovascular responses to different exercise training intensities in patients with
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heart failure: a systematic review and meta-analysis. JACC. Heart failure.
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2013;1:514-522. 35.
home-based intervention on unplanned readmissions and mortality among patients
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with congestive heart failure. Arch. Intern. Med. 1999;159:257-261.
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Stewart S, Vandenbroek AJ, Pearson S, Horowitz JD. Prolonged beneficial effects of a
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O'Connor CM, Whellan DJ, Lee KL, et al. Efficacy and safety of exercise training in
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patients with chronic heart failure: HF-ACTION randomized controlled trial. JAMA.
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2009;301:1439-1450.
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37.
Belardinelli R, Georgiou D, Cianci G, Purcaro A. Randomized, controlled trial of long-
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term moderate exercise training in chronic heart failure: effects on functional
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capacity, quality of life, and clinical outcome. Circulation. 1999;99:1173-1182. 38.
Kokkinos P, Faselis C, Myers J, Sui X, Zhang J, Blair SN. Age-specific exercise capacity
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threshold for mortality risk assessment in male veterans. Circulation. 2014;130:653-
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658. 39.
Paterson DH, Cunningham DA, Koval JJ, St Croix CM. Aerobic fitness in a population
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of independently living men and women aged 55-86 years. Med. Sci. Sports Exerc.
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Warburton DE, Taylor A, Bredin SS, Esch BT, Scott JM, Haykowsky MJ. Central
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haemodynamics and peripheral muscle function during exercise in patients with
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chronic heart failure. Appl. Physiol. Nutr. Metab. 2007;32:318-331. 41.
Wegrzynowska-Teodorczyk K, Rudzinska E, Lazorczyk M, et al. Distance covered
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during a six-minute walk test predicts long-term cardiovascular mortality and
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hospitalisation rates in men with systolic heart failure: an observational study. J
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Physiother. 2013;59:177-187. 42.
interval exercise in patients with chronic heart failure--application to exercise
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training. Eur. Heart J. 1996;17:1040-1047.
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Meyer K, Samek L, Schwaibold M, et al. Physical responses to different modes of
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Heart Failure of the European Society of Cardiology. Recommendations for exercise
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S0828-282X(16)00092-1
DOI:
10.1016/j.cjca.2016.01.031
Reference:
CJCA 2017
To appear in:
Canadian Journal of Cardiology
Received Date: 10 December 2015 Revised Date:
27 January 2016
Accepted Date: 27 January 2016
Please cite this article as: Safiyari-Hafizi H, Taunton J, Ignaszewski A, Warburton D, The Health Benefits of a 12 Week Home-Based Interval Training Cardiac Rehabilitation Program in Patients with Heart Failure, Canadian Journal of Cardiology (2016), doi: 10.1016/j.cjca.2016.01.031. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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The Health Benefits of a 12 Week Home-Based Interval Training Cardiac Rehabilitation Program in Patients with Heart Failure
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Hedieh Safiyari-Hafizi a,b, MSc, Jack Taunton b,d, MD, Andrew Ignaszewski b,c, MD, and
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Darren Warburton d,e, PhD a)
Copeman Healthcare Centre, Vancouver, British Columbia
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b)
Faculty of Medicine, University of British Columbia (UBC), Vancouver, British Columbia
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c)
Healthy Heart Program and Heart Function Clinic, St. Paul’s Hospital, Vancouver, British Columbia
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d)
Experimental Medicine Program, Faculty of Medicine, UBC, Vancouver, British Columbia
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e)
Physical Activity Promotion and Chronic Disease Prevention Unit, UBC, Vancouver, British Columbia
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Corresponding Author: Darren Warburton, 6018 Thunderbird Blvd, University of British Columbia, Vancouver, BC V6T1Z3
Summary
In a randomized controlled trial, we examined the safety and efficacy of a 12-week home-
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based rehabilitation program involving interval and resistance training in comparison to
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usual care. The novel training program was well tolerated and leading to improvements in
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cardiovascular fitness and Quality of Life in patients with heart failure. This research has
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important implications for cardiac rehabilitation and the treatment of heart failure.
