Nordic walking and standard exercise therapy in patients with chronic heart failure: A randomised controlled trial comparison

Exercise training in patients with heart failure (HF) has many benefits including the improvement of exercise capacity, reduction of symptoms and hospitalisations and enhancement of health-related quality of life (HRQL).1–4 Nordic walking (NW) is a form of exercise training using specialised walking poles which offers advantages over standard exercise therapy (SET; aerobic/resistance training) for HF patients, including the recruitment of core and upper-body muscles, enhanced oxygen consumption (VO2), increased walking speed and greater caloric expenditure during exercise without increasing perceived exertion.5 Poles may also assist with balance issues – enhancing confidence and stability. We sought to determine whether a 12-week programme of NW was more effective than SET at increasing exercise capacity and HF-specific HRQL in patients with HF. Secondary objectives were to assess whether NW was superior to SET for increasing physical activity and cardiopulmonary fitness, improving body composition, reducing neurohormonal activation, reducing left ventricular filling pressures and enhancing generic HRQL. We conducted a single-site, parallel group, randomised controlled trial. Individuals with stable HF recruited from cardiac rehabilitation underwent baseline assessment and were randomly assigned in a 1:1 ratio to either SET or NW using a blocked, random sequence that was computer generated by a statistical consultant. Treatment assignments were placed in sealed, opaque, numbered envelopes to ensure concealment until baseline data were collected. Follow-up measures were taken at the end of the intervention (12 weeks) and after a 14-week no-intervention observation period (26 weeks). A random subset of participants completed an echocardiogram and cardiopulmonary exercise test (CPET) before and after the 12-week intervention. The trial was prospectively registered (clinicaltrials.gov #NCT02061319) and received ethical approval from the Ottawa Health Science Network Research Ethics Board (#20130774). Both groups attended supervised, group-based, on-site (at the University of Ottawa Heart Institute) exercise classes twice weekly for 12 weeks. Participants in the NW group were provided with walking poles (Gymstick) and were trained on proper techniques by a physiotherapist who is a Gymstick certified NW instructor. Their classes included: a 15-minute chair warm-up (excluded resistance exercise); 10–15 minutes of walking with NW poles for the first 1–3 weeks, progressing to 30 minutes for the remaining weeks; and 15 minutes of cool-down exercises. Participants were instructed to take the walking poles home and perform additional NW for a total of 200–400 minutes per week. Participants assigned to the SET group received similar instruction but it included aerobic exercise (e.g. walking, cycling) and resistance training in place of NW and were instructed to perform additional aerobic exercise (total of 200–400 minutes per week) and one additional strength training session a week. All participants followed the same prescription for exercise intensity, which included achieving a heart rate of 20–30 beats above resting or a rating of perceived exertion of 11–15 (light–hard) on the Borg scale (range 6–20). Exercise capacity was one of two primary outcomes and was measured using a 6-minute walk test (6MWT). The 6MWT is an indicator of the capacity to undertake day-to-day activities in patients with HF; a change of 50 metres in distance walked was considered clinically meaningful.6 The second primary outcome was HF-specific HRQL measured using the Minnesota living with heart failure questionnaire (MLHFQ); improvements of five points were considered clinically meaningful.7 Secondary outcomes included: generic HRQL measured using the medical outcomes study short form (SF-36) which yielded separate physical component summary (PCS) and mental component summary (MCS) scores; symptoms of anxiety and depression assessed using the hospital anxiety and depression scale (HADS); physical activity measured using an ActiGraph GT3X accelerometer; left ventricular filling pressure assessed using the E/e′ ratio; cardiopulmonary fitness (peak VO2) assessed using a CPET; anthropometrics (height, body mass, calf circumference, waist circumference); and neurohormonal activation measured by blood levels of N-terminal pro B-type natriuretic peptide (NTproBNP). Analyses were conducted with SPSS version 25 (IBM Corp., NY, USA). Data were tested for normality using plots and Sharpiro–Wilks test statistics. Descriptive data were reported using means ± SD or frequencies (percentages). Baseline clinical and sociodemographic characteristics were compared between the groups to identify any chance statistical (P < 0.05) differences that may have occurred despite random assignment. For the primary analyses, group differences in 6MWT distance and MLHFQ scores over the study intervention time points were examined using linear mixed effects modelling; change over 12 weeks is considered the primary outcome. Similar analyses were used for all secondary outcomes of interest. The intention to treat principle was followed by using the full maximum likelihood estimation model with an unstructured variance–covariance structure for all available data from each participant without the need to omit patients with missing data from the analysis or impute missing values. Binary logistic regression modelling was used to identify potential correlates of clinically meaningful improvements in the primary outcomes. Of the 527 screened patients, 77 (14.6%) met eligibility criteria and