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Abstract
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Background: Recently, high intensity interval training has been advocated for the
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rehabilitation of persons living with heart failure (HF). Home-based training is more
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convenient for many patients and could augment compliance. However, the safety and
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efficacy of home-based interval training remains unclear. Methods: We evaluated the safety
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and efficacy of a supervised home-based exercise program involving a combination of
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interval and resistance training. Measures of aerobic power, endurance capacity,
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ventilatory threshold, and Quality of Life in forty patients with heart failure (HF), were
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taken at baseline and after 12-weeks. Patients were matched and randomized to either
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control (CTL; n = 20) or experimental (EXP; n = 20) conditions. The EXP group underwent a
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12-week high intensity interval and resistance training program while the CTL maintained
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their usual activities of daily living. Results: In the EXP, we found a significant improvement
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in aerobic power, endurance capacity, ventilatory threshold, and Quality of Life. There were
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no significant changes in CTL. Conclusions: We have shown that a home-based cardiac
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rehabilitation program involving interval and resistance training is associated with
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improved aerobic capacity and Quality of Life in patients with HF. This research has
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important implications for the treatment of HF.
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Introduction Heart failure (HF) is a major public health problem in North America. It is associated with significant morbidity, mortality, frequent hospital admission, and marked health care
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costs. In Canada, approximately 3.5% of adults aged 40 or older have HF with an incidence
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rate of 511 per 100,000 1. There is a lifetime risk of one in five of developing HF with the
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majority of cases and related deaths being observed in those aged 65 or older 2.
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Despite gains in the treatment and prevention of cardiovascular disease, the
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prevalence of HF is anticipated to continue to rise as the result (in part) of an aging
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population, improvements in the treatment of acute HF, and improved survival in patients
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with hypertension and coronary artery disease 2. As such the burden of HF will continue to
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be of great concern including increased hospitalizations and re-hospitalizations, and
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increased costs to society and the individual 2.
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Exercise training is a widely accepted intervention for HF leading to marked health
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benefits 3, 4. Most cardiac rehabilitation programs within Canada employ hospital-based,
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moderate intensity, continuous exercise training for 2 days/week for 12-16 weeks 5.
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Various research groups have recently advocated interval training for the rehabilitation of
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patients with cardiovascular disease including patients with HF 5-12. A growing body of
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evidence has examined the safety and efficacy of interval training in HF in medically
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supervised settings 6, 13-17. A recent meta-analysis 18 reported that interval training was
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more effective for improving peak aerobic power (VO2peak) versus traditional training
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patients with HF. Despite continuous aerobic training being the mainstay of rehabilitation,
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recommendations have increasingly incorporated messaging related to the potential health
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benefits of interval training. For instance, various agencies (including the Canadian
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Association of Cardiovascular Prevention and Rehabilitation, the American Association of
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Cardiovascular and Pulmonary Rehabilitation, the Canadian Cardiovascular Society, and
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the European Association for Cardiovascular Prevention and Rehabilitation) have included
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messaging on high intensity interval training for implementation within cardiac
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rehabilitation settings 5, 19.
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Researchers have begun to examine the effectiveness of interval training in homebased settings with patients living with coronary heart disease 11, 20, 21. This research has
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demonstrated the potential for long-term exercise adherence and the maintenance of
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VO2peak over a 1- yr period 21. Recently, home-based exercise interventions have also been
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advocated for the treatment of stable HF 22-25. However, the optimal home-based exercise
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intervention has yet to be clearly established.
To our knowledge, no study has examined the effectiveness of a high intensity
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home-based cardiac rehabilitation program in HF. Accordingly, the primary purpose of this
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research was to evaluate the effectiveness of a comprehensive home-based cardiac
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rehabilitation program involving interval training on the health status of patients with HF.
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We hypothesized that a novel home-based exercise intervention (involving high intensity
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interval training) would lead to significant improvements in aerobic power, exercise
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capacity, and overall Quality of Life in patients with HF in comparison to control.
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Methods
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Forty patients with HF were recruited, stratified (according to body mass, VO2peak,
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age, and New York Heart Association (NYHA) classification) and randomized to control
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(CTL; n = 20) or experimental (EXP; n = 20) conditions. Twenty-nine patients completed
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the trial (CTL = 15; EXP = 14) (see Supplementary Table S1 for inclusion and exclusion
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criteria). Ethical approval and written informed consent were obtained. Measures of VO2peak, cardiorespiratory responses at ventilatory threshold (V-slope
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method), endurance capacity (6-min walk test), and self-reported Quality of Life were
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assessed at baseline and following the 12-week training program. The EXP group
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underwent a 12-week high intensity interval aerobic and resistance training program. The
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CTL patients were asked to maintain usual activities of daily living; however, this was not
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documented.
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Measurements
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Exercise Capacity
Submaximal exercise capacity was estimated using the 6-min walk test 26. The 6-min
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walk test was performed on a flat, non-carpeted, unobstructed, indoor 20-m walking
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course. Participants were required to cover as much distance as possible during 6 min with
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no verbal encouragement. All participants were provided a practice session to minimize
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the learning effect. A tester that was blind to the treatment allocation of the participants
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performed all tests.
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Cardiopulmonary Stress Testing
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All patients performed an incremental exercise test using an electronically braked
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cycle ergometer with direct gas monitoring to assess VO2peak. The patients completed a
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symptom-limited incremental exercise protocol (10 W/min) with continuous 12-lead
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electrocardiography and the assessment of blood pressure and oxygen saturation every 2
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min. Criteria for terminating the exercise test included electrocardiogram changes
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associated with myocardial ischemia, volitional fatigue, a respiratory exchange ratio of
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>1.1, a levelling off in oxygen consumption, systolic blood pressure >200 mmHg, diastolic
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blood pressure >100 mmHg, dyspnea, or calf/thigh pain.
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Quality of Life Quality of Life was assessed via self-report using the Minnesota Living with Heart
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Failure Questionnaire 27. This validated questionnaire contains 21 questions related to
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physical, socioeconomic, and psychological impairments. It is scored on a 6-point Likert
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scale (0-5) with total scores ranging from 0 to 105 with higher scores reflecting greater
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impairment.
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Exercise Program
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The EXP group was enrolled in a 12-week supervised home-based walking program that was individualized according to the stress test, medications, and activity level.
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Participants exercised using bouts of high intensity work phases (80-85% VO2peak)
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followed by periods of active recovery (40-50 % VO2peak). The duration of each interval
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varied and was carefully individualized for each patient depending on their functional
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capacity to ensure the safety and efficacy of the program. The patients’ intensity, frequency
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and time were adjusted on a regular basis according to the capacity of the patient and
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according to changes in the heart rate response to exercise (Supplementary Table S2) 8, 30.
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Patients were provided portable heart rate monitors and pedometers to keep track of their
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workouts. In addition, patients in EXP were also instructed on a series of strengthening
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exercises owing to its additive health benefits 31 (Supplementary Table S2).
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To ensure compliance and safety, the qualified exercise professional also contacted
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each patient within EXP initially for three times a week for the first month, twice a week for
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the second month, and once a week for the third month. The CTL was not provided any
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formal exercise prescription and follow-ups. They were simply encouraged to continue
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exercising moderately on a regular basis by the nurse at the intake clinic without being
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given any specific guidelines (as per usual clinical practice).
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Statistical Analyses
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Descriptive and inferential statistical analyses of all data were conducted using Statistica 6 and reported as mean ± SD. The alpha level set a priori at p < 0.05. A two
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(Group) x two (Time) mixed model ANOVA was used to evaluate significant changes in each
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dependent variable in CTL versus EXP over the 12 wk. Tukey post hoc comparisons were
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used to determine where differences existed. Independent t-tests were used to establish
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group differences for baseline characteristics.