consented to participate; 38 were randomly assigned to each group (Figure 1). There were no statistically significant baseline demographic or medication differences and only resting diastolic blood pressure was different between the two groups (higher in NW). Overall, 67.5% of the randomly assigned participants completed the study (26 per arm). During the study, four adverse events unrelated to the intervention were reported. Attendance at the supervised sessions was 91.1 ± 0.2% and 84.9 ± 19.3% for the NW and SET groups, respectively (P = 0.129). Consort flow diagram. Table 1 summarises the effects of SET and NW at 12 weeks. Both groups achieved similar clinical improvements in 6MWT distance (SET 54.6 m ± 62.3 m vs. NW 68.2 m ± 47.8 m, difference –13.6 m, 95% confidence interval (CI) –42.6–15.4) and MLHFQ scores (SET –12.9 ± 16.3 vs. NW –10.9 ± 18.0, difference 2.0, 95% CI –7.3–11.3). A comparable proportion of both groups achieved clinically meaningful improvements in 6MWT distance (SET 47% vs. NW 62%, χ2 = 1.409, P = 0.235) and MLHFQ scores (SET 60% vs. NW 64%, χ2 = 0.092, P = 0.761). Similar findings were observed at 26 weeks (not shown). We observed greater improvements in the MCS of the SF36 in NW compared to SET. Both forms of exercise intervention led to similar improvements in NTproBNP and symptoms of anxiety and depression. Adiposity increased over time in both groups. Living with others compared to living alone was associated with a 3.5 times greater likelihood of achieving clinically meaningful improvements in 6MWT (odds ratio 3.5, 95% CI 1.15–10.63). Outcome values at baseline and 12 weeks by treatment group. All values presented as estimated marginal means ± standard error, significant results in bold type. 6MWT: 6-minute walk test; BMI: body mass index; NTproBNP: N-terminal pro b-type natriuretic peptide; DBP: diastolic blood pressure; HADS: Hospital Anxiety and Depression Scale; MCS: mental component summary; MLHFQ: Minnesota Living with Heart Failure Questionnaire; MVPA: moderate-to-vigorous intensity physical activity; PA: physical activity; PCS: physical component summary; SBP: systolic blood pressure.; VO2: oxygen consumption. Outcome values at baseline and 12 weeks by treatment group. All values presented as estimated marginal means ± standard error, significant results in bold type. 6MWT: 6-minute walk test; BMI: body mass index; NTproBNP: N-terminal pro b-type natriuretic peptide; DBP: diastolic blood pressure; HADS: Hospital Anxiety and Depression Scale; MCS: mental component summary; MLHFQ: Minnesota Living with Heart Failure Questionnaire; MVPA: moderate-to-vigorous intensity physical activity; PA: physical activity; PCS: physical component summary; SBP: systolic blood pressure.; VO2: oxygen consumption. A systematic review of randomised controlled trials of NW previously found that, in individuals with coronary artery disease or HF, there were no statistically significant differences in 6MWT distance in those undertaking NW compared to standard cardiac rehabilitation.8 All studies did, however, show an improvement in HRQL, with changes significantly greater following NW than in standard cardiac rehabilitation, similar to what was observed in our study.8,9,10 NW promotes the uptake of exercise outdoors (due to the need for larger walking spaces); an added benefit for the improvement of mental health outcomes. Our previous pilot work found that compared with SET, 12 weeks of NW led to higher functional capacity, self-reported physical activity, grip strength and fewer depressive symptoms.10 The current trial improved on the previous work by blinding outcome assessors, increasing follow-up time to 26 weeks and assessing a larger number of outcomes. Both groups in the present study saw similar improvements in depressive symptoms. The present trial did not observe differences for physical activity levels, but this possibly reflects the use of accelerometers which remove potential response bias. It is not clear why we did not observe higher 6MWT distances in the NW group as seen in the previous trial. Participants in the pilot presented with a lower average ejection fraction than the current study (27% vs. 34%). It is also possible, in our pilot, that the unblinded assessors could have introduced a measurement bias. Unfortunately, based on our a priori sample size, we were underpowered to examine differences in outcomes. The trial was designed to detect clinically meaningful differences in 6MWT and MLHFQ between groups; equating to a targeted sample of 194 (97/group) and 168 participants (84/group), respectively. Given the large number of outcomes examined, it is also possible that differences were observed by chance alone. Unfortunately, recruitment was difficult, future trials may benefit from recruiting directly from HF clinics. In conclusion, 12 weeks of NW or SET led to similar clinical improvements in exercise capacity and HF-specific HRQL in individuals with HF, with these changes maintained 14 weeks following completion of the intervention. Future studies are needed to assess the repeatability of findings. The authors would like to express their gratitude to the participants of this study and their nursing and physiotherapy colleagues at the UOHI Cardiac Rehabilitation Program, who provided support to the project throughout the investigation period. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: this study was funded by a Heart and Stroke Foundation Grant (#G-13-0001621). SAP is funded by a Canadian Institutes of Health Research – Public Health Agency of Canada Health System Impact Fellowship. LMC is funded by a UOHI Strategic Research Endowed Fellowship.

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