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Results
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At baseline, patients from both groups were well matched based on age, body mass index, initial VO2peak and NYHA functional class (Supplementary Table S3). There was a
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significant interaction effect for VO2peak representing an improvement in EXP and a
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reduction in CTL over the intervention (Figure 1A). There were no significant
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improvements in peak power output, oxygen pulse, and minute ventilation in EXP group
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compared to the CTL group (Supplementary Table S4). There was a significant interaction
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effect for Quality of Life as reflected by fewer adverse symptoms in the EXP in comparison
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to the CTL who exhibited a slight increase in adverse symptoms (Figure 1B). There was a
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significant interaction effect for the 6 min walk test reflecting an improvement in EXP and a
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decline in CTL (Figure 1C). There was a significant improvement in power output and VO2
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at ventilatory threshold in EXP versus CTL (Table 1). There were no adverse exercise-
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related events in EXP and CTL and the adherence to the exercise prescription was high in
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EXP (77 ± 20%).
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Discussion The major new finding of this investigation was that supervised home-based cardiac
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rehabilitation including a combination of high intensity interval and resistance training
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resulted in a significant improvement in VO2peak in patients with HF. Furthermore, we
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showed a significant improvement in exercise capacity, Quality of Life, and the oxygen
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consumption at ventilatory threshold. These findings have significant implications for the
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health status and overall Quality of Life in HF. Given the important role aerobic power and
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functional status plays in morbidity and mortality in HF 32, 33, these findings may also have
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potentially important implications for improving survival in HF and reducing
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hospitalizations and the health care costs associated with treating HF.
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High intensity exercise training has been advocated as a safe and effective means of
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cardiac rehabilitation providing a viable option to traditional programming for patients
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living with cardiovascular disease 6, 13-17. Previously, we 8 revealed that interval training led
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to similar changes in VO2peak and greater improvements in strenuous exercise capacity in
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comparison to traditional continuous training. A compelling body of literature has also
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demonstrated the safety and efficacy of high intensity interval training in HF in medically
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supervised settings 6, 13-17. For instance, two recent systematic reviews 18, 34 established the
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potential health benefits and limited risks associated with interval training in HF. For
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instance, Haykowsky et al. 18 examined seven randomized controlled trials in patients with
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HF and found that there were significantly greater increases in VO2peak with interval
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training in comparison to traditional cardiac rehabilitation (weighted mean = 2.14
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mL/kg/min). There was no difference after training in resting left ventricular ejection
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fraction. Similarly, Ismail and colleagues 34 examined 74 studies of different exercise
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intensity training programs in patients living with HF. The authors reported that high
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intensity training increased VO2peak by 3.3 mL/kg/min (23%) in comparison to control.
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They also revealed a direct relationship between exercise training intensity and the
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magnitude of improvement in aerobic fitness, with very low risks for adverse exercise-
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related events (i.e., no exercise-related deaths occurred). Based on the current literature,
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interval training has gained more acceptance in traditional, medically supervised, cardiac
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rehabilitation settings including specific messaging from major international cardiac
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rehabilitation agencies 5, 19. However, its implementation within traditional rehabilitation
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settings has been remarkably slow 5.
Despite a relatively limited uptake in traditional rehabilitation environment, the
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research in the area has translated directly into an increased evaluation of high intensity
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interval training in home-based settings. This research has been largely confined to
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patients living with coronary heart disease demonstrating improvements in aerobic fitness,
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high exercise adherence rates, and the maintenance of aerobic/functional capacity over
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prolonged periods 11, 20, 21. To the best of our knowledge, this is the first study to examine
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the health benefits of a home-based walking program using an interval training method
19
combined with resistance training. We revealed that this closely monitored home-based
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cardiac rehabilitation program (employing high intensity interval and resistance training)
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resulted in significant improvements in physiological well-being and overall Quality of Life.
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This is consistent with other trials of HF management that support the use of home-based
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aerobic training programs that include close monitoring and interaction with patients via
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follow-ups 23, 35. We demonstrated an average 11.4 ± 18.4% (approximately 2 mL/kg/min)
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change in VO2peak in our patients after a 3-month home-based program. Our findings
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compare quite well to other large clinical trials employing traditional cardiac rehabilitation
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(i.e., moderate intensity, continuous exercise training). For instance, the HF-ACTION 36 and
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EXERT 25 trials demonstrated 4 and 10% increase in VO2peak, respectively, after 3 months
6
of traditional cardiac rehabilitation, while Belardinelli and coworkers 37 revealed 18%
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increases in VO2peak after 2 months of traditional cardiac rehabilitation (3 times a week
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for 8 weeks at 60% of VO2peak) with little change over a 1 year period of supervised
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training (2 times per week). Our findings also compare well to the findings from the
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systematic reviews 18, 34 that demonstrated mean changes of 2-3 mL/kg/min after interval
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training in medically supervised environments with patients living with HF. This speaks
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directly to the applicability and efficacy of home-based interval training in persons living
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with HF. There were no exercise-related adverse events in the patients assigned to interval
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training.
The changes observed in aerobic power have important implications for the overall
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health and well-being of patients with HF. For instance, the mean 11% improvement in
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VO2peak (13 ± 4 to 15 ± 3 mL/kg/min) has important prognostic implications 32. Moreover,
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this aerobic power level has significant implications for the ability to complete activities of
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daily living and functional dependence. For instance, Myers and colleagues 38 recently
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developed age-specific exercise capacity thresholds (i.e., 8-9, 7-8, 6-7, and 5-6 METs for
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<50, 50-59, 60-69, and ≥70 yr, respectively) for mortality risk in males 38. Mortality risk
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was progressively higher in those individuals with a peak MET level below each threshold.
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The authors revealed that for every 1-MET increase in exercise capacity, mortality risk was
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12% lower for the entire cohort, 15% for those <60 yr, and 11% for those ≥60 yr. Similarly,
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Paterson and colleagues 39 revealed that the minimum level of aerobic power compatible
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with an independent life at age 85 yr was approximately 18 and 15 mL/kg/min in men and
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women, respectively. As such, many patients with HF live at or below the functional
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threshold for dependence 4, 40. The significant improvement in aerobic power is important
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for improving the functional reserve of the patients with HF and reducing the risk for
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disability/functional dependence and premature mortality 4. Similarly, our improvements
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in 6 min walk time have important health implications. For instance, Bittner and colleagues
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revealed that those individuals with HF in the lowest 6 min walk performance level had the
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greatest chance of dying prematurely, while those with the highest score had the lowest
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risk (10 vs. 3%, respectively) 33. Similar findings were also recently observed in another
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clinical trial 41. During a 3-yr follow-up, the authors revealed that the shorter the distance
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covered the greater the 1- and 3-yr morality risk. Also, the distance covered was inversely
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related with hospitalization rates in HF 41.
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Other large clinical trials suggested that supervised exercise training may enhance
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survival and lower hospital admission and overall cost associated with HF 28, and some are
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still examining the importance of formal exercise training over a general exercise
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recommendation with no guidance 29. Despite this growing body of evidence, relatively
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limited HF clinics offer closely monitored and structured home-based exercise programs.
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Unique to this investigation, we requested that the patients to follow a home-based interval
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training routine (in combination with resistance training) rather than low to moderate
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intensity aerobic training at a continuous pace that is currently used in traditional cardiac
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rehabilitation settings.
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Unlike previous investigations of interval training (including our own work 8), the current investigation utilized an individualized interval training program rather than a
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single (generic) pre-set training intensity. This is quite distinct from most previous studies.
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For instance in our previous work with patients with coronary artery disease 8 we utilized
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2-min, high-intensity work phases at 90% of heart rate reserve (range 85% to 95%)
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followed by 2 min recovery bouts at 40% of heart rate reserve (range 35% to 45%).
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Another study with HF used four 4-min walking intervals at 90-95% of peak heart rate
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interspersed with 3-min active recovery stages (50-70% of peak heart rate) 6. Others have
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advocated shorter bouts of work/recovery phases such as 15s/60s and 10s/60s with 70%
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and 80% of maximum short-term exercise capacity 42, and others demonstrated use of
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short work/recovery phases (30s/ 60s), by using a lower intensity of 50% of maximum
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short-term exercise capacity for work phases 43. Thus, there is widespread variability in the
15
recommended intensity and work to rest ratio for interval training in patients with
16
cardiovascular disease and HF. For the present investigation, we decided that an
17
individualized approach to interval training was the best for the home-based setting,
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particularly from an exercise adherence perspective. The high exercise adherence rate and
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no adverse exercise-related events are evidence of the success of this intervention.
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The improvements in subjective indicators of Quality of Life have important
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implications for the health and overall well-being of our patients. In our investigation, there
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were significantly fewer adverse symptoms in the EXP in comparison to the CTL who
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exhibited a slight increase in adverse symptoms. These findings are similar to those of
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Belardinelli et al. 37 who reported that Quality of Life improved in parallel to VO2peak after
2
a traditional cardiac rehabilitation program. Our findings are also consistent (albeit more
3
pronounced) than the findings from the HF-ACTION trial that demonstrated modest, but
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statistically significant improvements in Quality of Life after traditional rehabilitation. Our
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results also compare well to other home-based interval training programs in patients with
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coronary heart disease 11.
7
Limitations
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We recognize that our small sample size may have limited our ability to detect significant differences in some of our secondary outcome measures. Moreover, our
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participants generally consisted of male patients with HF that were less than 75 yr,
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potentially limiting the generalizability to other patients.
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Conclusions
In conclusion, the findings of our investigation support strongly the hypothesis that
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an individualized and closely supervised (by consistent follow-ups) home-based interval
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exercise program is an effective means of functionally rehabilitating patients with HF.
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These findings have important implications for the treatment of HF, particularly for
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outpatients who do not have accessibility to hospital-based cardiac rehabilitation. Further
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research is warranted to determine whether this program can reduce the health care costs,
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morbidity, and premature mortality associated with HF.
20
Acknowledgements
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This study was supported by BC Sports Medicine Research Foundation Grant.
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Table 1: Cardiovascular responses at ventilatory threshold in control and experimental group over the 12-week intervention. Baseline
Post
p
Power Output (W) Experimental
Variable
56 ± 21
62 ± 25
0.010*
Control
54 ± 21
43 ± 15
Experimental
10.1 ± 3.1
11.2 ± 2.9
Control
10.1 ± 2.8
9.4 ± 2.4
RER Experimental
1.00 ± 0.04
Control
1.01 ± 0.07
0.99 ± 0.10
VE (L/min) Experimental
33.0 ± 8.0
35.3 ± 12.9
Control
32.9 ± 9.7
30.4 ± 6.8
92 ± 12
95 ± 22
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VO2 (mL/kg/min)
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1 2 3 4
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0.08 ± 0.08
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Heart Rate (bpm) Experimental Control Heart Rate (% max) Experimental
86 ± 24
60 ± 12
63 ± 19
65 ± 24
62 ± 19
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Control
96 ± 38
0.040*
0.758
0.082
0.069
0.475
Oxygen Pulse (mL O2/beat)
Control
5 6 7
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Experimental
9.8 ± 4.2
10.5 ± 3.1
9.3 ± 3.8
9.0 ± 2.9
0.266
VE, minute ventilation; RER, respiratory exchange ratio; VO2, oxygen consumption. Values are means ± SD; the p values for the interactions effect are shown. * significant interaction effect (p < 0.05).
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Figure Legend
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walk distance (C) over the 12-week intervention. * Significant interaction effect
5
reflecting an improvement in the experimental group and no change in the control
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group.
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Figure 1: Changes in peak aerobic power (VO2peak; A), Quality of Life (B), and 6 min
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